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Natural Gas Glossary

A-Z Terms

  • A

    2-PSIG Gas Piping System

    A gas piping system that utilizes 2-psig pressure downstream of the point of delivery. This type of gas piping system allows greater versatility in the design of branch systems and in a multi-family building that could reduce the cost of installing the piping system when compared to the traditional 1/4 psig system.

    Abandoned Well

    A well not in use because it was a dry hole originally, or because it has ceased to produce. Statutes and regulations in many states require the plugging of abandoned wells to prevent the seepage of oil, gas, or water from one stratum to another.


    Regulatory authorization for a utility to cease provision of a particular service and/or to shut down a particular facility.

    Abandonment Costs

    Costs associated with the abandonment of facilities or services, including costs for the removal of facilities and restoration of the land.

    Abbreviated Application

    An abbreviated application for a certificate of public convenience and necessity that may be filed under Section 7 of the NGA whenever the proposed action does not require all of the data and information normally filed in a certificate application in order to disclose fully the nature and extent of the proposed undertaking.

    Above the Line


    Absolute Open Flow (AOF)

    The number of cubic feet of gas per 24 hours that would be produced by a well if the only pressure against the face of the producing sand in the wellbore were atmospheric pressure.

    Absolute Pressure

    Gauge pressure plus barometric pressure. Absolute pressure can be zero only in a perfect vacuum.

    Absolute Viscosity

    The measure of a fluid's tendency to resist flow, without regard to its density. By definition, the product of a fluid's kinematic viscosity times its density.

    Absolute Zero

    The zero point on the absolute temperature scale. It is equal to -273.16 degrees C, or 0 degrees K (Kelvin), or -459.69 degrees F, or 0 degrees R (Rankine).


    A material which, due to an affinity for certain substances, extracts one or more such substances from a liquid or gaseous medium with which it contacts, and which changes physically, or both, during the process.


    The extraction of one or more components from a mixture of gases when gases and liquids are brought into contact. The assimilation or extraction process causes (or is accompanied by) a physical or chemical change, or both, in the sorbent material. Compare ADSORPTION.

    Absorption Plant

    A device that removes hydrocarbon compounds from natural gas, especially casinghead gas. The gas is run through oil of proper character, which absorbs the liquid constituents, which are then recovered by distillation.

    Absorption Refrigerating System


    Absorption Type Air Conditioner, Direct Fired

    A self-contained device that provides cooling by direct application of heat.

    Accelerated Cost Recovery System (ACRS)

    A depreciation system enacted as part of the Economic Recovery Tax Act of 1981 that allows rapid depreciation of assets for tax purposes. It was repealed in the Tax Reform Act of 1986.

    Acceptance for Filing (of a Rate Schedule)

    Commission action by which a rate schedule is accepted for filing and becomes a legal rate schedule when made effective by the Commission.

    Acceptance Test

    An investigation performed on an individual lot of a previously qualified product (e.g., plastic pipe) by, or under the observation of, the purchaser to establish conformity with a purchase agreement stipulating specified requirements.


    The recording on the books of account, in a given period, of expenses or charges incurred and/or of income earned for the period, to reflect the matching of income and expenses to the fullest extent possible, independent of the dates on which settlements of such items are made.

    Accumulated Deferred Income Taxes

    Account(s) shown on a corporation's balance sheet, typically a net liability, that represents a future (deferred) claim by the government against the corporation's assets. Deferred income taxes arise from the use of accelerated or liberalized depreciation for tax purposes instead of straight-line or other non-liberalized depreciation methods used for book purposes, and from other temporary differences in the recognition of revenue and expense items for income tax purposes and for financial reporting purposes.

    Accumulated Provision for Depletion

    The net accumulated credit resulting from offsetting charges to income for the pro-rata cost of extracted depletable natural resources such as coal, gas, oil, etc.

    Accumulated Provision for Depreciation and Amortiz

    The net accumulated credit balance arising from provisions for depreciation and/or amortization (both defined herein) of assets, usually utility plant, and non-utility property. The net balance reflects current and prior credits fewer charges but is not a measure of actual depreciation.

    Acetone test

    A process control test for PVC pipe indicates how well the rigid vinyl compound has been fused together in the extruder. The improperly fused pipe will tend to flake when placed in anhydrous acetone.

    Achievable Potential

    In DSM, an estimate of energy savings based on the assumption that all energy-efficient options will be adopted to the extent that they are cost-effective and possible through utility DSM programs. Compare ECONOMIC POTENTIAL, MARKET POTENTIAL, and TECHNICAL POTENTIAL.

    Acid Gases

    Gases that produce an acidic solution when dissolved in water. Examples of such compounds, often found in natural gas, are hydrogen sulfide and carbon dioxide.

    Acid Rain

    Abnormally acidic rainfall, most often containing dilute concentrations of sulfuric acid or nitric acid.


    The practice of applying acids to the walls of oil and gas wells to remove any material which obstructs the entrance of fluids. Also used in carbonate formations, such as limestone, to increase porosity.

    Acquisition Adjustments


    Acre Feet of Water

    The volume of water that would cover one acre to a depth of one foot, or 43,560 cubic feet of water, or 325,841.1 gallons of water.

    Acre Foot

    A unit of measurement applied to petroleum and natural gas reservoirs. It is equivalent to an acre of producing formation one foot thick.

    Acrylonitrile-Butadiene-Styrene (ABS)

    Plastics containing polymers and/or blends of polymers, in which the minimum butadiene content is 6%, the minimum acrylonitrile content is 15%, the minimum styrene and/or substituted content is 15%, and the maximum content of all other monomers is not more than 5%, and lubricants, stabilizers, and colorants.

    Acrylonitrile-Butadiene-Styrene (ABS) Pipe and Fit

    Plastics that contain more than 50% ABS polymers, more than 5% of other polymers, and lubricants, stabilizers, and colorants.

    Action Plan

    A component of IRP, describing utility actions in the short-term (about two years) to meet the supply and demand objectives of the integrated resource plan.

    Actual Cost

    In rate base determination. See ORIGINAL COST, HISTORICAL COST, WEIGHTED COST.

    Ad Valorem

    Taxes imposed at a percent of a value.

    Adaptor Plate, Instrument

    A specially designed plate mounted between a meter and an instrument to provide for a proper drive to the instrument.

    Additions to Utility Plant

    a. Gross Additions - Expenditures for construction (including Allowance for Funds Used During Construction) and/or utility plant purchased and acquired. b. Net Additions - Gross additions fewer retirements and adjustments of utility plant. It is the net change in the utility plant between the two dates.


    A substance capable of holding materials together by surface attachment.

    Adhesive, Solvent

    An adhesive having a volatile organic liquid as a vehicle. See SOLVENT CEMENTING.


    A term indicating that no heat is lost or gained by a material being subjected to a thermodynamic process. An adiabatic process is one in which there is no exchange of heat with the surroundings.

    Adjustment Clause


    Administrative Law Judge (ALJ)

    The officer designated by the FERC to conduct the proceedings in a rate or other tariff filing.


    The extraction from a mixture of gases or liquids of one or more components, by surface adhesion to that material with which the gases or liquids come in contact. The adsorption or extraction process does not cause and is not accompanied by either a physical or chemical change in the sorbent material. Compare ABSORPTION.

    Advance Payments

    Amounts paid by interstate gas pipelines to natural gas producers, including affiliated companies, for exploration, development, or production of natural gas, which amounts were to be repaid in cash or by future delivery of gas. During a brief period during the 1970s the Commission allowed such advances to be included in the pipeline's rate base (with adjustments when repaid) and hence to be recovered by the pipeline through its cost of service. The purpose of the advance payments was to induce producers to sell natural gas at regulated prices to the interstate pipelines, rather than at higher, unregulated prices to intrastate pipelines.

    Advances for Construction

    A deferred credit account representing cash advances paid to the utility by customers requiring the construction of facilities in their behalf. These advances are refundable -- the time or extent of refund is dependent on the contract provisions of the advance (usually dependent on whether or not during a specified period the revenue from the installation warrants the refund). The unrefunded balance, if any, must be transferred to the appropriate plant account. Compare CONTRIBUTIONS IN AID OF CONSTRUCTION.

    Affiliated Entities Test

    A test to determine if the amount paid for gas to an affiliate exceeds the amount paid in comparable first sales between non-affiliated entities.

    Affiliated Marketer

    A marketer that is owned either by a distribution or transmission company, or by a corporation that also owns a distribution or transmission company.


    The process of cooling a compressed air or gas immediately after compression.



    Age Interval

    A standard period of time, usually one year. A series of such consecutive intervals facilitates observing the pattern of survivors and developing the survivor curve. Age interval should not be confused with calendar year.


    A legal representative of buyers, sellers or shippers of natural gas in negotiation or operations of contractual agreements.


    Effect on materials in service of exposure to an environment for an interval of time.

    Agreement and Undertaking

    A document which an independent gas producer may be allowed to file, at the discretion of the Commission, in lieu of a bond, agreeing to refund that portion of an increased rate which has been made effective subject to refund and is ultimately found not justified by the Commission.

    Agreement on Principles

    The Agreement between the United States of America and Canada on the ALASKA NATURAL GAS TRANSPORTATION SYSTEM (ANGTS). The agreement was signed by representatives of the two governments on September 20, 1977.

    Air Change

    A method of expressing the amount of air infiltration and/or ventilation of a building or room in terms of the number of building volumes or room volumes exchanged per unit of time.

    Air Conditioner, Room

    A factory-made encased assembly, designed as a unit for mounting in a window, through a wall, or as a console, for the purpose of delivering conditioned air to an enclosed space without ducts.

    Air Conditioning

    The process of heating, cooling, humidifying, filtering, drying, deodorizing, or otherwise treating air in a room or building to maintain a specified temperature and/or relative humidity and to remove impurities.

    Air Conditioning Central

    A mechanical system that is designed to provide air conditioning, which may include cooling, heating, dehumidifying, circulation and cleaning. The air is treated by the conditioner at one or more central locations outside the space served and conveyed to and from the space by means of fans and pumps through ducts and pipes.

    Air Diffuser

    An air delivery device or louver so arranged as to promote mixing of the air introduced by it into a room with the room air, without causing objectionable drafts or noise.

    Air Heater

    Combustion air (fed to burners) can be heated to approximately 500 degrees F by transferring heat from the flue gases to the air.

    Air Receiver

    A storage tank for compressed air.

    Air Shutter

    An adjustable device for varying the primary air inlet(s) regulating primary or secondary air.

    Air-Gas Ratio

    The ratio of the air volume to the gas volume. A specified ratio is necessary to achieve a desired character of combustion.

    Alaskan Natural Gas Transportation System (ANGTS)

    A proposed pipeline system to transport gas from the Prudhoe Bay field in Alaska to the vicinity of Chicago and San Francisco through Canada. Portions from Canada towards San Francisco (the Western Leg) and from Canada towards Chicago (Northern Border Pipeline) were "prebuilt" to import gas from Canada prior to the flow of Alaskan gas. The project was authorized by the ANGTA of 1976 and the President's Decision and Report to Congress in September 1977.


    Hydrocarbon that does not contain an aromatic ring structure. See AROMATIC.

    Allocated Pool

    A pool in which the total oil or natural gas production is restricted and allocated to various wells therein in accordance with proration schedules.


    The process of determining ownership rights to the gas delivered to a meter.

    Allocation Method

    A method of allocating volumes to affected parties when an imbalance occurs.


    A process by which capacity available in a pipeline is distributed to parties in the event requests for volume (i.e., nominations) are in excess of the available space. Typically the allocation is based on service type, contract type and a company's tariff provisions. Also called NOMINATION ALLOCATION.


    The assignment of a total measured quantity of gas at a point to the various contracts active at that point during a specific period of time.


    The process by which supply is assigned to purchasers in accordance with a given priority during periods when total sales requests exceed the seller's total supply.

    Allocation-Supplies to End-Use Customers

    The amount of gas supply available to the customer in accordance with a given priority during periods of curtailment. See COST OF SERVICE, DESIGN DAY AVAILABILITY.

    Allowable Working Stress

    The maximum hoop stress permitted by code for the design of a piping system. See HOOP STRESS.


    The permitted rate of production from a well or group of wells that is allowed by a particular state or governing body. The rate is set by rules which vary among the various states or governing bodies.

    Allowance for Funds Used During Construction (AFUD)

    AFUDC is a component of construction costs representing net cost of borrowed funds and a reasonable rate on other funds used during the period of construction. AFUDC is capitalized until the project is placed in operation by concurrent credits to the income statement and charges to utility plant, based generally on the amount expended to date on the particular project. Effective January 1, 1977, FERC amended the Uniform System of Accounts establishing formulas for maximum allowable AFUDC rates.

    Allowed Rate of Return

    The rate of return that a regulatory commission allows on a rate base in establishing just and reasonable rates for a utility. It is usually based on the composite cost of financing rate base from debt, preferred stock, and common equity. See RATE OF RETURN.

    Alternate Fuel Capability

    The ability to use an alternate fuel whether or not the facilities for such use have actually been installed.

    Alternate Fuels

    Other fuels that can be substituted for the fuel in use. In the case of natural gas, the most common alternative fuels are distillate fuel oils, residual fuel oils, coal and wood.

    Amagat's Law

    See LAWS.

    Ambient Vaporizer

    A vaporizer which derives energy for vaporizing and heating LNG from storage conditions to send out conditions from naturally occurring sources such as the atmosphere, sea water, or geothermal waters.

    American Gas Association (AGA)

    Trade group representing natural gas distributors and pipelines.


    Gas Advanced Metering Infrastructure (AMI) is a full two-way communications network which provides time-synchronized interval meter data collected a minimum of daily and includes a data management system. It is a multi-purpose expandable network that can monitor and control devices deployed throughout the pipeline system. It enables efficient measurement and operations of the gas network and provides timely information to utility personnel and consumers.


    Devoid of crystallinity. Most plastics are in the amorphous state at processing temperatures; many retain this state under normal conditions.


    The gradual extinguishment (or accumulated provision or reserve therefor) of an amount in an account by pro-rating such amount over a predetermined period, such as the life of the asset or liability to which it applies, or the period during which it is anticipated the benefit will be realized.


    Automated Meter Reading is a one-way remote collection of consumption data from customers’ utility meters using telephony, radio frequency, power-line and satellite communications technologies.


    An instrument for measuring the velocity of wind.


    A process involving controlled heating and subsequent controlled, generally slow, cooling applied usually to induce ductility in metals. The term also is used to cover treatments intended to remove internal stresses, alter mechanical or physical properties, produce a definite microstructure, and remove gases.

    Annealing, Bright

    A process which is usually carried out in a controlled furnace atmosphere so that metal surface oxidation is eliminated or reduced to a minimum, and the surface remains relatively bright.

    Annual Fuel Utilization Efficiency (AFUE)

    AFUE measures average annual seasonal efficiency of a gas furnace or boiler and may be expressed as total heating output divided by total energy (fuel) input. AFUE's for furnaces can range from 55% to 97%.

    Annual Gas Consumption (Sales) Per Customer (By Class of Service)

    Average annual sales used per customer in Btu's or therms by class of service; annual Btu's or therms sales to a class divided by the average number of customers for that class of service.

    Annual Gas Revenue Per Customer

    Annual revenue exclusive of forfeited discounts and penalties from a class of service, divided by the average number of customers in that class of service.

    Annual Volume Method

    A method to allocate commodity costs by function to customer classes based on the Test Period volume level for that customer. See COST OF SERVICE.


    To adjust to a full-year basis any item not included in the Base Period or included in the Base Period for less than a full year. Also called KNOWN CHANGE ADJUSTMENTS.

    Anode, Sacrificial

    In corrosion protection, a formed metal-usually zinc, aluminum, or magnesium-buried near and connected to a structure of lesser galvanic potential such that the metal corrodes in favor of the structure.

    Anodic Inhibitor

    A chemical substance or combination of substances that prevents or reduces the rate of the anodic or oxidation reaction by a physical, physio-chemical or chemical action.

    Anodic Polarization

    (1) Polarization of anode, that is, the decrease in the initial anode potential resulting from current flow effects at or near the anode surface. The potential becomes more noble (more positive) because of anodic polarization. (2) That portion of the cell polarization occurring at the anode.

    Anodic Protection

    (1) A technique to reduce corrosion of a metal surface under some conditions by passing sufficient anodic current to it to cause the electrode potential of the surface to enter and remain in the passive region. (2) An appreciable reduction in corrosion by making a metal an anode and maintaining this highly polarized condition with very little current flow.

    ANS Preferred Number

    Series of numbers preferentially selected for standardization purposes. They are defined in "American National Standard Preferred Numbers, ANSI Z17.1-1958."


    American National Standards Institute - The coordinating organization for America's federated national standards system. The ANSI federation consists of nine hundred companies, large and small, and some two hundred trade, technical, professional, labor, and consumer organizations.

    ANSI X12

    American National Standards Institute X12 Committee - The committee sanctioned by ANSI for developing and maintaining U.S. standards for business-to-business electronic data interchange pertaining to trade transactions, with business-to-business defined broadly to include all organizations but excluding all individual consumers.

    Anthracite Coal

    A hard, black, lustrous coal that burns efficiently, containing a higher percentage of fixed carbon and a low percentage of volatile matter differing from bituminous, and generally having a heating value of 11,000-12,000 Btu/lb. Commonly referred to as hard coal; it is mined in the U.S., mainly in eastern Pennsylvania, although in small quantities in other states. Most of the anthracite is used as a fuel in household heating systems. When anthracite burns, it produces almost no smoke.


    A compounding ingredient added to a plastic composition to retard possible degradation from contact with oxygen (air), particularly in processing at, or exposures to, high temperatures.


    An upfold or arch in rock strata in which the beds or layers dip in opposite directions from the crest, permitting possible entrapment of oil and gas.

    Appropriate State Regulatory Agency

    Term used in Part 284 of the Regulations to refer to a state agency that regulates intrastate pipelines and local distribution companies within such state. When used in reference to rates and charges, the term includes only those agencies which set rates and charges on a cost-of-service basis.

    Aquifer Storage


    Arms-Length Bargaining or Negotiation

    Bargaining between two or more unaffiliated parties carried out in a truly competitive manner.


    A term for any hydrocarbon containing a benzene ring or similar structure.


    A method by which a pipeline includes in its rates, and charges its customers, the costs of gas or transportation services in the same manner as it is billed by its pipeline suppliers or transporter.


    American Standards Association. Superseded by the American National Standards Institute. See ANSI.

    Asset Depreciation Range (ADR)


    Assets (and other Debits)

    Items of value owned by or owed to a business. Utility assets include Utility Plant, Other Property and Investments, Current and Accrued Assets, and Deferred Debits. Accumulated Provision for Depreciation and Amortization is usually shown as a deduction from the listed assets, but some companies show this account in the liability section.


    In law generally a transferee; a recipient of an interest in the property or a contract.

    Associated Gas


    Associated Gas Proration

    Restrictions state place on the production of associated gas. See GAS, ASSOCIATED.

    Associated Liquids

    Condensates (liquid hydrocarbons without free water) produced in conjunction with the production of gas to be transported or liquefiable hydrocarbons contained in such gas, but not including oil.

    Atlantic Seaboard


    Atlantic-Seaboard Classification Method

    A method of classifying costs as demand or commodity costs promulgated by the FPC in Opinion 225, April 25, 1952. Generally, this method allocates 50% of the pipeline's fixed storage and transmission costs to the demand component and 50% to the commodity component of the rates.


    The outdoor air in general. Also a mixture of gases within any specified chamber, such as a heat-treating furnace.

    Atmospheric Pollution


    Atmospheric Pressure



    The smallest complete particle of an element that can be obtained yet retain all physical and chemical properties of the element.


    To reduce a liquid to a fine spray or mist.




    Erosion of earnings on invested capital resulting from the regulatory practice of setting utility rates based on past costs during an inflationary period.

    Authorized Over-Run


    Automatic Adjustment Clause


    Automatic Ignition


    Automatic Meter Reading (AMR)

    "Real-time" monitoring of natural gas quantities and characteristics as it passes through a specific location.

    Auxiliary Devices

    Devices used with a meter to provide an adjustment of the meter reading to permit obtaining special information, or to transmit information to a remote location.

    Available Heat

    The amount of energy that is converted into

    Average Invested Capital

    The sum of the capitalization, long-term debt due within one year, and short-term debt outstanding at the end of each month, for a period of time (usually 12 months), divided by the number of such months. The computation may also be made for individual classes of capital, i.e., long-term debt, short-term debt, preferred stock, and common stock equity.

    Average Revenue Per Unit of Gas Sales (By Class of

    Revenue from the sale of gas to a class of service, exclusive of forfeited discounts and penalties, divided by the corresponding number of units sold. Units may be therms, Btu's, or cubic feet.

    Average Service Life


    Avogadro's Law

    See LAWS.

    Avoided Cost

    The incremental cost that a utility would incur to purchase or produce an amount of gas equivalent to that saved by a DSM measure. Components may include energy, capacity, storage, transmission, and distribution. Avoided costs are generally used to represent the benefits of utility-sponsored DSM programs.

  • B

    Back Pressure

    Pressure against which a fluid is flowing. May be composed of friction in pipes, restrictions in pipes, valves, pressure in vessels to which fluid is flowing, hydrostatic head, or other resistance to fluid flow.


    Earth or other material that has been used to refill a ditch or trench. Also, the act of refilling a ditch or trench.




    A transaction that results in the transportation of gas in a direction opposite of the aggregate physical flow of gas in the pipeline. This is typically achieved when the transporting pipeline redelivers gas at a point(s) upstream from the point(s) of receipt. A backhaul condition will exist as long as the aggregate backhaul transactions total less than the aggregate forward haul transactions. A backhaul transaction can result in delivery by non-delivery or cut back (reduction) of physical flow at a delivery point.

    Badge, Meter

    A permanent plate, affixed in a conspicuous place on a meter, containing basic meter information.


    Plates, louvers, or screens placed in the path of fluid flow to cause a change in the direction of flow; these are used to promote the mixing of gases or to eliminate undesirable solid or liquid particles in the fluid stream. Sometimes baffles are inserted in a flue to lengthen the travel of flue gases and increase the efficiency of operation.

    Bag Hole

    A hole cut into a main in preparation for a bag-off.


    Inflatable bags and stoppers placed in a main to seal off the gas flow.


    A device used in cable tool drilling to remove drill cuttings from a well. It consists of a simple tube suspended on a cable, open at the top, with a foot-valve at the bottom. The foot-valve opens when the bailer touches the bottom of the drilled hole, permitting water with drill cuttings in suspension to enter the tube. When the bailer is raised to be emptied, the foot-valve closes instantly as it loses contact with the bottom of the hold and retains the water and drill cuttings.

    Balance, Gas

    An instrument used for determining the specific gravity of gases.


    Making receipts and deliveries of gas into or withdrawals from a company equal. Balancing may be accomplished daily, monthly, or seasonally, with penalties generally assessed for excessive imbalance.

    Balancing Agreement

    A contractual agreement between two or more legal entities to account for differences between chart measured quantities and the total confirmed nominated quantities at a point. They have been used to keep track of over/under production relative to entitlements between producers; over/under deliveries relative to confirmed nominations between operators of wells, pipelines, and LDCs.

    Balancing Penalty

    A daily or monthly penalty assessed on the difference between volumes tendered and volumes received by the shipper. The purpose of balancing penalties is to prevent a shipper from tying up storage and line pack with excess deliveries of transportation gas, or from depleting storage and line pack by taking more gas off the system than it delivers, both of which disrupt other sales and transportation services.

    Balancing Provisions

    A requirement that gas entering a pipeline for transportation (receipts) must equal the amount leaving the pipeline (deliveries). This requirement is enforced by levying penalties on any difference between receipts and deliveries on an hourly, daily, and monthly basis.

    Balancing Units

    The unit of measure used for the purpose of balancing the amount of gas received by the transporter at the transporter receipt point(s) with the amount of gas delivered by the transporter for the shipper's account at the transporter delivery point(s). The Balancing Unit shall be reported in MMBtu's which shall be determined by multiplying each Mcf of dry gas so received or delivered by the dry heating value thereof.

    Band Clamp


    Bar Hole

    Small diameter holes made in the ground in the vicinity of gas piping for the purpose of extracting a sample of the ground atmosphere for analysis such as when searching for leaks.

    Bar Test Survey (For Gas Mains)

    Leakage surveys made by driving or boring holes at regular intervals along the route of an underground gas pipe and testing the atmosphere in the holes with a combustible gas detector or another suitable device.


    The instrument used for measuring atmospheric pressure.

    Barrel (Oil)

    A volumetric unit of measurement equivalent to 42 U.S. gallons, 9,702 cubic inches, 5.6146 cubic feet, 34.9722 Canadian Imperial gallons, 158.99 liters, or .15899 cubic meters. It is the unit of measurement commonly used to measure oil production and oil reserves within the U.S.

    Base Conditions

    The ANSI Z132 has established 60oF and 14.73 psia as the base temperature and pressure to which all volumes are commonly referred.

    Base Contract Price

    The stated per unit price for natural gas in a contract between a producer and a purchaser.

    Base Cost of Gas

    The component in the BASE TARIFF RATE represents the average cost of purchased gas.

    Base Gas

    The gas required in a storage reservoir to provide the pressure to cycle the normal working storage volume. See also CUSHION GAS: STORAGE, UNDERGROUND.

    Base Load

    As applied to gas, a given consumption of gas remaining fairly constant over a period of time, usually not temperature-sensitive.

    Base Load, Residential

    The gas consumed by clothes dryers, water heaters, ranges, and cooling. Baseload does not vary with heating degree-days.

    Base Period

    Recently available 12 consecutive months of actual experience. Not always the most recent 12 months. In a rate proceeding, 12 months of actual operations ending no more than 4 months before the date a rate change application is filed. In reference to the EQUITABLE SHARING MECHANISM, a representative base period must reflect a representative level of purchases by a pipeline's firm customers during a period preceding the onset of changed conditions which resulted in reduced purchases and growth of the take-or-pay problem. See EQUITABLE SHARING MECHANISM, DEFICIENCY PERIOD, PURCHASE DEFICIENCY METHODOLOGY, and TEST PERIOD.

    Base Pressure

    The pressure used as a standard in determining gas volume. Volumes are measured at operating pressures and then corrected to base pressure volume. Base pressure is normally defined in any gas measurement contract. The standard value for natural gas in the United States is 14.73 psia, established by the American National Standards Institute as standard Z-132.1 in 1969.

    Base Pressure Index

    A device that continuously and automatically compensates to correct gas volume at operating pressure to the volume at base pressure, without regard for any correction for temperature.

    Base Tariff Rate

    The effective rate on file with the Commission, excluding adjustments. It is the rate level established in a general Section 4 rate proceeding or Section 154.303(e) base rate restatement proceeding.

    Base Volume Index

    A device that continuously and automatically compensates to correct gas volumes measured at operating temperature and pressure to the volume at a specified base temperature and pressure.

    Baseboard Radiator

    A heat disseminating unit located at the lower perimeter of a room. Heat is supplied to these units by hot water, warm air, steam, or hot flue gases.

    Basic Air or Gas Time

    The time required to pass one cubic foot of air or gas through a given orifice in a flow prover at stated base conditions. This time is stamped on the prover orifice in seconds.

    Beam Loading

    The application of a load to a pipe between two points of support.

    Behind the Pipe

    Potentially producing reserves of oil or gas that have been penetrated by a wellbore but are separated from the wellbore by a casing (pipe) and cement and hence cannot be produced without recompleting the well. If the zone penetrated is known to be productive (by tests or production elsewhere) the reserves are classified as proven but non-producing.

    Bell Hole

    A hole dug to allow room for workmen to make a repair or connection in the buried pipe, such as caulking bell-and-spigot pipe or welding steel pipe. In the broad sense, any hole other than a continuous trench opened for working on a buried facility.

    Bell Joint Clamp

    A sealing device attached at the joint of the bell-and-spigot pipe to prevent leakage.

    Bell-and-Spigot Pipe

    Pipe made with a cup-like flare at one end (the bell) and plain at the other end (the spigot). The spigot fits into the bell and the joint is sealed with solvent cement or adhesive (in the case of plastic pipe) or packed with caulking, lead, and/or other material in the cast iron pipe annulus.

    Below the Line vs Above the Line

    A decision that is made to determine whether an item should be included in the cost of service for establishing rates (above the line) or should not be included (below the line). The "line" referred to is utility net operating income on the income statement. "Above the Line" refers to revenues collected for and costs included in providing utility service.

    Benefit-Cost Ratio

    The ratio of the value of a measure's savings to its cost.



    Best Available Control Technology (BACT)

    A concept is taken from the Clean Air Act designed to preserve air quality from degradation by requiring that emissions from new facilities, temporary facilities, and even existing facilities in some instances be controlled to the extent possible using the best available technology.

    Best Efforts

    An agreement by a contracting party to do its best to complete some specified result. In a gas transportation contract, it might represent a pledge by the transporter to use best efforts to transport the shipper's gas. BESS is the acronym for best efforts in storage service.


    A substantial enlargement or improvement of existing structures, facilities, or equipment by the replacement or improvement of parts, which has the effect of extending the useful life of the property, increasing its capacity, lowering its operating cost, or otherwise adding to the worth through the benefit it can yield.


    Beveled pipe ends are for welding purposes. The pipe is cut at an inclination so that two ends form an angle other than a right angle.

    Bi-Monthly Billing

    A customer billing procedure in a distribution company where bills are rendered every month, but meters are read every other month. An estimate is made of the volume of gas used in months when meters are not read.

    Bill Frequency Analysis

    A tabulation of bills by size (consumption) and type of service rendered.

    Billing Cycle

    The regular, periodic interval used by a utility for reading the meters of customers for billing purposes. Usually, billing cycles are monthly or bi-monthly.

    Billing Determinant

    The demand is used to determine demand charges in accordance with the provisions of a rate schedule or contract. It does not necessarily coincide with the actual measured demand of the billing period.


    In a reinforced plastic, the continuous phase holds together the reinforcement. NOTE: During fabrication, the binder which may be either thermoplastic or thermoset, usually undergoes a change in state.


    Methane produced by the decomposition or processing of organic matter.


    Biologically produced organic matter.

    Biomass Conversion

    The process by which biomass materials are burned for direct energy or by which such materials are converted to synthetic fuels.

    Bit, Drilling

    A drilling tool that cuts the hole in the earth when drilling a well. Bits are designed on two basic and different principles; the cable tool bit, which moves up and down to pulverize; and the rotary bit which rotates to cut or grind.

    Bituminous Coal

    Ranking of soft coal generally having a heating value of 11,000-13,000 Btu/lb., high in volatile matter and ash.

    Black Steel Pipe

    Ordinary steel pipe, not galvanized.

    Blanket Certificate

    Authorizes open-access transportation by interstate pipeline companies on behalf of others and certain services by local distribution companies and Hinshaw companies under blanket certificates (of public convenience and necessity) subject to certain conditions and reporting requirements. Blanket certificates pre-grant authority for the abandonment of the transportation service upon expiration of the contractual term.

    Blanket Transportation Certificate

    A certificate that allows a pipeline to undertake individual transportation transactions without prior FERC approval. The pipeline is required to file periodic reports with respect to each such transaction.


    Insertion of a solid metal disc between the companion flanges of a flanged joint.

    Blind Flange

    A solid plate used to close off the end of a piping system or a device constructed with flanged ends.

    Block Valve

    Main transmission line valve designed to close in or shut down the gas flow.

    Blow Down

    The process of reducing gas pressures by means of releasing such pressures to the atmosphere.

    Blow Joint

    The perforated joint of the line pipe designed to capture "pig" after pigging and cleaning operations.

    Blow-off Valve

    The valve used to blow pressure off the pipeline. Also used in the purge.


    A device for forcing air or gas to flow in the desired direction at the required pressure. It may be either fan, centrifugal, or positive displacement type.

    Blue Gas

    See WATER-GAS.

    Boil Off

    A natural phenomenon that occurs when liquefied natural gas in a storage vessel warms to its boiling point and gases evolve.


    A closed vessel in which a liquid is heated and/or vaporized. Often classified as steam or hot water, low pressure or high pressure, capable of burning one fuel or a number of fuels.

    Boiler Efficiency

    The ratio of the useful heat output to the heat input, multiplied by 100 and expressed in percent.

    Boiler Fuel Gas

    Natural gas used as a fuel for the generation of steam (or hot water).

    Boiler Pressure

    The pressure of the steam of water in a boiler, depending on the type, generally expressed in pounds per square inch gauge and corresponding temperature.

    Boiler Rating

    The rating of a steam boiler expressed as the total heat transferred by the heating surfaces in Btu per hour. Sometimes expressed in horsepower or pounds of steam per hour.

    Boiler, High Pressure

    A boiler furnishing hot water at pressures in excess of 160 pounds per square inch (psi) and at temperatures in excess of 250oF (121oC) or steam at pressures in excess of 15 psi.

    Boiler, Low Pressure

    A boiler furnishing hot water at pressures not exceeding 160 pounds per square inch (psi) and at temperatures not more than 250oF (121oC) or steam at pressures not more than 15 psi.

    Boiling Point

    The highest temperature that can be reached by a liquid, under a given pressure, when the heat is applied externally and evaporation occurs freely from the surface.

    Bond Ratings

    Rating systems provide investors with a simple series of gradations by which the relative investment qualities or risks of bonds are indicated. Moody's Investors Service and Standard & Poor's Corporation are two principal bond rating agencies.

    Bond Yield Risk Differential (BYRD)


    Bonds (Mortgage)

    Certificates of indebtedness representing long-term borrowing of capital funds, the terms of which contain an indenture pledging the property as security for the loan and providing for the appointment of a trustee to represent the bondholders. If the lien of the mortgage is limited to specific property owned at the time the mortgage was created and to replacements thereof, the mortgage is described as "closed." If the lien extends to "after-acquired" property which may be used as the basis for issuance of additional bonds under the terms and provisions of the indenture, the mortgage is referred to as an "open-end" mortgage.

    Book Cost

    The amount at which property is recorded in plant accounts without deduction of related provisions for accrued depreciation, depletion, amortization, or for other purposes.

    Book Value

    The recorded plant cost less the accumulated depreciation.

    Book Value per Share of Common Stock

    Common stock equity divided by the number of common shares outstanding at the date of the computation.

    Boom Cat

    A tractor equipped with a boom used in laying pipe.


    A compressor used to raise the pressure in a gas or oil pipeline.

    Booster Station

    A facility containing equipment which increases pressure on oil or gas in a pipeline.

    Boston Box

    A square box installed flush with the pavement.


    A gas-tight container fabricated from pipe or plate with integral drawn, forged or spun end closures, tested in the manufacturer's plant, used for storing or transporting gas.

    Bottle, Cubic Foot

    A specially constructed device for calibrating bell provers. The bottle is designed to displace exactly one cubic foot of air when immersed in a tank containing light oil.

    Bottled Gas

    In the industry, liquefied petroleum gas contained under moderate pressure in cylinders sometimes referred to as bottles. Usually propane and/or butane.

    Bottom Gas

    The quantity of gas that is not normally recovered from storage field operation. The same as BASE GAS, or CUSHION GAS.

    Bottom Hole (Rock) Pressure

    The pressure at the bottom of a closed-in well.

    Bottom Hole Contract

    A contract providing for the payment of money or other consideration upon the drilling of a well to a specified depth.

    Bottom-Cycle Plants

    An energy system that produces heat first for process use and electricity as a by-product.


    The liquid or other residual matter that is withdrawn from the bottom of a fractionator or other vessel during processing or while in storage; also, the heaviest product remaining in the liquid phase after distillation.

    Bourdon Tube

    An arc-shaped, spiral, or helical metal tube that is approximately elliptical in cross-section and has one end attached to a pressure indicating, controlling, or recording device, while the other end is fixed. Pressure changes inside the tube affect its shape and actuate the device to which it is attached.

    Boyle's Law

    See LAWS.


    A packer (or fitting) installed on a well at the surface that enables the use of one size pipe inside another, for the subsequent control of products being delivered from either one of the two pipes.

    Bradenhead Gas


    Branch Connection

    The junction of one pipe with another, often a header.

    Branch Line or Take Off

    That portion of a supply line takes off the main header from the location of a tee on the main header.


    A passageway, usually constructed of sheet metal, to conduct the flue gases from the boiler to the chimney. Frequently referred to as "vent connectory". See VENT CONNECTOR.


    A strong saline solution such as common salt and water-cooled by a refrigerant and used for the transmission of heat without a change in its state, having no flash point or a flashpoint above 150 degrees Fahrenheit.

    British Thermal Unit (Btu)

    The quantity of heat necessary to raise the temperature of one pound of water one degree Fahrenheit from 58.5 to 59.5 degrees Fahrenheit under standard pressure of 30 inches of mercury at or near its point of maximum density. One Btu equals 252 calories, (gram), 778 foot-pounds, 1,055 joules, or 0.293-watt-hours.


    In CAPACITY ASSIGNMENT/BROKERING, a broker is one who sells or assigns firm transportation (or storage) capacity rights on an interstate pipeline to another entity. Also, an individual or company that buys or sells stocks, commodities, or services for others for a fee. A broker provides the function of bringing a buyer and seller together. A leasing broker leases to oil and gas leases for others or for the broker's own account for later sale.

    Brokerage of Gas

    The term applies to the activities and compensation in arranging for the sale of gas between producers and buyers.



    Btu Adjustment Clause

    A clause in a gas purchase contract that may adjust the contract price if the heat content of the gas delivered does not fall within a specified range.

    Btu Method

    A method of allocating costs between different operations or between different products based upon the heat content of products produced in the various operations or of the various produced products.

    Btu per Cubic Foot

    A measure of the heat available or released when one cubic foot of gas is burned.

    Btu, Dry

    The heating value contained in a cubic foot of natural gas measured and calculated free of moisture content. Contractually, dry may be defined as less than or equal to seven pounds of water per Mcf.

    Btu, Saturated

    The number of Btus contained in a cubic foot of natural gas fully saturated with water under an actual delivery pressure, temperature, and gravity conditions. See BTU, DRY.

    Buddy Swap

    An arrangement whereby, during a period of severe curtailment, one industrial or commercial customer that can use an alternate fuel agrees to do so temporarily and transfers that part of his gas allocation to another customer that cannot use an alternate fuel.

    Budget-Type Certification

    A budget-type application is an abbreviated, single certificate application filed under Section 7 of the NGA covering a number of minor or routine construction projects expected to be completed during the calendar year or fiscal year of the applicant, where the facilities proposed are to be used for miscellaneous rearrangements not resulting in any change in service or exceeding a specified dollar amount. Budget-type applications started with the Commission's Order No.185, issued February 8, 1956.

    Building Envelope

    The walls, doors, windows, and roof separates the inside of a building from the outside.

    Bulk Plants for LP Gas

    A distributing point with permanently installed pressure tanks and required accessory equipment for storing large volumes of liquid petroleum gas and, in dealer's plants, withdrawing it for refilling bottles, delivery trucks, and trailers; in consumer's plants, withdrawing it for vaporization and utilization.


    A wall installed along a coastline or waterway to protect a pipeline from washout or soil erosion.

    Bull Plug

    A plug that is inserted into the end of an unfinished pipeline to keep out dirt and moisture; also a plug of a particular shape with a male thread on one end and considerable length to the closed-end for convenient use of a wrench.

    Bundled Sales Service

    Natural gas sold on an as-needed basis, without prior scheduling, to the local distribution company at FERC-approved rates. Prior to the implementation of various transportation programs, this constituted all gas delivered to an LDC.

    Bunker "C" Fuel Oil

    Heavy residual fuel oil used by ships, industry, and for large scale heating installations. The United States Navy calls it "Navy heavy"; in industry, it is often referred to as No. 6 fuel oil.


    A pit, usually earthen and of shallow depth used to burn-off and dispose of petroleum distillates.

    Burner Capacity

    The maximum Btu per hour that can be released by a burner while burning with a stable flame and satisfactory combustion. Also called burner rating.

    Burner Head

    The portion of the burner beyond the outlet end of the mixer tube which contains the ports.

    Burner Port

    See PORT.

    Burner Tip

    An attachment for a burner head which forms a burner port modified for a specific application. Also, a generic term that refers to the ultimate point of consumption for natural gas.

    Burner Unit

    An assembly of one or more burner heads receiving gas through a single set of control valves.

    Burner, Automatically Lighted

    Where fuel to the main burner is normally turned on and ignited automatically.

    Burner, Conversion

    A burner designed to supply gaseous fuel to an appliance originally designed to utilize another fuel. a. Firing Door Type - a conversion burner designed specifically for boiler or furnace firing door installation. b. Inshot Type - a conversion burner normally designed for boiler or furnace ash pit installation and fired in a horizontal position. c. Upshot Type - a conversion burner normally designed for boiler or furnace ash pit installation and fired in a vertical position at approximately grate level.

    Burner, Gas

    A device for the final release of air/gas, or oxygen/gas mixtures, or air and gas separately into the combustion zone. Gas burners may be classed as atmospheric burners or blast (pressure) burners.

    Burner, Manually Lighted

    Where fuel to the main burner is turned on only by hand and ignited under supervision.

    Burst Strength

    The internal pressure required to cause a pipe or fitting to fail. NOTE: This pressure will vary with the rate of buildup of the pressure and the time during which the pressure is held.

    Burst Test

    Method of the hydrostatic testing plastic pipe by a uniformly increasing internal pressure so that the pipe fails in 60 to 70 seconds. See ASTM D 1599. Also called a quick burst test.

    Butane (C4H10)

    A low-boiling paraffin hydrocarbon generally stored and delivered in liquefied form and used as a fuel in gaseous form, obtained by processing natural gas as produced and also from a process in petroleum refining. Contains approximately 3,260 Btu per cubic foot.

    Butane-Air Plant

    A gasification plant where liquid butane is vaporized and mixed with air and delivered into a gas distribution system for the use of consumers.


    The joining of two pieces of pipe or other material by full penetration welds.

    Butylene Plastics

    Plastics based on resins made by the polymerization of butene or copolymerization of butene with one or more unsaturated compounds, the butene being in greatest amount by weight.

    Buy-Out Costs (Buy-Down Costs)

    Payments made by pipelines to producers to extinguish (buy-out) outstanding take-or-pay liabilities under existing contracts, or to reform (buy-down) the contracts.

    Buyer Protection Clause

    A provision in a gas purchase contract permitting the buyer, under certain circumstances, to reduce the price below the amount specified in the contract.

    Buyer's Right of First Refusal

    In negotiating situations where the seller of gas has the right to solicit third-party bids for his gas, a right of first refusal provision gives the buyer of the gas the option of meeting the third party bid price and continuing the contract on such terms.


    An auxiliary piping arrangement, generally to carry gas around specific equipment or an integral section of a piping system. A by-pass is usually installed to permit passage through the line while adjustments or repairs are made on the section which is by-passed.

    By-Products (Residuals)

    Secondary products are obtained from the processing of raw material and have commercial value. They may be the residues of the gas production process, such as coke, tar, and ammonia, or they may be the result of further processing of such residues, such as ammonium sulphate.


    Obtaining service from a new supplier without utilizing the facility of the former supplier.

  • C

    Cable Tool

    One of two principal methods of drilling for gas and oil; the other is rotary. Cable tool, the older method, consists of raising and dropping a heavy drill bit, suspended from the end of a cable so that it pounds and pulverizes its way through the subsurface structures. Water in the hole keeps the cuttings in suspension for removal at intervals by bailing.

    Calculated Bill (Also Interim Bill or Estimated Bill)

    A bill for service not based on meter readings for the period being billed but based on calculations of how much gas a customer used during a particular period of time utilizing the gas consumption history of that customer and temperatures during the period.

    Calculated Depreciation Reserve



    To ascertain, usually by comparison with a standard, the locations at which scale or chart graduations should be placed to correspond to a series of values of the quantity which the instrument is to measure, receive or transmit. Also, to adjust the output of a device, to bring it to the desired value, within a specified tolerance for a particular value of the input. Also, to ascertain the error in the output of a device by checking it against a standard.


    An apparatus for measuring the amount of heat released by the combustion of a compound or mixture.


    A cup-shaped fitting placed on the end of a pipe to seal the pipe usually threaded on the inside and screwed over the end of the pipe. Also, the act of placing a cap on a pipe. Also, to close off gas or oil well.

    Capacity Allocation


    Capacity Assignment/Brokering

    The sale or assignment of a specific right to firm transportation (or storage) on an interstate natural gas pipeline to another entity. In some instances, transportation capacity rights may be rebrokered. The Commission's general policy is to require the initial assignor or broker to remain obligated to the pipeline for scheduling and payment of charges.

    Capacity Factor

    The ratio of the actual sales during any specified period to the maximum amount of sales the system is capable of delivering during that time.

    Capacity Release

    A mechanism by which holders of firm interstate transportation capacity can relinquish their rights to utilize the firm capacity to other parties that are interested in obtaining the right to use that capacity for a specific price, for a given period of time, and under a specifically identified set of conditions. The firm transportation rights may include transmission capacity and/or storage capacity.

    Capacity Rights

    Refers to the level of firm transportation service to which a customer has a contractual right.

    Capacity, Effective

    The maximum load which a machine, apparatus, device, plant, or system is capable of carrying under existing service conditions.

    Capacity, Heat


    Capacity, Installed

    The maximum load for which a machine, apparatus, device, plant, or system is designed or constructed, not limited by existing service conditions.

    Capacity, Peaking

    The capacity of facilities or equipment normally used to supply incremental gas under extreme demand conditions; generally available for a limited number of days at the maximum rate.

    Capital Asset Recovery

    A method to determine the cost of the common equity component of return using the rate of risk-free investments plus a risk premium based on the stock market and the company's market volatility.

    Capital Costs

    Costs incurred in acquiring capital assets. Capital costs are capitalized and recovered through yearly charges for depreciation and amortization rather than being expensed and recovered in the year incurred.

    Capital Structure

    The long term debt and equity of a company. In remaking the capital structure is projected at the end of the test period (or when new rates are expected to go into effect) and used to determine the rate of return on the rate base.

    Capital Structure, Hypothetical

    When a subsidiary company has a parent company that provides consolidated financing and other services that affect the subsidiary's capital structure, the subsidiary typically must prepare a hypothetical capital structure for use in a rate case filing.


    The impervious geological stratum overlays the reservoir rock and retains gas or oil in a reservoir.

    Captive Customers

    Buyers who can purchase gas only from one pipeline or supplier and have no access to alternate fuel sources.

    Carbon Black

    Almost pure amorphous carbon consisting of extremely fine particles, usually produced from gaseous or liquid hydrocarbons by controlled combustion with a restricted air supply or by thermal decomposition.

    Carbon Dioxide (CO2)

    A gas is a product of combustion resulting when carbon unites with sufficient oxygen to produce complete combustion; a component of many natural gases.

    Carbon Monoxide (CO)

    A poisonous, combustible gas formed by incomplete combustion of carbon, or reduction of carbon dioxide.

    Carbon/Hydrogen Ratio

    The ratio, either on weight or on a molecular basis, of carbon-to-hydrogen in a hydrocarbon material. Materials with a high carbon/hydrogen ratio (e.g., coal) are solid. The ratio is useful as a preliminary indication of the hydrogen quantity needed to convert the hydrocarbon to gas and/or liquid.

    Carbonaceous Material

    A material that contains carbon.


    A heat-treating process in which carbon is introduced into a solid iron-base alloy by heating above the transformation temperature range while in contact with a carbonaceous material which may be a solid, liquid, or gas. Carburizing is frequently followed by quenching to produce a hardened case.


    A feature in some curtailment plans that allows volumes not used in one period to be used in the following period or periods.

    Cascade Cycle

    A liquefaction process in which a series of refrigerants are used to obtain successively lower temperatures.


    The position of the company, of staff, or of intervenors in a rate or other proceeding prepared in the event of a hearing. The rate case filing is typically the company's Case-in-Chief if the rate case goes to hearing.

    Cash Incentive

    An incentive in the form of a rebate or cash payment is used to induce customers to participate in a DSM program.

    Cashout Provisions

    To the extent a shipper violates balancing provisions, any difference between receipts and deliveries will be "cashed out", with the pipeline purchasing excess receipts at below-market prices and selling receipt shortages at above-market prices.


    A length of pipe used for encasing a smaller diameter carrier pipe for installation in a well or under a road, etc.

    Casing, Well

    Steel pipe inserted (and sometimes cemented) into a gas or oil well, intermittently as the well is drilled, to line the well as is found necessary to eliminate ground caving and water infiltration and to prevent gas and/ or oil from escaping or leaking from the native reservoir into other formations.

    Casinghead Gas

    Unprocessed natural gas containing natural gasoline and other liquid hydrocarbon vapors produced from an oil well. Frequently called WET GAS, ASSOCIATED GAS (but not all wet gas or associated gas is casinghead gas), and in the past, BRADENHEAD GAS. Technically, the term should apply only to gas produced from the casing of an oil well, and not from the tubing, but it is often applied to any gas produced in association with oil.

    Cast Iron Pipe

    Pipe made of pouring molten iron into molds.

    Catalyst (Catalyzer)

    A material that brings about a chemical reaction without being permanently changed itself in the process.

    Catalytic Cracking

    The decomposition or breaking down of oil or hydrocarbons through the action of a catalyst and heat.

    Catalytic Rich Gas (CRG)

    An SNG process developed in England by the British Gas Council. See SNG.

    Catenary Support

    A steel cable or cables strung between two supports and sagged to the point of minimum tension for a given evenly distributed load. Used to support a heavy electrical cable, gas main or other load which is not designed to be self-supporting and is too heavy to be carried by a normal messenger wire strung with minimum sag.


    Negative electrode in an electrolytic system. See ANODE.

    Cathodic Protection

    A technique to prevent the corrosion of a metal surface by making that surface the cathode of an electrochemical cell.


    Abbreviation for CONTRACT DEMAND.

    CD Conversions

    The conversion of a portion or all of a firm sales customer's contract demand to firm transportation. Part 284 of the regulations requires an open-access interstate pipeline to offer its firm sales customers a yearly option of converting a specified portion of its sales entitlements under any ELIGIBLE FIRM SALES SERVICE AGREEMENT to transportation.

    Ceiling Panel Heating

    A system using ceiling panels as heating surfaces. Such panels can be heated by embedding hot-water pipes, warm air ducts, or electric resistance units in the panels.

    Ceiling Price

    The maximum lawful price which may be charged for regulated gas.

    Cellulose Acetate Butyrate Plastics (CAB)

    Plastics made by compounding a cellulose, acetate, butyrate ester with plasticizers and other ingredients. Cellulose acetate butyrate ester is a derivative of cellulose (obtained from cotton and/or wood pulp) made by converting some of the hydroxyl groups in cellulose to acetate and butyrate groups with chemicals.

    Celsius Scale

    The favored name for centigrade scale, with freezing points and boiling points of water at 0 degrees and 100 degrees, respectively.

    Ceramic Radiants

    Baked clay devices that become incandescent and radiate heat released to them by a gas flame.

    Certificate Condition

    A condition imposed by the FPC or FERC when granting a Certificate of Public Convenience and Necessity.

    Certificate of Necessity (for Amortization)

    A certificate issued by a Federal authority certifying that certain facilities are necessary in the interest of national defense, which permits accelerated amortization of the cost of the facilities or a certain specified percentage thereof, for income tax purposes, over a 60-month period.

    Certificate of Public Convenience and Necessity

    A special permit (which supplements the franchise), commonly issued by a state commission, authorizes a utility to engage in business, construct facilities or perform some other service. Also, a permit issued by the Federal Energy Regulatory Commission to engage in the transportation or sale for resale of natural gas in interstate commerce or to construct or acquire and operate any facilities necessary, therefore, to which certificate the Commission may attach such reasonable terms and conditions as the public convenience and necessity may require.

    Certified Capacity

    The total certified capacity of a pipeline is the sum of the increments authorized in various certificates by the FERC. If a particular construction program will change the transmission or storage capacity of the pipeline, the certificate filing must explain the change.


    In refrigeration, the quantity of refrigerant in a system; also, to put in the refrigerant charge.

    Charles' Law

    See LAWS.

    Check Meter

    A device for measuring utility service consumption within individual dwelling units where the utility service is supplied through a master meter.

    Check Valve


    Chemical Resistance

    (1) The effect of specific chemicals on the properties of plastic piping with respect to concentration, temperature, and time of exposure. (2) The ability of a specific plastic pipe to render service for a useful period in the transport of a specific chemical at a specified concentration and temperature. (3) The ability to resist chemical attack.

    Chill Factor

    The temperature (at zero wind velocity) would produce the same chilling effect as a particular combination of temperature and wind velocity. See also the WIND CHILL FACTOR.

    Chimney Connector

    The pipe connects a fuel-burning appliance to a chimney.

    Chimney Effect

    The tendency of air or gas in a duct, vertical passage, or building to rise when heated due to its lower density compared to the surrounding air or gas.

    China Walls

    An expression that refers to the complete separation of operations for affiliated companies within a corporation to prevent undue business advantages. Pipeline companies, for example, are expected to have "china walls" separating their transportation departments from marketing affiliates to ensure that all customers moving gas on the pipeline get equal treatment.

    Choke (Nipple)

    An adjustable or removable bored steel fitting designed to reduce pressure and/or control production from a gas well or an oil well.

    Christmas Tree

    The valve assembly at the top of tubing strings and casing of a gas well or an oil well to provide primary pressure reduction, production rate control, and shut-in service.


    An instrument used to analyze the make-up of various substances and often used to determine the Btu content of natural gas.

    Circulated Gas-Oil Ratio

    The number of cubic feet of gas introduced into the well for gas-lift operations, per barrel of oil lifted.



    City Gate (Town Border Station)


    City Gate Rate

    The rate charged a distribution company by its supplier(s). It refers to the cost of the gas at the point at which the distribution utility takes title to the gas.

    City Gate Station

    Point at which a distribution gas company receives gas from a pipeline company. See GATE STATION.

    Class Life Asset Depreciation Range System (CLS)

    A depreciation system effective in the year 1971, based on broad industry class of assets which can provide faster capital cost recovery through depreciation by using shorter useful lives, more advantageous first-year convention and more flexibility for changing depreciation methods as well as administrative simplification.

    Class of Service

    Defines the type of customer. The common classes of service applied to ultimate consumers, and considerably more completely described in the A.G.A. publication "Definitions of a Gas Customer and Classes of Service for Industry Reporting Purposes", are: 1.Residential Service: Covers service to customers for domestic purposes (single, multifamily, or mobile homes, etc.). In residential service, the number of housing units within a structure determines the customer classification. 2.Commercial Service: Covers service to customers engaged in wholesale or retail trade, agriculture, communications, finance, fisheries, forestry, government, insurance, real estate, transportation, etc., and to customers not directly involved in other classes of service. 3.Industrial Service: Covers service to customers engaged primarily in a process which either involves the extraction of raw materials from the earth or a change of raw unfinished materials into another form or product.

    Classification of Costs

    A two-step process to take functionalized costs and (1) determine whether they are fixed or variable and then (2) determine whether the fixed costs will be recovered through the demand rate or the commodity rate.

    Clause, Adjustment

    A provision in a utility tariff provides for periodic changes in charges or credits to a customer due to increases or decreases in certain costs over or under those included in base rates and incurred by the seller such as purchased gas cost, transportation costs, or advance payments made for gas.

    Clause, Favored Nations


    Clean Air Act of 1970 (as amended)

    Mandated restrictions on sulfur dioxide and nitrogen oxide emissions from power plants.

    Clear Gas

    Tar free gas occurring between the carbonization and gasification zones in a coal gasification plant.

    Clearing Accounts

    Accounts used for the accumulation of expenses which cannot be equitably distributed at the time of the charge. These accounts are cleared by distribution to other accounts on the basis of past experience, benefits received, or on some other reasonable basis.

    Closed Water Piping System



    The process of burning natural gas in conjunction with another fuel.

    Coal Equivalent of Fuels Burned

    The quantity of coal (tons) of a stated kind and heat value which would be required to supply the Btu equivalent of all fuels burned. In determining this coal equivalent, the Btu content of other fuels is generally divided by the representative heat value per ton of coal burned.

    Coal Gas

    Manufactured gas made by distillation or carbonization of coal in a closed coal-gas retort, coke oven, or other vessel.

    Coal Gasification

    A controlled process of reacting coal, steam, and oxygen under pressure and elevated temperature. The crude gas is purified and has a low heating value. Subsequent catalytic upgrading can be employed to produce high-Btu pipeline grade gas.

    Coal Liquefication (Coal Hydrogenation)

    The conversion of coal into liquid hydrocarbons and related compounds by hydrogenation.

    Coal Rank

    Classification of coal based on carbon content and fuel value.

    Coal Seam Gas


    Coalbed Methane

    Methane derived from a coal seam.

    Coated Pipe


    Coefficient of Expansion

    The change in length per unit length or the change in volume per unit volume, per degree change in temperature.

    Coefficient of Performance

    The ratio of the effect produced to the energy supplied -- effect produced and energy supplied being expressed in the same thermal units.


    The use of a single prime fuel source in a reciprocating engine or gas turbine to generate electrical and thermal energy in order to optimize the efficiency of the fuel used. The dominant demand for energy can be either electrical or thermal. Usually, it is the latter with excess electrical energy, if any, being transmitted into the local power supply company's lines (with a reciprocal situation existing when electrical demands exceed the cogeneration plant's output). A parallel exists with total energy plants, which are typically designed for electrical demands rather than thermal. Under the 1978 Public Utility Regulatory Policies Act (PURPA), regulated utilities are required to purchase electricity furnished by cogenerators and small power producers at rates set by regulatory bodies having jurisdiction over the utility receiving the electricity based on "full avoided cost."

    Coincidence Factor

    The ratio of the maximum demand of a group, class, or system as a whole to the sum of the individual maximum demands of the several components of the group, class, or system. Reciprocal of the diversity factor. Compare DIVERSITY FACTOR.

    Coincident Demand

    The sum of the simultaneous demands of a group of consumers.


    A porous, solid residue resulting from the incomplete combustion of coal heated in a closed chamber, or oven, with a limited supply of air. Coke is largely carbon and is a desirable fuel in certain metallurgical industries.

    Cold Expanded Pipe

    The pipe is formed and then expanded in the pipe mill while cold so that the circumference is permanently increased by at least 1/2 percent and tensile strength is increased.

    Cold Flow

    The dimensional change with time of plastic under load, following the instantaneous elastic or rapid deformation. (Also referred to as Creep.)

    Combination Utility

    Utility which supplies both gas and some other utility service (electricity, water, etc.). For purposes of A.G.A. statistics, a combination utility derives at least 5 percent but less than 95 percent of its total operating revenues from the gas operation.

    Combined Accounts

    When two or more meters are combined for billing purposes under the following conditions: Where combinations of meter readings are specifically provided for in rate schedules. Where the maintenance of adequate service and/or where a company's operating convenience shall require the installation


    The utilization of waste heat from large gas turbines to generate steam for conventional steam turbines, thus

    Combo Heater

    A single gas appliance that provides both space heating and domestic hot water. These systems are designed primarily for use as a forced-air heating system, but can also be adapted for new hydronic baseboard installations.

    Combuster Basket, Can or Chamber

    That part of a gas turbine into which fuel is injected and burned.

    Combustible Constituents

    The components of a fuel that will burn. In natural gas, this is mostly methane.

    Combustible Limits


    Combustible Material

    Combustible material, as pertaining to material adjacent to or in contact with heat-producing appliances, chimney connectors and vent connectors, steam and hot water pipes, and warm air ducts means material made of or surfaced with wood, compressed paper, plant fibers, or other material that will ignite and burn. Such material shall be considered as combustible even though flameproofed, fire retardant treated, or plastered.


    The rapid chemical reaction of oxygen with fuel accompanied by the production of heat, or heat and light.

    Combustion Analysis

    The determination of combustion characteristics, such as exhaust gas composition and temperature, air-fuel ratio, the relation of these to perfect combustion.

    Combustion Control

    A device that manually or automatically proportions combustion air to fuel over the whole operating range of the burner or burners.

    Combustion Tests

    The sampling of combustion products to determine the percentage of constituents and their temperature.

    Combustion, Products of

    Constituents resulting from the combustion of a fuel with the oxygen of the air including the inerts but excluding excess air. (Not to be confused with flue gases). Compare GAS, FLUE.

    Commercial Paper

    Short-term promissory notes issued and sold by utilities and other companies usually through dealers in such paper.

    Commercial Service


    Commingled Gas

    A homogeneous mix of gas obtained from various physical and contractual supply sources.


    Federal Energy Regulatory Commission (FERC), or local public utility regulatory commission (PUC).

    Commodity Charge

    A charge per unit volume or heat content (i.e., therm) of gas delivered to the buyer. Compare DEMAND CHARGE.

    Commodity Costs (Rate)

    That part of the total cost of service must be recovered through the use of a commodity rate; i.e., a rate for each Mcf of gas sold. Revenue from a commodity rate varies with throughput.

    Common Capital Stock or Common Stock

    Shares of stock issued and stated at par value stated value or the cash value of the consideration received for such no-par stock; none of which is limited nor preferred as to the distribution of earnings or assets.

    Common Carriage

    The obligation to carry, for a fee, a gas that belongs to another party. Also called MANDATORY CARRIAGE.

    Common Costs


    Common Plant

    Utility plant used by a combination utility company (i.e., one which renders more than one utility service, such as gas and electric) to such extent and in such manner as to render segregation impractical, as would be the case of a garage housing gas utility and electric utility trucks.

    Common Stock Dividends

    Payment declared on common stock and charged to unappropriated retained earnings during a stated period.

    Common Stock Equity

    The funds (including retained earnings) invested in the business by the residual owners whose claims to income and assets are subordinate to all other claims.

    Common Stock Equivalent

    A security which is not, in form, a common stock but which usually contains provisions to enable its holder to become a common stockholder and which, because of its terms and circumstances under which it was issued, is in substance equivalent to common stock. Convertible debt, convertible preferred stock, stock options, and stock warrants meeting certain criteria are considered common stock equivalents.

    Common Trench

    A trench containing two or more utilities.

    Communities (Served)

    A community is a contiguous built-up area, incorporated or unincorporated, commonly recognized as a separate entity. Any incorporated area and its adjacent built-up unincorporated area may be counted as one community.

    Company Storage

    Natural gas storage facilities owned and controlled by the LDC.

    Company Used Gas

    The quantity of gas consumed by a gas distribution or gas transmission company or the gas department of a combined company for the use of the gas company or gas department in its gas operations such as fuel for

    Comparability of Service

    Refers to the comparability of quantity and quality of firm transportation service offered to the pipeline's firm bundled sales service. Aspects of comparability include access to storage and production area facilities, the flexibility of receipt and delivery points, balancing requirements, and other terms and conditions of service. There must be sufficient comparability of service, as well as DIVERTIBLE GAS SUPPLIES, in order to determine that a pipeline's market is competitive as firm transportation cannot be a viable alternative to the pipeline's sales service if transportation service is not comparable. The Commission has found that one way of enhancing comparability is for customers to convert all of their sales entitlements to firm transportation and for the point of sale from the pipeline to be moved upstream to the wellhead or to a HEADSTATION. In this way, all gas on the mainline is transportation gas.

    Comparable Earnings


    Comparison Group

    A selected group of customers that do not participate in a DSM program, but otherwise have the same characteristics as the participating group. The comparison group is used to isolate program effects from other factors that affect demand. Also known as CONTROL GROUP.


    A condition wherein components of a piping system and/or different specific materials can be joined together to form satisfactory joints.

    Composite Book Depreciation

    A method of determining an allowance for depreciation to be included as an element of cost in a cost of service study. The method looks to the service life of the total plant investment for determining depreciation rates, rather than the individual plant components. Under a composite method, an item of plant is not considered fully depreciated until that item is retired from service.

    Compressed Natural Gas (CNG)

    Natural gas in high-pressure surface containers that is highly compressed (though not to the point of liquefaction). CNG is used extensively as a trans-portation fuel for automobiles, trucks and buses in some parts of Italy, New Zealand, and in Western Canada, and has recently begun to penetrate some regions of the United States. Small amounts of natural gas are also transported overland in high-pressure containers.


    The property of a material which permits it to decrease in volume when subjected to an increase in pressure. In gas-measurement usage, the compressibility factor "Z" is the deviation from the ideal Boyle and Charles' law behavior. See SUPERCOMPRESSIBILITY FACTOR.

    Compressibility Factor



    The action on a material which decreases its volume as the pressure to which it is subjected increases.

    Compression Cycles

    Adiabatic (isentropic) compression takes place when there is not heat added to or removed from the system. Compression follows the formula p1V1k=p2V2k, where exponent k is the ratio of the specific heat capacities. Although an adiabatic cycle is never totally obtained in practice, it is approached typically with most positive-displacement machines and is generally the base to which they are referred. Isothermal compression takes place when the temperature is kept constant as the pressure increases, requiring continuous removal of heat generated during compression. Compression follows the formula p1V1=p2V2. However, in practice it is never possible to remove the heat of compression as rapidly as it is generated. Polytropic compression is a compromise between the two basic processes, the adiabatic and the isothermal. It is primarily applicable to dynamic continuous-flow machines such as centrifugal or axial compressors. Compression follows the formula p1V1n=p2V2n, where exponent n is experimentally determined for a particular type of machine. It may be lower or higher than the exponent k used in adiabatic cycle calculations.

    Compression Efficiency

    The ratio of the theoretical work requirement (using a stated process) to the actual work required to compress a given quantity of gas. It accounts for the gas friction losses, internal leakage and other variations from the idealized thermodynamic process.

    Compression Ratio

    The relationship of absolute outlet pressure at a compressor to absolute inlet pressure.

    Compressive Strength

    The ratio of crushing load at failure to area of minimum original cross section of a specimen.


    A mechanical device for increasing the pressure of a gas.

    Compressor Fuel

    Natural gas consumed by the engines in a compressor station, reported as a percentage of the gas transported through the station. Thus, a transporter whose gas passes through one or more compressor stations will be entitled to take delivery of less than 100 percent of the gas introduced into the pipeline network.

    Compressor Station

    Any permanent combination of facilities which supplies the energy to move gas at increased pressure from fields, in transmission lines, or into storage.

    Compressor Stations

    Locations along the interstate pipeline at which large (thousands of horsepower) natural gas-powered engines increase the pressure of the market natural gas stream flowing through the station by compression.


    A number expressing the percent of the specified constituent in a mixture to the total quantity of the mixture, as pounds of salt per pound of brine.


    The liquid resulting when a vapor is subjected to cooling or application of pressure. Also, liquid hydrocarbons condensed from gas and oil wells. Compare LIQUIDS, NATURAL GAS.


    A heat exchanger which removes heat from vapor causing it to condense into a liquid.

    Conditional Demand Analysis

    A method that is used to estimate equipment-specific energy consumption, without requiring end-use metered data for the appliances. Instead, it relies on the statistical analysis of consumption data, appliance saturation data, and other data such as demographic, household, weather, economic and market data.

    Conditionally Effective Rates

    Rates that have been allowed by FERC subject to refund pending final disposition of the rate hearing.

    Conduction, Thermal

    Process of heat transfer through a material medium in which kinetic energy is transmitted by the particles of the material from particle to particle without gross displacement of the particles.

    Conductivity, Thermal

    Time rate of heat flow through a unit area and unit thickness of a homogeneous material under steady conditions when a unit temperature gradient is maintained in the direction perpendicular to area, expressed in Btu per hour per square foot of surface, per foot or inch of thickness, per degree Fahrenheit temperature difference across the thickness. Materials are considered homogeneous when the value of the thermal conductivity is not affected by variation in thickness or the size of the sample within the range normally used in construction.

    Conductor, Thermal

    A material which readily transmits heat by means of conduction.

    Confined Space

    Any space not intended for continuous employee occupancy, having a limited means of egress.

    Confirmed Nomination

    An agreement by a seller to deliver/cause delivery or a transporter to receive and deliver a specific quantity of gas for a specified period at various points under a Sales or Transportation Agreement or for all contracts at one specific point. The confirmed nomination is in response to a purchaser's or shipper's nomination. See NOMINATION.

    Confiscatory Rates

    Approved rates which yield a rate of return insufficient to attract new capital.

    Conjunctive Billing

    Tariff provisions which permit the grouping of delivery points for billing purposes. These provisions permit customers having multiple delivery points to fill up the "valleys" in gas takes at some points by taking in excess of contract demand at other points for resale industrial loads without paying additional demand charges for such excess volumes.

    Consenting Party

    A party (the company, staff, a customer, or other interested party) that supports a stipulation and agreement or settlement in a rate or other proceeding. See STIPULATION & AGREEMENT, CONTESTING PARTY.

    Conservation Program

    A utility-sponsored program that attempts to reduce a customer's energy consumption, over most, or all hours of the day.

    Conservation Supply Curve

    A graph showing the quantity of energy savings of individual efficiency measures on the x-axis and the total cost per unit of energy saved on the y-axis.


    Means of reducing the energy resources required to do a task such as heating a house, transporting freight between two points, or producing steel.

    Construction Expenditures

    Cost of construction, including work-in-progress (CWIP), overhead or contributions in aid of construction and allowances for funds used during construction (AFUDC), for additions to, renewals and replacements of plant facilities, but excluding the purchase cost of an acquired operating unit or system of utility plant, accounting transfers and adjustments to utility plant, and cost to remove plant facilities from service.

    Construction Work in Progress (CWIP)

    Balances of work orders for utility plant in the process of being constructed but not yet placed in service. Most of the items shown as CWIP are eventually closed to utility plant in service.

    Consumer, Gas

    The ultimate user of gas, as contrasted to a "customer" who may purchase gas for resale.


    The quantity of natural gas used by ultimate consumers.

    Content of Fuel

    The heat value per unit of fuel expressed in Btu as determined from tests of fuel samples. Examples: Btu per pound of coal, per gallon of oil, per cubic foot of gas.

    Contesting Party

    A party (staff, a customer, or other interested party) that does not support a stipulation and agreement or settlement in a rate or other proceeding, and prefers to take the case to hearing. The filing company can not be a contesting party; in that case there is no settlement. See STIPULATION & AGREEMENT, CONSENTING PARTY.

    Continuing Property Record (CPR) Unit

    A Continuing Property Record Unit is the minimum division of plant selected to be continuously associated with its cost in the plant records.

    Contract Area

    For the purpose of FERC Form 15, the area encompassed by one or more fields under a single purchase contract but not larger than the area covered by a single supply source.

    Contract Assignment

    A mutual agreement to release or ascribe a contractual obligation from the original contractor to another party.

    Contract Balancing

    A process of managing the difference between the quantities received and delivered at various points under a contract during a defined period of time (i.e., hourly, daily, monthly, etc.).

    Contract Carriage

    Transportation, by a company, of gas quantities belonging to another party, for which the company charges a fee.

    Contract Carrier

    A transporter that voluntarily provides its services on a contractual basis for other parties.

    Contract Demand (CD)

    The amount of the system's capacity to deliver gas which a natural gas pipeline or distributor agrees to reserve for a particular customer and for which the customer agrees to pay a demand charge as specified in the applicable tariff. Also, the daily quantity of gas which a supplier agrees to furnish and for which the buyer agrees to pay, under a specific contract.

    Contract Imbalance Quantity

    The cumulative difference between all quantities of gas received and quantities of gas delivered for a contract from inception through the most current billing period.

    Contract Pressure

    The maximum or minimum required operating pressure at a receipt or delivery point as specified in the Service Agreement.

    Contract Quantity Method

    A method to allocate demand costs by function to customer classes based on the customer classes' contract quantity or a company's obligation to serve the customer class.

    Contract Request

    A customer request for transportation or sales service.

    Contract Storage

    Storage facilities, or a portion of storage facilities, which are leased to others for the purposes of storing gas. The portion of storage facilities which has been made available to others may not be used by the pipeline for system supply. See SYSTEM STORAGE.

    Contract Storage Service

    A service provided by a pipeline, or other owner of storage facilities, whereby storage customers may lease a portion of the facilities for the purposes of storing customer-owned gas. Contract storage service generally involves the injection of customer-owned gas into the facility during the off-peak period, the holding of the accumulated inventory for the customer, and the withdrawal of gas during the peak heating season.

    Contracted Reserves

    Natural gas reserves dedicated to the fulfillment of gas purchase contracts.

    Contributions in Aid of Construction (Non-Refundab

    The contributions or donations in cash, property, or services from companies, states, municipalities, other governmental agencies, individuals, and others for construction purposes, now carried as a plant item. Compare ADVANCES FOR CONSTRUCTION.


    A device designed to regulate the gas, air, water, and/or electrical supply to a gas-consuming or any other device.

    Control Gas

    That part of the main gas flow which is separated and used to actuate the automatic valve through a moving member such as the diaphragm in a diaphragm valve.

    Control Group


    Control, Limit

    An automatic safety control responsive to changes in level, pressure, or temperature and normally set beyond the operating range for limiting the operation of the controlled equipment.

    Control, Operating

    A control other than a safety control or interlock, to start or regulate burner firing according to load demand and to stop or regulate fire on satisfaction of demand or upon reaching normal temperature or pressure in the device being fired. Operating controls may also actuate auxiliary equipment.

    Control, Primary Safety, Combustion Safeguard

    A control responsive directly to flame properties, sensing the presence of flame and, in event of ignition failure or unintentional flame extinguishment, causing safety shutdown.

    Control, Safety

    Automatic controls and interlocks, including relays, switches, and other auxiliary equipment used in conjunction therewith to form a safety control system, which is intended to prevent unsafe operation of the controlled equipment.


    Internal procedures to monitor the components of cost of service based on updated actual costs.


    Heat transfer by the movement of fluid.


    An agency of convection. In heat transfer, a surface designed to transfer its heat to a surrounding fluid largely or wholly by convection. The heated fluid may be moved mechanically or by gravity (gravity convector). Such a surface may or may not be enclosed or concealed.

    Conversion Burner


    Conversion to Natural Gas

    Changing the gas service to ultimate customers from a fuel other than natural gas to natural gas, including adjustment of consumers' appliances to perform satisfactorily with natural gas. Natural gas does not necessarily mean straight natural gas; stabilizing the heat content of the sendout gas by diluent gases or enriching gases is not considered to change the basic character of natural gas. For the purpose of uniform reporting, a company should be considered a natural gas company when 95 percent of the system has been converted.

    Conversion Unit

    A unit consisting of a burner together with associated thermostat and safety controls, which can be used to convert heating equipment from one fuel to another.

    Convertible Securities

    Securities which are convertible into other classes of securities (usually common stock) of the same corporation at the option of the security holder, but only in accordance with prescribed conditions.

    Cooling Coil

    A coil of pipe or tubing used as a heat exchanger to cool material inside or outside the coil by means of colder material passing over or through the coil respectively.

    Cooling Degree Day


    Cooling Tower


    Copper Insert

    Insertion of a copper liner into a steel service line.

    Core Customers

    Residential and small commercial customers who must rely on the traditional distributor bundled service of sales and transportation. Compare NON-CORE CUSTOMERS.

    Correlative Rights

    Ownership rights of multiple oil and/or gas producers within a common reservoir.


    Destruction of a metal by chemical or electrochemical reaction with its environment.

    Corrosion Fatigue

    Reduction of fatigue durability by a corrosive environment.

    Corrosion Mitigation

    The reduction of metal loss or damage through use of protective methods and devices.

    Corrosion Prevention

    The halting or elimination of metal damage through use of protective methods and devices.

    Corrugated Stainless Steel Tubing (CSST) Piping Sy

    An assembly of corrugated stainless steel tubing, distribution manifold(s), tube connection fittings, and tube shielding devices, intended for field assembly and installation in residential or commercial buildings to distribute fuel gas to gas utilization equipment within the building. The piping system may also include a gas pressure regulator(s), a shutoff valve(s), and other approved devices or components.


    The amount of money actually paid for property, material or services. When the consideration given is other than cash in a purchase and sale transaction, as distinguished from a transaction involving the issuance of common stock in a merger or a pooling of interest, the value of such consideration shall be determined on a cash basis.

    Cost Allocation

    The rate design step that allocates the demand and commodity costs of the various functions to the customer classes. See COST OF SERVICE.

    Cost Based GIC


    Cost of Capital

    The weighted average of the cost of various sources of capital, generally consisting of outstanding securities such as mortgage debt, preferred and preference stock, common stock, etc., and retained earnings, but which may include other interest-bearing obligations or sources of capital such as short-term notes, customer security deposits; and which may also include noninterest-bearing sources such as funds generated through use of deferred taxes, i.e., accelerated amortization, accelerated depreciation, and accumulated investment tax credit (subject to tax law limitations). The weight to be used for each source of funds generally is the percentage of each fund outstanding to the total amount outstanding of all sources of funds considered; however, target or projected ratios may also be used. The cost rate assigned each source may be the average cost of all obligations outstanding or projected costs for each source or a rate specifically assigned by a commission. The summation of the product of the weight (percentage) of each source to the total source times its cost is the cost of capital.

    Cost of Removal

    The cost of demolishing, dismantling, tearing down or otherwise removing plant, including the cost of transportation and handling incidental thereto.

    Cost of Service

    A term used in public utility regulation to mean the total number of dollars required to supply any total utility service (i.e., revenue requirements); it must include all of the supplier's costs, an amount to cover operation and maintenance expenses, and other necessary costs such as taxes, including income taxes, depreciation, depletion, and amortization of the property not covered by ordinary maintenance. Included also is a fair return in order that the utility can maintain its financial integrity, attract new capital, and compensate the owners of the property for the risks involved. A "cost of service study" is made in order to assist in determining the total revenue requirements to be recovered from each of the various classes of service. The amounts to be recovered from each of the classes of service are determined by the management or a commission after study of the various factors involved in rate design. Cost analysis or cost allocation is an important factor in rate design but only one of several important factors. Cost analysis does not produce a precise inflexible "cost of service" for any individual class of service because cost analysis involves judgment in certain cost areas. Its principal value is in determining the minimum costs attributable to each class of service. Other factors that must be considered in rate design are the value of the service, the cost of competitive services, the volume and load factor of the service and their relation to system load equalization and stabilization of revenue, promotional factors and their relation to the social and economic growth of the service area, political factors such as the sizes of minimum bills, and regulatory factors.

    Cost of Service Tariff

    A special type of tariff which allows a gas pipeline to adjust periodically for any overage or underage in recovery of its cost of service (including per unit adjustments for loss of load). In contrast, a normal fixed-rate tariff, while specified based upon a cost of service estimate, does not provide for recovery of any previous underage or return of any overage above actual costs incurred.

    Cost Zones

    Geographic areas of the company's operations established for the purpose of accumulating certain costs to facilitate a fair distribution of such costs among all customer classes. Common cost zones for a long line pipeline are supply zones and market zones.

    Cost, Original

    The direct and indirect cost of utility property at the time it was first dedicated to public service.

    Cost, Reproduction

    The cost of reproducing utility property at current cost.

    Cost-Effectiveness Test


    Costs, Common

    Those costs incurred by combination utilities which are not directly or solely identified with a specific department (e.g., gas and electric), and which are normally allocated to each department on the basis of some reasonable and factual relationship. Compare COSTS, JOINT.

    Costs, Joint

    Those costs (e.g., supervisory costs) not directly assignable to either construction or operation accounts which are accumulated in clearing accounts to be distributed to appropriate accounts on some reasonable basis. Compare COSTS, COMMON.

    Council of Petroleum Accountants Societies (COPAS)

    An organization that publishes industry guidelines for oil and gas accounting and shipping.


    A sleeve-type fitting used to connect two pipes of similar or different materials, providing insulation or continuity.


    Processing that breaks down and rearranges the molecular structure of hydrocarbon chains. In thermal cracking, high temperature and high pressures are applied; in catalytic cracking, temperature and pressure are applied in the presence of a catalyst. See CATALYST.

    Cream Skimming

    Installing only the lowest cost or easy-to- install DSM measures while ignoring other cost-effective opportunities.


    The time-dependent part of strain due to a constant stress (also referred to as cold flow).

    Critical Temperature and Pressure

    That temperature above which a gas cannot be liquefied by pressure alone. The pressure under which a substance may exist as a gas in equilibrium with the liquid at the critical temperature is the critical pressure.

    Cross Over

    Piping used to connect two or more pipelines.

    Cross Subsidization

    Practice of charging one customer class with rates that are higher than the cost of service for that class, thus allowing another class to be charged rates that are lower than the respective cost of service for that class.

    Crude Oil (Crude, Mineral Oil, Crude Oil, Petroleu

    A geological liquid consisting of hydrocarbons and relatively small amounts of sulfur, nitrogen, and oxygen in the form of derivatives of hydrocarbons. Crude is formed under pressure from residual plant matter accumulated in a swamp over a period of time. It may come from the earth with varying quantities of water, gas, and other organic matter. Some crudes are very volatile and others are very viscous liquids. Crude oil may contain such impurities as sulfur and hydrocarbons. These are compounds containing a variety of combinations of carbon with hydrogen. There are a very large number of these compounds and they form the basis of a number of petroleum products. These compounds may exist as gases or liquids or solids. A number of hydrocarbons are also contained in bituminous coal, oil shale and tar sands. Crude is generally classified into three basic types: paraffin base crude oils contain a high degree of paraffin wax and little or no asphalt. Besides wax, they also yield large amounts of high-grade lubricating oil. Asphalt base crudes contain large proportions of asphaltic matter, and mixed base crudes contain quantities of both paraffin wax and asphalt. This is why crude oils do not always look alike. Some are almost colorless or pitch black. Others can be amber, brown or green. They may flow like water or creep like molasses. Some crudes, containing relatively large amounts of sulfur and other mineral impurities, are called "sour" crudes. Others, having a fairly low sulfur content, are called "sweet" crudes.


    A material that is a gas at ambient conditions but can be liquefied at below-ambient temperatures. This includes all of the ambient temperature gases.


    The science of producing very low temperatures such as natural gas liquefaction.


    A state of molecular structure in some resins which denotes uniformity and compactness in the molecular chains forming the polymers.

    Cubic Foot

    The most common unit of measurement of gas volume. It is the amount of gas required to fill a volume of one cubic foot under stated conditions of temperature, pressure, and water vapor.

    Cubic Foot Metered

    The quantity of gas that occupies one cubic foot under pressure and temperature conditions in the meter.

    Cubic Foot, Standard

    That quantity of gas which under a pressure of 14.73 psia and at a temperature of 60oF occupies a volume of one cubic foot without adjustment for water vapor content.

    Curb Box

    A vertical tube, capped at ground level, and usually located near the street, that protects access to the underground shut-off valves on service lines to residential and small commercial customers. (Usually found in sidewalk with gas company name).

    Curb Line

    Street or highway map line which shows the curb location.

    Curb Stop or Curb Valve

    A shut-off valve in a gas service line, usually between the curb and the customer's property line.

    Current Adjustment

    Applicable to pipelines which have a PGA mechanism in effect. The Current Adjustment is a rate component in a pipeline's tariff used to reflect the difference between 1) the current weighted average projected purchased gas costs and 2) the weighted average projected purchased gas costs reflected in the effective period of the previous scheduled PGA.

    Current and Accrued Assets

    Generally consists of items realizable or to be consumed within one year from the date of the balance sheet. Includes Cash, Special Deposits, Working Funds, Temporary Cash Investments, Notes and Accounts Receivable, Materials and Supplies, (including Fossil Fuel), Prepayments, and Other Current and Accrued Assets (receivable, for interest, dividends, rents, etc.).

    Current Gas


    Current Reservoir Capacity



    Curtailment of gas service is a method to balance a utility's natural gas requirements with its natural gas supply. Usually there is a hierarchy of customers for the curtailment plan. A customer may be required to partially cut back or totally eliminate his take of gas depending on the severity of the shortfall between gas supply and demand and the customer's position in the hierarchy.

    Cushion Gas

    The gas required in a reservoir, used for storage of natural gas, so that reservoir pressure is such that the storage gas may be recovered.

    Custody Transfer

    The legal and commercial transfer of a commodity such as natural gas, LNG, etc. from one party to another.

    Custody Transfer Transaction

    The Custody Transfer Transaction is the hand-off of the physical commodity from one operator to another.


    An individual, firm, or organization which purchases service at one location under one rate classification, contract, or rate schedule. If service is supplied at more than one location or under more than one rate schedule, each location and rate schedule shall be counted as a separate customer unless the consumption at the several locations is combined before billing and billed on one rate schedule. See CLASS OF SERVICE.

    Customer Advances for Construction


    Customer Charge

    A fixed amount to be paid periodically by the customer without regard to demand or energy consumption.

    Customer Costs

    The costs directly related to serving the customer, regardless of sales volume such as meter reading, billing, and fixed charges for the minimum investment required to serve a customer.

    Customer Density

    Number of customers in a given unit or area or on a given length of distribution line.

    Customer Imbalance Quantity

    The cumulative difference between quantities of gas received and quantities of gas delivered for all of a customer's transportation contracts from inception through the most current billing period.

    Customer Nomination Method

    A method to allocate a portion of demand cost to customer classes based on those classes' nominated level of service.

    Customers, Average Number of

    The average number of customers is determined by summing the customers for each of the periods involved and dividing by the number of periods. See CUSTOMER.


    The rock fragments dislodged by the bit and brought to the surface in the drilling mud. Cuttings are analyzed by geologists to obtain information about the formations drilled through.

    Cycle Billing

    A billing procedure which provides for the billing of a portion of utility customers each working day so that all customers are billed within a predetermined period, such as one month, two months, etc. (In some companies, each day's billing is referred to as a "billing cycle day," "billing day," or "billing cycle." Other companies use "billing cycle" to refer to the total period which covers billing of customers within a specific period).

  • D

    Daily Average Send-Out

    The total quantity of gas delivered for a period of time divided by the number of days in the period.


    A valve, or plate, used to regulate the flow of air or other gases.


    A measure of permeability. A permeability of one darcy means that the material will pass a fluid of one centipoise viscosity through a section of one cubic centimeter at a rate of one cubic centimeter per second with a drop in pressure of one standard atmosphere.

    Data Request



    The apparatus used to separate the dissolved gases from the condensate.


    Certificates of indebtedness issued under an indenture agreement (administered by a trustee) representing long-term borrowings of capital funds, secured only by the general credit of the issuing corporation. Compare BONDS.

    Debt Coverage Principle

    A method to determine the cost of common equity component of return based on cost of the fixed components, debt and preferred stock.


    To remove (as a ship) from service.


    The act of ending federal government control over the wellhead price of new natural gas sold in interstate commerce. Also termed "deregulation".

    Dedicated Acreage

    Acreage dedicated to a company by contract. More specifically, all gas produced from the dedicated acreage is dedicated to the purchasing company by contract.

    Dedicated Gas Reserves

    Gas reserves dedicated to a natural gas pipeline company by contract. For a pipeline it is the sum of all reserves dedicated to the company by contract.

    Dedicated to Interstate Commerce

    Gas reserves under contract to an interstate pipeline company and hence subject to the jurisdiction of the Commission and wellhead price controls under the NGA of 1938. The NGPA of 1978 extended the Commission's jurisdiction for wellhead pricing to essentially all gas but provided for phasing out wellhead price controls over time for certain gas.

    Deep Gas

    Gas found at depths greater than the average for a particular area; for FERC purposes, it is gas found at depths of more than 15,000 feet.

    Deferred Credits

    Accounts carried on the liability side of the balance sheet in which are recorded items being amortized as credits to income over a period of time (such as Unamortized Premium on Debt) and items held in suspense pending final transfer or disposition (such as Customer Advances for Construction, etc.)

    Deferred Debits

    Accounts carried on the asset side of the balance sheet in which are recorded items being amortized as charges against income over a period time (such as Unamortized Debt Discount and Expense) and items held in suspense pending final transfer or disposition (such as Extraordinary Property Losses, Clearing Accounts (Net Debit), etc.).

    Deferred or Future Income Taxes

    Amounts representing the tax effects of temporary differences in the recognition of revenue and expense items for income tax purposes and for financial reporting purposes such as the use of accelerated amortization and/or liberalized depreciation in income tax returns.

    Deficiency Based GIC


    Deficiency Period

    Used in association with the EQUITABLE SHARING MECHANISM. A period during which the current take-or-pay liabilities of the pipeline were incurred. A customer's cumulative deficiency in purchases during this period, in comparison to a BASE PERIOD, is compared to the system's total cumulative deficiencies to determine that customer's proportionate share of fixed take-or-pay charges. See BASE PERIOD, EQUITABLE SHARING MECHANISM and PURCHASE DEFICIENCY METHODOLOGY.

    Deflection Temperature

    The temperature at which a specimen will deflect a given distance at a given load under prescribed conditions of test. See ASTM D 648. Formerly called heat distortion.


    A deleterious change in the chemical structure, physical properties or appearance of a plastic.

    Degree Day, Cooling

    A measure of the need for air conditioning (cooling) based on temperature and humidity. Although cooling degree days are published for many weather stations, a specific procedure has not been generally accepted.

    Degree Day, Heating

    A measure of the coldness of the weather experienced, based on the extent to which the daily mean temperature falls below a reference temperature, usually 65 degrees F. For example, on a day when the mean outdoor dry-


    To reduce by any process the quantity of water vapor contained in a solid or gas.


    The process of removing liquids and moisture content from gas or other matter.


    A unit of heating value equivalent to 10 therms or 1,000,000 Btu's.


    The volume of gas a well, field, pipeline, or distribution system can supply in a given period of time. Also, the practical output from a storage reservoir. Compare CAPACITY, INSTALLED; STORAGE, UNDERGROUND.

    Delivery by Non-Delivery

    The delivery of gas through a meter where gas is currently being physically received. The delivery is accomplished by reducing physical receipts for the quantity delivered.

    Delivery Point

    Point at which gas leaves a transporter's system completing a sale or transportation service transaction between the pipeline company and a sale or trans-portation service customer.


    The rate at which gas is delivered to or by a system, part of a system, or a piece of equipment, expressed in cubic feet or therms or multiples thereof, for a designated period of time called the demand interval. Compare LOAD.

    Demand Based GIC


    Demand Charge

    The portion of a rate for gas service which is billed to the customer whether they use the service or not. Depending on the rate design this charge is based on actual or estimated peak usage (1 or 3 days), annual needs or a combination of the two. Compare COMMODITY CHARGE.

    Demand Costs (Rate)

    That part of the total cost of service which must be recovered through use of a demand rate; i.e., a rate for each Mcf of gas representing the customer's demand on the Company's system.

    Demand Day

    That 24-hour period specified by a supplier-user contract for purposes of determining the purchaser's daily quantity of gas used (e.g., 8 AM to 8 AM, etc.). This term is primarily used in pipeline-distribution company agreements. It is similar to, and usually coincides with, the distribution company "sendout day".

    Demand Diversity

    The overall variation in the time at which individual demands occur. Compare DEMAND, COINCIDENT and DEMAND, NON-COINCIDENT.

    Demand Interval

    The period of time during which the flow is averaged in determining demand, such as 60-minute or 30-minute.

    Demand Load

    The rate of flow of gas required by a consumer or a group of consumers, often an average over a specified short time interval (cf/hr or Mcf/hr). Demand is the cause; load is the effect.

    Demand Meters

    A device which indicates or records the instantaneous, maximum or integrated (over a specified period) demand.

    Demand Side Bidding

    Process in which a utility issues a request for proposals to acquire DSM resources from energy service companies and customers, reviews proposals, and negotiates contracts with winning bidders for a specified amount of energy savings.

    Demand Side Management (DSM)

    Utility activities designed to influence the amount and timing of customer demand, producing changes to the

    Demand Side Resource Portfolio

    Comprehensive collection of DSM resources, both viable and non-viable, that are available, both currently and in the future to the utility.

    Demand Side Resources

    Resources obtained through the implementation of DSM that may be used as an alternative to traditional supply-side resources.

    Demand, Average

    The demand on a system or any of its parts over an interval of time, determined by dividing the total volume in therms by the number of units of time in the interval.

    Demand, Billing

    The demand upon which billing to a customer is based, as specified in a rate schedule or contract. It may be based on the contract year, a contract minimum, or a previous maximum and, therefore, does not necessarily coincide with the actual measured demand of the billing period.

    Demand, Coincident

    The sum of two or more demands which occur in the same demand interval.

    Demand, Contract

    The daily quantity of gas which the supplier agrees to furnish and for which the buyer agrees to pay, under a specific contract.

    Demand, Integrated

    The demand averaged over a specified period, usually determined by an integrating demand meter or by the integration of a load curve. It is the average of the instantaneous demands during a specified demand interval.

    Demand, Maximum

    The greatest of all the demands under consideration occurring during a specified period of time.

    Demand, Minimum

    The smallest of all the demands under consideration occurring during a specified period of time.

    Demand, Non-Coincident

    The sum of two or more individual maximum demands, regardless of time of occurrence, within a specified period.

    Demonstration Scale Plant

    A plant between pilot and commercial size built to demonstrate the commercial feasibility of a process.


    An instrument used to determine the ratio of the density of a substance to the density of a given substance (as water or hydrogen) taken as a standard, when both densities are obtained by weighing in air.


    The weight of a unit of volume, usually expressed as pounds per cubic foot.

    Density, Bulk

    The weight per unit volume of a material including voids inherent in the material as tested.

    Department of Energy (DOE)

    The Department of Energy is the twelfth Cabinet Position, and it consists of the Office of the Secretary of Energy and the Federal Energy Regulatory Commission. It was created on August 4, 1977 as a result of the Department of Energy Organization Act of 1977. There are many subdivisions within the DOE, but the Economic Regulatory Administration and Energy Information Administration are two groups which have significant bearing on gas utility operations.


    As applied to natural gas producing land and land rights, means the loss in value incurred in connection with the exhaustion of a natural resource.

    Depletion Allowance

    A charge against income for the extraction of natural resources, commonly called "wasting assets" (i.e., gas, oil, coal, etc.).

    Depreciable Plant

    Usually tangible plant in service which is subject to depreciation, depletion, or amortization.


    Return of investment through inclusion in cost of service (and rates) of a pro rata part of the cost of property, calculated to spread the total investment cost over a certain period of time or number of units that measure the useful life of the investment. Depreciation (in the Code of Federal Regulations) is to reimburse the company for "...the loss in service value not restored by current maintenance, incurred in connection with the consumption or prospective retirement of gas plant in the course of service from causes which are known to be in current operation and against which the utility is not protected by insurance. Among the causes to be given consideration are wear and tear, decay, action of the elements, inadequacy, obsolescence, changes in the art, changes in demand and requirements of public authorities, and, in the case of a natural gas company, the exhaustion of natural resources."

    Depreciation Accounting

    A system of accounting intended to distribute the cost of tangible capital assets, less salvage, (if any), over the estimated useful life of the unit in a systematic and rational manner.

    Depreciation Expense

    The cost of plant (less net salvage) recovered over the life of the plant through a reduction of income. This expense reflects the "using up" of plant (due to wear and tear, obsolescence, etc.) in the generation of income.

    Depreciation Reserve


    Depreciation Reserve Ratio

    The ratio of the accumulated depreciation to the recorded cost of surviving plant at any given date.

    Depreciation, Accelerated


    Depreciation, Asset Depreciation Range (ADR)

    A system of tax depreciation which enables a corporation to choose any life falling within 20% of the designated class life for determining its annual depreciation charge. ADR requires an annual election and all depreciation records must be maintained by vintage year.

    Depreciation, Declining Balance

    One of the liberalized methods of computing depreciation (normally used for tax purposes). Under this method, the depreciation rate is stated as a fixed percentage per year and the annual charge is derived by applying the rate to the net plant balance, which is determined by subtracting the accumulated depreciation reserve.

    Depreciation, Flow-Through

    An accounting procedure under which current Net Income reflects decreases or increases in current taxes on income, arising from the use of liberalized depreciation or accelerated amortization for tax purposes instead of the straightline method. See DEPRECIATION, NORMALIZED.

    Depreciation, Liberalized

    This refers to certain approved methods of computing depreciation allowance for federal and/or state income tax purposes. These methods permit relatively larger depreciation charges during the earlier years, in contrast to the straight-line method, under which the annual charges are the same for each year. This is sometimes referred to as accelerated depreciation.

    Depreciation, Normalized

    An accounting method under which Net Income includes charges or credits equal to the decreases or increases in current taxes on income, arising from the use of liberalized depreciation or accelerated amortization for tax purposes instead of the straight-line method. The contra entries for such charges to Net Income are suspended in Balance Sheet accounts. In future years, there is a feedback of these suspended amounts to Net Income when increases in the then current taxes on income occur because liberalized depreciation or accelerated amortization was used for tax purposes in prior years. See DEPRECIATION, FLOW-THROUGH; RESERVE FOR DEFERRED OR FUTURE INCOME TAXES.

    Depreciation, Straight-Line

    A method of computing depreciation under which equal annual amounts are set aside for the ultimate retirement of the property at the end of its service life. For a property with an assumed 25-year life, the annual charge would be 4% per year, usually applied to the cost of the property less estimated net salvage.

    Depreciation, Sum of the Years Digits (SYD)

    One of the liberalized methods of computing depreciation, normally used for tax purposes. Under this method, the annual deduction is derived by multiplying the cost of the property less estimated net salvage, by the estimated number of years of service life remaining, and dividing the resultant product by the sum of all the digits would be 25+24+23+22+ etc. +5+4+3+2+1 or 325. A simple way to compute this figure would be to multiply the number of years by the number of years plus one and divide by 2, i.e., (25 X 26) : 2 = 325. The first year's full depreciation deduction would be 25/325ths; the second year's would be 24/325ths, etc., of the cost of the property.

    Depreciation, Unit of Production

    A method of depreciation whereby the asset is depreciated over an estimated life expressed in units of output rather than over an estimated life expressed as a period of time.




    Adding heat to remove accumulated solid water or carbon dioxide constituents from low-temperature process equipment.


    Any absorbent or adsorbent, liquid or solid, that will remove water or water vapor from a material. In a refrigeration circuit, the desiccant must be insoluble in the refrigerant.

    Design Day

    A 24-hour period of demand which is used as a basis for planning gas capacity requirements.

    Design Day Availability

    The amount of each type of gas arranged to be available on the design day and the maximum combination of such supplies. (In the case of purchased natural gas, the maximum day allocation, maximum day contract quantity, or FERC authorization).

    Design Day Temperature

    The mean temperature assumed for the Design Day.

    Design Load

    The maximum average rate of gas use by a group of appliances or customers over a specified short time period, usually 15 to 30 minutes.

    Design Pressure

    The maximum operating pressure permitted by various codes, as determined by the design procedures applicable to the material and location involved.


    The process by which sulfur and sulfur compounds are removed from gases or liquid hydrocarbon mixtures.

    Detector, Holiday



    The drilling and related activities necessary to begin production after the initial discovery of oil or gas in a reservoir.

    Development Well


    Devonian Shale

    Geological formations, typically hundreds of feet thick, that underlie much of the Appalachian Basin. It is known to contain much natural gas, but usually lacks sufficient natural permeability for ordinary production.


    A bellows inside a displacement type gas meter. Also, a membrane separating two different pressure areas within a control valve or regulator.

    Die, Pipe Thread

    The tool used for cutting external threads, usually at one passage. The essential distinctive feature of a die is its multiple cutting edges, while a chasing or threading tool usually has one, or at most, only a few cutting edges.

    Dielectric Constant

    The ratio of the capacity of a condenser with given dielectric and the capacity of the same condenser with a vacuum as a dielectric.

    Dielectric Strength

    The voltage that will rupture or puncture the material when placed between electrodes of a given size.

    Differential Pressure

    The pressure difference between two points in a system. For example, the difference in pressure between the upstream and downstream taps of an orifice plate, used to measure volume passing through the orifice.


    The movement of a material, such as a gas or liquid, in the body of a plastic. If the gas or liquid is absorbed on one side of a piece of plastic and given off on the other side, the phenomenon is called permeability. Diffusion and permeability are not due to holes or pores in the plastic but are caused and controlled by chemical mechanisms.


    When buried gas facilities are damaged by excavators.


    A neutral fluid added to another fluid to reduce the concentration of the second fluid in a mixture.

    Dimension Ratio

    The average specified diameter of a pipe divided by the minimum specified wall thickness. NOTE: Each pipe can have two dimension ratios depending on whether the outside or inside diameter is used. In practice, the outside diameter is used if the standard requirement and manufacturing control are based on this diameter. The inside diameter is used when this measure is the controlling one.

    Direct Heating Equipment


    Direct Installation Program

    DSM program in which the utility directly installs DSM measures within customers homes or businesses.

    Direct Sale

    Contract sale of natural gas by producer to end user or local distribution company, usually for a term of a year or longer.

    Direct Vent Appliance

    Gas appliance designed so that all combustion air is derived directly from the outside, and all fuel gases are discharged to the outside through an exterior wall.


    A heating unit in which the combustion products are mixed with the air or liquid being heated. Compare INDIRECT-FIRED.

    Disabling Injury Illness Incidence


    Discount on Capital Stock

    The excess of par or stated value over the price paid to the company by the shareholders for original issue shares of its capital stock.

    Discounted Cash Flow (DCF)

    A method to determine the cost of common equity component of return using a discounted stream of future cash dividends.


    Part of the ratemaking process, after a rate or other filing and after suspension by the Commission which orders a hearing, where parties including the filing company can, through requests for data, obtain more information about the (rate) filing and the particular issues set for hearing.

    Dispatchability of DSM

    The ability of the utility to schedule and control, directly or indirectly, manually or automatically, the timing and volumes of DSM measures.


    The control of product flow in a system involving the assignment of load to the various sources of supply to meet the desired objectives.




    Displacement transactions permit the lateral movement of gas through a transportation network. The configuration of many pipelines is such that it may not be apparent whether a given movement of gas is forward or backward from the point of receipt. It can be argued that all transportation service is performed by displacement as the physical delivery of the same molecules of gas is impossible. See BACKHAUL.

    Dissolved (Solution) Gas

    Natural gas originally in solution within the reservoir crude oil. As the reservoir pressure is reduced due to production, gas is released from solution in the oil, allowing it to migrate as free gas to a wellbore and be produced or to the crest of the reservoir where it can collect and form a secondary gas cap. In addition, gas is released from solution in the oil within the wellbore as the oil is produced. Thus, most oil wells, except stripper wells producing from reservoirs where the pressure and solution gas has been depleted, produce gas with the oil. Even oil fields with no free gas originally present can produce large volumes of gas since considerable gas can be present in solution in the oil.

    Distillate, Natural Gas



    The act or process of distributing gas from the city gas or plant that portion of utility plant used for the purpose of delivering gas from the city gate or plant to the consumers, or to expenses relating to the operating and maintenance of distribution plant.

    Distribution Company

    Gas Company which obtains the major portion of its gas operating revenues from the operation of a retail gas distribution system, and which operates no transmission system other than incidental connections within its own system or to the system of another company. For purposes of A.G.A. statistics, a distribution company obtains at least 90 percent of its gas operating revenues from sales to ultimate customers, and classifies at least 90 percent of mains (other than service pipe) as distribution. Compare INTEGRATED COMPANY; TRANSMISSION COMPANY, GAS.

    Distribution System, Gas


    Distrigas Method

    A formula used to allocate overhead costs of a parent to its affiliates. This method deviates from the "Mass Formula" by replacing the gross revenue factor with a factor that is computed based on net operating revenues (operating income before interest and federal taxes). This modification to the "Mass Formula" was the result of the Commission's concern, that the gross revenue factor would be distorted when allocating costs from an unregulated entity because of the inclusion of purchase gas costs in gross revenue for regulated pipelines. See MASSACHUSETTS (MASS) FORMULA.


    A characteristic of the variety of gas loads whereby individual maximum demands usually occur at different times. Therefore, the maximum coincident load of a group of individual loads is less than the sum of the individual maximum loads. Diversity among customers' loads results in a diversity among the loads of distribution mains and regulators as well as between entire systems. Compare LOAD DIVERSITY.

    Diversity Factor

    The ratio of the sum of the non-coincident maximum demands of two or more loads to their coincident maximum demands for the same period. Compare COINCIDENCE FACTOR.

    Diversity, Demand


    Diverter, Down Draft


    Divertible Gas Supplies

    Gas supplies that are free to be sold to the highest bidder. They must be uncommitted, or committed under contract to a buyer for no longer than some short period (such as one year). They may be totally uncommitted to any buyer. In addition, they must be available to a pipeline's customers at delivered city-gate prices that are competitive enough to prevent the pipeline from exercising market power. In GAS INVENTORY CHARGE proceedings, the Commission has stated that there must be sufficient divertible gas supplies, as well as COMPARABILITY OF SERVICE, in order to find that the pipeline is operating in a competitive environment.

    Dividend Appropriations

    Amounts declared payable out of unappropriated retained earnings as dividends on outstanding preferred or common stock.


    A formal proceeding with the Federal Energy Regulatory Commission or local Public Utility Regulatory Commission for construction or abandonment of facilities, changes in rates and rulemaking.

    Docket Number

    At the time a document is filed with the Commission it is assigned a number. Docket numbers take different forms for different types of filings, i.e., RP89-147-000 : RP = Rate Proceeding, 89 = the year filed, 147 = the number assigned by the Commission, 000 = Subdocket number assigned sequentially by the Commission.


    The aggregate years of service for plant dollars during the life of the plant. Expired dollar-years are the aggregate years of service realized as of any given date. Future dollar-years are the aggregate years of service remaining. The area under the survivor curve represents the total dollar-years of service.

    Double Block and Bleed System

    A valuing system wherein a full-flow vent valve is located on piping between two shut-off valves in series for the purpose of bleeding to atmosphere excess pressure between the valves.

    Double Glazing

    Two panes of glass, usually parallel, with an air space between, used to provide increased thermal and/or sound insulation.

    Double Leverage

    Concept used in developing a company's proper capital structure. It occurs when the company participates in a project financed joint venture through a wholly owned subsidiary. See CAPITAL STRUCTURE.

    Double-Breasted Buying

    A practice that pipelines are sometimes accused of employing-buying large packages of gas, and deciding later whether its marketing subsidiary bought it for system supply, or whether its marketing subsidiary bought it for resale on the spot market. Independent marketers complain that this practice gives pipelines an undue advantage in the marketplace. Pipelines counter that their pipeline sales and marketing departments are now completely separate functions.

    Down Draft (Back Draft)

    A flow of air down the chimney or flue because of adverse draft conditions.


    Any point in the direction of flow of a liquid or gas from the reference point. Compare UPSTREAM.

    Downstream Pipeline

    The pipeline receiving natural gas at a pipeline inter-connect point.


    A difference of pressure which causes a flow of air and/or flue gases through the boiler, flue connector, breeching, flue, or chimney.

    Draft Fan, Forced

    A blower type fan used to force draft air to the furnace.

    Draft Fan, Induced

    An exhaust-type fan used to draw flue gases through the superheater, economizer, air heater and precipitator.

    Draft Hood

    A device built into an appliance, or made a part of the flue or vent connector from an appliance, which is designed to (a) assure the ready escape of the products of combustion from the combustion chamber in the event of no draft, back draft, or stoppage beyond the draft hood; (b) prevent a back draft from entering the combustion chamber of the appliance; and (c) neutralize the effect of stack action of the chimney or gas vent upon the operation of the appliance.

    Draft Regulator (Draft Stabilizer)

    A device which functions to maintain a desired draft in the appliance by automatically reducing the draft to the desired value.

    Draft, Mechanical

    Draft that is caused by mechanical means, such as a fan.

    Draft, Natural

    Draft that is caused by a thermal upset in which temperature differences change the weight (pressure) of air.

    Drill Pipe

    See PIPE, DRILL.




    A container or segment of piping placed at a low point in a system to collect condensate, dust, and foreign material, enabling their removal. Also known as Drip Leg and Drip Pot. Compare SERVICE DRIP.

    Drip Box

    A box around a drip, accessible at grade level, which protects the drip and pipe.

    Drip Oil

    The light oil or hydrocarbon liquids condensed in a piping system when the gas is cooled. Both natural and manufactured gas can be sources of condensates.

    Drip Riser or Drip Stock

    A small diameter pipe (with or without valve control) connecting drip with surface level.

    Dry Gas


    Dry Hole

    A well which does not yield gas and/or oil in quantity or condition to support commercial production.

    DSM Costs, Administrative

    Costs incurred by a utility for DSM program planning, design, marketing, implementation, and evaluation. Included are labor-related costs, office supplies and expenses, data processing, and other such costs. Excluded are costs of marketing materials and advertising, purchases of equipment for specific programs, and rebates or other incentives.

    DSM Costs, Equipment

    The price of all equipment that a utility directly purchases for a DSM program, whether for its own use or for distribution to program participants.

    DSM Costs, Marketing

    All DSM costs directly associated with the preparation and implementation of the strategies designed to encourage participation in a program.

    DSM Costs, Monitoring and Evaluation

    DSM expenditures associated with the collection and analysis of data used to assess program operation and effects.

    DSM Costs, Non-Utility

    DSM expenses incurred by customers and trade allies associated with participation in a DSM program that are not reimbursed by the utility.

    DSM Costs, Participant

    Costs associated with participation in a DSM program that are paid by the participating customer and not reimbursed by the utility.

    DSM Costs, Planning

    Any expenditures that are required for a DSM program prior to program implementation.

    DSM Costs, Utility

    All expenses incurred by a utility in a given year for operation of a DSM program, including administrative, equipment, marketing, and any others, regardless of whether the costs are capitalized or expensed.

    DSM Potential


    Dual Fuel

    An energy use for which there is an alternative fuel.

    Dual-Fuel Capability

    Ability of an energy-using facility to alternately use more than one kind of fuel.


    A passageway made of sheet metal or other suitable material, not necessarily leak-tight, used for conveying air or other gas at low pressures.

    Duct System

    A series of ducts, elbows, and connectors to convey air, or other gas at low pressure, from one location to another.


    A filler-piece used to close a gap between two pieces of pipe or between a pipe or fitting and a piece of equipment where the pipe is too short to effect the closure or where the pipe and equipment may be out of alignment.

    Dye Penetrant Weld Examination

    A method for inspecting for surface defects of welds by using a dye and developer applied to the weld.

  • E

    Earnings/Price Ratio (E/P)

    A method to determine the cost of common equity component of return using the ratio of earnings per share to the stock price.


    An acquired privilege or right, distinct from ownership of the soil, to use a specified area for certain specified uses.

    Economic Out

    Contract provisions enabling a company to get out of gas purchase contracts based on economic changes that are detrimental to the company.

    Economic Potential

    In DSM, an estimate of energy savings based on the assumption that all energy-efficient options will be adopted and all existing equipment will be replaced with the most efficient measure possible whenever it is cost-effective to do so, without regard to market acceptance. Compare ACHIEVABLE POTENTIAL, MARKET POTENTIAL and TECHNICAL POTENTIAL.

    Economic Regulatory Administration (ERA)

    Formerly the agency in the Department of Energy charged with the responsibility for imports of natural gas. In 1989, the ERA was eliminated and its functions were transferred to the Office of Fossil Energy (FE) in the Department of Energy.

    Economic/Market Clauses

    Contract provisions which allow price redetermination at specified times or conditions at prices prevailing in the area, or at market prices.


    An arrangement of tubes through which the feed water passes before entering boiler drum and flue gases leave burners. Economizers are invariably counter flow; meaning the water flows opposite to the gases, and heat of gases is transferred to the water.

    Edge Water

    Subsurface water that surrounds gas and oil in reservoir structures.

    Edwards Balance

    An instrument for determining the specific gravity of gases. Compare BALANCE, GAS.


    An energy efficient mortgage, often funded by Freddie Mac, Fannie Mae, VA or FHA, that recognizes the energy efficiency of a home and allows the lender to stretch the


    Relating to heat, a percentage indicating the available Btu input to combustion equipment that is converted to useful purposes.


    A material which at room temperature can be stretched repeatedly to at least twice its original length and upon immediate release of the stress, will return to its approximate original length and shape.

    Electric Energy

    Available heat in electricity; one kilowatt hour equals 3,412.97 Btu.

    Electric Heating Pump and Air-Conditioning Efficie

    Energy Efficiency Ratio (EER) - a ratio calculated by dividing the cooling capacity in Btu per hour by the power input in watts at any given set of rating conditions. Heating Seasonal Performance Factor (HSPF) - the total heating output of a heat pump during its normal annual usage period for heating divided by the total electric power input in watt-hours during the same period. Seasonal Energy Efficiency Ratio (SEER) - the total cooling capacity of a central unitary air conditioner or unitary heat pump in Btu's during its normal annual usage period for cooling divided by the total electric energy input in watt-hours during the same period.

    Electric Log


    Electric Space Heating

    Space heating of a dwelling or business establishment or other structure using permanently installed electric heating as the principal source of space heating for a specific area or areas of the premises.

    Electric Well Log

    A record of electrical characteristics of formations drilled through. Electric logs are used to identify the formations, determine the nature and amount of fluids they contain, and estimate their depth. See LOG, ELECTRIC.


    In a pipeline, the decomposition or destruction of the pipe wall by stray electrical currents. The chemical decomposition of a substance when electricity is passed through it in solution or in the molten state. When the process is applied to water or hydrogen, a potential energy source is formed.

    Electronic Data Interchange (EDI)

    The computer-to-computer exchange of business documents and information through the use of standard document formats.

    Electronic Data Transfer

    The computer-to-computer exchange of data for business transactions.

    Electronic Gas Measurement (EGM)

    "Real time" monitoring of natural gas quantities, and characteristics, as it passes through a specific location.

    Electronic Ignition

    A spark ignition device designed to electrically initiate the combustion process.

    Elevated Temperature Testing

    Tests on plastic pipe above 23oC (73oF).

    Eligibility Criteria

    Standards that describe the customers who can participate in a utility's DSM program.

    Eligible Firm Sales Service Agreement

    For purposes of establishing an open access pipeline's obligations to offer CD CONVERSION, an agreement between an open access interstate pipeline and a sales customer that was entered into before the date the pipeline became an open access transporter. See CD CONVERSIONS.

    Eligible Market

    The subset of the total market that is allowed to participate in a utility's DSM program based on eligibility criteria.

    Ell or Elbow

    A pipe fitting that makes an angle in a piperun. Unless stated otherwise, the angle is usually assumed to be 90 degrees. Compare STREET ELL.


    The actual purpose for which gas is used by the ultimate consumer to whom it is delivered.

    End-Use Metering

    The direct measuring of consumption by specific end-use appliances, typically as part of load research studies or to measure the impacts of DSM programs.


    An entity which is the ultimate consumer for natural gas. An end-user purchases the gas for consumption but not for resale purposes.


    Heat absorbing. An endothermic reaction is one in which heat must be supplied to further the reaction.

    Energy Audit

    A review of a customer's energy usage, often including recommendations to alter the customer's demand or reduce energy usage. An audit normally involves a visit to the customer's facility.

    Energy Conservation Measure

    A device, material, or appliance used or installed to improve energy efficiency.

    Energy Conservation Practice

    Actions or practices taken to reduce energy consumption.

    Energy Factor

    A measure of the overall efficiency of a water heater, based on its recovery efficiency, standby loss and energy input as set out in standardized Department of Energy test procedures.

    Energy Information Administration (EIA)

    The statistical information collection and analysis branch of the Department of Energy.

    Energy-Efficiency Program

    A DSM program aimed at reducing overall consumption, often without regard for the timing of the program-induced savings. Such savings are generally achieved by substituting technically more efficient equipment to produce the same level of end-use services with less energy.

    Engine, Reciprocating

    An apparatus which converts the energy in a fluid to mechanical energy by means of the expansion of the fluid (gas) against a piston. It normally includes a cylinder closed by a piston connected by means of a connecting rod to a crankshaft; a valve mechanism admits and discharges fluid at appropriate times in the cycle. Compare TURBINE, STEAM OR GAS.

    Enhanced Oil Recovery (EOR) Fields

    Reservoirs in which secondary recovery techniques are used to extract oil. Most notably, EOR fields in Kern County, California, are expected to use large amounts of natural gas in the future to produce steam for secondary recovery, as well as electricity to be sold to local utilities.


    Increasing the heat content of a gas by mixing with it a gas of higher Btu content.


    Working interest owner's share of production. This volume may not equal actual sales due to contractual or market conditions. Also, the amount of gas to which a customer is entitled from a seller.


    The aggregate of all surrounding conditions, influences, or forces affecting the life, development, and survival of an organism.

    Environmental Protection Agency (EPA)

    A federal agency created in 1970 to permit coordinated and effective governmental action, for protection of the environment by the systematic abatement and control of pollution, through integration of research monitoring, standard setting, and enforcement activities.

    Environmental Stress Cracking (ESC)

    Cracks that develop when the material is subjected to stress or strain in the presence of specific chemicals.

    Epoxy Resins

    Resins made by the reaction of epoxides or oxiranes with other materials such as amines, alcohols, phenols, carboxylic acids, acid anhydrides, and unsaturated compounds.

    Equal Rate Treatment

    Term used to designate a test of the reasonableness of an allocation of costs. In this test the rates designed to recoup the costs allocated to jurisdictional business are applied to the billing units of non-jurisdictional business to determine whether such rates will produce more or less revenues than the costs which have been assigned to the non-jurisdictional business. The "equal rate treatment" is also used as an allocation methodology. In this instance rates are designed which will recoup the total cost of service and are applied equally to jurisdictional and non-jurisdictional business.

    Equitable Sharing Mechanism

    One of two distinct mechanisms for passthrough of take-or-pay buyout costs of interstate natural gas pipelines. The first is pursuant to the Commission's historic policy of permitting prudently incurred costs to be recovered in the sales commodity rate. The second, alternate method was developed in Order No.500. The EQUITABLE SHARING MECHANISM, is available to open access pipelines which agree to an equitable sharing of take-or-pay costs and permits them to recover costs over a specified amortization period, such as five years. Where a pipeline agrees to absorb from 25 to 50 percent of take-or-pay costs, the Commission permits the pipeline to recover through a fixed charge an amount equal to, but not greater than, the amount absorbed. Any remaining costs up to 50 percent of total buyout and buydown costs may be recovered either through a commodity rate surcharge or a volumetric surcharge on total throughput. Fixed charges are allocated among firm sales customers in accordance with the PURCHASE DEFICIENCY METHODOLOGY. See BASE PERIOD and DEFICIENCY PERIOD.


    Equity refers to the considerations of fairness or justice in the setting of rates - fairness between investors and consumers when the general level of rates is at issue, and the fairness among different classes of consumers when the rate relationships are under inquiry. Fair treatment in the setting of rates does not necessarily mean equal rates since, for example, the unit costs of serving different customer classes may be different. Also, that part of a business enterprise owned by the stockholders. Usually represented in the financial

    Equity Capital

    Investment capital provided by common and preferred stockholders.

    Equity Return

    The after-tax return to common and preferred stockholders.

    Equivalent Direct Radiation

    Heat expressed in terms of a square foot of steam radiator surface emitting 240 Btu per hour. (Btu per hour divided by 240).

    Equivalent Length of Pipe

    The resistance of pipe valves, controls, and fittings to gas flow expressed as equivalent length of pipe or pipe of other sizes, for convenience in calculating pipe diameters.

    Equivalent of Fuels Burned

    The Btu equivalent of fuels burned is the aggregate heat energy of all fuels burned. It is derived by calculating total Btu content of each kind of fuel burned and summing to establish the Btu content of all fuels burned. Based on its Btu content, any kind and quantity of fuel burned may be expressed as an equivalent quantity of some other kind of fuel.

    Equivalent Quantities

    A quantity of gas containing an amount of Btus equal to the amount of Btus received by Transporter for the account of Shipper at the Point(s) of Receipt reduced, where applicable, by the Btus removed for Transporter's compressor fuel and Transporter's lost-and-unaccounted for gas and BTU shrinkage in the treatment and processing of Shipper's gas, all as attributable to transportation of Shipper's gas.

    Equivalent Volumes

    The term "Equivalent Volumes" shall mean the sum of the volumes of gas measured in MMBtu received by Transporter for the account of Shipper at the Transporter Receipt Point(s) during any given period of time, (a) reduced by a percentage for Fuel Gas consumed and a percentage for Gas Lost and Unaccounted For on Transporter's system as provided in the Agreement, (b) reduced by any plant volume reductions assessed as a result of Shipper's or its supplier's election to process the gas, and (c) adjusted for any variations in Btu content. It is the intent of the parties that the volumes of gas delivered at the Transporter Delivery Point(s) after transportation shall be the equivalent in Balancing Units of the volumes of gas received at the Transporter Receipt Point(s) for transportation, as adjusted for items (a), (b) and (c) above.

    Escalator Clause

    A clause in a purchase or sales contract that permits adjustment of price or profit, under specific conditions.

    Estimated Bill


    Estimated Proved Recoverable Reserves


    Ethane (C2H6)

    A colorless hydrocarbon gas of slight odor having a gross heating value of 1,773 Btu per cubic foot and a specific gravity of 1.0488. It is a normal constituent of natural gas.

    Ethylene (C2H4)

    A colorless hydrocarbon gas of slight odor having a gross heating value of 1,604 Btu per cubic foot and a specific gravity of 0.9740. It is usually present in manufactured gas, constituting one of its elements.


    An instrument for the volumetric measurement and analysis of gases.

    Evaporative Cooling

    The adiabatic exchange of heat between air and a water spray or wetted surface. The water approaches the wet bulb temperature of the air, which remains constant during its traverse of the exchanger.


    Equipment or device that extracts or drives out vapors from liquid solutions or gases. Also, equipment that is part of refrigerating systems to permit liquid refrigerants to evaporate in the process of absorbing heat.

    Evergreen Clause

    A provision in a contract that provides for the automatic extension of the contract for specified periods beyond the primary term unless either party specifically elects to terminate the contract by giving the required notice prior to the anniversary date.

    Ex Parte Communications

    Off-the-record communication between any party to a proceeding before the Commission and any Commissioner, his or her staff, or any employee of the Commission.

    Excess Air

    Air which passes through a combustion zone in excess of the quantity theoretically required for complete combustion.

    Exchange Agreement

    An agreement between two parties which defines the terms and conditions for the exchange of gas and title transfer.

    Exchange Gas

    Gas that is received from (or delivered to) another party in exchange for gas delivered to (or received from) such other party.

    Exchange Transactions

    In a gas exchange between two parties, gas is received from (or delivered to) the first party in exchange for gas delivered to (or received from) the second party. An exchange provides a means for delivering gas supplies to a customer without the necessity of constructing and operating duplicative facilities. Central to the concept of an exchange is mutual benefits to the two parties engaging in the exchange. The transaction must involve reciprocal benefit or the trade of comparable values.

    Exhaust Port

    In engines, the opening through which a fluid discharges out of a cylinder. In gas meter, the openings through which gas leaves the metering chamber.

    Exit Temperature

    The flue gas temperature taken at the point where the gas leaves the combustion chamber.


    That characteristic of a chemical reaction, such as fuel combustion, in which heat is liberated.

    Expander Cycle

    A liquefaction process using expansion turbines or engines to produce mechanical energy while refrigerating the gas to be liquefied.

    Expander Turbine

    A rotary motion machine employing the hot air blast of jet engines as the turning force.

    Expansion Loop

    Either a bend like the letter "U" or a coil in a line of pipe to provide for expansion and contraction.

    Expansion Ratio

    The ratio of gas volume after expansion to the gas volume before expansion.

    Expansion Valve

    A special valve used in refrigerating systems through which the liquid refrigerant (under high pressure) is allowed to escape into a lower pressure and thus expand into a gas.




    Generally, the act of searching for potential subsurface reservoirs of gas or oil. Methods include the use of magnetometers, gravity meters, seismic exploration, surface mapping, exploratory drillings, and other such methods.

    Exploratory Well

    A well drilled either in search of a new and as yet undiscovered accumulation of oil or gas, or in an attempt to significantly extend the limits of a known reservoir.

    Explosion Head

    A term applied to a protective device that is arranged to blow out a disk, usually if an air-gas mixture explodes in a piping system. Thereafter, the gas will escape until a shut-off valve is closed.

    Explosive Limits

    The lowest (lower limit) and highest (upper limit) concentrations of a specific gas or vapor in mixture with air that can be ignited at ordinary temperature and pressure of the mixture. Also called COMBUSTIBLE LIMITS or FLAMMABLE LIMITS.




    A substance, generally having some adhesive action, added to a plastic composition to reduce the amount of the primary resin required per unit volume.

    Extension (of Gas Reserves)

    Any new reserve credited to a previously producing reservoir because of enlargement of its producing area due to new well drilling or completions outside the previously known producing limits of the reservoir.

    Exterior Zones

    The portions of a building, with significant amounts of exterior walls, windows, roofs, or exposed floors. Such zones have heating or cooling needs largely dependent upon weather conditions. Compare INTERIOR ZONES.

    Externality, Environmental

    The environmental costs to society of the production, distribution and consumption of energy that are not reflected in the price to the end-users.

    Extraction Loss

    The reduction in volume of natural gas resulting from the removal of the natural gas liquid constituents of natural gas at extraction plants. See SHRINKAGE, NATURAL GAS.

    Extraction Plant

    A plant in which products, such as propane, butane, oil, ethane, or natural gasoline, which are initially components of the gas stream, are extracted or removed for sale. See GASOLINE PLANT.

    Extraordinary Property Losses

    An amortizable (Deferred Debit) account, which includes the depreciated value of property abandoned or damaged by circumstances that could not have been reasonably anticipated and which is not covered by insurance.


    The process whereby heated or unheated plastic forced through a shaping orifice becomes one continuously formed piece.

  • F


    Fair and Equitable as in F&E cost distribution.

    Failure, Adhesive

    Rupture of an adhesive bond, such that the plane of separation appears to be at the adhesive-adhered interface.


    As in "fair" rate of return. In ratemaking "fair" is a subjective term requiring significant study to support the proposed level.

    Fair Value

    In determining the company's Rate Base by this method you can either (1) estimate the cost to rebuild, (2) inflation adjust or trend Original Cost, or (3) estimate the market value. See ORIGINAL COST.

    Farm Tap

    A small meter station off of a transmission line usually to serve one customer.


    An arrangement whereby the owner of a lease assigns the lease, or some portion of it, to another party for drilling.

    Favored Nation Clause

    A provision in a gas purchase contract between a purchaser and a producer which increases the price to be paid for natural gas if any producer in the same field receives a higher price for natural gas than the price stipulated in the contract.

    Federal Energy Regulatory Commission (FERC)

    An agency of the government of the United States created by an Act of Congress, the Department of Energy Organization Act, in 1977. This Act transferred to the FERC most of the former Federal Power Commission's interstate regulatory functions over the electric power and natural gas industries. The Act also transferred from the Interstate Commerce Commission the authority to set oil pipeline transportation rates and to set the value of oil pipelines for ratemaking purposes. In 1978, Congress passed the Natural Energy Act, broadening the FERC's jurisdiction and regulatory functions. The FERC now also regulates producer sales of natural gas in intrastate commerce. The FERC establishes uniform ceiling prices for each of several categories of natural gas, and these prices apply to all sales on a nationwide basis.

    Federal Power Commission

    An agency of the government of the United States created by an Act of Congress, the Federal Water Power Act, in 1920. Originally charged with regulating the nation's water resources, the FPC later assumed responsibility for regulating the electric power and natural gas industries that sell or transport electricity or gas for resale in interstate commerce. With respect to the gas industry, the general regulatory principles of the FPC were defined in the Natural Gas Act, as amended. In 1977, the FPC passed into history and the Department of Energy was created, incorporating the independent regulatory agency known as the Federal Energy Regulatory Commission.

    Feed Points

    Connections between gas feeder lines and distribution networks.

    Feeder (Main)

    A gas main or supply line that delivers gas from a city gate station or other source of supply to the distribution networks.


    Crude oil, a derivative thereof, or other raw material utilized in process equipment.

    FERC Out

    Contract provisions enabling a company to get out of gas purchase contracts based upon regulatory changes that are detrimental to the company.

    FHLMC/Freddie Mac

    Federal Home Loan Mortgage Corporation is a publicly chartered agency in 1970 that buys qualifying residential mortgages from lenders, pools them into securities, provides certain guarantees, and then resells the securities on the open market.

    Fiber Stress

    The stress acting on a fiber or a strand of fibers in a piece of material that is subjected to an applied load.


    The general area encompassed by one or more oil or gas reservoirs or pools that are located on a single geologic feature, that are otherwise closely related to the same geologic feature (either structural or stratigraphic). See POOL.

    Field and Gathering Lines


    Field Pressure

    The pressure of natural gas as it is found in the underground formations from which it is produced.

    Field Price

    The price paid for natural gas at the wellhead or outlet of a central gathering point in a field.

    Field Sales

    Total sales from any field. Also, those sales made by a pipeline which occur in the gas supply areas and which typically do not require any part of the pipeline's transmission facilities.

    Field Uses

    Generally refers to any use of gas (or oil) within a field for the purpose of producing or treating the gas recovered or any associated oil produced. It may also include any gas taken by the lessor for his local use.


    First-in, first-out method of inventory valuation by which the earliest-acquired natural gas in storage is assumed to be sold first and the most recently acquired is assumed to be still on hand.

    Filed Rate Doctrine

    The legal principle that protects regulated customers from receiving retroactive rate hikes.

    Filed Rates

    Rates in a general rate filing that a pipeline company proposes to place in effect one month after the filing date. These rates are usually suspended for five additional months by FERC.


    A relatively inert material added to a plastic to modify its strength, permanence, working properties, or other qualities, or to lower costs.


    A metal projection (of various design configurations) from the exterior surface of tubes in heat exchange equipment to increase the heat transfer area.

    Fin-Fan Cooler

    A dry cooler that passes cooling air over finned tubes, through which some hot fluid is being passed, during the cooling process. A fan is used to create movement of air over the finned tubes. Air movement is regulated in a number of ways, the most common being a variable speed fan.

    Fire Brick

    Heat resistant refractory ceramic material formed into bricks and used to line fire boxes of boilers, furnaces, or other combustion chambers.

    Fire Clay

    A special kind of clay that will not melt or fuse at high temperatures.

    Fire Point

    Minimum temperature at which a substance will continue to burn after being ignited.

    Firing Rate

    The rate at which fuel is fed to a burner, expressed as volume, heat units, or weight per unit time.

    Firm Service

    Service offered to customers (regardless of Class of Service) under schedules or contracts which anticipate no interruptions. The period of service may be for only a specified part of the year as in Off-Peak Service. Certain firm service contracts may contain clauses which permit unexpected interruption in case the supply to residential customers is threatened during an emergency. Compare INTERRUPTIBLE SERVICE and OFF-PEAK SERVICE.

    Firm Transportation Service (FTS)

    Transportation services for which facilities have been designed, installed, and dedicated to a certified quantity. Firm transportation service takes priority over interruptible service.

    First Come, First Served

    A capacity allocation method under which the first shipper to have requested service shall be the first to be offered such service. The pipeline is only obligated to provide service to a particular customer to the extent capacity is available.

    First Hour Rating

    The amount of hot water that the water heater can supply in the first hour of operation. It is a combination of how much water is stored in the water heater and how quickly the water heater can heat cold water to the desired temperature and is determined by the method of test developed by the Department of Energy.


    An object left in the wellbore during drilling or workover operations that must be recovered or drilled around before work can proceed.


    A metallic or plastic component used in joining lengths of pipe into various piping systems; includes couplings, ells, tees, crosses, reducers, unions, caps, and plugs.

    Five Light Meter

    Historically, a meter capable of measuring the volume of gas consumed by five gas lights. The capacity of these meters was about 150 cubic feet per hour.

    Fixed Cost

    Certain costs which in the aggregate do not vary in amount regardless of the quantity of gas sold or transported. See VARIABLE COSTS.

    Fixed Variable

    A classification method that assigns 100% of fixed costs to the demand component of the rate.

    Fixed-Variable Method

    A rate design method which assigns all fixed costs to the demand component and all variable costs to the commodity component of rates. This method was used by the FPC prior to 1952 and was superseded in 1952 by the Atlantic-Seaboard Method. See ATLANTIC SEABOARD, UNITED METHOD, and MODIFIED FIXED VARIABLE METHODS.


    An ordinarily visible condition resulting from the rapid oxidation of a fuel which produces self-evident heat, light, or both.

    Flame Detector

    An element of the equipment used for flame supervision.

    Flame Front

    The plane along which combustion starts.

    Flame Geometry

    The measure of flame shape and dimension. Such shape can be produced by single or multiple burners.

    Flame Test

    Detection and identification of certain elements in gas by characteristic coloration imparted to a flame.

    Flame Velocity

    The speed at which flame progresses through a fuel-air mixture.

    Flammable Limits



    For pipe, a metal collar drilled with bolt holes and attached to the pipe with its flat surface at right angles to the pipe axis so that it can be securely bolted to a mating flange on a valve, another pipe section, etc.

    Flange, Insulated

    A pair of mating flanges equipped with insulating materials in a manner so that there is no electrical continuity between the flanges when installed.


    Burning of gas for the purpose of safe disposal.

    Flash Back

    The burning of gas in the mixing chamber of a burner or in a piping system, usually due to an excess of primary air or too low a velocity of the combustible mixture through the burner part.

    Flash Gas

    Gas resulting from the process of gas liquefaction.

    Flash Point

    The lowest temperature at which the vapors arising from a liquid surface can be ignited by an open flame.

    Flex Rates

    Monthly price changes in rates, within a minimum/ maximum range.

    Flexible Connector

    A flexible tubing connecting a rigid pipe gas supply line to gas utilizing equipment.

    Flexible Coupling

    A mechanical connection between two pieces of machinery or two pipes to allow limited movement of the two parts relative to each other.

    Flexural Strength

    The stress, usually in pounds per square inch (psi), a specimen will withstand when subjected to a bending moment.

    Flow Formulas

    In the gas industry, formulas used to determine gas flow rates or pressure drops in pipelines, regulators, valves, meters, etc.

    Flow Prover

    Apparatus used to determine the accuracy of displacement meters. Types of provers include bell, critical flow, low pressure flow, piston and transfer.

    Flow Restrictor

    A device which reduces water flow at faucets or showerheads.

    Flow-Through Method

    An accounting method under which decreases or increases in state or federal income taxes resulting from the use of liberalized depreciation and the Investment Tax Credit for income tax purposes are carried down to net income in the year in which they are realized. For rate-making purposes, the flow-through method passes on savings from liberalized depreciation and investment credit to the benefit of rate payers through lower rates.


    Passage for combustion products within furnace or boiler. Compare VENT, FLUE GAS.

    Flue Collar

    That portion of an appliance designed for the attachment of the draft hood or vent connector.

    Flue Exhauster

    A device installed in and made a part of the vent to provide a positive, induced, or balanced draft.

    Flue Gas

    See GAS, FLUE.

    Fluidized Bed Combustion

    Coal is burned in a bed of limestone that is suspended by an upward flow of air and gases and forms a dry calcium sulfate waste.

    Fly Ash

    All solids, including cinders, ash, soot, or other partially incinerated matter, that are carried in a gas stream.

    FNMA/Fannie Mae

    Federal National Mortgage Association that is a publicly owned, government-sponsored corporation chartered in 1938 to purchase mortgages from lenders and either to hold them in portfolio or resell them to investors.

    Foam Generation

    Equipment, normally consisting of a generator and related material to produce foam for fire control particularly necessary for LNG spillover.


    In a boiler, the carry-over of slugs of water into the piping due to dirty water or overloading of the boiler. Compare PRIMING.

    Force Majeure

    A superior force, "act of God" or unexpected and disruptive event, which may serve to relieve a party from a contract or obligation.


    A geological term applied to an underground rock stratum; in the gas industry, usually the one from which gas or oil is produced.

    Forward Haul

    A transaction that results in the transportation of gas in the same direction of the aggregate physical flow of gas in the pipeline. This is typically achieved when the transporting pipeline redelivers gas at a point(s) downstream of the point(s) of receipt.

    Fossil Dismantlement

    The dismantlement and disposal of all buildings, structures, equipment, tanks and stacks at the site and restoration of the site to a usable condition.


    Industry term used to refer to the method used to increase the deliverability of a production or underground storage well by pumping a liquid or other substance into a well under pressure to crack (fracture) and prop open the gas-bearing formation.


    Process whereby saturated hydrocarbons from natural gas are separated into distinct parts of propane, butane, ethane, etc.


    A process of opening up underground channels in hydrocarbon-bearing formations by force rather than by chemical action such as in acidizing. High pressure is hydraulically or explosively directed at the rock, causing it to fracture.

    Franchise Gas

    Natural gas provided by a utility to a governmental body, in a particular municipality, in exchange for franchise rights in that municipality.

    Franchises and Consents

    The right or privilege granted by a political subdivision to do business or perform specific services.

    Free Driver

    A customer who takes the same conservation actions as those customers who participate in a utility DSM program, without participating in the program.

    Free Gas Reservoir

    A gas reservoir without a related oil zone or oil ring where essentially all of the reservoir fluids are in a gaseous state.

    Free Rider

    A customer who participates in a utility DSM program, and thereby receives the services or financial incentives provided by the utility, who would have taken the same conservation actions in the absence of a DSM program.

    Free Service

    In DSM, an incentive in the form of assistance offered by utilities, such as energy audits and maintenance of equipment such as furnace tune-up programs.

    Fuel and Shrinkage

    The difference between the amount of gas produced at the wellhead and the gas that enters a pipeline. This includes separator losses, field uses including fuel, flare gas, and plant extraction losses.

    Fuel Cell

    System in which hydrogen is chemically reacted with oxygen to produce electricity.

    Fuel Gas

    A quantity of gas required by a transporter to provide the transportation service. Fuel gas includes, but is not limited to, gas consumed in transporter's mainline compressor stations, gathering system booster stations and processing plants.

    Fuel Price Adjustment Clause


    Fuel Substitution

    The conversion of an end-use from one fuel source to another.

    Full Requirements

    A sale of power or energy by a utility in which the utility pledges to meet all of the customer's requirements.

    Full Scale Program

    A DSM program that is available to all eligible customers within a utility's service territory.

    Functional Accounts

    Groupings of plant and expense accounts according to the specified function or part they play in the rendition of utility service. Utility Plant Functional Accounts - Includes Intangible, Production, Transmission, Distribution, and General Plant. Operation and Maintenance Functional Expense Accounts - Includes Production, Storage, Transmission, Distribution, Customer Accounts, Sales and Administrative and General Expenses.


    The process of assigning each component of a company's cost of service to the functions the company performs (e.g., production, storage, transmission, distribution).

    Fungi Resistance

    The ability of plastic pipe to withstand fungi growth and/or their metabolic products under normal conditions of service or laboratory tests simulating such conditions.


    When used in a central heating system, this is a self-contained appliance for heating air by transfer of heat of combustion through metal to the air.

    Furnace (Condensing)

    Furnaces which recirculate the products of combustion and extract available heat to a point that causes condensation to occur. Some of this latent heat of vaporization is recovered as usable energy and results in higher operating efficiencies.

    Furnace, Downflow

    A forced-air type central furnace designed with air flow through the furnace essentially in a vertical path, discharging air at or near the bottom of the furnace.

    Furnace, Duct

    A central furnace designed for installation in a duct of an air distribution system to supply warm air for heating and which depends for air circulation on a blower not furnished as part of the furnace.

    Furnace, Forced-Air

    A central furnace equipped with a fan or blower which provides the primary means for circulation of air.

    Furnace, Horizontal

    A forced-air type central furnace designed with air flow through the furnace essentially in a horizontal path.

    Furnace, Upflow

    A central furnace designed with air flow through the furnace essentially in a vertical path, discharging air at or near the top of the furnace.


    To join two plastic parts by softening the material with heat.

  • G


    That state of matter which has neither independent shape nor volume. It expands to fill the entire container in which it is held. It is one of the three forms of matter, the other two being solid and liquid.

    Gas Absorption

    The extraction of a gaseous substance from an atmosphere by liquid or solid material.

    Gas Bag

    A gas-proof, inflatable bag which can be inserted in a gas pipe and inflated to seal off the flow of the gas.

    Gas Balance Report

    A monthly accounting report containing month-end meter station allocations for each customer/shipper contract. The report may be sorted by meter station or by contract.

    Gas Bubble

    An excess of natural gas deliverability relative to demand requirements at current prices.

    Gas Cap

    A layer of free gas on top of the oil zone in an underground structure or reservoir.

    Gas Central Furnace and Boiler Efficiency Measures

    The annual efficiency ratings of furnaces and boilers based on average usage, including on and off cycling as determined by standardized Department of Energy test procedures.

    Gas Conditioning

    The removal of objectionable constituents and addition of desirable constituents.

    Gas Controller

    A person or persons assigned the task of monitoring and controlling daily gas system operations and ensuring safety of a pipeline or distribution system.

    Gas Cycling

    A petroleum recovery process which takes gas produced with condensate and injects it back into the reservoir to aid in producing more condensate. See REPRESSURING.

    Gas Day

    A period of twenty-four (24) consecutive hours commencing at a specified hour on a given calendar day and ending at the same specified hour on the next succeeding calendar day.

    Gas Detector

    A device which indicates the existence of combustible or noxious gas.

    Gas Generator

    The section of a gas-turbine that provides the high temperature gases needed to drive the power turbine.

    Gas Imbalance

    a. Producer/Producer - When one or more producers sell or utilize a volume of natural gas in excess of their gross working interest. b. Pipeline/Pipeline - When a pipeline receives a volume of natural gas and redelivers a larger or smaller volume of natural gas under the terms of a transportation agreement. c. Producer/Pipeline - When a producer delivers a volume of natural gas that is larger or smaller than the volume of natural gas that the pipeline redelivers for the producer's account to another party.

    Gas Impurities

    Undesirable matter in gas, such as dust, excessive water vapor, hydrogen sulphide, tar, and ammonia.

    Gas in Place (GIP)

    The amount of gas in a reservoir at any time, calculated at standard conditions. This includes recoverable and nonrecoverable gas.

    Gas Injection


    Gas Inventory Charge (GIC)

    A forward-looking mechanism for the current recovery of take-or-pay costs, established in Commission Order No.500. Section 2.105 sets forth the general guidelines for GICs. The GIC is intended to recover costs, on a current basis, associated with contractually committing gas service tailored to meet the customer's nominations. GIC's generally fall into two categories. Some GIC's are cost based, that is, they are designed to recover certain identified costs, subject to a reconciliation mechanism. Other GIC's are market based or market responsive. Market Based GIC commodity charges are based upon a measure of the current market price for gas. Market Based GIC demand charges are generally designed to recover any premiums which must be paid above the current market price for long term gas supply commitments. GIC charges generally are assessed either based on a customer's nominated contract demand (Demand Based GIC) or on the amount by which the customer's takes are less than a percentage of its nominations (Deficiency Based GIC). Prior to receiving authority to implement a Market Based GIC mechanism, the Commission must first find that the pipeline is operating in a market that is sufficiently competitive and that the pipeline's firm transportation service is comparable in quality to its firm sales service. See COMPARABILITY OF SERVICE.

    Gas Lift

    The effect of gas pressure in an oil well which causes the oil to flow from the well. May be either natural or artificially induced by injecting gas into the hole under pressure. Below the surface, gas intermixes with the oil, lightens the oil column, and allows it to flow.

    Gas Plant

    Any plant which performs one of the following functions: removing liquefiable hydrocarbons from wet gas or casinghead gas (gas processing); removing undesirable gaseous and particulate elements from natural gas (gas treatment); removing water or moisture from the gas stream (dehydration). Also, the original cost of property, plant and equipment owned and used by the utility in its gas operations and having an expectation of life in service of more than one year from the date of installation.

    Gas Research Institute (GRI)

    An organization sponsored by a number of U.S. gas companies to investigate new sources of supply and new uses (applications) for natural gas.

    Gas Sand

    The underground porous strata which contains natural gas and from which it is produced. "Sand" as used here is a generic term that may denote a porous limestone or dolomite, as well as a sandstone or unconsolidated sand formation.

    Gas Supply Coordinator

    A representative of a company assigned the task of managing the operations under Transportation, Sales or Purchase Service agreements. Responsibilities typically include scheduling activity, imbalance management and volume confirmation.

    Gas Transported for Others

    That volume of gas owned by another company received into and transported through any part of the transmission or distribution system under a transportation tariff.

    Gas Turbine

    A prime mover in which gas, under pressure or formed by combustion, is directed against a series of turbine blades; the energy in the expanding gas is converted into mechanical energy supplying power at the shaft.

    Gas Used

    The total quantity of gas used by the transmission or distribution company in the operation (i.e., fuel), the maintenance and the construction of facilities.

    Gas Well

    See WELL, GAS.

    Gas Zone

    A porous, permeable formation containing natural gas under pressure. Compare STORAGE, UNDERGROUND.


    A set of standard record formats supporting the electronic data interchange of the documents described in the Nominations/Allocations Subcommittee and the Volume Imbalance Subcommittee reports.

    Gas, Associated

    Free natural gas in immediate contact, but not in solution, with crude oil in the reservoir.

    Gas, Associated

    Gas produced in association with oil, or from a gas cap overlying and in contact with the crude oil in the reservoir. In general, most states restrict associated gas production since its indiscriminate production could reduce the ultimate oil recovery. Also, since some wells producing associated gas cannot be shut-in without also shutting-in the oil production, natural gas pipelines are generally required to take allowed associated gas produced from oil wells on a priority basis. See also GAS CAP.

    Gas, Blast Furnace

    Gas obtained from blast furnaces. It is low in heat content.

    Gas, Casinghead

    Gas produced with oil in oil wells. The gas being taken from the well through the casinghead at the top of the well.

    Gas, Conventional

    Gas that can be produced with current technology at a cost that is no higher than its current market value.

    Gas, Dissolved

    Natural gas in solution in crude oil in the reservoir.

    Gas, Dry


    Gas, Extraneous


    Gas, Field

    A district or area from which natural gas is produced.

    Gas, Flue

    The products of combustion and excess air before the draft hood or draft regulator consisting principally of carbon dioxide, carbon monoxide, oxygen, and nitrogen.

    Gas, Foreign


    Gas, Illuminating

    A gas containing relatively large amounts of unsaturated and/or heavy hydrocarbon gases which burn with a luminous flame.

    Gas, Liquefied Petroleum (LPG)

    A gas containing certain specific hydrocarbons which are gaseous under normal atmospheric conditions but can be liquefied under moderate pressure at normal temperatures. Propane and butane are the principal examples.

    Gas, Manufactured

    A gas obtained by destructive distillation of coal, or by the thermal decomposition of oil, or by the reaction of steam passing through a bed of heated coal or coke, or catalyst beds. Examples are coal gases, coke oven gases, producer gas, blast furnace gas, blue (water) gas, and carbureted water gas. Btu content varies widely.

    Gas, Natural

    A naturally occurring mixture of hydrocarbon and nonhydrocarbon gases found in porous geologic formations beneath the earth's surface, often in association with petroleum. The principal constituent is methane. 1. Dry. Gas whose water content has been reduced by a dehydration process. Gas containing little or no hydrocarbons commercially recoverable as liquid product. Specified small quantities of liquids are permitted by varying statutory definitions in certain states. 2.Liquefied (LNG). See LIQUEFIED NATURAL GAS. 3. Sour. Gas found in its natural state, containing such amounts of compounds of sulfur as to make it impractical to use, without purifying, because of its corrosive effect on piping and equipment. 4.Sweet. Gas found in its natural state, containing such small amounts of compounds of sulfur that it can be used without purifying, with no deleterious effect on piping and equipment. 5. Wet. Wet natural gas is unprocessed natural gas or partially processed natural gas produced from strata containing condensable hydrocarbons. The term is subject to varying legal definitions as specified by certain state statutes. (The usual maximum allowable is 7lbs./MMcf water content and .02 gallons/Mcf of Natural Gasoline.)

    Gas, Non-Associated

    Free natural gas not in contact with, nor dissolved in, crude oil in the reservoir.

    Gas, Oil

    A gas resulting from the thermal decomposition of petroleum oils, composed mainly of volatile hydrocarbons and hydrogen. The true heating value of oil gas may vary between 800 and 1600 Btu per cubic foot depending on operating conditions and feedstock properties.

    Gas, Sour


    Gas, Stack

    See GAS, VENT.

    Gas, Sweet


    Gas, Synthesis

    A mixture of CO and H2 containing small amounts of nitrogen, some carbon dioxide, and various trace impurities prepared for petrochemical synthesizing processes. It is also used in the manufacturing of SNG.

    Gas, Unconventional

    Gas that can not be economically produced using current technology.

    Gas, Vent

    Products of combustion from gas appliances plus excess air plus dilution air in the gas vent or chimney above the draft hood or draft regulator.

    Gas, Waste


    Gas, Wet


    Gas-Oil Ratio

    The quantity of gas produced with oil from an oil well, usually expressed as the number of cubic feet of gas produced per barrel of oil produced.


    The conversion of carbonaceous material into gas or the extraction of gas from another fuel.


    The process during which liquified natural gas (LNG) is returned to its vapor or gaseous state through an increase in temperature and a decrease in pressure.

    Gasoline Plant

    A plant in which hydrocarbon components common to the gasoline fractions are removed from "wet" natural gas, leaving a "drier" gas. See EXTRACTION PLANT.

    Gate Station

    Generally a location at which gas changes ownership, from one party to another, neither of which is the ultimate consumer. It should be noted, however, that the gas may change from one system to another at this point without changing ownership. Also referred to as city gate station, town border station, or delivery point.


    A legal entity which has responsibility for the collection of the gas from the wellhead and the delivery of that gas to either a gas plant or a pipeline.


    The act of operating extensive low-pressure gas lines which aggregate the production of several separate gas wells into one larger receipt point into an interstate pipeline.

    Gathering Agreement

    Agreement between a producer and a gathering system operator specifying the terms and conditions for entry of the producer's gas into the gathering system.

    Gathering Line

    A pipeline, usually of small diameter, used in gathering gas from the field to a central point.

    Gathering Station

    A compressor station at which gas is gathered from wells by means of suction because pressure is not sufficient to produce the desired rate of flow into a transmission or distribution system.

    Gathering System

    The gathering pipelines plus any pumps, tanks, or additional equipment used to move oil or gas from the wellhead to the main pipeline for delivery to a processing facility or consumer.

    Gauge, Pressure

    Instrument for measuring the relative pressure of a fluid. Types include gauge, absolute, and differential.

    General Plant

    A group of utility plant accounts not includible in the other functional utility plant accounts. Includes: Land and Land Rights, Structures and Improvements, Office Furniture and Equipment, Transportation Equipment, Stores Equipment, Tools, Shop and Garage Equipment, Laboratory Equipment, Power Operated Equipment, Communication Equipment, Miscellaneous Equipment, and Other Tangible Property.

    General System Supply

    Gas that is purchased by a pipeline or distribution company for the purpose of resale. See SYSTEM SUPPLY.

    Generation, Non-Utility

    Generation by producers having generating plants for the purpose of supplying electric power required in the conduct of their industrial and commercial operations. Generation by mining, manufacturing, and commercial establishments and by stationary plants of railroads and railways for active power is included.

    Geophysical Survey

    Searching and mapping of the subsurface structure of the earth's crust by use of geophysical methods, to locate probable reservoir structures capable of containing gas or oil.


    A study of subsurface geological conditions of structure or material through the interpretation of measurement variations in density, magnetics, elasticity, electrical conductivity, temperature, and/or radioactivity.

    Geopressured Brines

    Saltwater found in underground formations in which the pressure is much higher than commonly exists at such depths (primarily in the Gulf Coast states and under the Gulf of Mexico). Gas is soluble in water, just as it is in crude oil, but in much lower amounts. Solubility increases with pressure. Geopressured brines (with formation pressures of 10,000 psi or higher) contain sufficient gas in solution that were the pressure reduced (by producing the saltwater) significant quantities of gas could be produced. The total amount of gas held in geopressured brines is quite large and represents a potential energy resource for the U.S. However, the production of such gas is currently not economic.




    See PIG.

    Golden Rule

    Certain parties have advanced the concept of the "Golden Rule" in pipeline rate cases. Under this concept, the pipeline as a merchant must be subject to all of the terms and conditions as other shippers on the pipeline's system. The pipeline, as a merchant, must contract with itself for transportation service and receive a priority for scheduling and curtailment under the same terms as other shippers. See COMPARABILITY OF SERVICE.


    Gas-oil ratio. Generally, in the U.S., the volume of natural gas produced in cubic feet per barrel of oil produced.


    A groove or scooped out cavity damage to pipe caused by a foreign object.

    Governor, Zero Gas

    A gas pressure regulating device common to industrial combustion systems used for controlling and reducing varying inlet gas pressures to atmospheric pressure at the device outlet.

    GRADE (Gas Revenue Accounting Data Exchange)

    An acronym for a system for the electronic communication of gas production and sales data between companies in the energy industry.

    Grandfather Clause

    The continuation of a former rule, clause, or policy (usually in a contractual agreement) where a change to a new rule or policy would be patently unfair to those covered by the former.

    Gravity Survey

    A method, using a gravity instrument, to detect variations in the gravitational pull of rocks in the subsurface. Variations or anomalies are contoured on a map and give evidence of geologic structures.


    The layout of a gas distribution system in which pipes are laid in both directions in the streets and frequently connected at intersections. Also, a series of equally spaced parallel bars held together by equally spaced crosspieces; a screen.

    Grille (Grill)

    A covering over an air inlet or outlet with openings through which air passes.

    Ground Temperature



    An underground installation of anodes and coke breeze, etc. which is utilized for the control of corrosion of pipe and other metals; generally a rectifier is used in such installations.

    Guideline Lives

    Useful asset lives (by general categories) as determined and allowed for income tax depreciation charges by The Internal Revenue Service.


    A resinous material formed in regulators, meters, and orifices from the polymerization of certain gas components present in manufactured gas, primarily heterocyclic and/or unsaturated hydrocarbons.

    Gun Perforator

    A device for making a hole through the casing, cement, and into the producing formation of a well to provide channels for flow of gas and/or oil into the well.

  • H


    The differential or pressure, usually expressed in terms of the height of a liquid column that the pressure will support. Also, the differential across a primary measuring device in feet of flowing fluid.

    Head Up

    To tighten the bolts on a hatch cover or manhole plate so that no leakage will occur from or into the vessel when operating.


    A pipe or fitting that interconnects a number of branch pipes.


    A point at which gas enters the pipeline's main transmission line, either at the interconnection of the gathering system or of a third party transporter. See POOLING POINT.


    A formal meeting of interested parties in a rate proceeding before an administrative law judge or regulatory commission to obtain a decision on differences in a filing. Hearing may include written testimony, cross-examination of company witnesses, rebuttal testimony, recross-examination of these witnesses by the company, initial briefs, reply briefs addressing arguments raised by other in the initial briefs, and oral arguments.

    Heat Balance

    The accounting of the energy output and losses from a system to equal the energy input.

    Heat Capacity

    Quantity of heat required to raise the temperature of a unit quantity of a substance one degree. Interchangeable with "specific heat" in common usage.

    Heat Exchanger, Direct

    A heat exchanger in which heat generated in the combustion chamber of the device is transferred directly through walls of the heat exchanger to the heating medium such as air, steam, or water, held in close contact with the combustion-chamber walls. It is a self-contained combustion and heat-transfer device, hence a direct heat-transfer device.

    Heat Exchanger, Indirect

    A heat exchanger which encloses or contains a heating medium such as air, steam, or water, the heat from which is transferred to another heating medium separately contained in close contact with or directed through the heat exchanger. It is an indirect heat-transfer device.

    Heat Fusion Joint

    A joint made in thermoplastic piping by heating the parts sufficiently to permit fusion of the materials when the parts are pressed together.

    Heat Gain

    The amount of heat gained by a space from all sources, including people, lights, machines, sunshine, etc.

    Heat Joining

    Making a pipe joint by heating the mating surfaces of the parts to be joined so that they fuse and become essentially one piece with or without addition of material. NOTE: Also known as Heat fusion and Fusion.

    Heat Liberation Rate

    The amount of heat which is liberated per unit time per cubic foot of combustion space.

    Heat Loss

    The sum cooling effect of a building structure when the outdoor temperature is lower than the desired indoor temperature.

    Heat of Combustion

    The heat released when a substance is completely burned in oxygen. Compare HEATING VALUE.

    Heat of Fusion

    The heat lost or gained by a substance in passing from

    Heat of Vaporization, Latent

    The quantity of heat required to change a unit weight of liquid to vapor with no change in temperature.

    Heat Pump

    A year-round air-conditioning system employing refrigeration equipment in a manner which enables usable heat to be supplied to a space during the winter period, and by reversing the operation cycle to extract heat from the same space during the summer period. When operating as a heating system, heat is absorbed from an outside medium (either air, water, or the earth) and this heat, together with the heat equivalent of the work of compression, is supplied to space to be heated. When operating on the cooling cycle, heat is absorbed from the space to be cooled and this heat, together with the heat equivalent of the work of compression, is rejected to the outside medium.

    Heat Transfer

    Flow of heat by radiation, convection, or conduction. This term is sometimes used to mean rate of heat transfer. See CONVECTION; CONDUCTION; RADIATION.

    Heat Transfer Coefficient

    The quantity of heat transferred through a unit area of a material in a unit time per unit of temperature difference between the two sides of the material.

    Heat, Latent

    Change in heat content of a substance when its physical state is changed without a change in temperature; i.e., boiling or melting.

    Heat, Sensible

    That heat which, when added or subtracted, results in a change of temperature, as distinguished from latent heat.

    Heat, Specific

    The heat required to raise a unit mass of a substance through a degree of temperature difference. Also, the ratio of the thermal capacity of a substance to that of water at 60 degrees F (15.6 degrees C). Interchangeable with "heat capacity" in common usage.

    Heater, Construction

    A self-contained, unvented, portable heater intended for temporary use during construction, sometimes called a salamander.

    Heater, Infra-Red Radiant

    A self-contained, vented, or unvented heater used to convert the combustion energy to radiant energy, a substantial portion of which is in the infra-red spectrum, for the purpose of direct heat transfer.

    Heater, Make-Up Air

    A self-contained, vented, or unvented, gas-fired air heater used only to heat air from the outside to replace air which is leaking, being vented, or being discharged from a heated building. May be direct-fired or indirect-fired.

    Heater, Room

    A self-contained, free-standing, nonrecessed (except as noted below), gas-burning, air heating appliance intended for installation in the space being heated and not intended for duct connection. This shall not include heating appliances covered by other American Standard Approval or Listing Requirements. It may be of either the gravity or mechanical air circulation type, vented, or unvented. (In some areas, this is referred to as a space heater).

    Heater, Unit

    High static pressure type is a self-contained, automatically controlled, vented, gas-burning appliance, limited to the heating of nonresidential space.

    Heater, Vented Recessed

    A self-contained, vented appliance complete with grilles or equivalent, designed for incorporation in or permanent attachment to a wall, floor, ceiling, or partition, and furnishing heated air circulated by gravity or by a fan directly into the space to be heated, through openings in the casing. Such appliances shall not be provided with duct extensions beyond the vertical and horizontal limits of the casing proper, except that boots not to exceed 10 inches beyond the horizontal limits of the casing for extension through walls of nominal thickness may be permitted. Where such boots are provided, they shall be supplied by the manufacturer as an integral part of the appliance and tested as such. This definition shall exclude floor furnaces, unit heaters, and central furnaces.

    Heating Degree Day


    Heating Season Method


    Heating System, High-Pressure Steam

    A steam heating system employing steam at pressure above 15 psig.

    Heating System, High-Temperature Water

    A heating system in which water having supply temperature above 350 degrees Fahrenheit is used as a medium to convey heat from a central boiler, through a piping system, to the heating units.

    Heating System, Hot Water

    A heating system in which water having supply temperatures less than 250 degrees Fahrenheit is used as medium to convey heat from a central boiler, through a piping system, to the heating units.

    Heating System, Low-Pressure Steam

    A steam heating system employing steam at pressures below 15 psig.

    Heating System, Medium-Temperature Water

    A heating system in which water having supply temperatures between 250 and 350 degrees Fahrenheit is used as a medium to convey heat from a central boiler, through a piping system, to the heating units.

    Heating System, Steam

    A heating system in which heat is transferred from a boiler or other source to the heating units by means of steam.

    Heating Value

    The amount of heat produced by the complete combustion of a unit quantity of fuel. The gross of higher heating value is that which is obtained when all of the products of combustion are cooled to the temperature existing before combustion, the water vapor formed during combustion is condensed, and all the necessary corrections have been made. The net or lower heating value is obtained by subtracting the latent heat of vaporization of the water vapor, formed by the combustion of the hydrogen in the fuel, from the gross or higher heating value.


    Any method of minimizing the risk of price change. Since the movement of cash prices is usually in the same direction and about in the same degree as the movement of the present prices of futures contracts, any loss (or gain) resulting from carrying the actual merchandise is approximately offset by a corresponding gain (or loss) when the contract is liquidated.

    Helium (He)

    A colorless, odorless, inert gas, specific gravity 0.1368, found in some natural gas.

    Henry Hub

    A pipeline interchange, located in Vermilion Parish, Louisiana, which serves as the delivery point of natural gas futures contracts.

    Herfindahl-Hirschman Index (HHI)

    A measure of market concentration. The index is frequently used by the Department of Justice and the Federal Trade Commission to analyze mergers and acquisitions.


    Any of 5 isomeric, volatile, liquid, paraffin hydrocarbons C6H14 found in petroleum.

    High Btu Gas

    A term used to designate fuel gases having heating values of pipeline specification, i.e., greater than about 900 Btus per standard cubic foot.

    High Btu Oil-Gas Process

    A manufactured gas process in which oil is converted into a fuel gas having a higher heating value than that of coal gas or carbureted water gas. Often called Hi-Btu Gas Process.

    High Fire

    An expression used for the design maximum rate of fuel input to a burner.

    High Pressure Distribution System


    High Sulphur No. 6 Oil

    Oil with sulphur content of more than 1% by weight.

    High Wall

    The unexcavated face of exposed over-burden and coal.

    High-Density Polyethylene

    Type III polyethylene with a density of 0.941 to 0.965 g/cubic centimeters.

    High-Priority Customers

    Customers with priority in use in utility curtailment

    High-Priority Use

    The use of gas in a residence, commercial establishment using less than a set volume (i.e., 50,000 cubic feet per day), school, hospital, or similar institution, any use which, if curtailed, would endanger life, health or maintenance of physical property.

    Highest Allowed Regulated Rate Clause

    A provision in a gas sales contract that specifies that the price paid for the gas would be the highest allowed regulated price.

    Hinshaw Amendment

    An amendment to the Natural Gas Act which exempts from Federal Energy Regulatory Commission regulation the transportation and sale for resale of natural gas received within the boundaries of a state, provided (1) all such gas is ultimately consumed within the state, and (2) the facilities and rates are regulated by the state. Pipelines qualifying under this amendment are called Hinshaw Pipelines.

    Historical Cost

    The actual cost of land, buildings, pipelines and other plant items to the company, when used in ratemaking it assumes the company's acquisition costs are prudent. The difference with original cost is the acquisition adjustment. See ORIGINAL COST.


    A European term used to describe the surface below the range burner. Sometimes referred to as the burner unit.

    Holder, Gas

    A gas-tight receptacle or container in which gas is stored for future use. (1) at approximately constant pressure (low pressure containers) in which case the volume of the container changes; and (2) in containers of constant volume (usually high pressure containers) in which case the quantity of gas molecules stored varies with the pressure.


    A common term which usually refers to the well bore. Mouse Hole and Rat Hole are shallow bores under the derrick in which the kelly joint and joints of drill pipe are temporarily suspended while making a connection. Rat Hole also refers to a hole of reduced size in the bottom of the regular well bore. Sometimes the driller "rat holes ahead" to facilitate the taking of a drill stem test when it appears that such tests will be desirable.


    A discontinuity or break in the anticorrosion protective coating on pipe, tubing, or fitting that leaves the bare metal exposed to corrosive processes.

    Holiday Detector

    An electronic device for locating discontinuities or breaks in the protective coating on a pipe, tubing, or fitting.

    Hoop Stress

    The tensile stress, usually in pounds per square inch (psi), acting on the pipe along the circumferential direction of the pipe wall when the pipe contains gas or liquid under pressure.

    Horsepower (hp)

    A unit of power; equivalent to 33,000 ft-lb per minute, or 550 ft-lb per second (mechanical horsepower), or 0.746 kilowatts.

    Horsepower Hour

    The equivalent of one horsepower expended for one hour. One horsepower hour equals 1,979,980 foot-pounds.

    Horsepower, Boiler (Bhp)

    The equivalent evaporation of 34.5 lbs. of water per hour at 212 degrees F and above. This is equal to a heat output of 33,475 Btu per hour.

    Horsepower, Brake (bhp)

    The power developed by the engine, as measured at the crank shaft or flywheel by the Prony brake or other device.

    Horsepower, Compressor

    The horsepower rating on the name plate.

    Horsepower, Indicated

    The horsepower determined from the pressure-volume indicator diagram. This is the power developed within the cylinder of the engine and is more than the power delivered at the driving shaft by the amount of mechanical friction.

    Hot Tap

    The connection of branch piping to an operating line, and the tapping of the operating line while it is under pressure.

    Hot Work

    Maintenance or construction work requiring welding, burning, grinding, or drilling.

    Hourly Peak

    The maximum demand for gas from a transmission or distribution system in a one hour period of time.

    House Riser, Gas

    The principal vertical pipe which conducts the gas from the meter to the different floors of the building.


    A market or supply area pooling/delivery where gas supply transaction point occur that serve to facilitate the movement of gas between and among interstate pipelines. Transactions can include a change in title, a change in transporter, or other similar items.


    A mechanical means of increasing the relative humidity by injecting water or water vapor into the air.


    A regulating device, actuated by changes in humidity, used for the automatic control of relative humidity.


    The entrained weight of water per unit weight of moisture-free gas or air.

    Humidity, Relative

    The ratio of the weight of water vapor in the atmosphere to the weight the air would hold if completely saturated at that temperature, expressed as a percentage.

    HVAC System

    A system that provides either collectively or individually the processes of comfort heating, ventilation and/or cooling within or associated with a building.


    A copyrighted name of an operation whereby producing formations are fractured by hydraulic pressure to increase productiveness.


    A solid ice-like material resulting from the combination of a gas with water under pressure. Of natural gas constituents -- methane, ethane, propane, isobutane, normal butane, and also hydrogen sulfide and carbon dioxide will form hydrates. The greater the pressure in the equipment, the higher the temperature at which the hydrate will form, usually well above freezing. Hydrates can cause restriction or stoppage of flow, and can be controlled by alcohol injection or by dehydration of the gas. Methane hydrates are found in some permafrost regions and beneath portions of the ocean floor and may eventually be a source of methane gas.


    A chemical compound composed solely of carbon and hydrogen. The compounds having a small number of carbon and hydrogen atoms in their molecules are usually gaseous; those with a larger number of atoms are liquid, and the compounds with the largest number of atoms are solid.

    Hydrocarbon, Saturated

    A chemical compound of carbon and hydrogen in which all the valence bonds of the carbon atoms are taken up with hydrogen atoms.

    Hydrocarbon, Unsaturated

    A chemical compound of carbon and hydrogen in which not all the valence bonds of the carbon atoms are taken up with hydrogen atoms.


    A catalytic process for converting high boiling hydrocarbon liquids to lighter, high-quality fractions such as gasoline, diesel fuel, etc., in the presence of hydrogen. Sufficient hydrogen is added such that no coke formation occurs.


    Process involving a reaction with hydrogen to remove sulfur compounds from hydrocarbon feedstock.


    The gasification of a suitable fuel by reacting it directly with hydrogen.

    Hydrogen (H2)

    A colorless, odorless, highly flammable gas used in hydrogenation of petroleum and for producing ammonia. Also, an important constituent of manufactured gas.

    Hydrogen Sulfide (H2S)

    A poisonous, corrosive compound consisting of two atoms of hydrogen and one of sulfur, gaseous in its natural state. It is found in manufactured gas made from coals or oils containing sulphur and must be removed. It is also found to some extent in some natural gas. It is characterized by the odor of rotten eggs.


    A process whereby hydrogen atoms are added to an organic molecule to form a new compound; such reactions usually require heat and pressure in the presence of a catalyst.


    Heating and/or cooling with circulated water.


    A method of effecting the pyrolysis of a fuel by contacting it with hot hydrogen.

    Hydrostatic Design Stress

    The estimated maximum tensile stress that can act in the wall of the pipe along the circumferential direction due to internal hydrostatic pressure, with a high degree of certainty that failure of the pipe will not occur. See PRESSURE RATING.

    Hydrostatic Strength (Quick)

    The hoop stress calculated by means of the ISO equation at which the pipe fails due to an internal pressure buildup, usually within 60 to 70 seconds.

    Hydrostatic Test

    A strength test of equipment (pipe) in which the item is filled with liquid, subjected to suitable pressure, and then shut in, and the pressure monitored. Also a test to determine whether a container will hold a certain pressure.


    A coal gasification process developed by the Institute of Gas Technology.

  • I

    Ideal Gas Law

    The ideal gas law is the combination of the volume, temperature, and pressure relationships of Boyle's and Charles' laws resulting in the relationship PV=RT. Real gases deviate by varying amounts from the ideal gas law. See SUPERCOMPRESSIBILITY FACTOR and LAWS.

    Ignition Temperature

    The temperature at which a substance, such as gas, will ignite and continue burning with adequate air supply.

    Ignition, Automatic

    A means which provides for automatic lighting of gas at the burner when the gas valve controlling flow is turned on and will effect relighting if the flame on the burner has been extinguished by means other than closing the gas burner valve.

    Ignition, Continuous

    Ignition by an energy source which is continuously maintained through the time the burner is in service, whether the main burner is firing or not.

    Ignition, Intermittent

    Ignition by an energy source which is continuously maintained through the time the burner is firing.

    Ignition, Interrupted

    Ignition by an energy source which is automatically energized each time the main burner is fired and subsequently is automatically shut off during the firing cycle.

    Ignition, Manual

    Ignition by an energy source which is manually energized and where the fuel to the pilot is lighted automatically when the ignition system is energized.


    The group of unsaturated or heavy hydrocarbons in a manufactured gas, such as ethylene and benzene, which burn with a luminous flame.


    When a party receives or delivers a quantity of natural gas, then delivers or redelivers a larger or smaller quantity of natural gas to another party.

    Immersion Length

    The length from the free end of a thermometer bulb or well to the point of immersion in the medium, the temperature of which is being measured.

    Impact Evaluation

    Examination of the effects of a DSM program, including quantitative documentation of a program's costs and benefits, program participation and measure adoption, performance of technologies, and energy impacts.

    Impact Resistance

    Energy required to break a specimen by a sudden blow.

    Impact, Izod

    A specific type of impact test made with a pendulum-type machine. The specimens are molded or extruded with a machine notch. See ASTM D 256.

    Impact, Tup

    A falling weight (tup) impact test developed specifically for pipe and fittings. There are several variables that can be selected. See ASTM D 2444.


    Any formation that prohibits the passage of fluid or gas through it.

    Impounding Area

    An area which is defined through the use of berms,

    Imputed Capitalization

    A method to adjust a projected capital structure for accumulated deferred income taxes.

    In Situ Coal Gasification

    Gasification of coal underground by introduction of air or oxygen into the coal seam.


    In DSM, a cash or non-cash award that is offered to encourage participation in a utility-sponsored DSM program.

    Incentive or Industrial Sales Programs (ISP)

    Special marketing programs that make gas available at more competitive prices, usually accomplished by reducing gas costs rather than redistributing fixed costs from one customer group to another.

    Incentive Program

    A DSM program in which an incentive is offered to encourage participation and adoption of the recommended measure.

    Incentive Rate of Return (IROR)

    A variable regulatory rate that reduces the allowed return in the event of cost overruns.

    Inch of Mercury

    A pressure unit representing the pressure required to support a column of mercury one inch high at a specified temperature; 2.036 inches of mercury (at 32 degrees F and standard gravity of 32.174 ft/sec2) is equal to a gauge pressure of one pound per square inch.

    Inch of Water

    A pressure unit representing the pressure required to support a column of water one inch high. Usually reported as inches W.C. (water column) at a specified temperature; 27.707 inches of water (at 60o and standard gravity of 32.174 ft/sec2) is equal to a gauge pressure of one pound per square inch.


    The process of reducing refuse material to ash.


    The trade name of an instrument used to determine whether or not the well bore is proceeding in a vertical orientation at any point. In most drilling operations, either government bodies or contract stipulations or both, provide a maximum deviation of the well bore from the vertical; commonly, this maximum is three degrees. When deviation is in excess of the allowable, it is necessary to modify drilling procedures to bring it back in line.

    Incremental Cost

    The additional costs incurred from the production or delivery of an additional number of units of gas, usually the minimum capacity or production that can be added. The additional cost divided by the additional capacity or output is defined as the incremental cost. Also, in DSM, the difference in costs between an efficient technology or measure and the alternative standard technology.

    Incremental Pricing

    A pricing mechanism established by the Natural Gas Policy Act of 1978. It is the passing through of certain costs of acquiring new gas by way of a surcharge and applying the surcharge to certain end uses by certain industrial facilities. In 1987, Title II, incremental pricing, of the NGPA of 1978 was repealed.

    Indefinite Price Clauses

    Contract clauses that cause the price of natural gas to increase. Usually of two types - favored nation clauses and oil related clauses. Favored nation clauses place


    As used in the oil industry, usually refers to a nonintegrated producing company. The integrated company usually operates production, transportation, refining, and marketing facilities. Generally, the independent producer has operations only in the field of petroleum production.

    Independent Petroleum Association of America (IPAA

    A trade group representing independent oil and gas producers.

    Independent Power Producer (IPP)

    Wholesale electric producer unaffiliated with the franchised utility in the area in which it is selling power.


    A general term for a measure; also applied to the mechanism, composed of gears, dials, and dial face, that indicates the quantity of gas passing through a meter.

    Index, Constant-Pressure Compensating

    An index used to indicate a gas volume converted to a constant base pressure when used in conjunction with a gas meter operated at a constant pressure other than the contract base pressure.

    Index, Meter

    The mechanism which displays the volume of gas that has passed through the meter. Indexes consist of two general types: The circular dial type employs a pointer which sweeps through a circle marked with numerals indicating volume registered. The direct reading (digital or counter type) type employs a display marked with numerals indicating volume registered.

    Index, Temperature Compensating

    A meter index display used to correct volume under flowing gas conditions to a base temperature, commonly 60oF.


    Tying the commodity price in a contract to other published prices, such as spot prices for gas or alternate fuels, or general indexes like the Consumer Price Index or Producer Price Index.

    Indicator, Demand

    A device that indicates on a scale, chart, or tape the maximum volume metered during a predetermined period of time.

    Indicator, Engine

    A mechanical device connected to an engine to draw a chart of cylinder pressure versus piston position from which the relation of the energy input and energy output of the engine may be computed.

    Indicator, Volume

    A component of a auxiliary device designed to indicate on a scale or chart, or both, the volume of gas passing through a meter in relation to time, temperature, pressure, or any combination thereof.

    Indirect Oven Thermostat System

    A control system of two or more integrated automatic devices to maintain a selected oven temperature. That portion of the system responsive to oven temperature causes operation of another portion of the system to turn on or shut off the gas supply to the oven burner.


    A heater in which combustion products do not come in contact with the material to be heated; heating of the material is accomplished by radiation or conduction from the heated surfaced. Compare DIRECT-FIRED.

    Industrial and Railroad Generating Stations

    Electric generating stations operated by industrial establishments and railroads to supply all or part of their own power requirements.

    Industrial Fuel Switching

    Switching from natural gas to alternate fuels such as residual or clarified oil by large industrial customers, primarily motivated by the relative fuel prices.

    Industrial Service



    A material not acted upon chemically by the surrounding environment. Nitrogen and carbon dioxide are examples of inert constituents of natural gases; they dilute the gas and do not burn, and thus add no heating value.

    Infield Exchange Agreement

    Contract specifying the terms and conditions for the exchange of wellhead gas production between different companies usually within the same producing field.

    Infill Drilling

    Drilling between existing well locations to extract pockets of gas that might otherwise be missed, or to increase deliverability from a production or storage field.

    Infill Well

    Any well drilled on a closer than normal well spacing pattern or requirement. Also, any well drilled between existing wells producing from the same reservoir.


    The air entering a space through a wall, crack, doors, and other openings.

    Infra-Red Radiation



    A chemical agent which slows or reduces chemical action. Inhibitors are used principally in liquid coolants to reduce corrosion of metal parts of the system and in well drilling fluids to reduce corrosion of metals in piping of equipment used in well drilling operations.

    Initial Delivery

    The first gas to flow under an agreement at a new facility or for a new contract.



    Injected Gas


    Injection Molding

    The process of forming a material by forcing it, under pressure, from a heated cylinder through a sprue (runner, gate) into the cavity of a closed mold. Fittings are usually made by this process.

    Injury/Illness Incidence Rate, Disabling

    The number of disabling occupational injuries and illnesses per 200,000 employee hours of exposure. This is computed by multiplying the number of disabling injuries and illnesses by 200,000 and dividing by the number of employee-hours worked. The hours worked should not include any non-work time such as holidays, vacations, and sick leave.

    Injury/Illness, Disabling

    An occupational injury or illness that results in a fatality or one or more days away from work.

    Input Rate

    The rate at which gas is supplied to an appliance. It may be expressed in Btu per hour (Btuh), thousands of Btu per hour (MBtuh); in cubic feet per hour (cfh); or thousands of cubic feet per hour (Mcfh); in therms (th) or dekatherms (Dth) per hour.

    Input Rating

    The gas-burning capacity of an appliance in Btu per hour as specified by the manufacturer. Appliance input ratings are based on sea level operation and need not be changed for operation up to 2,000 feet.


    Plastic, copper, etc., tubing inserted into a run of existing pipe, thereby eliminating the need for a new trench.

    Instantaneous Technical Potential

    An estimate of energy savings based on the assumption that all existing appliances, equipment, building-shell measures, and industrial processes are instantly replaced with the most efficient commercially available units.

    Instrument Piping

    All piping, valves, and fittings used to connect instruments to main piping, other instruments and apparatus, or measuring equipment.

    Insulation (Thermal)

    A material having a relatively high resistance to heat transfer.

    Intangible Plant

    Organization, Franchises and Consents, Patent Rights, Licenses, Privileges, and other intangible property necessary or valuable in the conduct of the utility's operations.

    Integrated Company

    A company which obtains a significant portion of its gas operating revenues from the operations of both a retail gas distribution system and gas transmission system.

    Integrated Gasification Combined Cycle

    A system to convert coal to clean combustible gas which fuels a combustible turbine generator.

    Integrated Resource Planning

    A utility planning method whereby alternative resource mixes, including demand-side and supply-side options, are evaluated in order to determine which resource plan minimizes the overall cost of service, subject to reliability and various other constraints.

    Integrating Device

    A mechanism designed to automatically correct a gas-volume-related input to some predetermined base conditions.

    Integrating Pressure-And-Temperature Instrument

    The integrating pressure-and-temperature instrument registers, on a counter, the total quantity of gas passed through the meter, reduced to standard cubic feet at a definite base pressure and base temperature. Each increment of volume is multiplied by a temperature-factor corresponding to the line-temperature and base-temperature. It is then multiplied by the pressure-multiplier corresponding to the line pressure and base pressure. The product is totaled on a counter index. A supplementary index is furnished which reads the total quantity passed at line conditions.

    Integrating Pressure-Instrument

    The integrating pressure-instrument registers the total volume of gas metered in cubic feet at a specified base pressure. This instrument is equipped with a second register which records the total volume at the flowing pressure. Each unit of volume flowing through the meter causes the integrating mechanism to make one cycle and apply the correct pressure multiplier for that unit. The summation of these products is registered on a counter index indicating the displaced volume at base pressure.

    Interactive Effects

    The effects that a change in one end-use's consumption in a given structure has on another end-use's consumption in that structure.


    A measure of the degree to which combustion characteristics of one gas are compatible with those of another gas. Two gases are said to be interchangeable when one gas may be substituted for the other gas without interfering with the operation of gas burning appliances or equipment.

    Interconnection, System

    A connection between two utility systems permitting the transfer of gas in either direction.

    Interest Charged to Construction-Credit


    Interested Parties

    In a rate case, interested parties are the pipeline company, its customers, the FERC Staff, and "others". The "others" are commonly known as intervenors, and they include such groups as state regulatory agencies, consumer groups, competing pipeline companies, and customers of customers.


    In ratemaking intergeneration refers to costs that are incurred by more than one generation of rate payers (e.g., depreciation). Section 9 of the Natural Gas Act requires a separate just and reasonable finding on any intergeneration costs even in Settlements.

    Interim Bill


    Interim Relief

    Relief granted by the Commission in response to an applicant's claim that a regulation would cause irreparable injury, special hardship or inequity to himself or the public.

    Interior Zones

    The portions of a building which do not have significant amounts of exterior surfaces. Such zones have heating or cooling needs largely dependent upon internal factors such as lighting. Compare EXTERIOR ZONES.


    A control to prove the physical state of a required condition, and to furnish that proof to the primary safety control circuit.

    Internal Combustion

    Pertains to any engine in which the heat or pressure necessary to produce power is developed in the engine cylinder by the combustion of a fuel.

    Interruptible Service

    Low priority service offered to customers under schedules or contracts which anticipate and permit interruption on short notice, generally in peak-load seasons, by reason of the claim of firm service customers and higher priority users. Gas is available at any time of the year if the supply is sufficient and the supply system is adequate.

    Interruptible Transportation Service (ITS)

    Low priority service offered to customers under schedules or contracts which anticipate and permit interruption on short notice, generally in peak-load seasons, by reason of the claim of firm service customers and higher priority users.


    With respect to natural gas companies, the transporting and sale of gas for resale across state lines.

    Interstate Gas

    Gas transported in interstate pipelines to be sold and consumed in states other than that state in which the gas was produced.

    Interstate Natural Gas Association of America (ING

    Trade group representing the interstate pipelines.


    A person, business entity, or public body that is granted the right to participate in a rate case or hearing.


    With respect to natural gas companies, the transporting and sale of gas for resale within the boundaries of a state.

    Intrastate Gas

    Gas sold and consumed in the state where it is produced and not transported in interstate pipelines.


    An electrical device for conversion of direct current to alternating current.

    Investment Tax Credit (ITC)

    The credit against federal income taxes provided by the Revenue Act for qualified depreciable assets after December 31, 1961, except for suspension periods October 10, 1966 to March 9, 1967, and April 18, 1969 to August 15, 1971. Tax Reform Act of 1986 repeals regular ITC for property placed in service after December 31, 1985.

    Investment Tax Credit Adjustments, Net

    The income account used by those companies which do not apply the entire benefit of the investment tax credit to income in the year in which such credit is realized. This account is used to record the charges for the current year's investment tax credit less the current year's amortization of the accumulated investment tax credits under a plan which spreads over the useful life of the qualified property additions or some shorter period the investment tax credit benefits applicable to that property.

  • J


    Just and Reasonable as in J&R rates. This is a subjective term in ratemaking.


    The space surrounding a cylinder of an engine through which a cooling liquid flows. Steam engine cylinders are sometimes heated by steam circulating through a jacket to prevent condensation on the inside cylinder walls. Also, the enclosure on an appliance such as a water heater, furnace, or boiler.


    A device used in cable drilling, shaped like two elongated links, attached to the drilling tool, and used to jar the bit on the upward stroke, thus preventing the bit from sticking in the well-bore; also used to increase the impetus of a force exerted to free objects stuck in the well-bore.


    A hydraulic device operated by pump pressure for the purpose of cleaning fluid out of the pits and tanks on a rotary drilling location.


    The process of burying offshore or river crossing pipelines by hydraulically blowing sand or dirt from beneath the pipelines.


    The connection between two lengths of material such as pipe. See LENGTH.


    The location at which two pieces of pipe or a pipe and a fitting are connected together. NOTE: The joint may be made by an adhesive, a solvent-cement, heat joining, or a mechanical device such as threads or a ring seal.

    Joint Compounds

    Materials to be used on pipe joints, primarily to lubricate the threads and secondarily to prevent leakage.

    Joint Costs


    Joint, Leaded

    A connection using lead as a sealant.

    Joint, Mechanical

    A connection in which two pieces of pipe are held together by mechanical means, bolts, or similar fasteners.

    Joint, Screwed (Threaded Joint)

    A connection in which an internal threaded fitting and an external threaded piece of pipe or other fitting are screwed together.

    Joint, Welded

    A connection made by the joining of metal parts in the plastic or molten state.

    Joule-Thomson Effect

    The cooling which occurs when a compressed gas is allowed to expand in such a way that no external work is done. The effect is approximately 7 degrees Fahrenheit per 100 psi for natural gas. See LAWS.

    Joule-Thomson Expansion

    The throttling effect produced when expanding a gas or vapor from a high pressure to a lower pressure with a corresponding drop in temperature.


    Portion of the company's activities that are subject to the rules and regulations of the particular government entity which regulates it.


    That part of a natural gas company's business which is subject to the rules and regulations of the Commission. Generally, the Commission has (1) rate jurisdiction over transportation and sales of gas for resale in interstate commerce and (2) certificate jurisdiction over those facilities (except purely gathering) used to transport gas across state lines in interstate commerce.

    Just and Reasonable

    Section 4(a) of the NGA of 1938 specifies that all rates and charges made, demanded, or received by any natural gas company for or in connection with the transportation or sale of natural gas ... shall be "just and reasonable." The term "just and reasonable" has been interpreted to apply to rates which are assessed without undue bias or discrimination that allow the natural gas companies to recover all prudently incurred costs applicable to rate payers, including a return on capital (i.e., the cost of capital) sufficient to maintain and support its credit and enable it to raise the money necessary for the proper discharge of its public duties.

  • K

    Kansas-Nebraska (KN) Method

    A method used to functionalize Administrative and General (A&G) costs. The "KN Method" initially classifies A&G costs as being related to either labor, gas plant, or other. The expenses classified as "other" are allocated to labor and plant on a pro rata basis. This pro rata basis is determined by the ratio of the total labor-related A&G costs and the total plant-related A&G costs to the total of both plant and labor-related A&G costs.


    The heavy square or hexagonal steel pipe which goes through the rotary table and turns the drill string (also called grief stem).


    The hydrocarbon that occurs naturally in oil shale.

    Kerosene, also Kerosine

    An oily liquid obtained in the distilling of gasoline in a temperature range from 174-288 degree C. A hydrocarbon of specific gravity of 0.747 to 0.775. Used as fuel for some internal combustion engines, heating equipment, and illuminating purposes. A heavy grade known as range oil is used for cooking and heating.

    Key Bed

    A rock stratum that can be identified over large areas and from which measurements can be taken to determine geologic structure.

    Key Seat

    In drilling a well, a channel, or groove cut in the side of the hole, parallel to the axis of the hole. Key seating takes place as a result of dragging action of pipe on a dog-leg. In machine work, a groove cut in a shaft or pulley bore parallel with the axis.


    A small diameter pipeline connected to the inlet side of a sending scraper trap which contains gas pressure exceeding that in the main pipeline for the purpose of propelling a cleaner-scraper into a main gas stream.

    Killing A Well

    The act of bringing under control a well which is blowing out; also applied to the procedure of circulating water and mud into a completed well before starting well operations.

    Kilowatt (KW)

    A unit of electrical work equivalent to 1,000 watts, 1.3414 horsepower, or .9478 Btu/sec. (See ELECTRIC ENERGY).

    Kinetic Energy

    Energy possessed by a body due to its own motion.

  • L


    Asbestos and magnesia plaster used on process equipment and piping as a thermal insulation.



    Land Man

    A person concerned with the acquisition of leases, clearing of land titles, payment of lease rentals, and other related activities.

    Landfill Gas

    Gas produced by aerobic and anaerobic decomposition of a landfill generally composed of approximately 55% methane and 45% carbon dioxide, sometimes refined with membrane methods to eliminate the carbon dioxide.


    Term usually applied to an interval in the cased hole (of an oil or gas well) where the top of a liner overlaps the bottom of a string of casing.


    To attach elevators to a section of pipe. Also, a slang term meaning to take hold of a variety of different objects around the drilling rig.

    Latent Heat



    A pipe in a gas distribution or transmission system which branches away from the central and primary part of the system.

    Laws, Physical - AMAGAT'S.

    See LEDUC'S below.

    Laws, Physical - AVOGADROS'.

    Under the same condition of temperature and pressure, equal volumes of all gases contain the same number of molecules.

    Laws, Physical - BOYLE'S.

    The volume of a perfect gas is inversely proportional to the absolute pressure at constant temperature.

    Laws, Physical - CHARLES'.

    The volume of a perfect gas under any condition of constant pressure is proportional to the absolute temperature.

    Laws, Physical - DALTON'S.

    Every constituent of a mass of gas enclosed within a vessel contributes to the pressure against the sides of the vessel the same amount that it would have exerted by itself had no other gas been present. The total pressure within a vessel is the sum of the partial pressures of each of the constituent gases.

    Laws, Physical - GRAHAM'S.

    The relative rates of diffusion of gases under the same conditions are inversely proportional to the square roots of the density of those gases.

    Laws, Physical - IDEAL GAS.

    The terms "ideal gas" and "perfect gas" are used in technical literature to describe a hypothetical gas which would follow a characteristic equation under all conditions; that is, PV=RT, where P=the absolute pressure, V=specific volume, R=constant for the specific gas, and T=absolute temperature.

    Laws, Physical - JOULE'S.

    There is no change of temperature when a gas expands without doing external work and without receiving or rejecting heat.

    Laws, Physical - JOULE-THOMSON EFFECT.

    The cooling which occurs when a compressed gas expands in such a manner that no external work is done and no heat is interchanged.

    Laws, Physical - LEDUC'S (AMAGAT'S).

    The volume of a gas mixture is equal to the sum of the volumes that would be occupied by each of the components of the mixture if at the temperature and pressure of the mixture.

    Laws, Physical - MARRIOTTE'S.

    See BOYLE'S.

    Laws, Physical - PASCAL'S.

    A pressure exerted on a confined liquid is transmitted equally in all directions throughout the liquid.

    Laws, Physical - PERFECT GASES.

    See IDEAL GAS.

    Laws, Physical - RAOULT'S.

    The vapor pressure of the solvent in a solution is proportional to the mole fraction of the solvent. This law has been of fundamental importance in the development of the theory of solutions.

    Laying Mains

    The complete operation of installing piping systems in towns or cities including trenching, joining sections of pipe, placing pipe in trenches, back-filling trenches, and cleaning up.


    A solution mining process to remove salt and form gas storage caverns in salt domes.

    Leak Clamp

    A clamp used to press and hold tight a gasket against a leaking section of pipe or pipe joint to seal the leak.

    Leak Detector

    A device for identifying and locating a gas leak.

    Leak Limiter

    A device to limit the escape of gas from the vent opening of a regulator in the event of a diaphragm failure, to not more than 1 cubic foot per hour of a gas having a specific gravity of 0.6 at 7 inches water column.

    Leakage Survey

    A systematic search for the purpose of locating leaks in a gas piping system.


    A contract between an owner (lessor) and a tenant (lessee), setting forth the compensation, terms, and conditions upon which the lessee may occupy or use property, real or personal, of the lessor. This may include the right to engage in exploration for and production of oil, gas, or other minerals.

    Lease and Plant Fuel

    Natural gas used in lease or plant operations as a fuel or for other lease or plant uses such as for gas lift operations.

    Lease Condensate

    A mixture consisting primarily of pentanes and heavier hydrocarbons which is recovered as a liquid from natural gas in lease or field separation facilities. See CONDENSATE.

    Lease Hound

    A landman whose primary duty is to procure leases on tracts of land for exploration and development of gas and oil products.

    Lease Separator

    A surface facility installed on a lease for the purpose of separating gases and/or water from liquid hydrocarbons.

    Leased Storage

    Natural gas storage facilities owned and controlled by a storage operator, quite often the interstate pipeline's affiliate. Capacity within these facilities is leased by customers, such as LDCs, who use the stored gas during cold weather. Leased storage gas is returned to the customer either in the market area (close to the recipient) or supply area (close to production).

    Leasehold Costs

    All costs related to obtaining an oil and gas lease.

    Least-Cost Planning



    A piece of pipe of the length delivered from the mill. Each piece is called a length regardless of its actual dimensions. This is sometimes called "joint", but "length" is preferred.


    A rock formation of local extent, formed by variation in sedimentation in the original formation of sedimentary beds.

    Life-of-the-Field Contract

    A contract where the producer commits his reserves for the life of the field.

    Lifeline Rates

    A rate structure applicable for residential customers which includes a specified block of energy use which is priced below the allocated cost to serve. The block of energy may be priced at a flat amount for the entire block or on a per unit basis.


    Last-in, first out method of inventory valuation in which the earliest acquired inventory is assumed to be still on hand; the most recently acquired is assumed to be sold first.


    One of the movable sections of a liquid-sealed gas holder. The vertical distance a liquid is pumped.

    Line Loss

    The amount of gas lost in a distribution system or pipeline. Compare UNACCOUNTED FOR GAS.

    Line Pack

    Natural gas occupying all pressurized sections of the pipeline network. Introduction of new gas at a receipt point "packs" or adds pressure to the line. Removal of gas at a delivery point lowers the pressure (unpacks the line).

    Line Pack, Gas Delivered From

    That quantity of gas delivered to the markets supplied by the net change in pressure in the regular system of mains, transmission, and/or distribution. For example, the change in the content of a pipeline brought about by the deviation from steady flow condition.

    Line Packing

    Increasing the amount of gas in a line section by increasing pressure to meet a heavy demand, usually of short duration.

    Line Pipe

    Steel pipe generally used to construct pipelines to transport petroleum and natural gas.

    Line Rider

    An employee who inspects a pipeline right-of-way for leaks or potential hazards. At one time, the line rider walked or rode horseback. Today, an automobile or light aircraft is used.


    An employee who inspects a pipeline right-of-way for leaks or potential hazards. At one time, he walked or rode horseback; today, he uses an automobile or a light aircraft.

    Liquefaction of Gases

    Any process in which gas is converted from the gaseous to the liquid phase.

    Liquefied Natural Gas (LNG)

    Natural gas which has been liquefied by reducing its temperature to minus 260 degrees Fahrenheit at atmospheric pressure. It remains a liquid at -116 degrees Fahrenheit and 673 psig. In volume, it occupies 1/600 of that of the vapor at standard conditions.

    Liquefied Petroleum Gas (LPG)

    A gas containing certain specific hydrocarbons which are gaseous under normal atmospheric conditions, but can be liquefied under moderate pressure at normal temperatures. Propane and butane are the principal examples.

    Liquids, Natural Gas

    Those liquid hydrocarbon mixtures which are gaseous at reservoir temperatures and pressures but are recoverable by condensation or absorption. Natural gasoline and liquefied petroleum gases fall in this category.

    Live Oil

    See OIL, LIVE.


    The amount of gas delivered or required at any specified point or points on a system; load originates primarily at the gas consuming equipment of the customers. Also, to load a pressure regulator is to set the regulator to maintain a given pressure as the rate of gas flow through the regulator varies. Compare DEMAND.

    Load Center

    A point at which the load of a given area is assumed to be concentrated.

    Load Curve

    A graph in which the load of a gas system or segment of a system is plotted against intervals of time.

    Load Density

    The concentration of gas load for a given area expressed as gas volume per unit of time and per unit of area.

    Load Dispatching


    Load Diversity

    The difference between the sum of the peaks of two or more individual loads and the peak of the combined load. See DIVERSITY FACTOR.

    Load Duration Curve

    A graph made by plotting data in order of magnitude against time intervals for a specified period. The ordinate may be an absolute quantity or percentage.

    Load Factor

    The ratio of the average requirement to the maximum requirements for the same time period, as one day, one hour, etc.

    Load Profile

    Pattern of a customer's gas usage, hour to hour, day to day, or month to month.

    Load Research

    The systematic gathering, recording, and analyzing of data describing customers' patterns of energy usage.

    Load Shape Effects

    The estimated changes in energy usage at specific times during the year that are caused by a DSM or other measure.

    Load Water

    Water used to prime a well after acidizing.

    Load, Base

    See BASE LOAD.

    Load, Connected

    The sum of the capacities or ratings of the gas-consuming apparatus connected to a supplying system or any part of the system under consideration.

    Load, Net

    The active requirement for gas at a particular time. Compare LOAD, CONNECTED.

    Local Distribution Company (LDC)


    Lock In (Unlock)

    Generally, to unseal a gas meter and start gas service by opening the meter stop (valve). Compare TURN-ON.

    Lock Out (Lock)

    Generally, to seal and lock a gas meter and shut off the stop (valve) so that gas cannot be used. Compare TURN-OFF.

    Lock-Up or Lock-Off

    The point at which a regulator or governor shuts of completely.

    Locked-In Period

    Normally settlement rates are developed using actual cost experience of the base period, as adjusted in the test period, allocated to estimated annual sales volumes. The company is at risk for any variations in costs and sales volumes. On rare occasions a pipeline company may settle on the basis of actual costs and sales volumes for a defined period of time called the locked-in period. The company has less downside risk in this type of settlement.

    Lockout Timing

    That period of time between the initial ignition trial and lockout by the ignition system.


    A record of performance. (a) The record of an engine, boiler, or other test. (b) A record of the progress in drilling a well.

    Log, Electric

    The recorded graph of the natural and induced electrical characteristics of rocks used as an indication of permeability and porosity and the possibility of contained fluids.

    Logging, Mud Analysis

    A continuous examination of the drilling fluid circulating in the well bore for the purpose of discovering evidence of oil or gas regardless of how small the quantities may be entrained in the fluid. When this service is utilized, a portable mud logging laboratory which is incorporated in a trailer is set up at the well. This method is widely used in drilling wildcat wells.

    Logging, Radioactive

    The logging process whereby a neutron source is lowered down the hole followed by a recorder. When a hydrogen-bearing strata is located (which may be petroleum or water), the neutrons are absorbed. They disintegrate the hydrogen atoms, releasing alpha particles. The higher the alpha concentration, the higher the hydrogen concentration.

    Long-term Burst

    The internal pressure at which pipe or fitting will, most likely, fail after 100,000 hours (11.43 years).

    Long-term Hydrostatic Strength

    The estimated tensile hoop stress in the wall of the pipe along the circumferential direction that when applied continuously will cause failure of the pipe, at 100,000 hours (11.43 years). This strength value is usually obtained by extrapolation of log-log regression equations or plots.

    Longitudinal Seams

    The weld which is used to manufacture pipe rolled or formed from plate.


    A paralleling of an existing pipeline by another line over the whole length or any part of it to increase capacity.

    Loss of Load Risk

    The evaluation of the risk of a system not adequately meeting the load demand of firm customers under normal operating conditions. It is based upon the evaluation of supply and capacity reliabilities and the uncertainty of demand forecast, weather variability, and other uncertainties.

    Lost Opportunity

    In DSM, an efficiency measure that is cost-effective but does not get installed, and which is unlikely to be cost-effective at a later time.

    Lost Opportunity Resources

    DSM resources that, if not installed initially, become more costly to exploit. An example is extra insulation when constructing a new building.

    Lost Revenues

    Revenues not collected by a utility due to the loss of sales as a direct result of DSM programs.


    Overlapping and sloping slats arranged to prevent entrance or exit of some substances but allow ventilation air to pass.

    Low Btu Gas

    Gas with a heating value of less than 250 Btu's per cubic foot. Typically heating values fall between 120 and 180 Btu's per cubic foot.

    Low Pressure Distribution System


    Low Priority Users

    An interruptible, industrial customer that has the ability to switch to an alternate fuel.

    Low Sulphur No. 6 Oil

    Oil with sulphur content of 1% or less.

    Low Water Cut-Off

    A device constructed so as to automatically cut off the gas supply when the surface of the water in a boiler falls to the lowest safe water level.

    LP Gas


    LP Gas--Air Mixtures

    Liquefied petroleum gases distributed at relatively low pressures and normal atmospheric temperatures which have been diluted with air to produce desired heating value and utilization characteristics.



  • M


    A distribution line that serves as a common source of supply for more than one service line.

    Main Extension

    The addition of pipe to an existing main to serve new customers.

    Main System


    Mains, Distribution

    Pipes transporting gas within service areas to the point of connection with the service pipe.

    Mains, Field and Gathering


    Mains, Gas

    Pipes used to carry gas from one point to another. As contrasted with service pipes, they carry gas in large volume for general or collective use.

    Mains, Transmission


    Major Natural Gas Company (Pipeline)

    Any natural gas company with combined sales for resale and gas transported or stored for a fee exceeding 50 million Mcf at standard conditions in each of the three previous calendar years.

    Make Up

    To attach, as drill pipe or a string of tools.

    Make-Up Air


    Make-Up Gas

    The contractual right to take gas volumes at a future date that were available but not taken on their designated date as with take-or-pay contracts.

    Make-Up Water

    Water added to a tank, boiler, or other vessel to maintain a pre-determined liquid level.

    Mandatory Carriage

    The obligation to carry, for a fee, gas offered by another party. Also known as COMMON CARRIAGE.


    An opening into a tank, boiler, furnace, vault, or other equipment through which a person can enter to service equipment; can be sealed with a removable plate or door.


    The conduit of an appliance which supplies gas to the individual burners. Also, a pipe to which two or more outlet pipes are connected.


    A tube in the shape of a U, partially filled with


    A lace-like hood or envelope (sack) of some refractory material which, when placed in position over a flame, gives light by incandescence.

    Manufactured Gas

    A gas obtained by destructive distillation of coal, by the thermal decomposition of oil, or by the reaction of steam passing through a bed of heated coal or coke. Examples are coal gases, coke or oven gases, producer gas, blast furnace gas, blue (water) gas, or carbureted water gas. The Btu content varies widely.

    Marginal Cost

    The cost of the next unit if it were purchased. See INCREMENTAL COST.

    Market Area

    Any area in which the company feels that gas can be sold in the public convenience and necessity to the benefit of the company and stockholders.

    Market Out

    A gas purchase contract provision which enables a pipeline to get out of its contract based upon changes in the marketability of gas.

    Market Potential

    In DSM, an estimate of the possible energy savings that would occur because of normal market forces, without the implementation of a DSM program. Compare ACHIEVABLE POTENTIAL, ECONOMIC POTENTIAL and TECHNICAL POTENTIAL.

    Market Requirement

    Volumes of gas needed by gas consumers and expressed in volume of daily demand and total annual volumes.

    Market Sensitive Contract

    A contract whose pricing and sales quantity terms can be adjusted to reflect changes in supply and demand conditions.

    Market-Based Pricing

    The basing of a longer-term contract or rate schedule on published current market prices of competing supplies of natural gas or alternate fuels. Also known as MARKET-RESPONSIVE PRICING.

    Market-Responsive Pricing



    Entity which sells natural gas it has purchased from a producer or other seller.

    Marketer (Broker)

    A non-regulated buyer and seller of natural gas.

    Marketing Affiliate

    A marketing company that has corporate ties to an interstate pipeline, an intrastate pipeline, or a local distribution company.

    Marsh Gas

    Methane (CH4) the primary constituent of natural gas. Results from the partial decay of plants in swamps.

    Massachusetts Formula

    A method used to allocate costs incurred by a parent company on behalf of its affiliates to those affiliates. The "Mass Formula" has three parts using the allocation factors (ratios comparing the affiliate to the company as a whole) of gross plant, gross revenues, and labor, which are added together and then divided by three to arrive at a simple average of the three factors. This formula attempts to weight various aspects of each of the affiliates so that a fair distribution of the overhead cost is allocated to each affiliate member. Compare to DISTRIGAS METHOD.

    Materials Transportation Bureau (MTB)

    An independent office reporting to the Secretary of Transportation of the United States Government, charged with enforcing the Pipeline Safety Act. MTB, among other functions, receives reports of safety-related incidents from gas system operators and periodically issues revisions and interpretations to the Minimum Federal Safety Standard (49 CFR 192).

    Maximum Actual Operating Pressure


    Maximum Allowable Operating Pressure


    Maximum Daily Quantity

    The greatest quantity of gas to be received and/or delivered in a twenty-four hour period by the transporting pipeline on behalf of the shipper under terms defined in a contract. See MDQ.

    Maximum Day Allocation


    Maximum Efficient Rate (MER)

    The maximum rate at which oil can be produced without excessive decline of reservoir energy or a loss in ultimate production.

    Maximum Gas in Storage


    Maximum Transportation Rate

    The maximum rate that an open-access transporter may charge for its services. Section 284.7(c) of the Commission's regulations states that maximum rates for both peak and off-peak periods should ration capacity during peak periods and maximize throughput.

    Maximum Working Pressure

    The maximum actual operating pressure existing in a piping system during a normal annual operating cycle or the maximum pressure for safe operation of a system.


    The quantity of natural gas occupying a volume of one thousand cubic feet at a temperature of sixty degrees Fahrenheit and at a pressure of fourteen and seventy-three hundredths pounds per square inch absolute.


    The term MDQ refers to maximum daily quantity of gas which a buyer, seller, or transporter is obligated to receive or deliver at each receipt or delivery point or in the aggregate as specified in an agreement.

    Measuring and Regulating Station

    Facilities installed at a given location for measuring and regulating the flow of gas in connection with distribution system operations other than the measurement of gas deliveries to customers.

    Mechanical Equivalent of Heat

    The conversion factor for transforming heat units into mechanical units of work. One Btu equals 778 foot-pounds.

    Mechanical Rig

    A drilling rig whose source of power is one or more internal combustion engines.


    When the Federal Energy Regulatory Commission (FERC) issued a Notice Of Proposed Rulemaking (NOPR) wherein it served notice of its intention to totally restructure the natural gas industry, the NOPR was referred to as the "Mega" NOPR because of its scope.


    A group of organic chemical compounds containing an SH group having distinctive odors in small concentrations is often added to natural or LP gases to warn of leaks. Compare ODORANT.

    Merchant Obligation

    The buying and gathering of natural gas for resale.

    Meter Bar

    A metal bar for mounting a gas meter having fittings at the ends of the bar for connecting the inlet and outlet connections of the meter and to which, in turn, the gas service line and house piping are connected.

    Meter Book

    Book in which successive readings of utility customers' meters are recorded by gas utility meter readers. The difference between successive readings is the gas consumption for the period.

    Meter Class

    A designation for a range of meter capacity. The class for a given type of meter is determined by its minimum capacity based on 0.6 specific gravity gas at 0.5 inches of water column differential pressure, under specified test conditions. The capacity so determined must equal or exceed the class designation, but be less than the next higher class.

    Meter Cock


    Meter Density

    The number of meters per unit of area or per unit length of distribution main.

    Meter Index (Meter Register)

    That part of a meter which indicates the volume of gas passed through the meter.

    Meter Manifold

    Gas piping between gas service line and meter. Also, gas piping supplying two or more meters.

    Meter Seal

    A metal wire or tape seal attached to a gas meter or a service stop in such a way as to prevent its being opened by an unauthorized person.

    Meter Set (Meter Installation)

    The meter and appurtenances thereto, including the meter, meter bar, and connected pipe and fittings. Also called METER SET ASSEMBLY.

    Meter Stop

    A shut-off valve located on the inlet side of the meter. It may be integral with the meter bar.

    Meter Swivel

    The fitting that connects to the inlet and the outlet of a small gas meter.

    Meter, Diaphragm

    A meter which uses a flexible diaphragm in a bellows-type arrangement to measure the volume of gas. Compare METER, POSITIVE DISPLACEMENT.

    Meter, Gas

    An instrument for measuring and indicating or recording the volume of gas that has passed through it.

    Meter, Hard Case

    A meter in which the case is made of an inflexible metal, such as iron or aluminum.

    Meter, Orifice

    A meter using the differential pressure across an orifice plate as a basis for determining volume flowing through the meter. Ordinarily, the differential pressure is charted.

    Meter, Positive Displacement

    An instrument which measures volume on the basis of filling and discharging gas in a chamber. Compare METER, WET TEST.

    Meter, Proportional

    A meter which measures automatically a proportional part of the volume flowing past a metering point.

    Meter, Rotary Displacement

    An instrument which measures volume by means of rotating impellers, matching gears, or sliding vanes.

    Meter, Temperature Compensated

    One in which the measurement of gas volume is automatically corrected for variation in gas temperature.

    Meter, Tinned Case

    A meter in which the case is made of tinned sheet metal, with joints sealed with tin solder.

    Meter, Turbine

    A velocity measuring device in which the flow is parallel to the rotor axis and the speed of rotation is proportional to the rate of flow. The volume of gas measured is determined by the revolutions of the rotor and converting them to a continuously totalized volumetric reading.

    Meter, Venturi

    A meter using the static pressure differential between the meter entrance and the throat as a basis for determining volume flowing through the meter.

    Meter, Wet Test

    A positive displacement meter using a liquid, usually water, as a sealant and as one side of the displacement chamber, to measure gas volume.


    Catalytic upgrading of synthetic fuel gas to high Btu. Hydrogen and carbon monoxide react to form methane.

    Methane (CH4)

    The first of the paraffin series of hydrocarbons. The chief constituent of natural gas. Pure methane has a heating value of 1012 Btu per cubic foot.


    The second stage of the anaerobic conversion of a biomass feedstock to methane. The first stage converts the feedstock to an acid such as acetic acid. This acid is then converted to methane by microorganisms in the methanogenesis stage.

    Methyl ethyl ketone (MEK)

    An organic solvent widely used for preparing solvent cements, formula C2H5COCH3.


    The movement of oil, gas or water through porous and permeable rock.

    Mile Post Location

    The location in miles along a pipeline from 0.00, usually expressed in hundredths of a mile.


    One tenth of a cent.

    Mined Cavern

    A storage concept for LNG that is under investigation in which LNG is stored in the earth in caverns mined in various rock formations (e.g., limestone, shale, chalk, granite, dolomite) by conventional or solution mining. Both insulated and uninsulated cavern storage have been proposed. The concept has been used successfully with liquefied petroleum gases (LPG).

    Mineral Right

    The ownership of the minerals under a given surface with the right to enter thereon, mine, and remove them. It may be separated from the surface ownership, but if it is not so separated by distinct conveyance, the latter includes it.

    Minimum Bill Clause (Minimum Charge)

    A clause in a rate schedule which provides that the charge for a prescribed period shall not be less than a specified amount.

    Minimum Commodity Bill

    Provisions in a rate schedule (jurisdictional) or contract (nonjurisdictional) requiring customers to purchase minimum annual volumes of gas or, under certain circumstances, pay the fixed cost portion of the commodity rate on any volumes which fall below the minimum volume level. The Federal Energy Regulatory Commission has stated in Atlantic Seaboard the three factors needed to justify a minimum bill: (1) protecting the pipeline against the risk of not recovering the fixed costs in the commodity component; (2) protecting full requirements customers from bearing a disproportionate share of the fixed costs resulting from swings off the system by partial requirements customers; and (3) protecting customers from take-or-pay liabilities that the pipeline might otherwise bear.

    Minimum Federal Safety Standard--Part 192

    This refers to Title 49, Part 192, of the code of Federal Regulations and contains the legal minimum requirements for gas transportation within the United States.

    Minimum Transportation Rate

    The minimum rate which an open-access transporter may charge for service. Section 284.7(d) (4) (ii) states that any minimum rate must be based on the average variable costs which are properly allocated to the service to which the rate applies.

    Minor Items

    (Definition taken from the FERC Uniform System of Accounts, effective April 1, 1986). "Minor Items of Property" means the associated parts or items of which retirement units are composed ("Definitions" Item 18).

    Mixed Gas

    Fuel gas in which natural or LP gas is mixed with manufactured gas.


    The combination of mixer head, mixer throat, and mixer tube. Mixer Head. That portion of an injection type burner, usually enlarged, into which primary air flows to mix with the gas stream. Mixer Throat. That portion of the mixer which has the smallest cross sectional area and which lies between the mixer head and the mixer tube. Mixer Tube. That portion of the mixer which lies between the throat and the burner head.

    Mixer Face

    The air inlet end of the mixer head.

    Mixture, Lean

    A gas-air mixture of which the air content is more than adequate for complete combustion and the resultant combustion gases will contain an excess of oxygen.

    Mixture, Rich

    A gas-air mixture of which the air content is not sufficient for complete combustion.


    A thermal unit of energy equal to 1,000,000 Btus, that is, the equivalent of 1,000 cubic feet of gas having a heating content of 1,000 Btus per cubic foot, as provided by contract measurement terms. See DEKATHERM.


    A million cubic feet. See CUBIC FOOT.

    Modified Btu Method

    A modification of the Btu Method of allocating costs between different operations or between different products.

    Modified Fixed Variable


    Modified Fixed-Variable (MFV) Method

    A method for classifying fixed costs among demand and commodity charges in which all fixed costs except return on equity capital and related income tax items are classified to the demand charge. This method generally replaced other methods used by the Commission for classifying demand costs when first approved in the mid-1980s. The MFV method of cost classification usually is accompanied with a rate design methodology which employs a two-part (D-1 and D-2) demand and a commodity rate structure. See FIXED-VARIABLE METHOD, ATLANTIC-SEABOARD METHOD, CLASSIFICATION UNITED METHOD and VOLUMETRIC RATES.

    Modified Seaboard Method


    Molecular Weight

    The sum of the atomic masses of the elements forming the molecule. In high polymers the molecular weights vary so widely they must be expressed as averages.

    Molecular Weight Distribution

    The ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) gives an indication of the distribution.

    Molecular Weight, Weight Average (Abbreviation Mw)

    The sum of the total weight of molecules of each size multiplied by their respective weights divided by the total weight of all molecules.


    To sense the presence of a flame. The device which does this is called a flame monitor. Also, to analyze and record various desired and undesired components of an atmosphere, or stream of flowing gas or fluid.

    Monitoring Regulator

    A pressure regulator set in series with a control pressure regulator for the purpose of automatically taking over the control of the pressure downstream in case that pressure tends to exceed a set maximum.

    Monthly Service

    A predefined monthly period in which daily services are summarized for invoicing and imbalance statements. Typically billing months are not calendar months, except for large volume and special use customers. See CYCLE BILLING.


    Rating Quality Description:

    Moody's Bond Ratings


    Moody's Bond Yield (Annual Averages of Monthly Yie

    Represents the average yield on 40 operating utility companies' bonds (10 each of Class Aaa, Aa, A, and Baa) as determined and rated by Moody's Investors Service. This "yield" is the arithmetic average of 12 months and is calculated on the basis of market price, interest rate, and on being "held to maturity".

    Moody's Stock Quality Groups

    Preferred and Common Stocks: High Quality - High quality by all standards. Good Quality - Possesses many favorable high-grade investment attributes. Medium Quality - Medium grade equity securities.

    Motion Rates

    Rates placed into effect subject to refund at the end of the five month suspension period by the motion of the company. These rates are not necessarily the same as the company's filed rates.

    Moving-Bed Gasifier

    A gasifier in which coke is fed into the top keeping the gasifier essentially full when operating. Ash is removed at the bottom while the coal is consumed as it moves downward through the bed.

  • N


    National Appliance Energy Conservation Act of 1987 mandates minimum energy efficiency standards for most major residential appliances.

    Name Plate Rating

    The full-load continuous rating of a generator, prime mover, pump, compressor, or other equipment under specified conditions as designated by the manufacturer. It is usually indicated on a name plate attached mechanically to the individual machine or device.


    A loosely defined petroleum fraction containing primarily aliphatic (linear) hydrocarbons with boiling points ranging from 125o to 240o C. It is thus intermediate between gasoline and kerosene, and contains components of both. Its principal uses are in solvents and paint thinners and as a raw material for the production of organic chemicals, but it has been used as a raw material for the production of synthetic natural gas.

    Naphtha Stripper

    A piece of equipment in which light hydrocarbon fractions are removed from naphtha for recovery or sale.

    National Association of Regulatory Utility Commiss

    A voluntary organization composed of federal and state regulatory commissioners who have jurisdiction over transportation agencies and public utilities.

    National Energy Act of 1978 (NEA)

    A comprehensive energy statute comprised of five separate but intertwined public laws dealing with energy conservation (The National Energy Conservation Policy Act, P.L. 95-619); coal conversion (The Powerplant and Industrial Fuel Use Act, P.L. 95-620); public utility rates (The Public Utility Regulatory Policy Act, P.L. 95-617); natural gas pricing (The Natural Gas Policy Act, P.L. 95-621); and a series of taxes (Energy Tax Act, P.L. 95-618) designed to discourage energy consumption and to accelerate the transition to alternative fuels. The five bills were signed into law on November 9, 1978. The main purpose of the NEA is to reduce oil imports and promote more efficient use of energy in this country.

    National Fuel Gas Code

    A code that provides general criteria for the installation and operation of gas piping and gas equipment on consumers' premises. The code is sponsored by both the National Fire Protection Association (NFPA-54) and the American National Standards Institute (ANSI Z223.1).

    National Gas Transportation Association (NGTA)

    Formerly the National Transportation & Exchange Association. A group that promotes understanding of the national pipeline grid and is working toward standardization in the industry.

    National Historic Preservation Act (NHPA)

    Federal legislation requiring archaeological and cultural review of areas identified for new pipeline construction and other utility right-of-way.

    National Transportation Safety Board (NTSB)

    An independent agency reporting administratively to the Secretary of Transportation, charged with the investigation of all safety-related incidents involving transportation. These include air, rail, highway, and liquid and gas pipeline transportation. The NTSB has no power to issue regulations; however, it issues reports and recommendations.

    Native Base Gas


    Native Gas


    Natural Gas


    Natural Gas Act of 1938

    A federal law giving the Federal Energy Regulatory Commission (formerly the Federal Power Commission) jurisdiction over companies engaged in interstate sale or transportation of natural gas.

    Natural Gas Condensate


    Natural Gas Design Stress

    The estimated maximum tensile stress in the wall of the pipe in the circumferential orientation due to internal natural gas pressure that can be applied continuously with a high degree of certainty that failure of the pipe will not occur.

    Natural Gas Distillate

    Material removed from natural gas at the "heavy end" portion; that is, aliphatic compounds ranging from C4 to C8.

    Natural Gas Liquids

    The hydrocarbon components: propane, butanes, and pentanes (also referred to as condensate), or a combination of them that are subject to recovery from raw gas liquids by processing in field separators, scrubbers, gas processing and reprocessing plants, or cycling plants. The propane and butane components are often referred to as liquefied petroleum gases or LPG.

    Natural Gas Pipeline Safety Act of 1968 (Amended b

    The federal law providing jurisdiction by the Federal Government over the transportation of gas which includes transmission and distribution and gathering operations in urban areas. The Secretary of Transportation, acting through the Materials Transportation Bureau, enforces the Act. Title 49 of the code of federal regulations, Part 192, contains the regulations issued under this Act. Department of Transportation (DOT) contracts with state regulatory agencies for some aspect of enforcement.

    Natural Gas Reserves


    Natural Gas Shrinkage


    Natural Gas Supply Association (NGSA)

    A trade group representing major integrated gas producers, medium-sized companies and independents.

    Natural Gas Vehicle (NGV)

    A vehicle that is equipped to operate using natural gas, either as the sole fuel (a dedicated NGV) or as an option (a dual-fuel NGV).

    Natural Gasoline

    Liquid removed from natural gas by absorption or refrigeration and containing hydrocarbons heavier than butane.

    Needle, Fixed

    A tapered projection, the position of which is fixed, coaxial with an orifice which can be moved with respect to it, to regulate the flow of gas.

    Net Plant

    In accounting, Utility Plant less Accumulated Provision for Depreciation (including Depletion) and Amortization.

    Net Salvage

    In accounting, the difference between gross salvage and cost of removal resulting from the removal, abandonment or other disposition of retired plant. Positive net salvage results when gross salvage value exceeds removal costs. Negative net salvage results when removal costs exceed gross salvage value. Positive net salvage decreases the cost to be recovered through depreciation expense and negative net salvage increases it.

    Net-Back Pricing

    A contractual arrangement in which the price of gas at the wellhead is based upon what it sells for at the burnertip less applicable transportation and distribution charges.

    Netback Pricing Basis

    The supplier receives a percentage of the price for which the product is sold.


    A system of transmission or distribution lines so cross-connected and operated as to permit multiple supply to any principal point on it.

    Neutron Log

    A log of geological strata and the fluid contents therein, recorded by a nuclear device.

    New Construction Program

    A DSM program that affects the design and construction of new buildings and facilities.

    New Field Discoveries

    The volumes of proven reserves of crude oil, natural gas, or natural gas liquids discovered in new fields during the current or report year.

    New Gas

    Gas produced from wells drilled on production leases acquired on or after February 19, 1977.




    See NATURAL ENERGY ACT of 1978.


    Tubular pipe fitting, usually threaded at both ends.

    Nitrogen (N2)

    An odorless, colorless, generally inert gas. It comprises 79% of the earth's atmosphere in the free state.

    Nitrogen Purge

    To purge piping or other container with an inert agent such as nitrogen to remove combustible gases and minimize the possibility of fire or explosion.

    No-Bump Rule (or Flowing Gas No-Bump Rule)

    A tariff provision applicable to interruptible transportation which provides that a shipper may temporarily lose its ability to receive its full contract volumes if it ships at a lower volume. Under the no-bump rule, a shipper currently flowing gas cannot be bumped (lose capacity) because a shipper with a higher priority in the interruptible transportation queue decides to increase its receipt of gas within its transportation contract.

    No-Notice Delivery Service

    Delivery of natural gas on as-needed basis, without the need to precisely specify the delivery quantity in advance. No-notice delivery is generally made at the city gate or burner tip.

    Nominal Pipe Size (NPS)

    Designates a method of identifying the size of steel pipe without compromising the actual diameter data. Thus nominal 1 inch pipe with the actual external diameter of 1.315 inch (33.40 mm) becomes NPS 1; nominal 14 inch pipe with internal diameter of 13.250 inch (336.55 mm) becomes NPS 14.

    Nominal Wall Thickness


    Nominated Volume

    The physical quantity of gas requested, typically in MMBtu/day, for a specific contract or for all contracts at a specific point.


    A request for a physical quantity of gas under a specific purchase, sales or transportation agreement or for all contracts at a specific point. A nomination will continue for specified number of days or until superseded by another service request for the same contract.

    Nomination Allocation



    A precise listing of the quantities of gas to be transported during any specified time period. A nomination includes all custody transfer entities, locations, compressor fueled and other volumetric assessments, and the precise routing of gas through the pipeline network.

    Non-Core Customers

    End-users with enough gas volume to justify consideration of transportation-only service from the distributor. Compare CORE CUSTOMERS.

    Non-Hydrocarbon Gases

    Typical non-hydrocarbon gases which may be present in natural gas are carbon dioxide, nitrogen, hydrogen sulfide, and helium.

    Non-Operating Interest

    A share in the mineral interest which is without operating burdens. Close to royalty interest.


    The working interest owner(s) other than the owner designated as the operator of the property.


    Any customer who is eligible but does not participate in a utility DSM program in a given year.


    Failure to deliver gas under a contract or agreement.


    A substance or gas that will not burn.

    Nondestructive Testing

    A method of testing strength or mechanical integrity of a piece of equipment without damaging the item being tested. Examples are radiography, ultrasonic testing, acoustic emissions testing.

    Nonfirm Gas

    Gas which is not required to be delivered or not required to be taken under the terms of a gas purchase contract.


    Generally used to denote activities or companies not subject to control and regulation by the Commission. (Much of the natural gas business not subject to control and regulation by the Commission and, therefore, referred to as nonjurisdictional is subject to regulation by State Regulatory agencies).

    Nonmajor Natural Gas Company

    Any gas company having gas sales or volume transactions exceeding 200,000 Mcf at standard conditions in the previous calendar year and is not classified as a MAJOR NATURAL GAS PIPELINE.

    Nonutility Property

    Title of Account 121, which includes the book cost of land, structures, equipment or other tangible property owned by the utility but not used in utility service and not property includible in Account 105 Utility Plant Held For Future Use.

    Normal Recovery Capacity

    Amount of water in U.S. gallons raised 100 degrees F per hour or per minute when calculated on a thermal efficiency of 70%, representing the water heated by a gas input of 1,190 Btu per gallon.

    Normal Test Pressures

    Those pressures specified for testing purposes at which adjustment of burner ratings and primary adjustments are made.

    Normalization, Accounting

    A method of allocation used for accounting for timing differences (such as differences between book and tax depreciation and income before taxes and taxable income). Under this method, income taxes for book purposes will be based on book income.

    Normalization, Weather

    The adjustments to historic or base period data to include the annual effect of changes in sales, revenues, and gas expenses (including Plant) to reflect differences from expected normal weather patterns or which are known and measurable with reasonable accuracy at the time of the filing and which will become effective by the end of the Test Period. See NORMALIZATION, ACCOUNTING.

    Notice of Inquiry (NOI)

    Procedure used by the Federal Energy Regulatory Commission to gather information on a specified industry issue. Normally calls for comments from all interested parties and in some cases, reply comments and/or public hearings.

    Notice of Proposed Ruling (NOPR)

    A proposal by the FERC to change its rules. Sometimes preceded by a Notice of Inquiry. Normally calls for comments from all interested parties and in some cases, reply comments and/or public hearings. A NOPR may or may not result in a final rule.

    Nozzle, Flame Retaining

    Any burner nozzle with built-in features to hold the flame close to the burner at high mixture pressure or high velocities.

  • O


    Shredded hemp fibers used to caulk or fill joints, as in bell-and-spigot pipe; oakum may be dry or saturated with tar or oil.

    Observation Well


    Observed-Life Table

    A table of plant experience relating (1) survivors exposed to retirement at the beginning of each age interval to (2) the actual retirements during each interval. The table may reflect all past experience or only a selected band of years.


    A process that brings about the retirement of plant prior to its physical degeneration by the development of new types of plant which are more economical, efficient, versatile and reliable.

    Occupational Safety and Health Act (OSHA)

    A federal law, Public law 91-596, enacted in 1970, comprising federal standards for safety and health for people at work. The regulations issued under this Act can be found in Title 29, Part 1910, and Part 1926 of the Code of Federal Regulations.


    Any material added to natural or LP gas in small concentrations to impart a distinctive odor. Odorants in common use include various mercaptans, organic sulfides, and blends of these. Compare MERCAPTANS.


    The period during a day, week, month, or year when the load being delivered by a gas system is not at or near the maximum volume delivered by that system for the corresponding period of time.

    Off-Peak Service

    Service made available on special schedules or contracts but only for a specified part of the year during the off-peak season. Compare INTERRUPTIBLE SERVICE.

    Office of Fuels Programs

    The division of the U.S. Department of Energy that regulates imports and exports of natural gas.

    Offset Well

    A well drilled in the next location to another well according to the spacing rules of the state.

    Offshore Block

    A square in the geographic grid dividing offshore waters. The federal government leases them for oil and gas exploration.

    Oil Fogging

    Spraying a fine mist of oil into a gas stream of a distribution system to avoid the drying effects of gas in certain distribution and utilization equipment.

    Oil Gas

    See GAS, OIL.

    Oil Gravity

    The density of oil compared to the density of water, i.e., the specific gravity of the oil. (Measured in degrees by API, American Petroleum Institute). Oil with a low number is less valuable than with a high number.

    Oil Parity Clause

    A clause in some gas purchase contracts that ties the price of gas in the absence of price controls to some fraction of the Btu equivalent of the price of No. 2 fuel oil, No. 6 fuel oil, or crude oil.

    Oil Reforming

    Step in producing carbureted water gas in which a fraction of the carburetion oil is cracked to useful gas in the water gas carburetor and superheater.

    Oil Ring

    Oil in a reservoir underlying a gas-cap. In a reservoir on an anticlinal structure with a large gas-cap the center of the field area may consist only of gas wells with a ring of oil wells surrounding the gas producing area, hence the term oil ring.

    Oil Scrubbing

    The removal of certain impurities from manufactured or natural gas by passing the gas through an oil spray or bubbling the gas through an oil bath.

    Oil Shale

    A convenient expression used to cover a range of materials containing organic matter (kerogen) which can be converted into crude shale oil, gas, and carbonaceous residue by heating. Compare SHALE OIL.

    Oil, Heavy

    Heavy, thick, and viscous oils. Usually refinery residuals commonly specified as grades 5 and 6.

    Oil, Light

    Generally, all oils lighter than residual fuel oil No. 5 and No. 6. Oils that have a low specific gravity, usually products of controlled distillation of crude oil but also including by-product benzol and toluol.

    Oil, Live

    An oil containing dissolved gas.

    Oil, White

    The term given to natural gas liquids produced from refrigeration units at the well site.

    Oil-Gas Parity Pricing

    Conversion of costs per gallon oil price to an equivalent gas price in dollars per Mcf by application of appropriate oil/gas heat (Btu) conversion factors.

    Oilless Bearing

    Sleeve bearings of porous metal which depend solely on the porosity of the metal for oil storage.

    Old Gas

    Gas produced from wells as a result of well workover or stimulation of existing production wells on leases acquired prior to February 19, 1977.

    Old Gas Subsidy Cushion

    The difference between the price of gas from regulated, pre-NGPA gas suppliers and the market price of unregulated gas.

    Olefin Resin

    A resin made by the polymerization of any member of the ethylene series having but one double bond with the general formula CnH2n, e.g., ethylene, propene, etc.

    On-Site Generation

    Generation of any electrical energy on a customer's property, with or without utilization of recoverable heat.

    Open Access

    The non-discriminatory access to interstate pipeline transportation services.

    Open Access Transporter

    Once an intrastate or interstate pipeline commences self-implementing transportation services under Section 311 of the NGPA, it becomes an OPEN ACCESS TRANSPORTER and must then provide transportation services on an open access, nondiscriminatory basis and comply with the regulations set forth in Part 284 of the Commission's regulations. In addition, once an interstate pipeline accepts a Part 284 blanket certificate, it is then an open access transporter. A pipeline which is "open" under Section 311 may terminate such service and "close" its system. However, once a pipeline accepts a blanket, it may not terminate open access services without first receiving Commission authorization to abandon its blanket certificate.

    Open Pressure

    The pressure on a gas well that has been open long enough for the pressure to stabilize.

    Open Season

    Generally refers to a period of time when all parties are given equal consideration. Also, when a company becomes an open access transporter, it is generally expected to have an "open season" to accept bids for transportation. During that time all shippers are treated equally in the queue for service, with space divided on a pro rata basis. After the open season is over, shippers are generally treated on a first-come, first-served basis.

    Open-Flow Test

    A test made to determine the volume of gas that will flow from a well in a given time when flowing unrestricted and open to the atmosphere. This is usually calculated from pressure tests of restricted flow.

    Operating Costs

    Recurring costs related to day-to-day operations of a facility that are paid out of current revenue.


    An entity which manages and controls a facility and the gas moving through that facility. The operator performs the day to day operations, contract scheduling, communications, and routinely monitors, tests, and repairs facilities and/or measurement equipment. The operator is not necessarily the owner. A producer operator operates a well. A transportation operator operates a gathering system, pipeline or local distribution company. A plant operator operates a processing or extraction plant. A consumer operator operates an end user facility.

    Opportunity Cost

    A method to determine the cost of common equity component of return using the cost of capital of other investments of similar risk.

    Optimum Air Supply

    Volume of air delivered to a burner that will produce the maximum thermal efficiency under specific operating conditions.

    Optional Expedited Certificate

    A certificate provided for by FERC Order 436 aimed at reducing regulatory hurdles for obtaining a certificate of public convenience and necessity prior to commencing construction of an interstate pipeline or any extension thereof.

    Order 636

    The FERC order which implemented the provisions outlined in the Mega-NOPR.

    Order to Show Cause

    An order issued by the Commission or a court to bring a question for hearing. The party served with the order is directed to show cause, on the date set in the order, why the action desired by the party bringing the order should not be taken.

    Organic Sulfur

    Compounds of carbon, sulfur, and hydrogen that are found in gas, such as thiophene.


    The opening in an orifice cap, orifice spud, or other device whereby the flow of gas is limited and through which the gas is discharged.

    Orifice Cap (Hood)

    A movable fitting having an orifice which permits adjustment of the flow of gas by the changing of its position with respect to a fixed needle or other device.

    Orifice Meter


    Orifice Plate

    A plate of noncorrosive material which can be fastened between flanges or in a special fitting perpendicular to the axis of flow and having a concentric circular hole. The primary use is for the measurement of gas flow.

    Orifice Plug

    A small plug with an orifice to admit gas into the mixing chamber of a burner. Sometimes called a spud.

    Orifice Spud

    A removable plug or cap containing an orifice which permits adjustment of the flow of gas either by substitution of a spud with a different sized orifice or by motion of a needle with respect to it.

    Original Cost

    The actual cost of land, buildings, pipelines and other plant items (in the Code of Federal Regulations) "to the person first devoting it to public service." (Distinguished from the cost to a subsequent owner of acquiring such property after it is already "devoted to public service"). In ratemaking a rate base developed on original cost will not include the difference between the pipeline's acquisition cost and the original cost of facilities acquired. See HISTORICAL COST.

    Orsat Analysis

    Measurement of the quantitative amounts (by volume) by selective absorption of carbon dioxide, oxygen, and carbon monoxide in a gas using an Orsat apparatus.

    Other Entries (To Utility Plant)

    Includes Transfers between functional utility plant groups, adjustments to utility plant to record its "Original Cost," direct credits to utility plant for depreciation, depletion, or amortization, and other charges or credits not properly classifiable as gross additions or retirements.

    Other Property and Investments

    A group of balance sheet accounts which includes Non-Utility Property, Accumulated Provision for Depreciation and Amortization of Non-Utility Property, Investment in Associated Companies, Other Investments, and the Special Funds Accounts.

    Outdoor Exposure

    Plastic pipe and plastic equipment stored so that it is not protected from the elements of normal weather conditions, i.e, the sun's rays, rain, air and wind.

    Outer Continental Shelf (OCS)

    The submerged lands extending from 3 miles offshore to some undefined outer limit, usually a depth of 200 meters. It is the portion of the shelf under U.S. jurisdiction.

    Oven, Indirect

    One in which the flue gases do not flow through the oven compartment.



    Overfire Air

    Modification to allow an increase of air entering the furnace above the fire and reduction of air entering near the coal.


    The technique of increasing the maximum pressure in a natural gas storage reservoir above the discovery pressure.

    Overrun, Authorized

    On a daily basis, gas allowed in advance to be taken, within specified parameters, above contract demand volume. On a monthly, seasonal or annual basis, gas allowed in advance to be taken above a customer nominated level. Generally must be offset by reduced volumes being taken within some specified period subsequent to the allowed excess volumes taken. See OVERRUN, UNAUTHORIZED.

    Overrun, Unauthorized

    Gas taken that is not authorized is unauthorized. On a daily basis, that quantity of gas taken over and above the contract demand and not provided for by special authorization is unauthorized. On a monthly, seasonal or annual basis gas taken above a customer's nominated level without advance authorization. See OVERRUN, AUTHORIZED.


    A legal entity which has ownership interest in a fixed asset, product, pipeline or well.

    Oxygen (O2)

    A gas which forms about 21%, by volume, of the atmosphere. It is chemically very active and is necessary for combustion. The combination of oxygen with other substances generally produces heat.

    Oxygen Deficiency

    An atmosphere containing oxygen at a concentration of less than 19.5% by volume and is not safe for breathing.

  • P


    See LINE PACK.

    Panhandle Formula

    A formula for calculating gas flow in large diameter pipelines, particularly at relatively high pressures and velocities. Compare WEYMOUTH FORMULA.

    Paper Hearing

    A procedure established by the Commission designed to permit the full development of a record for Commission decision, without the need for full adjudication before an Administrative Law Judge. The purpose of "paper hearings" is to shorten the amount of time necessary for the Commission to reach a final decision concerning a complex matter. Generally, the Commission itself requests the filing of information it believes necessary in order to render a decision, and permits parties to file comments on the information provided. "Paper hearings" were first established in Gas Inventory Charge cases.


    A white, tasteless, odorless, waxy substance composed of natural hydrocarbons and obtained from petroleum.


    Temporarily storing a shipper's excess gas so that shipper doesn't have to sell it at depressed prices.

    Partial Looping

    A method for increasing carrying capacity of a pipeline by constructing a series of pipe sections parallel to the main pipeline for a portion of the distance between compressor or pump stations and connecting them to the main pipeline at the beginning and end of each segment. This reduces pressure drop in the portions of the pipeline that are "looped" (i.e., with parallel sections), allowing an increased pressure drop in the unlooped sections and, thus, an increased flow rate. Over time, a series of partial loops may be constructed resulting in a complete, second, parallel pipeline. At which time the pipeline will be totally looped.

    Partial Participant

    A DSM customer who has installed only some of the DSM program measures recommended for the facility.


    The unit used by a utility to measure participation in its DSM programs; usually customers or households in the case of residential programs.


    Separate and minute particles in a gas stream. Also, those appearing in the atmosphere as a result of chimney effluent. See POLLUTION, ATMOSPHERIC.

    Pay Zone

    The producing formation.

    Payback Period

    The time required for the cumulative operational saving of a DSM (or other) option to equal the investment cost of that option.

    Payout Ratio

    The ratio of cash dividends on common stock to earnings available for common stock.

    Peak Day

    The one day (24 hours) of maximum system deliveries of gas during a year. Peak day data is used to, among other things, determine the allocation of certain costs between classes of service. The Commission sometimes required allocation based on an average of three continuous days of maximum deliveries (i.e., three day peak). See also DESIGN DAY.

    Peak Day Allocation


    Peak Day Curtailment

    Curtailment imposed on a day-to-day basis during periods of extremely cold weather when demands for gas exceed the maximum daily delivery capability of a pipeline or distribution system. Peak day curtailment is applied independent of seasonal curtailment and does not affect overall authorized volumes to customers under seasonal curtailment. See SEASONAL CURTAILMENT.

    Peak Day Design


    Peak Day Method

    An allocation method used to allocate demand costs to customer classes based on peak day.

    Peak Day Sendout


    Peak Hour

    The one-hour period of greatest total gas sendout or use.

    Peak Load


    Peak Load

    The maximum load consumed or produced by a unit or group of units in a stated period of time.

    Peak Responsibility

    The load of a customer, a group of customers, or part of a system at the time of occurrence of the system peak.

    Peak Shaving

    The use of fuels and equipment to generate or manufacture gas to supplement the normal supply of pipeline gas during periods of extremely high demand. This method prevents the expensive alternative of expanding pipeline facilities.


    Providing the gas that an LDC or other customer needs to get though an unexpectedly high-demand period.


    An accumulation of partially decayed vegetable matter. It is geologically less mature than lignite or coal and has a lower density since it has not been subjected to elevated temperatures and pressures. Btu content per unit volume is substantially less than for coal.

    Penetration Rate

    The annual rate at which a DSM measure is implemented, as a percentage of the measure's technical potential.

    Percentage of Proceeds Sales

    Rather than receiving a specified price for raw gas delivered to a gas processing plant, a producer may instead receive a specified price for residue gas and a percentage of the plant proceeds from the sale of the extracted natural gas liquids.

    Perfluorocarbon Tracer Technology

    The use of tracer elements to measure the air infiltration rates within residential and commercial buildings. A number of tracers and capillary absorption tubes are placed within the facility. Natural air infiltration forces the migration of tracers to the capillary absorption tubes. After a set time period, the capillary absorption tubes are analyzed using a gas chromatograph. The level of tracer found within the capillary absorption tube is indicative of the building's air infiltration rate.

    Permanent Set

    Any deformation in a piece of plastic (or metal) which remains after the removal of the load which caused the deformation.


    A measurement of the ability of a rock to transmit fluid.


    A measure of the effectiveness, over time, of a DSM measure, usually represented by the percentage of energy savings that remains each year. A decline in the energy savings of DSM options is usually caused by the following two factors: equipment degradation and consumer behavior.

    Persistence Study

    A study to assess changes in DSM program load impacts over time. See PERSISTENCE.


    An oil, flammable bituminous liquid that may vary from almost colorless to black, occurs in many places in the upper strata of the earth; is a complex mixture of hydrocarbons with small amounts of other substances, and is prepared for use as gasoline, naphtha, or other products by various refining processes.

    Phenolic Resin

    A synthetic resin produced by the condensation of a phenol with an aldehyde. Phenolic resins form the basis of a class of thermosetting molding materials.


    An acronym for Petroleum Industry Data Exchange. The American Petroleum Institute Subcommittee which is an electronic data interchange action group for the oil and gas industry.


    An instrument for measuring pressure or compressibility.


    A device used to clean the internal surface of a pipeline. Pigs are usually barrel shaped, made of metal, and covered with metal brushes. They may also have rubber or plastic cups and be made entirely of plastic. They are inserted into the pipeline by means of a device called a pig-trap and pushed through the line by pressure of the flowing fluid, usually gas. The forward movement of the pig, together with its rotation, cleans the rust, liquids, and other undesired substances from the pipeline; also called a go-devil.

    Pile, Sacrificial

    A mass of metal, usually scrap metal, used as an anode when a rectifier is used in cathodic protection. Also, the magnesium and aluminum anodes used in cathodic protection but which do not require an outside impressed voltage.


    A small flame which is utilized to ignite the gas at the main burner(s).

    Pilot Program

    A DSM program that is generally limited in scope or targeted to a select group of customers and is designed to test or build capability to deliver a full scale program. Compare FULL SCALE PROGRAM.

    Pilot, Continuous

    A pilot that burns without turn-down throughout the entire time the burner assembly is in service, whether the main burner is firing or not.

    Pilot, Expanding

    A pilot that burns throughout the entire time the burner assembly is in service, whether the main burner is firing or not. Upon a call for heat, the pilot is automatically expanded so as to reliably ignite the main burner. This pilot may be turned down automatically at the end of main burner flame-establishing period.

    Pilot, Intermittent

    A pilot which is automatically lighted each time there is a call for heat, it burns during the entire period that the main burner is firing.

    Pilot, Interrupted

    A pilot which is automatically lighted each time there is a call for heat. The pilot fuel is cut off automatically at the end of the main burner flame-establishing period.


    See PIPING.

    Pipe Coating

    A corrosion resistant material (such as asphalt or tar), sometimes with an outer wrapping, used to protect pipe.

    Pipe Tongs

    A hand or power tool for gripping or rotating pipe.

    Pipe, Coated

    Pipe that has been covered with a corrosion resistant coating or compound (such as asphalt or tar) to prevent corrosion from soil conditions.

    Pipe, Direct Burial Plastic

    Plastic pipe not protected by a steel sleeve.

    Pipe, Drill

    In rotary well drilling, the rigid pipe connection between the collar of the drill at the working level and the rotary table on the derrick platform. In addition to transmitting the driving power to the drill bit, the open drill pipe is used to force mud to and through the perforated drill bit for the purpose of cooling and lubricating the bit and picking up the cuttings so that they can be washed to the surface and removed.


    All parts of those physical facilities through which gas is moved in transportation, including pipe, valves, and other appurtenances attached to pipe, compressor units, metering stations, regulator stations, delivery stations, holders, and fabricated assemblies. See SYSTEM TYPE./p>



    Pipeline Capacity

    The maximum quantity of gas that can be moved through a pipeline system at any given time based on existing service conditions such as available horsepower, pipeline diameter(s), maintenance schedules, regional demand for natural gas, etc.

    Pipeline Condensate

    A liquid containing lower boiling aliphatic and aromatic hydrocarbons which may be found in natural gas production, transmission, and distribution pipelines. Condensation to a liquid phase is induced by the higher pressure and lower temperature conditions in the pipeline.

    Pipeline Fuel

    Natural gas consumed in the operation of a natural gas pipeline, primarily in compressors.

    Pipeline Marketing Affiliate

    Marketer which is a subsidiary of an interstate pipeline.

    Pipeline Patrol

    A general inspection of the pipeline right of way by foot, airplane, or land vehicle to observe surface conditions and activity along or on the right of way and noting changes in vegetation growth for indication of gas leakage.

    Pipeline Peaking Service

    Any service provided by a pipeline company to assist its customers in smoothing the fluctuations in their demand for gas.

    Pipeline Quality Gas

    A term used to designate a fuel gas compatible with natural gas from pipelines. Such a gas can be substituted for methane. With respect to synthetic pipeline gas, a gas that meets the specifications for methane interchangeability.


    A conduit for fluids and gases consisting of pipe or tubing with all necessary valves and fittings. a.Pipe. Refers to rigid conduit of iron, steel, copper, plastic, or brass. b.Tubing. Refers to a semi-rigid conduit of steel, copper, plastic, brass, or aluminum.

    Piping, Trapped

    A system of piping that has a low spot that collects liquid at a point other than a drip location.

    Pitot Tube

    A small device that can be inserted into a pipe to measure the flow of a liquid or gas. This device is composed of two tubes arranged in such a manner that will allow the measurement of both the velocity and static pressures of the flowing liquid or gas. The difference in these pressures is a function of the flow within the pipe.


    Formation of small depressions in a surface due to sand blasting, mechanical gouging, acid etching, or corrosion.

    Plant Acquisition Adjustments

    Represents the difference between the cost to the utility of plant acquired as operating units or systems by purchase, merger, consolidation, liquidation or otherwise, and the Original Cost (defined herein) of such plant less the amount(s) credited at the time of acquisition to Accumulated Provision for Depreciation and Amortization and Contributions in Aid of Construction.

    Plant Protection Gas

    Minimum volumes required to prevent physical harm to the plant facilities or danger to plant personnel when such protection cannot be afforded through the use of an alternate fuel. This includes the protection of such material in process as would otherwise be destroyed, but shall not include deliveries required to maintain plant production.

    Plant Thermal Reduction (PTR)

    The Btu equivalent of the liquid products extracted from the producer's gas plus the portion of plant fuel necessary to extract those liquids, plant flare and other plant losses. When expressed as Mcfs this is referred to as Plant Volume Reduction or PVR.

    Plastic Insert

    Insertion of a plastic liner through an existing steel service.

    Plastic Pipe

    A hollow cylinder of a plastic material in which the wall thicknesses are ususally small when compared to the diameter and in which the inside and outside walls are essentially concentric.

    Plastic Tubing

    Same as plastic pipe except that it is usually of small diameter and sized on the same system commonly used for copper tubing.


    A material that contains as an essential ingredient one or more organic polymeric substances of large molecular weight, is solid in its finished state, and, at some stage in its manufacture or processing into finished articles, can be shaped by flow. NOTE: Rubber, textiles, adhesives and paint, which may in some cases meet this definition, are not considered plastics. See ASTM definitions of these terms.


    A material incorporated in a plastic to increase its workability, flexibility or distensibility.


    An above the water reinforced structure with pipe pile legs extending down into the ocean floor to support the above water structures and equipment installed for the measurement of gas, and for the operation of the offshore pipelines.

    Plenum Chamber (Plenum)

    Gas or air chamber connected with one or more distributing ducts usually located on a space heater.


    An external thread pipe fitting that is inserted into the open end of an internal thread pipe fitting to seal the end of a pipe. Also, sealing a hole in a vessel, such as a pipe or tank, by inserting material in the hole and then securing it. Also refers to the material used to plug the hole.

    Plug Back

    To seal off the bottom section of a well bore to prevent the inflow of fluid from that portion of the hole. This permits the inflow of oil and gas from the formations above the section so sealed off without contamination of fluids below that depth.

    Point Balancing

    A process by which the interconnected operators will transfer a quantity greater or less than the confirmed nominations scheduled quantity for various contracts at a point in an attempt to make the total gas received or delivered at the point as close as possible to the scheduled quantity during a specific billing period.

    Pollution, Atmospheric

    Degradation of atmospheric quality due to heat, particulate, or other products from industrial plants, power plants, refineries, or vehicular engines.


    A plastic or resin prepared by the polymerization of butylene as essentially the sole monomer.


    A plastic or resin prepared by the polymerization of ethylene as essentially the sole monomer.


    A substance consisting of molecules characterized by the repetition (neglecting ends, branch junctions and other minor irregularities) of one or more types of monomeric units. Polymers may be formed by polymerization (addition polymer) or polycondensation (condensation polymer). When two or more monomers are involved, the product is called a copolymer.


    A chemical reaction in which the molecules of a monomer are linked together to form polymers. When two or more different monomers are involved, the process is called copolymerization.


    A polymer prepared by the polymerization (copolymerization) of olefin(s) as the sole monomer(s).


    A polymer prepared by the polymerization of propylene as the sole monomer.

    Polypropylene Plastics

    Plastics based on polymers made with propylene as essentially the sole monomer.

    Polyvinylchloride (PVC)

    A polymer prepared by the polymerization of vinyl chloride with or without small amounts of other monomers.

    Polyvinylchloride (PVC) Plastics

    Plastics made by combining polyvinylchloride with colorants, fillers, plasticizers, stabilizers, lubricants, other polymers, and other compounding ingredients. Not all of these modifiers are used in pipe compounds.

    Pool, Oil or Gas

    In general, the term "pool" is synonymous with the term "reservoir". However, in certain situations a pool may consist of more than one reservoir; generally in the Appalachian Region where completion, gathering, and metering practices prevent segregating production from individual reservoirs.

    Pooling Point

    A common market point, generally located at the terminus of a pipeline's production area. Under a Pooling Point transportation arrangement, the shipper is responsible for ensuring that the total nominations of gas received at the pooling point are in balance with the amounts received into the main stream. Volumes are then transported downstream under corresponding transportation arrangements. Such arrangements are designed to increase the receipt point flexibility of the shipper. Also referred to as telescoping points or headstations.

    Population Density

    The number of buildings or dwelling units within a class location unit of a pipeline.

    Population Density Index, One Mile

    A number roughly proportional to population density in an area that extends 220 yards on either side of the center line of any continuous one-mile length of pipeline main and used in some cases to determine design and/or test requirements.


    Voids in a reservoir rock available for storage of fluids. Measured in percent of rock volume.


    Opening in the seat of a slide valve in diaphragm gas meters or an opening in any equipment for the flow of gases or vapors.

    Positive Displacement Pump

    Pump that delivers a constant volume of fluid per cycle of operation at whatever pressure is necessary, within the design limits of the mechanism of the pump.

    Postage Stamp Rates

    Flat rates charged for transportation service without regard to distance, as opposed to zone or mileage-based rates.

    Postage Stamp Rates

    A single rate for the entire system; in contrast to zone or mileage based rates.

    Posted Field Price

    Price for oil or gas in a given area, set by principal buyers. Price is available to any producer in the area.

    Pot Life (Working Life)

    The period of time during which a reacting thermosetting composition remains suitable for its intended processing after mixing with reaction-initiating agents.


    A measure of the capacity of a well to produce oil or gas. When a well is completed, its productive capacity is determined by an official test. The capacity as shown by this test is known as the well's potential. The allowable rate of production assigned to the well is based in whole or in part on its potential.

    Potential Energy

    Stored energy. Energy possessing the power of doing work but not actually performing such work.

    Potential, Pipe to Soil

    Electrical potential of pipe with reference to an electrode placed in the ground.

    Power Combustion Furnaces

    Furnaces that have a combustion blower, which may be located either upstream or downstream from the heat exchangers. If the blower is located upstream, blowing the combustion air into the heat exchangers, the system is called a forced-draft system. If the blower is downstream, the arrangement is called an induced-draft system. Power combustion systems have been commonly used with outdoor furnaces in the past; however, more indoor furnaces are being designed using this concept.

    Powerplant and Industrial Fuel Use Act of 1978 (PI

    Legislation prohibiting the use of natural gas and oil in new power plants and major fuel-burning installations. Officially repealed in May 1987.

    Pre Tax Return

    Is equal to the debt component of the rate of return plus the equity component adjusted upwards to reflect the impact of Federal Income Taxes.


    A device to remove fine ash, tars, dusts, or smoke particles from flue gases or other gaseous streams; the device may employ mechanical, electrostatic, chemical means, or a combination of these.

    Preferred Stock Dividends or Preferred Dividend

    Charges - 330

    Preferred Stock or Preferred Capital Stock - 331

    Capital stock to which preferences or special rights attach particularly as to dividends and/or proceeds in liquidation.

    Pregranted Abandonment

    FERC authorization to terminate sales or transportation service automatically upon the expiration of the underlying contract.

    Preliminary Determination

    A conditional approval issued by the FERC that reviews and authorizes all the terms and conditions of a proposed construction project, except the environmental aspects. A type of semi-certificate approval devised by the Commission to speed construction. Once the preliminary determination is issued, sponsors can line up financing and begin right-of-way acquisition and be ready to go when the lengthy environmental process is completed and they receive unconditional certificate authorization.

    Premium on Capital Stock

    The excess of the amount received by the company from the sale of an issue of the capital stock over the par or stated value of the stock. A premium also arises when a company issues a stock dividend and the market price of such stock exceeds its par or stated value. In this instance, an amount equal to the difference is transferred from retained earnings to premium on capital stock.


    These are payments for gas made to producers when the transmission company is unable to meet its contractual obligations to buy gas at a specified time. After the transmission companies' facilities are completed, the gas previously paid for is obtained from the producer over the period of the contracts as the producers' capacities permit.

    Presiding Administrative Law Judge (PALJ)



    When expressed with reference to pipe, the force per unit area exerted by the medium in the pipe.

    Pressure and Temperature Relief Valve

    A relief device activated by pressure and/or temperatures, commonly used on water heaters. (P and T relief valves).

    Pressure Base

    The standard pressure used in determining a gas volume, expressed in terms of pounds of pressure per square inch, usually 14.73 psia.

    Pressure Control

    Maintenance of pressure, in all or part of a system, at a predetermined level or within a selected range.

    Pressure Differential

    Difference in pressure between any two points in a continuous system. Compare PRESSURE DROP.

    Pressure Drop

    The loss in static pressure of the fluid (air, gas, or water) due to friction or obstruction in pipe, valves, fittings, regulators, burners, appliances, and breeching. See PRESSURE LOSSES.

    Pressure Gauge


    Pressure Limiting Station

    Equipment installed for the purpose of preventing the pressure on a pipeline or distribution system from exceeding some maximum pressure as determined by one or more regulating codes by controlling or restricting the flow of gas when abnormal conditions develop. See PRESSURE RELIEF STATION and PRESSURE REGULATING STATION.

    Pressure Loader

    Device in which the rate of gas flow controls the operation of a pressure governor or regulator.

    Pressure Losses

    Losses in static or velocity pressure in a piping system due to friction, eddies, leaks, or improper piping design. See PRESSURE DROP.

    Pressure Rating

    The estimated maximum pressure that the medium in the pipe can exert continuously with a high degree of certainty that failure of the pipe will not occur.

    Pressure Regulating Station

    Equipment installed for the purpose of automatically reducing and regulating the pressure in the downstream pipeline or main to which it is connected. Included are piping auxiliary devices such as valves, control instruments, control lines, the enclosures, and ventilating equipment. See PRESSURE LIMITING STATION and PRESSURE RELIEF STATION.

    Pressure Regulator


    Pressure Relief Station

    Equipment installed for the purpose of preventing the pressure on a pipeline or distribution system to which it is connected from exceeding the maximum allowable operating pressure by venting gas to the atmosphere whenever the pressure exceeds this valve.

    Pressure, Absolute (PSIA)

    Pressure in excess of a perfect vacuum. Absolute pressure is obtained by algebraically adding gauge pressure to atmosphere pressure. Pressures reported in "Atmospheres" are understood to be absolute. Absolute pressure must be used in equations of state and in all gas-law calculations. Gauge pressures below atmospheric pressure are called "vacuum."

    Pressure, Atmospheric

    The pressure due to the weight of the atmosphere (air and water vapor) on the earth's surface. The average atmospheric pressure at sea level (for scientific purposes) has been defined at 14.696 pounds per square inch absolute.

    Pressure, Boiler


    Pressure, Bottom Hole


    Pressure, Critical

    The minimum pressure required to liquefy a gas at its critical temperature.

    Pressure, Field


    Pressure, Gauge (PSIG)

    Pounds per square inch above atmospheric pressure.

    Pressure, Maximum Actual Operating

    The maximum pressure that occurs during normal operations over a one-year period.

    Pressure, Maximum Allowable Operating

    The maximum operating pressure at which a system or a device may be operated as determined by regulating codes.

    Pressure, Open


    Pressure, Standard Service


    Pressure, Static


    Pressure, Suction

    The inlet pressure to a compressor, pump, or fan.

    Pressure, Total

    The sum of the static pressure and the pressure due to the velocity motion.

    Pressure, Trap

    Pressure held at the trap or oil and gas separator.

    Pressure, Velocity

    The pressure which would be exerted by a fluid due to its motion if brought to rest. This is distinguished from the static pressure exerted against walls containing the fluid.

    Pressure, Working

    Normal operating gauge pressure in a device or system.

    Pressure-Decline-Curve Method

    A method of estimating nonassociated gas reserves in reservoirs which do not have a water drive.

    Preventive Maintenance

    Examination of plant and equipment on a schedule basis and the replacement or repair of parts that are worn by prescribed amounts or that are in such condition that further use will involve the risk of their failure while in service. It is designed to prevent operating breakdown.

    Price Ceiling

    Statutory maximum lawful prices for various categories of natural gas, including gas destined for both the intrastate and interstate markets.

    Price Earnings Ratio

    Market price divided by the annual earnings per share of common stock. The market price used may be a spot price, or an average of closing or the high and low prices for a period; the earnings are for the corresponding period.

    Price Elasticity of Demand

    A measurement of the sensitivity of demand to changes in price. Technically, the ratio between the percentage change in volumes demanded and the corresponding percentage change in price.

    Primary Air

    Air that is mixed with fuel before the mix reaches the ignition zone to enhance combustion.

    Prime Mover

    Mechanical equipment, such as an engine or turbine, which converts the energy of a fuel or fluid into mechanical power, usually rotational.


    In a boiler, the excessive carry-over of fine water particles with the steam due to insufficient steam space, faulty boiler design, or faulty operating conditions. Compare FOAMING.

    Prior Period Correction

    Restatement of a production month's measurement allocation or contract quantities in subsequent months. Also called prior month's adjustments (i.e., PMA's).

    Priorities of Service

    A predetermined schedule of service obligations or contracts which specifies where one such service or contract takes precedence over another for deliveries of natural gas.


    A feature of federal and state regulatory curtailment plans which ranks end-uses of natural gas. In the event of shortage, low priorities, i.e., boiler load, defer to higher priorities, i.e., human needs.

    Pro Forma

    Latin for "for the sake of form." Used to describe gas pipeline tariff sheets submitted as part of a certificate application or as part of a tariff filing. When made as part of a tariff filing, pro forma sheets do not contain a proposed effective date and are of no force or effect.

    Pro Rata Allocation

    A capacity or gas supply allocation methodology under which all customers would receive the same proportion of the natural gas service available as their portion of total volumes contracted for. Compare with FIRST COME, FIRST SERVED.

    Probable Life

    The total expected service life for survivors at any given age; the sum of the age attained and the remaining life.

    Probable Reserves

    In mining industries other than petroleum, the amount of reserves estimated to be available once additional development expenditures are incurred.

    Process Gas

    Gas use for which alternate fuels are not technically feasible, such as in applications requiring precise temperature controls and precise flame characteristics.

    Processing Plant

    A plant in which liquefiable hydrocarbons, such as propane, butane, ethane, or natural gasoline, which are initially components of the gas stream, are extracted or removed.


    A legal entity which processes or treats natural gas in a gas plant of any type.


    Any party owning, controlling, managing, or leasing any gas well and/or party who produces in any manner natural gas by taking it from the earth or waters.

    Producer Contracted Reserves

    The volume of recoverable, salable gas reserves committed to or controlled by the reporting pipeline company as the buyer in gas purchase contracts with independent producers, as sellers, including warranty contracts, and which are used for acts and services for which the company has received certificate authorization from the FERC.

    Producer Gas (Also Manufactured Gas)

    A combustible gas made in a furnace or apparatus by circulating air or a mixture of air and steam through a layer of incandescent material consisting chiefly of carbon monoxide, hydrogen, and nitrogen.

    Producing Sand

    A rock stratum that contains recoverable oil or gas.

    Producing Zone

    The interval of rock actually producing oil or gas.


    A functional classification relating to that portion of utility plant used for the purpose of producing gas; or to expenses relating to the operation or maintenance of production plant.

    Project Financing

    Method for financing projects where a company solicits money by pledging its expected revenues to cover the debt.

    Propane (C3H8)

    A gas, the molecule of which is composed of three carbon and eight hydrogen atoms. Propane is present in most natural gas and is the first product refined from crude petroleum. It has many industrial uses and may be used for heating and lighting. Contains approximately 2,500 Btu per cubic foot.

    Proper and Adequate

    As in "proper and adequate" depreciation rate. This is a subjective term.

    Property Retired

    As applied to plant, means property which has been removed, sold, abandoned, destroyed, or which for any cause has been withdrawn from service.

    Proprietary Capital

    A group of balance sheet accounts which includes common capital stock, preferred capital stock, other paid-in capital installments received on capital stock, discount on capital stock, capital stock expense, appropriated retained earnings, unappropriated retained earnings, and reacquired capital stock.


    The specified sharing of oil and/or gas production among the wells in a particular area. Dividing of consumption into parts and billing each at a different rate; generally, proportioning according to some calculable factor for billing period.


    A geographical area which exploration has shown contains sedimentary rocks and structure favorable for the presence of oil or gas.

    Proven Acreage

    Land under which it is known that gas or oil exists in quantity and condition sufficient to support commercial production.

    Proven Reserves




    Prover, Bell

    A device for testing the accuracy of a gas meter. A quantity of air is collected over water or oil in a calibrated cylindrical bell and then passed through the meter by allowing the bell to sink into the water or oil. A comparison of the measured amount of air passing through the meter and the amount registered on the meter dial gives a measure of meter accuracy.

    Prover, Critical-Flow

    Device utilizing an orifice for testing meters at a pressure of 20 psig or more by passing gas or air through both the meter and orifice and finally discharging it at a lower pressure which maintains critical-flow (sonic velocity) through the orifice. The time for a given quantity of gas to pass through the meter compared to the orifice standard time corrected for test conditions provides a measure of meter accuracy.

    Prover, Low Pressure Flow

    An apparatus utilizing an orifice for testing meters at low pressures by passing gas or air through the orifice and meter and finally discharging it to the atmosphere. The time for a given quantity of gas to pass through the meter compared to the orifice standard time corrected for test conditions provides a measure of meter accuracy.

    Prover, Piston

    A device for testing the accuracy of a gas meter consisting of a movable sealed piston contained in a calibrated cylindrical cavity. The air displaced by the moving piston is passed through the meter and a comparison is made between the volume swept out by the piston and the volume registered by the meter under test.

    Prover, Transfer

    A device for determining the accuracy of a meter under test by comparing its reading against the reading obtained from a calibrated reference meter connected in series with the meter under test.

    Provisions for Deferred Income Taxes

    The difference between taxes that would be due (paid) using straight-line depreciation and that actually paid using accelerated depreciation for tax purposes and other temporary differences in the recognition of revenue and expense items for income tax purposes and for financial reporting purposes. When determining a utility's cost of service an allowance is granted for income taxes that is computed using straight-line depreciation. When a utility is using accelerated depreciation for tax purposes this results in the utility receiving greater allowance for taxes than the actual taxes paid in initial years of an asset, and a lower allowance for taxes than actual taxes paid in later years of the asset. The Commission treats such excess income (in initial years) as a return-of-capital, similar to depreciation, and requires the utility to reduce its rate base by the amount of excess income (the deferred taxes). This reduces its profit (return-on-capital) in subsequent years. When the situation is reached in later years where taxes paid exceed the allowance for taxes in the cost of service the Commission allows the rate base to be increased by the amount of the shortfall in income (i.e., the negative deferred taxes). This treatment results in the utility only receiving its allowed rate of return on equity investment over the life of the property and flows the benefit from deferring taxes through to the ratepayer. See SOUTH GEORGIA METHOD and REVERSE SOUTH GEORGIA.


    Pounds per square inch.


    Pertaining to the state of the atmosphere with reference to moisture.


    A device for measuring the humidity in the air, employing a wet bulb and a dry bulb thermometer.

    Public Convenience and Necessity

    That which is necessary or desirable in the public interest. The Commission must find a particular facility or service "necessary or desirable in the public interest" as a condition for granting a certificate of public convenience and necessity.

    Public Interest

    Usually intended to mean the interest of the public generally as opposed to the interest of an individual or company.

    Public Utility

    A business organization performing a service relating to or affecting all of the people within a specified area, usually under provisions of a franchise, charter or "certificate", and subject to special governmental regulations. See SERVICE AREA.

    Public Utility Regulatory Policies Act of 1978 (PU

    A comprehensive federal law governing aspects of energy production, transportation, and utility regulation.

    Pulse Combustion

    A series of controlled mini-explosions (pulses) creating a pressure pulse and sustaining combustion through a type of chain reaction. This principle applied to a gas heating or water heating appliance will significantly increase the appliance's operating efficiency due to increased turbulence and the elimination of the need to operate a flue gas blower for venting.


    A reinforcing sleeve welded over a coupling.

    Purchase Deficiency Methodology

    The methodology used under the EQUITABLE SHARING MECHANISM to allocate take-or-pay buyout and buydown costs, to be recovered through fixed charges. Each firm sales customer's fixed charge is determined by comparing its cumulative purchase deficiency with that of the system. The intent is for each customer to bear a portion of take-or-pay responsibility commensurate with its reduced purchases during the period take-or-pay was incurred, as the build-up of take-or-pay liability, and the inability of the pipeline to recover it, resulted from the reduced purchases of its firm sales customers. See EQUITABLE SHARING MECHANISM, DEFICIENCY PERIOD and BASE PERIOD.

    Purchased Gas Adjustment (PGA)

    A provision approved by the regulatory agency allowing a company to make filings to change its rates, without the usual suspension period, for the purpose of recovering currently the changes in its cost of purchased gas. Pipelines with such tariff provisions are permitted to charge all purchased gas costs, net of storage injections and withdrawals, to a deferred expense account. As gas is sold, the deferred account is credited by an amount equal to the volume of gas sold multiplied by the base average cost and Btu content of gas used in the last rate filing. The difference between the charges and credits to this account is accumulated with interest and billed out to customers over the next annual period as a purchased gas surcharge (positive or negative) adjustment.

    Purchased Gas Adjustment Clause



    A purchaser is the party who buys the gas from a supplier. A purchaser has the obligation to pay for gas based on the gas purchase contract.

    Pure Volumetric



    To displace gas, liquids, or foreign matter from piping, tanks, and equipment with other gases or liquids.

    Purge Cycle

    As applied to electric pilot igniters, the period from the time of automatic closure of the main gas supply by the safety shutoff device to the time the electrical circuit is re-energized.


    The act of replacing the atmosphere within a container by an inert substance in such a manner as to prevent the formation of explosive mixtures.


    The process by which unwanted impurities, such as hydrogen sulfide, are removed from a gas mixture. Purification of gas is accomplished by two principal methods. The dry method in which the gas is passed through some purifying material such as iron oxide mixed with wood shavings, and the wet method in which the gas is brought in contact with some liquid containing an active purifying agent such as ethanolamine or arsenic trioxide.




    Plant Volume Reduction. See PLANT THERMAL REDUCTION.

  • Q


    An energy quantity of one quadrillion Btu, which is approximately the energy equivalent contained in one trillion cubic feet of natural gas.

    Qualification Test

    An investigation, independent of a procurement action, performed on a product to determine whether or not the product conforms to all requirements of the applicable specification. NOTE: The examination is usually conducted by the agency responsible for the specification, the purchaser, or by a facility approved by the purchaser, at the request of the supplier seeking inclusion of his product on a qualified products list.

    Quick Burst

    The internal pressure required to cause failure of a pipe or fitting due to an internal pressure buildup, usually within 60 to 70 seconds.

  • R


    A measure of thermal resistance of a material, equal to the reciprocal of the U-Value. The R-Value is expressed in terms of degrees Fahrenheit times hours, times square feet per Btu.


    A small plug that is run through a flow line by pressure to clean the line or test for obstructions. See PIG and SCRAPER.


    A channel for holding wires, cables, or bus bars which is designed expressly for and used solely for this purpose. Raceways may be of metal or insulating material, and the term includes metal conduit, flexible metal conduit, and wireways.


    The transmission of energy by means of electromagnetic waves. Radiant energy of any wave length may, when absorbed, become thermal energy and result in an increase in the temperature of the absorbing body.

    Radiation Shield

    A separate panel or panels interposed between heating surfaces and adjacent objects to reduce heat transmission by radiation.

    Radiation, Infra-Red

    The radiation in that portion of the electromagnetic spectrum between visible light and radio waves, originating from either incandescent or non-incandescent hot bodies or from flames. The energy is utilized as a means of direct heat transfer from the source to the object or objects to be heated without materially heating the intervening air.


    A heating unit which transfers heat by radiation to objects within visible range and by conduction to the surrounding air which, in turn, is circulated by natural convection; a so-called radiator is also a convector, but the term radiator has been established by long usage.

    Radiographic Inspection

    Method used to determine flaws in pipe or other metals by use of a machine which emits X-rays or gamma rays which penetrate the metal and are transcribed onto film.

    Range, Gas

    Cooking stove. GAMA lists the following types: (1) Free-standing; (2) Set-in; (3) High Oven; (4) Built-in, Commercial; (5) Luncheonette and Restaurant; (6) Heavy Duty (Quality, Battery Type).


    Ratio of maximum operating capacity to minimum operating capacity within a specified tolerance and operating condition.

    Rankine Scale of Temperature

    The absolute Fahrenheit scale. Degrees F + 459.67 = degrees R. (The factor is usually rounded to 460 for commercial usage).

    Ratchet Clause, Demand

    A clause in a rate schedule which provides that maximum past or future demands are taken into account to establish billings for previous or subsequent periods.


    The unit charge or charges made to the customers for natural gas.

    Rate Adjustment Provisions

    A provision in a tariff which provides for changes in rates or total charges because of changes in specified items of cost, such as fuel price, purchased gas, tax, etc.

    Rate Base

    The investment value established by a regulatory authority upon which a utility is permitted to earn a specified rate of return. Generally, this represents the amount of property used and useful in public service and may include plant held for future use and may or may not include all or part of construction work in progress. If all or part of construction work in progress is included in rate base, there may or may not be an offset or partial offset to its return requirements due to the inclusion of an allowance for funds used during construction in net operating income. The investment included in rate base may be based on the following values or combinations thereof: fair value, prudent investment, reproduction cost, or original cost. The rate base may provide for the inclusion of working capital with positive allowances for cash-working capital, materials and supplies including fuel supplies and gas stored underground, bank balances, prepayments, and deductions for expense items such as property taxes and income taxes which are expensed currently but not paid until a later date. Rate base may also be adjusted to reflect customer payments for construction, company payments for advances, accumulated deferred income tax, and accumulated deferred investment tax credits to the extent the tax laws permit rate base adjustments. (Some jurisdictions reflect accumulated deferred tax balances as reductions to rate base while other jurisdictions reflect accumulated tax balances as zero cost money in the cost of capital determination).

    Rate Case

    A proceeding before a regulatory commission involving the rates to be charged for a public utility service.

    Rate Design

    The term "rate design" refers to the method of classifying fixed and variable costs between demand and commodity components. Examples of different rate designs are single rate (100% commodity or volumetric), two-part rates (demand and commodity rates), three-part rates (two demand and one commodity rate) and multiple rates (zone rates).

    Rate Design - Modified Fixed Variable

    The term "modified fixed variable rate design" refers to a method of determining demand and commodity rates whereby all fixed costs except equity return and related taxes are classified to the demand component.

    Rate Design - Seaboard

    The term "Seaboard rate design" refers to a method of determining demand and commodity rates whereby 50% of fixed costs are classified in the commodity component and 50% in the demand component.

    Rate Design - Special Marketing Programs (SMP's)

    SMP's involves the direct sale of producer gas that has previously been committed to a pipeline or distribution company. The gas is released by pipeline or another distribution company and the producer sells the released gas to an end-user or distribution company at a price below the original contract price in order to be competitive. Transportation of the gas is typically provided by the releasing pipeline at a rate which contributes to full fixed cost recovery. The FERC intends for the SMP to act as a mechanism for gas producers to make necessary price concessions in order to market their production.

    Rate Design - Straight Fixed Variable

    The term "straight fixed variable rate design" refers to a method of determining demand and commodity rates whereby all costs classified as fixed are assigned to the demand component.

    Rate Design - Two Part Demand Rate

    The term "two part demand rate" normally refers to a method of cost classification whereby a portion of cost classified as demand would be recovered based on peak day usage, and the remainder of costs classified as demand would be based on annual usage.

    Rate Design - United

    The term "United rate design" refers to a method of determining demand and commodity rates whereby 75% of fixed costs are classified in the commodity component and 25% in the demand component.

    Rate of Flow

    The volume or units of a material passing a given point in a system per unit of time.

    Rate of Return

    The return allowed to be earned (generally based on a cost of capital determination) or earned by a utility enterprise, generally calculated by dividing the net operating income (as defined) by the rate base.

    Rate Schedule (Rates)

    The commonly known forms of rates may be divided into two main classes, and each of these classes into several different types of rates.

    Rate Schedule, Class

    A rate schedule which is applicable to a specific customer class of service.

    Rate Schedule, Cogeneration

    A special rate to encourage commercial and industrial customers to use gas-fired cogeneration (generate their own electricity and use the waste heat from this process for thermal requirements).

    Rate Schedule, Economic Development

    A discount from standard commercial and industrial rates for takes above a minimum level for new or expanded service within an existing service area.

    Rate Schedule, Flat

    A rate schedule which provides for a fixed per unit charge regardless of the quantity of gas used.

    Rate Schedule, Gas Cooling

    A discount for using gas for air conditioning during the summer or off peak period.

    Rate Schedule, Inverted

    A rate schedule which provides different, but increasing, unit charges for various blocks of increasing demand or energy.

    Rate Schedule, Lifeline

    A rate structure applicable for residential customers which includes a specified block of energy use which is priced below the allocated cost of service. The block of energy may be priced at a flat amount for the entire block or on a per unit basis.

    Rate Schedule, Natural Gas Vehicle (NGV)

    A special rate for vehicles fueled with natural gas.

    Rate Schedule, Straight Line

    The term straight line indicates that the price charged per unit is constant and does not vary with increases or decreases in the number of units sold.

    Rate Schedule, Transportation

    A rate schedule to move someone else's gas on a transmission or distribution system. Most transmission companies have a number of transportation rate schedules based on mileage, zones, firm or interruptible, and so on.

    Rate Schedule, Zone

    A rate schedule restricted in its availability to a particular geographic area.

    Rate Year

    Begins when rates take effect (normally at the end of a suspension order). See SUSPENSION ORDER.

    Rate Zones

    Geographic areas of the Company's operations established to facilitate a design of rates to properly reflect the cost of serving customers in different parts of the company's system.

    Rates, Demand

    The term "demand rate" applies to any method of charge for gas service which is based upon, or is a function of, the rate of use or size of the customer's installation or maximum demand (in Mcf or therms) during a given period of time.

    Rates, Demand - Block Hopkinson.

    Either the demand charge, the commodity charge, or both, in a Hopkinson demand rate, may be the block form.

    Rates, Demand - Flat.

    The term "flat demand rate" applies to a charge for gas service based upon the customer's installation of gas-consuming devices. This is usually so much per Mcf, therm, month, or year. Sometimes this type of rate is nominally so much per fixture (as gas lamps) per year or month but estimated demand and quantity of gas likely to be used play an important part in the determination. Such a rate may be modified by the "block" or "step" methods.

    Rates, Demand - Hopkinson.

    The term "Hopkinson demand rate" applies to that method of charge which consists of a demand charge based upon demand (either estimated or measured) or connected load plus a commodity charge based upon the quantity of gas used.

    Rates, Demand - Three Part or Three Charge.

    Any of the foregoing types of rates may be modified by the addition of a customer charge. When such a charge is introduced in the Hopkinson demand rate, it becomes a "three part rate" or "three charge rate" which consists of a charge per customer or per meter plus demand and commodity charges.

    Rates, Demand - Wright.

    The term "Wright demand rate" applies to that method of charge which was the first to recognize load factor conditions. Under this rate, the consumer pays a different unit charge for each successive block of consumption. The consumer's maximum daily or hourly demand is a factor in the determination of the block size.

    Rates, Inverted

    Rate structure that divides consumption into continuous blocks. The larger the consumption block, the larger the associated price.

    Rates, Meter

    The term "meter rate" is applicable to any method of charge for gas service based solely upon quantity, such as Mcf or therms used. Declining Block. The term "block" indicates that a certain specified price per unit is charged for all units of gas taken within specified increments of use. Reduced prices per unit are charged for all or any part of succeeding blocks of such units, each such reduced price per unit applying only to a particular block or portion thereof. Inverted. The term "inverted" indicates that an increasing unit charge will be applied to succeeding blocks of increasing energy use. Step. The term "step" indicates that a certain specified price per unit is charged for all gas taken during a billing period, the rate, or price depending on the particular step within which the total consumption falls. Straight-Line (Flat). The term "straight-line" indicates that the price charged per unit is constant, i.e., does not vary on account of an increase or decrease in the number of units.

    Rates, Mileage-Based

    Rates designed to reflect the difference in pipeline costs based on the distance between supply sources and delivery points.

    Ratification Agreement

    A document whereby the producer and the purchaser adopt the terms and provisions of another contract as those under which they will make their own sale and purchase.


    Limits placed on operating conditions of a machine, apparatus, or device based on its design characteristics.

    Ratio of Specific Heats

    For gases: The ratio of the specific heat at constant pressure to the specific heat at constant volume. This ratio is important in thermodynamic equations, and is given the symbol k where k=cp/cv. The ratio k lies between 1.2 and 1.4 for most gases.


    Any material that causes a chemical reaction when added to a second substance.

    Rebate Program

    A DSM program in which the utility offers a financial incentive for the installation of energy-efficient equipment. Non-DSM rebate programs also exist, in which the utility offers an incentive for purposes of gaining market share of a specific end-use.

    Rebound Effect

    The incremental increase in demand that occurs when customers, by undertaking conservation actions, perceive a lower relative cost of energy, and therefore, purchase more in terms of comfort or

    Receipt Point

    Point at which transportation (movement) begins pursuant to the transportation contract. Generally, a producer's gas well, the outlet (tailgate) of a gas processing plant, or the delivery point (end) of a previous transportation contract.

    Receiving Terminal

    Coastal plant that accepts deliveries of liquefied natural gas and processes it back into gaseous form for injection into the pipeline system. Also known as REGASIFICATION TERMINAL.

    Recoverable Heat

    That portion of thermal input to a prime mover that is not converted to mechanical power and can be reclaimed for utilization.

    Recovery Capacity, Water Heater

    The quantity of water that a water heating system can heat from supply temperature to required temperature in one hour.


    A device for converting alternating current to direct current, used in the gas industry for external corrosion control of pipe and other metals.


    The repetition of a particular process; the return of a stream or part of a stream to a previous process or location for additional recovery of the desired components.


    The delivery of natural gas by a pipeline to a shipper or for a shipper's account.


    A pipe fitting which enables the connection of two pipes differing in diameter.

    Refinery Gas

    See GAS, OIL.


    The reformer processes fuel used in the Fuel Cell Assembly. It takes a hydrocarbon fuel, such as natural gas, through a chemical transformation process in the presence of steam and a catalyst and dissociates the carbon and the hydrogen of the fuel into CO, CO2, and H2. A single cell of the assembly generates roughly one volt of DC and will create roughly 100-200 watts of electricity for each square foot of electrode cross-sectional area.


    A chemical process using heat in presence of a catalyst to break down a substance into desired components, such as in the reforming of natural gas or light oils into lower Btu fuel gas.

    Refractory Grate

    The assembly within or upon which refractory material is supported.


    A substance which will absorb heat while vaporizing and whose boiling point and other properties make it useful as a medium for refrigeration. (Chilled water, which by common acceptance is called a refrigerant, does not vaporize). See BRINE.

    Refrigerating System, Absorption

    A system whereby a secondary fluid absorbs the refrigerant, and in doing so, gives up heat, subsequently releasing the refrigerant, during which heat is absorbed.

    Refrigerating System, Vapor-Compression

    A refrigerating system in which the cooling effect results from expansion of a refrigerant after mechanical compression by either centrifugal or reciprocating compressors.

    Refrigeration Capacity

    The rate of heat removal by a refrigerating system, usually expressed in Btu per hour or in tons.

    Refrigeration Cycle

    The full sequence of condensation and evaporation. The heat of evaporation is obtained from the material to be cooled.

    Refrigeration Ton

    12,000 Btu per hour or 200 Btu per minute of heat removal. Originally, the amount of heat required to melt a ton of ice in 24 hours.


    The retirement of one security issue with the proceeds received from the sale of another to provide for maturing debt or to take advantage of more favorable money market conditions.

    Regasification Terminal


    Regenerative Heating (Or Cooling)

    Process of utilizing heat which must be rejected in one part of the cycle to perform a useful function in another part of the cycle.

    Regenerator (SNG Plant)

    A device which uses regenerative steam to reverse the absorption process. (For example, carbon dioxide is stripped from potassium bicarbonate which is formed in the absorption stage by regenerative steam, leaving regenerated potassium carbonate solution for reuse in the absorption stage).

    Register, Heat/Cold

    The grilled opening into a room by which the amount of warm air from a furnace or cold air from a cooling coil can be directed or controlled; it includes a damper assembly. See GRILLE.


    The meter-dial positions of a meter index. The difference between two successive registrations indicates the volume of gas that has passed through the meter.

    Regulator Vent

    An atmospheric connection to the diaphragm of the regulator.

    Regulator, Domestic Appliance Pressure

    A device either adjustable or non-adjustable for controlling and maintaining a uniform outlet gas pressure. Spring Type, Adjustable - A regulator in which the regulating force acting upon the diaphragm is derived principally from a spring, the loading of which is adjustable. Spring Type, Nonadjustable - A regulator in which the regulating force acting upon the diaphragm is derived principally from a spring, the loading of which is not adjustable. Either of the above types may be further classified as follows: Main Burner Load Application - A regulator capable of controlling the flow of gas to main burners only. In such applications, the pilot is taken off upstream from the regulator. Main Burner and Pilot Load Application - A regulator capable of controlling the flow of gas to main and pilot burners. In such applications the pilot is taken off downstream from the regulator valve.

    Regulator, Monitoring

    A pressure regulator set in series with a control pressure regulator for the purpose of automatically taking over, in an emergency, the control of the pressure downstream of the station in case that pressure tends to exceed a set maximum.

    Regulator, Pressure

    A device that maintains the pressure in a fluid flow line, less than its inlet pressure within a constant band of pressures, regardless of the rate of flow in the line or the change in upstream pressure.

    Regulator, Relief Pressure

    A device for the purpose of relieving pressures in excess of a predetermined pressure.

    Regulator, Service Pressure

    A device designed to reduce and limit the gas pressure at the customer's meter.

    Regulatory Adjustments

    Company costs in the Base period that can not be included in the Cost of Service and are deleted.

    Regulatory Lag

    The time interval between when a charge or credit originates and when it becomes a part of the charge for service approved by the regulatory agency. Also, the inability to have rates adequately reflect the current level of operating costs or throughput. Rates generally reflect costs incurred in a historical test period.

    Reinforced Plastic

    A plastic with high strength fillers imbedded in the composition, in some mechanical properties superior to those of the base resin. The reinforcing fillers are usually fibers, fabrics, or mats made of fibers.

    Relative Humidity


    Release Gas

    Gas previously contracted and dedicated between producers/brokers and a pipeline company which, through mutual agreement between the parties, was thereafter "released" from contract and ultimately made available for purchase by third parties.

    Relief Opening

    The opening provided in a draft hood to permit the ready escape to the atmosphere of the flue products from the draft hood in the event of no draft, back draft, or stoppage beyond the draft hood, and to permit inspiration of air into the draft hood in the event of a strong chimney updraft.

    Relief Valve


    Remaining Life

    The expected future service life of plant at any given age.

    Removal Costs

    The costs of disposing of plant, whether by demolishing, dismantling, abandoning, sale, or other. Removal costs increase the amount to be recovered as depreciation expense.

    Replacing or Replacement

    When not otherwise indicated in the context, means the construction or installation of plant in place of property retired, together with removal or abandonment of the property retired.


    Forcing gas, under pressure, into the oil reservoir in an attempt to increase the recovery of crude oil; also done with water. See GAS CYCLING.

    Reproduction Cost


    Required Depreciation Reserve


    Required Radiation

    The area of radiator surface required based on the heat loss computation for the space to be heated.

    Reservation Fee

    A charge for a unit of capacity reserved on a pipeline for firm transportation of customer-owned gas pursuant to Part 284 of the Commission's regulations. Section 284.8(d) of the regulations states that the fee may not recover any variable costs or any fixed costs in excess of those costs that would be recovered by using the same ratemaking methodology used for determining the demand charge in the pipeline's sales rates. The pipeline's tariff must state the maximum reservation fee. Because the reservation fee may not include any variable costs, the fee may be discounted to zero.



    Reserve for Deferred or Future Income Taxes

    An account prescribed by some state utility commissions, the accounting profession, and the FERC to record the accumulated balances (net after write-off) of the provisions made in prior years for income taxes to be paid in subsequent years.

    Reserve Life Index (RLI)

    The ratio of a pipeline's system supply reserves to annual sales expected, stated in years. This ratio is often used to help determine a pipeline's rate of return.

    Reserve Rates

    Rates used internally by the company to adjust the rates billed and subject to refund to an estimate of the final or settled rate. Accounting principles require such a reserve.

    Reserve Ratio


    Reserves, Energy

    Refers to the bank of natural resources, such as natural gas, natural gas liquids, petroleum, coal, lignite, energy available from water power, and solar and geothermal energy. Estimated Potential Natural Gas Resources. Refers to an estimate of the remaining natural gas in a specified area which are judged to be recoverable. Estimated Proved Natural Gas Reserves. An estimated quantity of natural gas which analysis of geologic and engineering data demonstrates with reasonable certainty to be recoverable in the future from known oil and gas reservoirs under anticipated economic and current operating conditions. Reservoirs that have demonstrated the ability to produce by either actual production or conclusive formation test are considered proved.

    Reserves-to-Production (R/P) Ratio

    A ratio of the size of a gas and/or oil field to the annual production capacity of that field which is used to estimate the productive life of the field.


    That portion of a resource that has been actually discovered and that is presently technically and economically extractable. Also, a rock stratum that forms a trap for the accumulation of oil and gas. Also, a natural, subsurface container of fluids.

    Reservoir Energy

    The amount of energy available in a gas or oil reservoir for producing the gas or oil by natural flow.

    Reservoir Pressure

    The pressure existing at the level of the oil or gas productive formation in a well.


    A solid, semisolid, or pseudosolid organic material, often of high molecular weight, which exhibits a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures conchoidally.

    Restructuring Proceedings

    Negotiations wherein each interstate pipeline and its customers determine how they will conduct business pursuant to the provisions of Order 636.

    Retirement Dispersion

    The pattern of retirements taking place at various ages in relation to the average service life or, simply, the scattering of retirements about average life.

    Retirement Frequency


    Retirement Frequency Curve

    A graphical presentation of the retirement dispersion.

    Retirement Units

    (Definition taken from the FERC Uniform System of Accounts, effective April 1, 1986.) "Retirement Units" means those items of plant which, when retired, with or without replacement, are accounted for by crediting the book cost thereof to the plant account in which included. ("Definitions" Item 32.) Each utility shall use list of retirement units as is in use by it at the effective date hereof or as may be prescribed by the Commission, with the option, however, of using smaller units, provided the utility's practice in this respect is consistent.


    Cost of utility plant retired from service, whether or not it has been physically removed or replaced.


    An investment made in an existing building or facility. May be equipment replacements, equipment add-ons, or shell and equipment improvements.


    Generally, interest on debt and the profit the company is allowed over and above the recovery of its operating expenses, depreciation and taxes.

    Return Air

    Air returning to a heater or conditioner from the heated or conditioned space.

    Return on Equity

    The ratio of net income or earnings (after all expenses are deducted) to the book value of common and preferred stock plus retained earnings.

    Revenue Requirement

    The amount of revenues the utility needs to receive in order to cover operating expenses, pay debt service, and provide a fair return to common equity investors.

    Reverse Circulation

    Normal course of drilling fluid circulation is downward inside the drill pipe and upward in the well bore space surrounding the drill pipe. On special problems, this normal circulation is sometimes reversed and the fluid returns to the surface through the drill pipe after being pumped down in the annular space.

    Reverse South Georgia Method

    Works in the reverse of the SOUTH GEORGIA METHOD. The method was adopted shortly after the Tax Reform Act of 1987 was enacted. The Act reduced the statutory corporate income tax rate from 46% to 34%, which caused the balance in the Deferred Tax Account to be overstated. The "Reverse South Georgia Method" determines the amount of the overstatement and amortizes the excess as a reduction to the cost of service income tax allowance over the remaining book life of the pipeline. See SOUTH GEORGIA METHOD, NORMALIZATION, ACCOUNTING and PROVISIONS FOR DEFERRED INCOME TAXES.

    Rig, Jackknife, or Folding Mast

    The type mast that can be folded for moving, as contrasted with the standard derrick, which has to be completely dismantled and re-erected.

    Rigging Up

    Before the work of drilling can be started but after the derrick has been built, tools and machinery must be installed and a supply of fuel and water must be established. This operation, which in substance is that of getting the rig ready, is conveniently described by the drillers' term "rigging up".


    A strip of land, the use of which is acquired for the construction and operation of a pipeline or some other facility; may be owned outright or an easement taken for a specific purpose.

    Rigid PVC

    Polyvinyl chloride or a polyvinyl chloride/acetate copolymer characterized by a relatively high degree of hardness; it may be formulated with or without a small percentage of plasticizer. Normally a straight piece of pipe, not readily flexible.


    A very short length of pipe cut for testing purposes, such as for the ring-tensile test.

    Ring-Tensile Test

    Method of determining apparent tensile strength of plastic pipe by applying tensile forces in the hoop direction to a ring-specimen cut from pipe.


    General term for vertical runs of gas piping.

    Risk Premium

    A method to determine the cost of common equity component of return using the bond yield plus a risk premium based on selected stock market yields to bond yields. Also called BOND YIELD RISK DIFFERENTIAL.


    Long, heavy iron or concrete sleeves installed on a pipeline to prevent injury to pipe laid in a river bottom and to weight the pipe. Sometimes known as river weights or dogs.





    Rock Pressure

    A term used for the initial pressure of gas in a well.

    Rolled-In Pricing

    Current practice where rates reflect the accumulation or overall cost of all gas purchases. See INCREMENTAL PRICING.

    Rolling Weighted Average Inventory Costing Methodo

    A method of pricing gas inventory for PGA purposes in which storage injections are priced at the month's jurisdictional system cost of purchased gas and storage withdrawals are priced by dividing the total purchase cost of the gas in storage by the quantity of gas in storage.


    The rapid release of vapor when stratified layers of LNG suddenly mix.

    Room Heater


    Rotary Bit

    The cutting tool attached to the lower end of the drill pipe of a rotary drilling rig. The bit does the actual drilling of the hole through the formation.

    Rotary Drilling

    A method for drilling wells using a cutting bit attached to a revolving drill pipe.


    A driller's helper and general all-around worker on a drilling rig.

    Round Trip

    The removal of drilling bit and drill pipe from a well and replacing them as required to change the bit or test the table.


    A laborer who assists the foreman in the general work about producing oil wells and around the property of the oil company. The roustabout is a semi-skilled laborer in that he requires considerable training to fit him for his work.


    The amount paid to the owner of mineral-rights as payment for minerals removed. In gas and oil operations, the royalty is usually based on a percentage of the total gas or oil production.


    An assembly of more than one piece of pipe; a portion of a fitting having its end in line or nearly so, as distinct from the branch or side opening, as of a tee.


    A failure in the pipeline for various reasons where a complete loss to atmosphere of the gas or other media is sustained.

  • S

    Sack Breakers

    Sacks filled with dirt or sand and cement, approximately one cubic foot, used to prevent erosion; or to form a barrier between pipelines and prevent coating or pipe damage when lowering in rocky trenches.


    A fitted plate held in place by clamps, straps, heat fusion or welding over a hole punched or drilled in a gas main to which a branch line or service line connection is made. The saddle also may serve as a reinforcing member for repair.

    Safety Coupling

    A friction coupling adjusted to slip at a predetermined torque to protect the rest of the system from overload.

    Safety Education (Training)

    The transmission of knowledge, skills, attitudes, motivations, etc., concerning the safety requirements of operations, processes, environments, etc., to workers, supervisors, managers, and others. The objective of safety education and training is a favorable behavior change.

    Safety Engineering

    The planning, development, improvement, coordination, and evaluation of the safety component of integrated systems of people, materials, equipment, and environments to achieve optimum safety effectiveness in terms of protection of people and property.

    Safety Hats

    Rigid headgear of varying materials designed to protect the workman's head -- not only from the impact but from flying particles and electric shock or any combination of the three. Safety helmets should meet the requirements of American Standard Z89, Standard For Industrial Protective Helmets.

    Safety Shoes

    Generally applies to footwear providing toe protection for the wearer. Safety-toe footwear has been divided into three classifications: 75, 50, and 30; based on its ability to meet the minimum requirements for both compression and impact as specified by the American Standard Z41 Series. Generally, the safety-toe shoe should be used for work requiring the handling of heavy materials. Safety shoes may also be obtained with conductive soles to drain off static charges, and with nonferrous construction, to reduce the possibility of friction sparks in environments with a fire or explosion hazard. Other safety shoes are designed to provide protection against splashes of molten metal, construction hazards such as protruding nails, contact with energized electrical equipment, wet conditions, hot surfaces, and other hazards.

    Safety Shutoff


    Safety Shutoff Device

    A device that will shut off the gas supply to the controlled burner(s) in the event the source of ignition fails. This device may interrupt the flow of gas to the main burner(s) only or to the pilot(s) and main burner(s) under its supervision.

    Safety Solvents

    Solvents are free from fire or toxicity hazards and are nondamaging to surfaces or materials being cleaned. This term is often misused. Depending on the conditions of use, none of these criteria may be met by so-called "safety solvents". For example, petroleum hydrocarbons are effective solvents, low in toxicity, and inexpensive but have relatively low flash and fire points. The following conditions must be kept in mind by users of "safety solvents": 1. The toxicological effects alone are not adequate to assess the hazard potential of a solvent. 2.The vapor pressure, ventilation, and manner of usage will determine the concentration in air. 3.Handling procedures and type of clothing will determine the degree of skin contact and absorption. 4.Ignition temperature, flash point, and other factors determining the potential for fire and explosion must be considered.

    Safety-Control Circuit

    A circuit classified as a safety-control circuit is one involving one or more safety controls in which failed due to grounding, opening, or shorting of any part of the circuit can cause unsafe operation of the valve or the controlled equipment.



    Sales Agreement

    An agreement between a purchaser/buyer and seller (e.g., producer, marketer, pipeline, LDC) defines the terms and conditions of a purchase/sale and title transfer of gas quantities.

    Sales for Resale

    Sales made to a local distribution company, pipeline, or municipality where the gas will be resold by the purchaser.

    Sales Level

    The sales volume being applied to the cost of service to develop rates. See TRANSPORTATION LEVEL, THROUGHPUT LEVEL.

    Sales Refund Objective (SRO)

    A provision included in many prior settlements and often examined by Staff, that if actual volumes exceed an agreed level during the period of time the rates are in effect, the pipeline agrees to refund the fixed costs received in the commodity rate. The SRO can be offset by increases in certain jurisdictional costs. The SRO has not been used with the Modified Fixed Variable classification method.

    Sales, Interdepartmental

    Sales to other departments of a company (gas, electric, steam, water, etc.) and dollar value of such sales if the charges are at tariff or other specified rates for the energy supplied.

    Sales/Transportation Service

    Under traditional sales service agreements, transmission and distribution companies purchase gas from suppliers, transport the gas to customers and sell it to them. Under transportation service agreements, transmission and distribution companies transport gas supplies for customers who have purchased the gas directly from other parties.

    Salt Cavern

    An underground natural gas storage cavern has been developed in a salt dome by the solution mining process.

    Salvage (Proceeds)

    The value realized from plant removed or otherwise disposed of. This value may be in the form of cash, debits to the materials and supplies accounts, trade-in allowance, or other considerations.

    Salvage Value

    The amount received for property retired, less any expenses incurred in connection with the sale or in preparing the property for sale; or, if retained, the amount at which the material recoverable is chargeable to Materials and Supplies, or another appropriate account.

    Salvage, Net

    The difference between the value of salvage and the cost of removal resulting from the removal, abandonment, or other disposition of plant. Positive net salvage results when salvage value exceeds removal costs. Negative net salvage results when removal costs exceed salvage value. Positive net salvage decreases the cost to be recovered through depreciation expense, and negative net salvage increases it.

    Satellite LNG Facility

    A facility for storing and vaporizing LNG to meet relatively modest demands at remote locations or to meet short-term peak demands. LNG is usually trucked to such facilities.

    Saturated Air

    Air containing all the water vapor it can hold at its temperature and pressure.

    Saturation, Appliance or Customer

    The number of specified appliances or users divided by the basic units or total potential of the universe involved, i.e., Gas Heating Saturation related to customers is the total number of customers with space heating divided by the total number of customers. Saturation should not be used alone but should be associated with customers, families, households, population, or other qualifying terms indicating the universe referred to. For industry statistics, saturation based on customers served is used.


    A pipe size system (outside diameters and wall thickness) originated by the iron pipe industry.


    A process by which nominations are first consolidated by receipt point, by contract, and verified with upstream/ downstream parties. If the verified capacity is greater than or equal to the total nominated quantities, all nominated quantities are scheduled. If verified capacity is less than nominated quantities, nominated quantities will be allocated according to scheduling priorities.

    Scheduling Penalty

    A monthly or daily penalty assessed on the difference between the volume scheduled to be tendered by the shipper to the pipeline and the volume actually tendered for delivery. The purpose of the penalty is to maintain high throughput on the pipeline and prevent disruption of deliveries to other transportation and sales customers. Because the damage caused by the shipper failing to tender scheduled volumes cannot be remedied after the fact, there is no notice or make-up period involved.


    An outline, systematic arrangement, diagram, scheme, or plan. An orderly combination of events, persons, or things according to a definite plan. A diagram showing the relative position and/or function of different components or elements of an object or system.


    Refers to electric good logging. It is derived from the name of a French scientist who first developed well logging.


    A device used to clean deposits of paraffin or other foreign substances from tubing or flow lines. See PIG and RABBIT.

    Scraper Trap

    A fitting in either end of a pipeline with a shut-off valve and a door to insert or remove a pipeline scraper which is pushed through the pipeline to clean it and increase flow efficiency.


    To remove certain constituents of gas by passing it through equipment (Scrubber) in which the gas is intimately mixed with a suitable liquid that absorbs or washes out the constituent to be removed from the gas.

    Scrubber, Rotary

    A piece of equipment for removing impurities from gas bypassing the gas over rotating surfaces or brushes that are partially immersed in liquid.

    Scrubber, Tower

    A vertical vessel filled with plates or suitable packing over which scrubbing liquid flows upward through the liquid, separating entrained liquids or solids from the gas.

    Seaboard Method

    A classification method that allocates fixed costs equally between the demand and commodity components of the rate.

    Sealed Burners

    Gas burners that are sealed to prevent spillovers from reaching the burner box.

    Seasonal Curtailment

    Curtailment imposed on a seasonal summer (April-October) or winter (November-March) basis because of gas supply deficiency. See PEAK DAY CURTAILMENT.

    Seasonal Gas

    Seasonal gas is gas sold during certain periods of the year. It may be sold either on a firm or on an interruptible basis.

    Seasonal Method

    An allocation method that allocates demand and/or commodity costs to customer classes by seasonal usage.

    Secondary Air

    The air for combustion externally supplied to the flame at the point of combustion.

    Secondary Gas Cap

    A gas cap to an oil reservoir, not present at the time of discovery of the reservoir, that results from the release of gas from solution within the reservoir oil as the reservoir pressure declines and its subsequent migration to the top of the reservoir due to the force of gravity.

    Secondary Measure Adoption

    Any conservation or energy efficiency measures that a customer adopts outside of a DSM program as a direct result of that program.

    Secondary Production or Recovery

    Oil and gas obtained by the augmentation of reservoir energy; often by the injection of air, gas, or water into production information. See REPRESSURING.

    Section 311 Transportation

    Refers to transportation pursuant to Section 311 of the NGPA, which authorizes interstate pipelines to transport "on behalf of" local distribution companies or intrastate pipelines without the necessity of obtaining a certificate under Section 7 of the NGA.

    Seepage (Or Weeping)

    Failure that occurs through essentially microscopic breaks in the pipe wall, frequently only at or near the test pressure.


    A device for detecting vibrations in the earth. It is used in prospecting for probable oil or gas-bearing structures. In this application, the vibrations are created by discharging explosives in shallow boreholes. The nature and velocity of the vibrations as recorded by the seismograph indicate the general nature of the section of earth through which the vibrations pass.

    Selective Catalytic Reduction

    A post-combustion control that taps flue gas off the boiler and injects ammonia with nitrogen oxide gas to reduce emissions.

    Self-Help Program

    A program promulgated by the FPC during the interstate natural gas shortage of the 1970s whereby industrial users could purchase natural gas directly from producers and utilize the natural gas pipelines as contract carriers to transport the gas. As end-users, self-help industrial users were not restricted by federal wellhead price ceilings (since the gas was not sold for resale) and thus could compete with intrastate pipelines for natural gas.


    A legal entity that has contractual signatory authority and warranty of title to sell natural gas services, natural gas, or its by-products as a commodity. The seller may have the legal authority to sell as an agent for or on behalf of other owners.

    Semiautomatic Valve

    A valve that is opened manually and closed automatically or vice versa.

    Sendout Curve

    Send out plotted as a function of temperature.

    Sendout, Gas

    Total gas produced, purchased (including exchange gas receipts), or net withdrawn from underground storage within a specified time interval, measured at the point(s) of production and/or purchase, and/or withdrawal, adjusted for changes in local storage quantity. It comprises gas sales, exchange, deliveries, gas used by the company, and unaccounted for gas. Expressed in various units such as therms, Btu, cubic feet, etc.

    Sendout, Maximum Day

    The greatest actual total gas sendout occurring in a specified 24-hour period. Compare DESIGN DAY; PEAK DAY.

    Sendout, Minimum Day

    The smallest actual total gas sendout occurring in a specified 24-hour period.


    A piece of equipment for separating one substance from another when they are intimately mixed, such as removing oil from water, oil from gas, ash from flue gas, or tramp iron from coal.

    Service (Service Line, Service Pipe)

    The pipe carries gas from the main to the customer's meter. Compare CLASS OF SERVICE.

    Service Area

    A geographic area where a utility provides service, usually under provisions of a franchise, charter, or certificate, and subject to special government regulations. See PUBLIC UTILITY.

    Service Charge

    The fee charged a customer by a utility for work on the customer's premises. Also, part of a rate schedule, such as a customer charge; generally does not include any gas.

    Service Drip

    A liquid-collecting trap at the low point in a customer's gas service piping when the piping cannot be sloped back to the distribution main. Compare DRIP.

    Service Factor

    A factor that is used to reduce the strength value to obtain an engineering design stress. The factor may vary depending on the service conditions, the hazard, the length of service desired the uncertainties and the properties of the pipe.

    Service Life

    The time between the date plant is includible in a plant in service, or plant leased to others, and the date of its retirement. If depreciation is accounted for on a production basis rather than on a time basis, then service life should be measured in terms of the appropriate unit of production.

    Service Pipe

    See SERVICE.

    Service Pressure, Standard

    The gas pressure that a utility undertakes to maintain on its domestic customers' meters. (Sometimes called the normal utilization pressure).

    Service Riser

    A vertical pipe, either inside or outside a foundation wall, from the grade of the service pipe to the level of the meter.

    Service Shutoff

    This may refer either to a service stop or to a meter stop used to cut off the supply of gas.

    Service Stop

    The plug-type valve located in the service line between the main and the building; however, it is often used synonymously with the meter stop which is located within the building or immediately before the meter or regulator in outside settings. Compare VALVE, SHUTOFF.

    Service Stub

    A piece of pipe connected to a main and usually extended to the curb line for the addition of a service.

    Service Tee

    A tee is a customer's service piping with one leg closed and used for access to the service pipe in case of plugging with solids. Also, a tee used for making a hot tap on a main to supply a service.

    Service Territory


    Service Value

    The difference between original cost and net salvage value of utility plant.

    Service, No-Notice

    A service which permits the delivery of gas without prior notification.

    Service, Standby

    Service through a permanent connection is not normally used but available in lieu of, or as a supplement to, the usual source of supply.

    Set Casing

    To install steel pipe or casing in a well bore. An accompanying operation is the cementing of the casing in place by surrounding it with a wall of cement extending for all or part of the depth of the well.

    Settlement Conference

    An informal meeting of interested parties to resolve differences in a rate case. It is scheduled after Staff TOP sheets are published. See TOP SHEETS.

    Settlement Rates

    Rates accepted by the interested parties which are effective retroactively to the end of the five month suspension period on order of the FERC.

    Sewage Gas

    A gas produced by the fermentation of sewage sludge low in heating value due to dilution with CO2 and N2; also marsh gas or firedamp.

    Shale Oil

    A liquid similar to conventional crude oil but obtained from oil shale by conversion of organic matter (kerogen) in oil shale.

    Shift Converter

    A reactor which catalytically converts carbon monoxide and water into hydrogen and carbon dioxide.


    Owner of the transportation contract, for whom gas is transported.


    Exploding nitroglycerine or other high explosives in a hole to shatter the rock and increase the flow of oil. Same as torpedoing. Also, in seismograph work, this refers to the discharge of explosives to create vibrations in the earth's crust. See SEISMOGRAPH.

    Shooting Rights

    Permission to conduct geological and geophysical activity only, without the option to acquire lease acreage.

    Short Form Certificate Application

    A statement, in lieu of a conventional certificate application, that may be filed by independent producers annually transporting or selling less than 1,000,000 Mcf of natural gas that is subject to the jurisdiction of the Commission.

    Short Form Rate Schedule

    A statement, in lieu of a conventional rate schedule, that may be filed by independent producers annually transporting or selling less than 100,000 Mcf of natural gas that is subject to the jurisdiction of the Commission.

    Short Term Sale

    Any short term purchase covering a period of two years or less. Purchases from intrastate pipelines pursuant to Section 311(b) of the NGPA of 1978 are classified as short term sales regardless of the stated contract term.

    Show Cause Order


    Shrinkage, Natural Gas

    The reduction in volume of wet natural gas due to the extraction of some of its constituents, such as hydrocarbon products, hydrogen sulphide, carbon dioxide, nitrogen, helium, and water vapor.


    Shut off so there is no flow; refers to a well, plant, pump, etc., when valves are closed at both inlet and outlet.

    Shut-In Royalties

    Amounts paid to lessors as compensation for loss of income from non-production of producible reserves.

    Shut-In Well

    A well that has been completed but is not producing. A well may be shut-in for tests, repairs, or to await construction of gathering lines.

    Side Tracking

    Drilling past a broken drill or casing which has become permanently lodged in the hole. This operation is usually accomplished by use of a special tool known as a whip-stock.

    Side Wall Coring

    The taking of geological samples of the formation which constitutes the wall of the well bore. Another term in general use for this operation is "side wall sampling".

    Silica Gel

    A desiccant, hygroscopic material that readily absorbs substantial quantities of moisture and is used to reduce the relative humidity of air or gas.

    Skidding the Rig

    Moving a rig from the location of a lost or completed hole preparatory to starting a new one. In skidding the rig, the move is accomplished with little or no dismantling of equipment.


    A piece of pipe or thimble for covering another pipe or joint or for coupling two lengths of piping.

    Slug the Pipe

    Before hoisting drill pipe, it is desirable to pump into the top section of it a quantity of very heavy mud which will cause the level of the fluid in the pipe to fall. When a stand of pipe is unscrewed, the drilling fluid will have been evacuated from it. This prevents crew members and tools from becoming covered with the drilling fluid.

    Snapback Effect


    Solar Radiation

    The total electromagnetic radiation emitted by the sun.

    Solar System, Active

    A system that uses natural convective currents or other nonmechanical means for collecting, storing, and distributing solar energy.


    Mixture in which the components lose their identity and are uniformly dispersed. All solutions are composed of a solvent (water or other fluid) and the substance dissolved called the "solute". A true solution is homogeneous, as salt in water. Air is a solution of oxygen and nitrogen.

    Solvent Cementing

    Joining pipe by the use of a solvent which dissolves the surface of the pipe and forms a continuous bond upon evaporation.


    A material which extracts one or more substances present in an atmosphere or mixture of gases or liquids with which it is in contact due to an affinity for such substances.

    Sound Attenuation

    A reduction in the sound level.

    Sour Gas

    Gas having a high sulphur content.

    South Georgia Method

    Method which bridges the gap between the Commission's past flow-through policies of book and tax timing differences to the Commission's current policy of tax normalization as expressed in the Commission's Order No.144. The first step in developing the "South Georgia Method" is to reconcile the book depreciable plant to the tax depreciable plant. The reconciliation determines the amount of excess tax depreciation claimed over time due to liberalized tax methods in comparison to book depreciation. The excess tax depreciation over book depreciation times the statutory Federal income tax rate determines the deficiency in the Deferred Tax Account, Account No. 282. The deficiency is amortized over the remaining book depreciable life. Once the deficiency is fully amortized, the deferred tax account will be fully funded.

    Space Heater


    Special Marketing Programs


    Specific Gravity

    The ratio of the density of a substance to the density of a reference substance, both at specified physical conditions. As applied to gas, air is the reference substance. Two specific gravity definitions are recognized in gas measurement: 1. Real Specific Gravity. The density ratio between a gas and air determined by measurement at the same temperature and pressure. 2. Ideal Specific Gravity. The ratio of the molecular weight of a gas to the molecular weight of air. (Mol. wt. of air = 28.9644).

    Specific Heat

    The heat required to raise a unit mass of a substance through a degree of temperature difference. Also, the ratio of the thermal capacity of a substance to that of water. The specific heat of fluids varies with temperature and pressure.

    Specific Weight

    The weight of a unit volume, usually expressed as pounds weight per cubic foot.

    Spillover Effects

    Reductions in energy consumption in a utility's service territory caused by the presence of DSM programs, beyond program-induced savings of the participants.



    Split System

    Historically, a combination of warm-air heating and radiator heating; the term is also used for other combinations such as hot water-steam, steam-warm air, as well as gas heat-electric cooling.


    A mixture of iron oxide and wood shavings for the removal of hydrogen sulfide from gas.

    Spot Market

    A market characterized by short-term, interruptible (or best efforts) contracts for specified volumes of gas. Participants may be any of the elements of the gas industry - producer, transporter, distributor, or end user. Brokers may also be utilized.

    Spot Price

    Current one-time purchase price.

    Spot Purchase

    Short term sale of gas to an end-user, LDC, or pipeline for which the duration varies.

    Spray Pond

    Arrangement for lowering the temperature of water by evaporative cooling of the water in contact with outside air; the water to be cooled is sprayed by nozzles into the space above a body of previously cooled water and allowed to fall into it.


    The small cap or plug, with an orifice through it, that admits gas into the mixing chamber of a burner. See ORIFICE PLUG.


    Refers to the act of hoisting the drill pipe and permitting it to fall freely so that the drill bit strikes the bottom of the well bore with considerable force. This is done to clean the bit of an accumulation of the sticky shale which has slowed down the rate of penetration. Careless execution of this operation can result in kinks in the drill pipe and damaged bits.

    Spudding In

    The very beginning of drilling operations of a well. The term has been handed down from cable tool operations in the early days of the oil industry.

    Square Foot of Radiation

    The amount of heating surface in the form of radiators, convertors, unit heaters, or other devices which will emit 240 Btu per hour.

    Stabbing Board

    A temporary platform erected in the derrick at an elevation of about 20 to 40 feet above the derrick floor. The derrickman or other crew members work on this board while casing is being run in a well. Derived from the term "to stab" meaning to guide a joint while it is being screwed into another joint or section.


    Stabilization is the addition of a gas to the gas normally supplied for the purpose of adjusting the heat content to a specified value. Air is often used for the purpose of reducing heat content and LP gases are used for the purpose of enriching or raising the heat content.


    An ingredient used in the formulation of some plastics, to assist in maintaining the physical and chemical properties of the compounded materials at their initial values throughout the processing and service life of the material.


    A chimney or conduit for smoke.

    Stack Effect

    The tendency of a heated gas to rise in a vertical passage as in a chimney, small enclosure, or stairwell.

    Stack Gases

    See GAS, FLUE.

    Stack Loss

    The flue gas loss; the sensible and latent heat lost up the chimney in the flue gas.


    Employees, other than the Commissioners and their staffs and the ALJs and their staff, of the FERC.

    Staff Audit

    Staff review of company's rate filing, usually within 60 days of the filings suspension order. See SUSPENSION ORDER, TOP SHEETS.

    Standard & Poor's


    Standard Dimension Ratio (SDR)

    The ratio of diameter to wall thickness of pipe. Each SDR category has the same pressure rating. One SDR series is based on inside diameters and another on outside diameters. Normally used with plastic pipe.

    Standard Industrial Classification Manual (SIC)

    A book prepared and issued by the Office of Statistical Standards, United States Bureau of the Budget, to enable classification of business establishments by the type of activity in which engaged.

    Standard Metering Base

    Standard conditions, plus agreed corrections, to which gas volume are corrected for purposes of comparison and payment.

    Standby Charge

    A charge related to STANDBY SALES SERVICE. The charge is designed to recover only the fixed costs incurred by the pipeline which are associated with its ability to stand ready to provide sales service. Such fixed costs are generally recovered through the pipeline's sales commodity rate. As such, the pipeline would not be able to recover those costs should the customer chose, instead, to use its capacity for transportation.

    Standby Loss, Water Heater

    The percentage of total energy stored in water which is lost each hour from a storage-type water heater.

    Standby Sales Service

    A service which permits a sales customer the option, on any day, of using up to a set percentage of its daily contract demand for transportation, rather than sales service. In return for this ability to "swing", the customer is assessed a STANDBY CHARGE. Trans-portation under Standby Sales Service is generally provided under the terms of the pipeline's Firm Trans-portation rate schedule.


    A vertical pipe or reservoir for water used to secure a uniform pressure.

    Start Cart

    A heating device which supplies load pressure steam for fuel cell heat up.

    Static Pressure

    The force exerted per unit area by a gas or liquid, measured at right angles to the direction of flow, or the pressure when no liquid is flowing.

    Station Meter

    A meter of high capacity for measuring the output of a gas plant or pipeline delivery station.

    Station, Pressure Regulating


    Steam Tracing

    A graphic recording of steam pressure and temperature done instrumentally.

    Steam Trap

    A device for allowing the passage of condensate or air and condensate and preventing the passage of steam.

    Steam Turbine

    A type of motive equipment powered by steam used to drive mechanical apparatus. It has a rotary motion in contrast to a reciprocating motion.

    Steam, Exhaust

    Generally, water vapor which has had most of the usable energy removed.

    Steam, Live

    Water vapor which includes recoverable energy.

    Steam, Saturated

    Steam at a temperature and pressure such that any lowering of the temperature or increase in pressure will cause condensation.

    Steam, Super-Heated

    Water vapor heated beyond the point at which complete vaporization occurs (100% quality).

    Stipulation and Agreement (S&A)

    A document prepared to express in writing the agreement of the parties to a controversial matter such as a rate case. A Stipulation and Agreement settling all or part of a rate case must be submitted to the Commission for approval. See CONSENTING PARTY, CONTESTING PARTY.

    Storage Cycle


    Storage Horizon


    Storage Mains

    Those mains used primarily for injection and withdrawal of gas to and from underground storage.

    Storage Rights


    Storage Zone


    Storage, Buried Pipe (Bottle-Type Holder)

    A system of storage in especially designed high pressure pipe sections or bottles capable of storing natural gas at pressures near or equal to the pressure of maximum super-compressibility. Not storage in ordinary steel pipe.

    Storage, Contract


    Storage, Local

    The storage facilities, other than underground storage, that are an integral part of a distribution system, i.e., on the distribution side of the city gate, whether for manufactured, mixed, natural, liquefied petroleum or liquefied natural gases.

    Storage, Underground

    The utilization of subsurface facilities for storing gas which has been transferred from its original location for the primary purposes of load balancing. The facilities are usually natural geological reservoirs such as depleted oil or gas fields or water-bearing sands sealed on the top by an impermeable cap rock. The facilities may be man-made or natural caverns.

    Storage, Underground - Aquifer Storage.

    The storage of gas underground in porous and permeable rock stratum, the pore space of which was originally filled with water and in which the stored gas is confined by suitable structure, permeability barriers, and hydrostatic water pressure.

    Storage, Underground - Base Gas.

    (Also called cushion gas). The total volume of gas which will maintain the required rate of deliver during an output cycle.

    Storage, Underground - Current Gas.

    The total volume of gas in a storage reservoir which is in excess of the base gas. Also called Working Gas.

    Storage, Underground - Current Reservoir Capacity.

    The total volume of gas which a storage reservoir can contain within the present design capacity.

    Storage, Underground - Deliverability.

    The capability of a storage reservoir to deliver gas, expressed in Mcf/day at a given flowing wellhead pressure.

    Storage, Underground - Extraneous Gas.

    See STORED GAS, this section.

    Storage, Underground - Foreign Gas.

    See STORED GAS, this section.

    Storage, Underground - Injectability.

    The capability of a storage reservoir to accept gas, expressed in Mcf/day at a given pressure condition.

    Storage, Underground - Injected Gas.

    See STORED GAS, this section.

    Storage, Underground - Input Well.

    A well utilized for injection of gas.

    Storage, Underground - Maximum Gas in Storage.

    The highest volumetric balance of total gas in storage during any storage cycle.

    Storage, Underground - Native Base Gas.

    That part of the volume of cushion gas which is indigenous to the storage reservoir.

    Storage, Underground - Native Gas.

    The volume of gas indigenous to the storage reservoir.

    Storage, Underground - Observation Well.

    A cased bore hole extending from the surface to any horizon which is used to obtain information relating to storage operations.

    Storage, Underground - Output Well.

    A well utilized for withdrawal of gas.

    Storage, Underground - Overburden.

    All sediments of rock that cover or overlie the reservoir rock.

    Storage, Underground - Overpressuring.

    The technique of increasing the maximum pressure in a natural gas storage reservoir above the discovery pressure.

    Storage, Underground - Spillpoint.

    An area of minimum structural closure where gas or fluids may escape or be forced out of the reservoir structure.

    Storage, Underground - Storage Cycle.

    A period commencing with an injection phase during which gas is stored and ending with a subsequent withdrawal phase during which gas is removed.

    Storage, Underground - Storage Horizon.

    See STORAGE ZONE, this section.

    Storage, Underground - Storage Reservoir.

    That part of the storage zone having a defined limit of porosity and/or permeability which can effectively accept, retain, and deliver gas.

    Storage, Underground - Storage Rights.

    The right to store gas in a reservoir by leasing, renting, or purchasing the gas rights and surface well location from the free-title landowner, the surface-rights owner, and the mineral-rights owner.

    Storage, Underground - Storage Well.

    A cased bore hole, extending from the surface into the storage zone, which is used for gas input and/or output purposes.

    Storage, Underground - Storage Zone.

    The geological name of that stratum in the earth's crust within which the storage reservoir is located.

    Storage, Underground - Stored Gas.

    Gas physically injected into a storage reservoir.

    Storage, Underground - Top Storage Capacity.

    Working gas capacity.

    Storage, Underground - Top Storage Gas.

    See WORKING GAS, this section.

    Storage, Underground - Total Input Gas.

    The volume of extraneous gas injected into a storage reservoir during a given period of time.

    Storage, Underground - Total Output Gas.

    The volume of gas withdrawn from a storage reservoir during a given period of time.

    Storage, Underground - Ultimate Reservoir Capacity

    The total estimated volume of gas that could be contained in storage reservoir when it is developed to the maximum design pressure.

    Storage, Underground - Ultimate Reservoir Pressure

    The maximum reservoir pressure permitted by the geological configuration of the reservoir.

    Storage, Underground - Withdrawn Gas.

    Gas taken out of storage.

    Storage, Underground - Working Gas.

    Gas in an underground storage field that is available for market. May also be called Current Gas.

    Stored Gas


    Straddle Point

    A gas plant constructed near a transmission company pipeline downstream from the fields where the gas is produced, also referred to as "on-line" plants. The gas is sold at the lease/field to the transmission company. The producer and/or plant owner(s) retain processing rights and reimburse the transmission company for the plant thermal reduction (PTR) either in cash or in additional gas deliveries.

    Straight Fixed Variable


    Straight Gas Utility

    Company which derives the major portion of its total operating revenue from gas operations. For purposes of A.G.A. statistics, a straight gas utility derives at least 95 percent of its total operating revenues from gas operations.

    Straightening Vanes

    Round, square, or other shaped tubing installed axially inside the piping preceding an orifice or turbine meter to eliminate swirls and cross-currents set up by the pipe fittings and valves. This considerably reduces the amount of straight pipe required preceding the measuring element.


    The ratio of the elongation to the gauge length of the test specimen, that is, the change per unit of original length. It is expressed as a dimensionless ratio.


    A method of checking a bell prover by determining the relation between displaced volume and linear movement of a bell prover by means of measuring scale length, bell circumference, and displacement of the sealing liquid.

    Strategic Conservation

    Utility-stimulated programs directed at reducing end-use consumption in specific (usually peak) periods.

    Strategic Load Growth

    A targeted increase in end-use consumption during certain time periods or among certain customer types. The result is a general increase in energy sales beyond the valley filling strategy. Strategic load growth may involve increased market share of loads that are, or can be, served by competing fuels, as well as area development.

    Stray Current

    Electrical current (normally DC) from either natural or man-caused source, which could result in corrosion if not drained properly or compensated for by other means.

    Street Ell

    An L-shaped pipe fitting with external threads on one end and internal threads on the other end. Compare ELL.

    Street Tee

    A tee with an external thread on one of the run connections and with internal threads on the opposite run connection and on the side outlet.


    The stress required to break, rupture or cause a failure.


    The resultant force that resists change in the size or shape of a body acted on by external or internal forces. "Stress" is often used as being synonymous with unit stress which is the stress per unit area (psi).

    Stress Crack

    Internal or external crack in a material caused by tensile or shear stresses less than that normally required for mechanical failure in air. The development of such cracks is frequently related to and accelerated by the environment to which the material is exposed. More often than not, the environment does not visibly attach, soften, or dissolve the surface. The stresses may be internal, external, or a combination of both.

    Stress Relaxation

    The decrease of stress with respect to time in a piece of plastic that is subject to an external load at constant deformation.

    Stress-Rupture Test

    Method of testing plastic pipe to determine the hydrostatic strength by applying a constant internal pressure and observing time to failure.


    The act of threading the drilling line through the sheaves of the traveling block and the crown block. One end of the line is secured to the hoisting drum and the other anchored to the derrick substructure.


    To remove light hydrocarbon fractions from gas for recovery and sale.


    A pressure vessel in which the carbon dioxide and heavy hydrocarbons are stripped from the liquid methanol by passing a clean stream of methane up through the methanol.


    A short piece of pipe used to connect parts of the drilling string that could not otherwise be connected due to differences in thread size or design.

    Subbituminous Coal

    Ranking of soft coal generally having a heating value of 8,300-13,000 Btu's/lb -- high volatile matter and ash.


    In the cryogenic area, e.g. LNG, subcooling is the cooling of liquid to below its saturation temperature for the pressure under consideration. In practice, subcooling has the effect of reducing boil-off in LNG storage and transportation.

    Subject to Refund

    A condition attached by the FERC on revised rates, after the suspension period has expired, denoting that a company is allowed to charge and collect such rates provided, however, that appropriate rate refunds and reductions, including interest, may be required upon resolution of the rate proceeding if such rates are found to be in excess of just and reasonable rates. Under certain conditions rates may go into effect subject to refund without suspension.


    The practice of remetering purchased energy beyond the customer's utility meter, generally for distribution to building tenants through privately owned or rented meters.

    Subscription Rights

    A privilege to the stockholders of a corporation to purchase proportionate amounts of a new issue of securities at an established price, usually below the current market price; also, the negotiable certificate or warrant evidencing such privilege.

    Substitute Natural Gas (SNG)

    A gas manufactured from carbonaceous material whose characteristics are substantially interchangeable with natural gas. The resultant gas is composed primarily of methane. At this writing, SNG feedstocks are the llight hydrocarbons, propane, butane, and the naphthas. Development is underway of processes for production from heavier feedstocks, coal, peat, and solid wastes. See SYNTHETIC NATURAL GAS.

    Successor Contract

    Any contract, other than a rollover contract, entered into on or after the date of enactment of the NGPA of 1978, for the first sale of natural gas that was previously subject to an existing contract, whether or not there is an identity of parties or terms with those of the previously existing contract.

    Sulfides (Organic)

    A group of organic compounds containing a sulfur atom that is directly bonded between two carbon atoms. Some of the organic sulfides, such as dimethyl sulfide and thiophene, are considered to be suitable odorants.

    Summer Valley

    The depression that occurs in the summer months in the daily load of a gas distribution system of pipeline.


    A method used to increase the pressure, and thereby the amount of charge per cycle, above that of a normally aspirated internal combustion engine; it permits more fuel to be burned and is a practical means to greater engine power.

    Supercompressibility Factor

    A factor used to account for the following effect: Boyle's law for gases states that the specific weight of a gas is directly proportional to the absolute pressure, the temperature remaining constant. All gases deviate from this law by varying amounts, and within the range of conditions ordinarily encountered in the natural gas industry, the actual specific weight under the higher pressure is usually greater than the theoretical. The factor used to reflect this deviation from the ideal gas law in gas measurement with an orifice meter is called the "supercompressibility factor Fpv". The factor is used to calculate actual volumes from volumes at standard temperatures and pressures from actual volumes. The factor is of increasing importance at high pressures and low temperatures.

    Superseding Rate Schedule

    A contract submitted as a rate schedule to replace an existing rate schedule. When a producer and purchaser have entered into a new contract to cover a sale being made under an existing rate schedule, the new contract is usually designated as a "superseding rate schedule" and assigned a new rate schedule number.

    Superseding Tariff Sheets

    Revised tariff sheets filed with the Commission to update or modify original or previously revised tariff sheets currently on file in a pipeline's FERC Gas Tariff. If the revised tariff sheets are accepted for filing by the Commission, they become effective on the date specified in the Commission's order, at which time they supersede the currently effective tariff sheets.

    Supplemental Gas

    Any SNG, propane-air mixtures, refinery gas, biomass gas, air injected to reduce heat content, or manufactured gas that is mixed and distributed with natural gas.

    Surcharge Adjustment

    A pricing mechanism of a PGA to administer prior period over/under recoveries of gas costs in the current period.

    Surface Pipe

    The first string of casing to be set in a well. The length will vary in different areas from a few hundred feet to three or four thousand feet. Some states require a minimum length to protect fresh-water sands. On some wells, it is necessary to set a temporary conductor pipe which should not be confused with surface pipe as described here.

    Survivor Curve

    A graphical presentation of survivors at the beginning of each of a consecutive series of age intervals. The area under a complete curve represents the total dollar years or unit years of service. A stub survivor curve is one which does not extend to zero survivors. The curve is plotted from the observed life table.


    The plant surviving at the beginning of an age of interval and exposed to the risk of retirement during that interval.

    Suspension Order

    FERC Order suspending the effectiveness of a new rate case for an additional five months beyond the pipeline's 30 day request.

    Sustained Pressure Test

    A constant internal pressure test for an extended period of time. One thousand hours is a commonly used period.

    Sweet Gas

    Natural gas not contaminated by corrosion inducing impurities such as hydrogen sulfide, or with a low level of impurities.

    Swing Connection

    The combination of fittings that will swing up, down, or sideways slightly for aligning pipe and for absorbing movement or strain.

    Swivel, Meter

    The fitting that connects to the inlet and the outlet of a small gas meter.


    Synthetic crude oil derived from coal or oil shale.

    Synthesis Gas

    A mixture of carbon monoxide and hydrogen frequently used to produce (synthesize) many chemicals depending on the reacting conditions and catalysts used. Examples are methanol, methane, acetic acid, ammonia, and numerous other chemicals.

    Synthetic Natural Gas

    A descriptive term used interchangeably with SNG and Substitute Natural Gas. It is a gas manufactured from naphtha , coal, etc., and is substituted for, or mixed with, natural gas by a pipeline or gas distribution utility.

    System Capacity

    The amount of gas that can be transported under specified conditions of pressure, temperature and loading (generally peak day requirements). Note that the maximum amount of gas that can be delivered during any period time may vary depending upon the amount of line pack, pressure differential, points of receipt and delivery, gas gravity and temperature conditions at the beginning of the period. Consequently, a system's capacity will vary from time to time depending upon existing conditions.

    System Sendout

    Total volume of gas delivered from the system in a specified period of time -- day, month, year.

    System Storage

    Storage facilities, or portion of storage facilities, which is used by the pipeline to store gas for its own use, to meet the peak day requirements of its sales customers and to provide flexibility on its system. See CONTRACT STORAGE.

    System Supply

    Purchases of natural gas for the purchaser's own system supply requirements (i.e., for resale by the purchaser).

    System Type - Distribution.

    Generally mains, services, and equipment which carry or control the supply of gas from the point of local supply to and including the sales meters. The system operates at various pressures as indicated below. a. High Pressure. A system which operates at a pressure higher than the standard service pressure delivered to the customer; thus, a pressure regulator is required on each service to control pressure delivered to the customer. Sometimes this is referred to as medium pressure. b. Low Pressure or Utilization Pressure. A system in which the gas pressure in the mains and service lines is substantially the same as that delivered to the customers' appliances; ordinarily a pressure regulator is not required on individual service lines.

    System Type - Field and Gathering.

    A network of pipelines (mains) transporting natural gas from individual wells to compressor station, processing point, or main trunk pipeline.

    System Type - Main.

    The network of distribution piping to which customers' service lines are attached. Generally, large pipes are laid in principal streets with smaller laterals extending along side streets and connected at their ends to form a grid; sometimes laterals are brought to dead ends. Compare with DISTRIBUTION, this section.

    System Type - Transmission.

    Pipelines (mains) installed for the purpose of transmitting gas from a source or sources of supply to one or more distribution centers, to one or more large volume customers, or a pipeline installed to interconnect sources of supply. In typical cases, transmission lines differ from gas mains in that they operate at higher pressures, are longer, and the distance between connections is greater.

    System-wide Cost

    Produced by rolled-in pricing. Where one total cost, regardless of the individual costs, is used for ratemaking (e.g., PGA). See ROLLED-IN PRICING.

    Systems, Burner, Type - High Pressure Air.

    A system using the momentum of a jet of high pressure air (in excess of 5 psig) to entrain gas or air and gas to produce a combustible mixture.

    Systems, Burner, Type - High Pressure Gas.

    A system using the momentum of a jet of high pressure gas (in excess of 1/2 psig or 14 inches of water column) to entrain from the atmosphere all, or nearly all, of the air required for combustion.

    Systems, Burner, Type - Low Pressure Air.

    A system using the momentum of a jet of low pressure air (up to and including 5 psig) to entrain gas to produce a combustible mixture.

    Systems, Burner, Type - Low Pressure Gas, or Atmospheric.

    A system using the momentum of a jet of low pressure gas (up to and including 1/2 psig or 14 inches of water column) to entrain from the atmosphere a portion of the air required for combustion.

    Systems, Burner, Type - Mechanical.

    A system which proportions air and gas and mechanically compresses the mixture for combustion purposes.

    Systems, Burner, Type - Suction.

    A system applying a vacuum to a combustion chamber to draw in the air and/or gas necessary to produce the desired combustible mixture.

    Systems, Burner, Type - Two-Valve.

    A system using separate control of air and gas, both of which are under pressure. The valves controlling the air and gas flows may or may not be interlocked.

  • T

    Tail Block

    The last or lowest priced block of energy in a declining block rate structure.

    Tail Gas

    The residue gas left after the completion of a treating process designed to remove certain liquids or liquefiable hydrocarbons.


    A clause that requires a minimum quantity to be physically taken and paid for, usually gas in association with oil, or wells that will be damaged by failure to produce.


    The clause in a gas supply contract provides for a specific period a specific minimum quantity of gas must be paid for whether or not delivery is accepted by the purchaser. Some contracts contain a time period in which the buyer may take later delivery of the gas without penalty.

    Take-or-Pay Credits

    Credits provided by FERC Order No.500 allow the pipeline to credit a quantity of gas it transports against its obligation to take a similar quantity of gas under a take-or-pay contract executed before June 23, 1987.

    Take-or-Pay Liabilities

    The liabilities incurred by many pipelines under contractual obligation to pay for volumes of gas they were unable to take because of reduced sales and lack of market demand. Some of the liability may in effect represent prepayment for gas that may be taken at a later time. Conversely, a portion of the liability may represent unrecoverable obligations due to contractual limitations or the inability of the pipeline to take the gas at a later period. See TAKE-OR-PAY CREDITS. Methods for recovery of Take-or-Pay liabilities were addressed by the Commission in Order No.500. See EQUITABLE SHARING MECHANISM.


    The process of sorting liquids in a tank, the capacity of tanks, or the price paid for tank storage of liquids.


    To cut threads in a round hole so that other fittings or equipment can be screwed into the hole. Also to make an opening in a vessel or pipe.

    Tar Sands

    Hydrocarbon bearing deposits distinguished from more conventional oil and gas reservoirs by the high viscosity of the hydrocarbon which is not recoverable in its natural state through a well by ordinary oil production methods.


    A gas company schedule detailing the terms, conditions, and rate information applicable to various types of natural gas service. This document is filed with and approved by FERC or a state regulatory body.

    Tariff Gas

    Gas purchased by gas distributors from gas pipelines. The term is usually used by natural gas distributors to distinguish gas they purchased from pipelines from the gas they purchased directly from producers and had transported.

    Tariff Volume

    The maximum amount of natural gas that a consumer is entitled to receive during any specified time period. Usually, the volume of gas is subject to a curtailment plan. Also referred to as contract obligations and entitlements.

    Tax Life

    The facility life permitted by the tax law for use in determining the tax depreciation deduction.

    Technical Potential

    In DSM, an estimate of energy savings based on the assumption that all existing equipment or measures will be replaced with the most efficient equipment or measure that is technically feasible, without regard to cost or market acceptance. Compare ACHIEVABLE POTENTIAL, MARKET POTENTIAL, and ECONOMIC POTENTIAL.

    Technically Feasible

    In DSM, an option which could be implemented for which equipment has been developed and tested and is available in the current marketplace, or will be in the future.

    Tee, Street



    Use of an electrical apparatus transmitting data to a distant point for indicating, recording, or integrating the values of a variable quantity.

    Telescoping Points



    The degree of "hotness" or "coldness" is measured on a definite scale.

    Temperature Limiting Device

    A device which automatically interrupts the gas flow to the burner when the temperature exceeds the limit set.

    Temperature Scale, Absolute (Kelvin)

    A temperature scale independent of the thermometric properties of the working substance. For convenience, the absolute (Kelvin) degree is identified with the Celsius degree. The absolute zero in the Kelvin scale is minus 273.160 Celsius (C). See THERMODYNAMICS.

    Temperature, Ambient

    The temperature of the air, atmosphere, or other fluid that completely surrounds the apparatus, equipment, or the workpiece under consideration. For devices that do not generate heat, this temperature is the same as the temperature of the medium at the point of device location when the device is not present. For devices that do generate heat, this temperature is the temperature of the medium surrounding the device when the device is present and generating heat. Allowable ambient-temperature limits are based on the assumption that the device in question is not exposed to significant radiant-energy sources such as sunlight or heated surfaces.

    Temperature, Critical

    The temperature above which a fluid cannot exist as a liquid and hence cannot be liquefied by pressure alone.

    Temperature, Dew-Point

    The temperature at which a vapor begins to condense and deposit as a liquid.

    Temperature, Dry Bulb

    Technically, the temperature registered by the dry-bulb thermometer of a psychrometer. It is identical to the temperature of the air.

    Temperature, Effective

    An arbitrary index that combines into a single value the effect of temperature, humidity, and air movement on the sensation of warmth or cold felt by the human body. The numerical value is that of the temperature of still, saturated air which would induce an identical sensation. See CHILL FACTOR.

    Temperature, Ground

    In the gas industry, the temperature of the earth at pipe depth.

    Temperature, Wet Bulb

    The temperature an air parcel would have if cooled adiabatically to saturation at constant pressure by evaporation of water from it, all latent heat being supplied by the parcel.

    Temperature-Compensated Meters

    These meters measure volume at pipeline conditions using a device that will convert volume at flowing temperature to the volume at base temperature. These temperature compensators use a temperature-sensitive device to continuously vary the diaphragm-stroke to provide a temperature-compensated volume output. Meters equipped with temperature-compensators are often identified by red badges on the index face.

    Temporary Certificate

    Temporary authorization from the Commission allowing a jurisdictional pipeline for a good cause to commence sales and service and/or construction of facilities prior to the time that the Commission issues a permanent certificate pursuant to Section 7 of the NGA of 1938.

    Tensile Strength

    The tensile stress necessary to cause failure in a short-time test. It is performed by pulling a specimen of a specified dimension at a specified rate.

    Test Period

    A period of time extending nine months beyond the end of the Base Period. Adjustments to Base Period data may be made for changes expected to occur during the Test Period, as provided in the Code of Federal Regulations. See BASE PERIOD, TEST YEAR.

    Test Weld

    The process of cutting out a portion of a weld in a pipeline for testing as to acceptability.

    Test Year

    The period selected as the base for presenting data in a case or hearing before a regulatory agency upon which revenue requirements are determined. The period is generally a 12-month period, and it may or may not include adjustment to reflect known or projected changes in operating revenues, expenses, and rate base.

    Test-Well Contribution

    An agreement to pay the owner of an adjacent tract for a portion of the cost of drilling an exploratory well on his property.

    Theoretical Air Requirements

    The volume of air necessary to ensure the complete combustion of unit mass or volume of fuel.

    Theoretical Depreciation Reserve

    A calculated or artificial reserve, rather than actual, used as a guide in analyzing the actual reserve condition. It is not an exact measurement for determining the condition of the actual reserve.


    A unit of heating value equivalent to 100,000 British thermal units (Btu).

    Thermal Conductivity


    Thermal Expansion (Coefficient of)

    The fractional change in length (sometimes volume, specified) of a material for a unit change in temperature.

    Thermal Stress Cracking (TSC)

    Crazing and cracking of some thermoplastic resins which results from overexposure to elevated temperatures.

    Thermally Actuated Valve

    An automatic valve which utilizes the heat generated by the resistance of an electrical component in opening or closing the valve.


    Two pieces of dissimilar metal welded or brazed together at one end. When the welded end is at a different temperature from the free ends, an electrical voltage is developed that can be measured across the free ends, and that is proportional to the temperature difference and can, therefore, be used to measure the temperature at the brazed end.


    The science and study of the relationships between heat and mechanical work. First Law: Energy can be neither created nor destroyed, but has a mass equivalent. Second Law: Heat cannot pass from a colder to a warmer body without the expenditure of energy; all systems tend to equilibrium. Third Law: At absolute zero, the entropy of a pure substance can be taken to be zero.


    A quality that allows a material to repeatedly soften when heated and hardens when cooled. Typical of the thermoplastics family are the styrene polymers and copolymers, acrylics, cellulosics, polyethylenes, vinyls, nylons, and the various fluorocarbon materials.


    A material that will undergo or has undergone a chemical reaction by the action of heat, catalysts, ultra-violet light, etc., leading to a relatively infusible state. Typical of the plastics in the thermosetting family are the aminos (melamine and urea), most polyesters, alkyds, epoxies, and phenolics.


    An automatic device actuated by temperature changes designed to control the gas supply to the burner(s) in order to maintain a temperature between predetermined limits, and in which the thermal actuating element is an integral part of the device: 1. Electric Switch Type: A device that senses changes in temperature and controls electrically, by means of separate components, the flow of gas to the burner(s) to maintain the selected temperature. 2. Graduating Thermostat: A thermostat in which the motion of the thermostat valve is in direct proportion to the effective motion of the thermal element induced by temperature change. 3. Quick-Acting Graduating Thermostat: A thermostat which changes from the completely closed position, or vice versa, but not with a snap. 4. Snap-Acting Thermostat: A thermostat in which the thermostatic valve travels instantly from the closed to the open position, or vice versa.


    Total of transportation volumes and tariff sales; all gas volumes delivered.

    Throughput Level

    The combination of Sales Level and Transportation Level. See SALES LEVEL, TRANSPORTATION LEVEL.


    In heating or air conditioning, the distance air will carry, measured along the axis of an air stream, from the supply opening to the position in the stream at which air motion reduces to 50 feet per minute.

    Tie In

    To make a connection to an existing pipeline or piping.

    Tight Sands

    Gas-bearing geologic strata that hold gas too tightly for conventional extraction processes to bring it to the surface at economic rates without special stimulation.

    Times Fixed Charges and Preferred Dividends Earned

    The ratio of (a) income before interest charges to (b) the sum of interest charges and dividends on preferred stock. Used as a measure of preferred dividend coverage or safety.

    Times Fixed Charges Earned Before Income Taxes

    The ratio of (a) income before interest charges, adjusted to exclude income taxes, too (b) interest charges (principally interest on long-term debt). Used as a measure of interest coverage or safety.

    Title tracking

    Detailing (in confidence to the appropriate client) the sales and parties in transactions involving units of natural gas, which can be lengthy and complex.

    Title Transfer

    The Title Transfer Transaction is the sale/purchase and associated title transfer of the commodity ownership.

    Top Sheets

    The FERC Staff's written response to a company's filing for a general rate change. This is the Staff's initial position for discussion in settlement conferences and is prepared at the end of the Staff Audit. See STAFF AUDIT.

    Top Storage Capacity


    Top Storage Gas


    Topping-Cycle Plants

    Energy systems that produce electricity first and heat as a by-product.

    Total Allowance


    Total Depth (T.D.)

    The greatest depth reached by a wellbore.

    Total Energy

    A concept under which the electricity required by a given facility is produced on-site by natural gas and possible alternate standby fueled engines or turbines with the recovery of the equipment's heat of rejection for space conditioning and/or process uses.

    Total Input Gas


    Total Output Gas


    Tower Scrubber


    Town Border Station


    Town Gas

    Purified crude gas, after CO2 removal, having a heating value of 400 to 700 Btu/cf.


    A special provision approved by the Commission giving the pipeline company the ability to change its rates at different points in time to recognize changes in the specific cost of service items without the usual suspension period of a rate filing. Examples of costs that have been or are tracked include PGA, including GRI charge and A.G.A. charge, certain TBO costs, SRO, and charges in Research and Development. See CLAUSE, ADJUSTMENTS.

    Trade Ally

    In DSM, an organization (architect, building contractor, etc.) that influences energy decisions of customers who are potential DSM program participants.


    Process equipment composed of vessels, piping, heat exchangers, etc., required to produce SNG or also the utilization system after customer metering.


    A device for converting energy from one form to another specifically called the measurement of pressure differential in natural gas gate stations.

    Transition Cost Recovery (TCR) Mechanism

    A mechanism designed to recover Order No.500 take-or-pay buyout and buydown costs. See EQUITABLE SHARING MECHANISM.

    Transmission and Compression of Gas By Others (TBO

    Also referred to as Transportation By Others. This component of cost of service refers to charges from others (e.g., other pipelines) to transport your system supply gas to your system or another designated area.

    Transmission and Compression of Gas For Others (TF

    Also referred to as Transportation For Others or just Transportation. This pipeline service refers to a pipeline's transportation of gas owned by others.

    Transmission Company, Gas

    A company which obtains at least 90% of its gas operating revenues from sales for resale and/or transportation of gas for others and/or mainline sales to industrial customers and classifies at least 90% of its mains (other than service pipe) as field and gathering, storage, and/or transmission.

    Transmission System


    Transmittance, Thermal (U Factor)



    A device which responds to a measured variable by means of a sensing element and converts it to a standardized transmission signal which is a function only of the measurement.


    The act of moving gas from a designated receipt point to a designated delivery point pursuant to the terms of a contract between the transporter and the shipper. Generally, it is the shipper's own gas which is being moved.

    Transportation Agreement

    An agreement between a shipper and transportation company which defines the terms and conditions of the transportation services and transportation transfer to be provided.

    Transportation Level

    The transportation for others (TFO) volumes being applied to the cost of service to develop rates. See SALES LEVEL, THROUGHPUT LEVEL.

    Transportation Service

    The act of moving gas from a receipt point to a delivery point pursuant to a contract between the shipper and the transporter. To the extent the shipper has paid for guaranteed, high-priority capacity in the pipeline, that shipper is entitled to firm service. Less expensive, lower-priority transportation


    A legal entity that has the capability of providing the service of transporting gas. Transporter includes gathering companies, pipeline companies, and local distribution companies.


    A device designed for removing liquids or solids from a gaseous stream; a low spot in a pipeline or main. Compare DRIP.

    Trap, Scraper (Trap, Pig)


    Triple Integrated Appliance

    A Combo Heater that includes a cooling unit operated from a standard air conditioning compressor using the same ductwork.

    Tube, Finned

    Heat transfer tube or pipe with the extended surface in the form of fins, discs, or ribs.

    Tube, Injection

    A tube with a venturi throat leads from the primary airport and gas orifice or a gas burner to the mixing chamber and burner ports. As the gas passes from the gas orifice through the tube, it draws air through the primary airport into the mixing chamber, after which the mixture is burned at the burner ports.


    See PIPING.

    Turbine Meter

    A meter using the rate of rotation of a rotor in the gas stream to measure the flow rate.

    Turbine Station

    A compressor station in which the power is supplied by a turbine.

    Turbine, Steam, or Gas

    An enclosed rotary type of prime mover in which heat energy in steam or gas is converted into mechanical energy by the force of a high-velocity flow of steam or gas-directed against successive rows of radial blades fastened to a central shaft. Compare ENGINE, RECIPROCATING.

    Turbo Blower

    A blower in which the rotating part is equipped with blades that rotate between stationary blades attached to the housing. The respective sets of blades are set at an angle such that, as the rotor turns, gases are pushed through the blades and discharged from the opposite side, pass through the stationary blades, and then are given another push by the next set of rotating blades, finally being discharged from the casing at the opposite end from which they entered.


    Discontinuance of utility service.


    Initiation of utility service.

    Turn-On Charge

    The fee paid by a customer to have his utility service turned on.

  • U

    U Gauge



    The quantity of heat transmitted per hour through one square foot of a building section (wall, roof, window, etc.) for each degree Fahrenheit of temperature difference between the air on the warm side and the air on the cold side of the building section.

    Ultimate Analysis

    The determination of the elements contained in a compound, i.e., carbon, hydrogen, oxygen, nitrogen, sulphur, and other compounds.

    Ultimate CO2

    The maximum theoretical percentage of flue gas CO2 that is possible to produce from the complete combustion of a fuel with the chemically-correct fuel-air ratio.

    Ultimate Customer

    The customer who purchases gas for consumption and not for resale purposes. See CONSUMER, GAS.

    Ultimate Reservoir Capacity

    Total volume of gas within a reservoir which exerts a pressure from 0 pounds per square inch gauge pressure to the maximum or ultimate reservoir gauge pressure.

    Ultimate Reservoir Pressure

    The maximum reservoir pressure permitted by the geological configuration of the reservoir.

    Ultimate Strength

    Term used to describe the maximum unit stress a material will withstand when subjected to an applied load in a compression, tension, or shear test.


    Zone of invisible radiations beyond the violet end of the spectrum of visible radiations. Since UV wavelengths are shorter than the visible, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastics.

    Unaccounted for Gas

    The difference between the total gas available from all sources, and the total gas accounted for as sales, net interchange, and company use. This difference includes leakage or other actual losses, discrepancies due to meter inaccuracies, variations of temperature and/or pressure, and other variants, particularly due to measurements being made at different times. In cycle billings, an amount of gas supply used but not billed as of the end of a period. See UNBILLED REVENUES. Compare SENDOUT, GAS.

    Unassociated Gas

    Natural gas unaccompanied by crude oil when produced. Also called non-associated gas or gas well gas.

    Unbilled Revenues

    Revenues applicable to gas or electricity consumed but not yet billed to the customer because of bimonthly or cycle billing or for other reasons.


    The separation of the various components of gas sales, storage, transmission, delivery and etc. into an ala carte menu of services from which a customer may choose only those desired.

    Unconventional Fuels Tax Credit

    An incentive tax credit applying to a variety of more costly energy production including, for natural gas, coalbed methane, tight sands, and Devonian shale production.

    Unconventional Gas

    Natural gas that can not be economically produced using current technology.

    Underground Storage


    Uniform System of Accounts

    A list of a company's account numbers and corresponding account titles, together with specific instructions for the use of individual accounts and general instructions as to the basis of accounting. For utilities, Uniform Systems of Accounts have been issued by both the National Association of Regulatory Utility Commissioners (NARUC) and the Federal Energy Regulatory Commission (FERC). These accounts differ between various utilities, i.e., gas versus electric.


    A threaded fitting used to couple two runs of pipe together without having to turn or dismantle either run of pipe.

    Unit Heater


    Unit of Purchase Methodology

    For purposes of the CURRENT ADJUSTMENT, a method for computing a pipeline's average projected purchased gas costs derived by dividing the pipeline's total projected purchased gas costs the pipeline anticipates purchasing during the PGA effective period by the quantities of gas used to compute its total projected purchased gas costs, as detailed in Section 154.305 of the Regulations.

    Unit of Sales Methodology

    For purposes of the CURRENT ADJUSTMENT, a method of computing a pipeline's average projected purchased gas costs derived by dividing the pipeline's total projected purchased gas costs the pipeline anticipates purchasing during the PGA effective period by the quantities of gas the pipeline anticipates selling during the PGA effective period.

    Unit-Years of Service

    The same as "dollar-years" except expressed in terms of units rather than plant dollars.

    United Method

    A classification method that allocates 25% of fixed costs to the demand component and 75% to the commodity component of the rate.


    Joint operation of several leases, usually for economic or conservation reasons. Frequently a whole pool or field is unitized to prevent unnecessary drilling and to conduct secondary recovery projects.


    A term used in connection with Continuing Property Record Unit. Unitization is the process of assigning work order costs to applicable property record units.

    Unsaturated Compounds

    Any compound having more than one bond between two adjacent atoms; usually carbon atoms and capable of adding other atoms at that point to reduce it to a single bond.


    From a reference point, any point located nearer the origin of flow, that is, before the reference point is reached.

    Upstream Pipeline

    The first pipeline to transport natural gas en route to an interconnect point for delivery to another pipeline. See DOWNSTREAM PIPELINE.

    Use or Lose

    A provision that decreases a shipper's right to capacity if the shipper does not use it at a certain level. The purpose of such a provision is to encourage accurate capacity nominations and full pipeline utilization. Because firm shippers pay a reservation charge for capacity, whether or not they fully utilize that capacity, the Commission has found that no use-or-lose provision may apply to firm transportation.

    Used and Useful

    Rate making principle regarding the timing and inclusion of plant in the rate base.

    Utility Gases

    Natural gas, manufactured gas, synthetic gas, liquefied petroleum gas-air mixture, or mixtures of any of these gases.

    Utility Plant

    Includes Plant: In-service, Purchased or Sold, In Process of Reclassification, Leased to Others, Held for Future Use, Completed Construction Not Classified, Construction Work in Progress, Plant Acquisition Adjustments, and Other Utility Plant. The Uniform System of Accounts prescribes for the deduction of Accumulated Provision for Depreciation and Amortization.

    Utility Plant in Service

    That portion of a utility's plant is devoted to the operations of the company. Excludes plant: purchased or sold, in process of reclassification, leased to others, held for future use, under construction, and acquisition adjustments and adjustment accounts, and without deduction of Accumulated Provision for Depreciation and Amortization.

  • V


    A pressure less than atmospheric pressure, measured either from the base of zero pressure or from the base of atmospheric pressure.

    Vacuum-Relieving Device

    A device to automatically admit air or gas into space at a pressure below atmospheric.


    A property of ions or of radicals determining the number of ions with which they can combine in chemical reactions.

    Valley Filling

    The building of off-peak loads.

    Value of Service

    The concept that the value of a utility service to a consumer cannot be greater than the cost of an equally satisfactory substitute service or the consumer will switch to the substitute.

    Value of Service Pricing

    A method of apportioning costs among utility customers so that users who place a greater value on the service are charged higher rates than the more price-sensitive customers.


    A mechanical device for controlling the flow of fluids and gases; types such as gate, ball, globe, needle, and plug valves are used.

    Valve Box

    A housing around an underground valve to allow access to the valve and to protect the valve from mechanical damage or the effects of weather.

    Valve Chamber

    The space in a dry gas meter containing the slide valves and mechanism for their operation.

    Valve Control

    A fuel-air control system that operates by means of a mechanical linkage of related valves, common in industrial combustion systems.

    Valve Seat

    The stationary portion of the valve, when in contact with the movable portion, stops flow completely.

    Valve, Automatic Input Flow Control

    A device for controlling the gas supply to the main burner without manual attention.

    Valve, Automatic Shut-Off

    A device designed to shut off gas flow upon flame failure, pilot outage, control impulse, overpressure, or under pressure without manual attention.

    Valve, Back Pressure

    A valve built to maintain a given pressure in a piping system by remaining in a closed position until the given pressure is reached, at which time it opens to permit flow until the pressure falls below the specified pressure. Compare VALVE, CHECK.

    Valve, Ball

    A valve in which a pierced sphere rotates within the valve body to control the flow of fluids. The sphere may be trunnion mounted or free.

    Valve, Butterfly

    A throttling valve made up of a disc that rotates on an axis within the valve body, thereby varying the cross-section that is open to fluid or gas passage.

    Valve, Check

    A valve built to pass fluid in one direction but to close automatically when the fluid tries to flow in the opposite direction. Compare VALVE, BACK PRESSURE.

    Valve, Expansion

    A valve for controlling the flow of refrigerant to the cooling element.

    Valve, Firing

    A lubricated plug-type variable position valve is usually operated with an attached handle or, in the large sizes, by a loose-fitting key or extended handle wrench. Compare VALVE, TEST FIRING.

    Valve, Gate

    A full-opening valve controlled by a vertical movement of a single or pair of solid discs perpendicular to the direction of flow. There are several other types such as the wedge, slab, expanding gate, etc.

    Valve, Globe

    A valve equipped with an orifice and a stem attached to a plug and matching circular seat. The shut-off is obtained by direct contact of the plug and the seat. The body of the valve is normally spherical.

    Valve, Input Flow Ratio Control


    Valve, Lubricated Plug

    A valve of the pierced plug and barrel type provided with means for maintaining a lubricant between the bearing surfaces. It is designed so that the lapped bearing surfaces can be lubricated and the lubricant level maintained without removing the valve from service.

    Valve, Main Burner Control

    A valve that controls the gas supply to the main burner manifold.

    Valve, Manual Input Flow Control

    A manual valve, usually with stops, can be set to limit the gas flow to the maximum required input to the burner or burners.

    Valve, Manual Main Shut-Off

    A manually operated valve or stop in the gas line for the purpose of completely turning on or shutting off the gas supply to the appliance except to pilot or pilots which are provided with independent shut-off valves.

    Valve, Manual Rest

    An automatic shut-off valve installed in the gas supply piping and set to shut off when unsafe conditions occur. The device remains closed until manually reopened.

    Valve, Needle

    A small valve that is opened and closed to permit or restrict fluid or gas flow by the movement of a pointed plug or needle in an orifice or tapered orifice in the valve body.

    Valve, Plug

    Metal valve in which a pierced plug rotates in a tapered or cylindrical body to control flow through the valve.

    Valve, Relief

    An automatic valve designed to discharge when a preset pressure and/or temperature condition is reached. 1. Pressure Relief Valve. An automatic valve opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value. 2.Temperature Relief Valve. a. Fusible Type. A valve that opens and keeps open a relief vent by the melting or softening of a fusible element at a predetermined temperature. b.Manual Reset Type. A valve which automatically opens a relief vent at a predetermined temperature and which must be manually returned to the closed position. c. Reseating or Self-Closing Type. An automatic valve opens and closes a relief vent when the temperature reaches a predetermined value. d. Vacuum Relief Valve. An automatic valve which opens or closes a vent for relieving a vacuum, depending on whether the vacuum is above or below a predetermined value. Frequently used in a hot water supply system.

    Valve, Safety Shut-Off (Cut-Off)

    A valve that automatically shuts off the supply of fuel through the functioning of a flame safeguard control or limiting device. This device may interrupt the flow of fuel to the main burner(s) only or to the pilot(s) and main burner(s).

    Valve, Shut-Off

    Stops or valves readily accessible and operable by the consumer, located in the piping system (to shut off individual equipment) or between the meter and gas main to shut off the entire piping system. Compare SERVICE STOP.

    Valve, Solenoid

    An automatic valve that is opened or closed by an electromagnet.

    Valve, Tamper-Proof

    A shut-off valve designed and constructed to minimize the possibility of the removal of the core of the valve or stop accidentally or willfully with ordinary household tools.

    Valve, Test Firing

    A firing valve downstream of all other valves on the valve train.

    Vanes, Straightening

    Round, square, or other shape tubing installed inside the piping preceding an orifice to eliminate swirls and crosscurrents set up by the pipe fittings and valves.


    The gaseous state of a substance as distinguished from permanent gases. A gaseous fluid may be classified as either a vapor or a gas. If it is near the region of condensation, it is called a vapor. If it is well above the region of condensation, it is called a gas. Vapors in general do not follow the ideal gas law, and engineers prefer to use tables and charts based on experimental data when working with vapors. Gases, however, may obey the ideal gas laws over a wide range of temperature and pressure.

    Vapor Barrier

    A moisture-impervious layer applied to the warm side for the purpose of preventing moisture travel.


    A heat exchange used to return liquid natural gas to a gaseous form and then continue to heat the gas to a temperature at which it can be sent into the distribution system.

    Variable Cost

    Operating costs which, in the aggregate, vary either directly or indirectly in relation to any change in the volume of gas sold and/or transported; i.e., compressor station fuel and expenses. See FIXED COST.


    An enclosed room or pit having an access opening in the top, sidewall, or both. Maybe in a building, a separate above-ground structure, or underground.

    Vegetation Survey

    Leakage surveys made for the purpose of finding leaks in underground gas piping by observing vegetation.

    Vehicle Accident Frequency Rate

    The frequency rate of motor vehicle accidents is the number of motor vehicle accidents per 1,000,000 miles. It is derived by multiplying the number of accidents by one million and dividing by the mileage.

    Velocity Pressure



    An opening in a tank or other piece of equipment sealed to prevent the escape of material within the equipment at normal pressures but so arranged that it automatically opens to relieve excessive pressure in the equipment. Can be arranged for the manual opening to depressure equipment as desired. Also, the relief opening in a pressure regulator, normally open to the atmosphere.

    Vent Connector

    That portion of the venting system connects the gas appliance to the gas vent or chimney.

    Vent Damper

    A device installed in the vent pipe that connects the furnace to the chimney. When the burner goes off, the damper closes automatically, restricting the amount of heated air that can be lost through the chimney.

    Vent Gas

    See GAS, FLUE.

    Vent, Flue Gas

    A conduit or passageway for conveying flue gases to the outer air.


    The process of supplying or removing air by natural or mechanical means to or from any space. Such air may or may not have been conditioned.

    Ventilation Air

    That portion of supply air which comes from outside, plus any recirculated air that has been treated to maintain the desired quality of air within a designated place.

    Venting System Categorizations

    For gas-fired, central furnaces, the venting systems are classified and furnaces marked as follows: Category I - A central furnace that operates with a non-positive vent pressure and with a vent gas temperature at least 140 degrees F (60 degrees C) above its dew point. Category II - A central furnace that operates with a non-positive vent pressure and with a vent gas temperature less than 140 degrees F (60 degrees C) above its dew point. Category III - A central furnace that operates with a positive vent pressure and with a vent gas temperature at least 140 degrees F (60 degrees C) above its dew point. Category IV - A central furnace that operates with a positive vent pressure and with a vent gas temperature less than 140 degrees F (60 degrees C) above its dew point.

    Venturi Meter


    Venturi Throat or Tube

    A tube tapered down to a lesser diameter and then expanding gradually to its original diameter. Pressure-measuring taps are provided at the entrance and at the constricted throat for determining pressure differential through the tube used for metering.

    Verified Nomination

    A nomination that has been validated against the conditions specified in the service contract and with any upstream/downstream or third parties involved in the transaction.


    The term used by FPC and FERC to indicate the period in which a gas sales contract was made and/or the date drilling was started on a well.


    The tendency of plastics to respond to stress as if they were a combination of viscous liquids and elastic solids.


    In general, resistance to flow; the property of semi-fluids and gases by virtue of which they resist an instantaneous change of shape or arrangement of molecules.

    Volatile Matter

    The matter is readily vaporizable at a relatively low temperature.

    Volume Imbalance


    Volume, Specific

    The volume of a unit weight of a substance at a specific temperature and pressure conditions.

    Volumetric Rates

    A classification method that assigns 100% of fixed costs to the commodity rate.

    VOM--Volt Ohmmeter

    A device for measuring the voltage or the resistance of an electrical circuit. Some models also measure current flow through components in electrical circuits.

  • W

    Wall Thickness

    The specified wall thickness of pipe without adding an allowance to compensate for the under thickness tolerances permitted in approved specifications.

    Warranty Contract

    A purchase agreement where the supplier (producer) agrees to supply a specified volume of natural gas over a specified period of time and warrants that it has sufficient reserves to meet its commitments over the life of the contract.


    Removal of impurities from a gas or vapor bypassing the gas through water or other liquid which retains or dissolves the impurity.


    A shell with internal baffler or packing, so arranged that gas to be cleaned passes up through the baffles counter-current to the flow of scrubbing liquid down through the washer. The baffler or packing causes intimate contact and mixing of the gas with the liquid stream.

    Washer Cooler

    A washer in the form of a tall tower in which the washing liquid is sprayed in at the top is collected in the bottom of the tower and then is cooled and recycled through the tower. Serves the dual purpose of washing the gas free of impurities and also cooling the gas.

    Waste Gas

    See GAS, FLUE.

    Water Gas (Blue Gas)

    Made by passing steam over hot coke or other carbonaceous material; it consists of carbon monoxide and hydrogen with varying amounts of carbon dioxide and nitrogen. It burns with a blue flame.

    Water Heater Blanket

    Insulated wrap attached to a water heater which supplements the insulation contained in the water heater.

    Water Heater Efficiency Measures

    Energy Factor (EF) - A measure of the overall efficiency of a water heater based on its recovery efficiency, standby loss, and energy input as set out in the standardized Department of Energy test procedures.

    Water Heater--Direct, Fired

    An appliance for producing hot water for domestic or commercial purposes other than for space heating.

    Water Piping System, Closed

    A heating system utilizing an air tank which provides a means of pressurizing the system for operation over a wide range of conditions and of circulating water which is used as a heat medium.

    Water to Carbon Ratio

    The ratio by weight of the amount of water to carbon compounds in a gas (vapor) stream.

    Water Year

    Measured water flows during a 12-month period starting October 1st and continuing to September 30th of the following year.

    Water, Jacket

    In a compressor or engine, the water used for cooling the cylinder head and/or walls.

    Water, Make-Up


    Water-Cooling Tower

    A device for evaporative cooling of water by contact with air.


    The reduction of air infiltration by methods such as caulking and weatherstripping.

    Weight, Specific

    Weight per unit volume of a substance.

    Weighted Average Cost of Gas (Wacog)

    The weighted average cost of gas purchases by a natural gas pipeline.

    Weighted Cost

    A combination of Actual Cost and Fair Value in rate base determination. See ACTUAL COST, FAIR VALUE.

    Well Input


    Well Land Rights

    Right to drill and operate storage wells in a storage reservoir.

    Well, Development

    A well drilled in order to obtain production of gas or oil known to exist.

    Well, Disposal

    A deep well in which to inject waste chemicals, etc., such as a well to dispose of salt brine from the solution mining of salt dome gas storage caverns.

    Well, Exploratory

    A well drilled to a previously untested geologic structure to determine the presence of oil or gas.

    Well, Gas

    A well that produces at surface conditions the contents of a gas reservoir; legal definitions vary among the states.

    Well, Marginal

    A well that is producing oil or gas at such a low rate that it may not pay for the drilling.

    Well, Observation


    Well, Output


    Well, Storage


    Well, Stripper

    Nonassociated gas well capable of producing no more than 90 Mcf/day at its maximum rate of flow.

    Well, Wildcat

    An exploratory well being drilled in unproven territory, that is, in a horizon from which there is no production in the general area.


    The assembly of fittings, valves, and controls located at the surface and connected to the flow lines, tubing, and casing of the well so as to control the flow from the reservoir.

    Wellhead Price

    The cost of gas as it comes from the well excluding cleaning, compression, transportation, and distribution charges.

    Welsbach Mantle Lamp (Incandescent Mantle Lamp)

    A type of lamp in which the flame impinges on a knitted cup or mantle saturated with certain chemical compounds that are heated to incandescence and emit a bright, white light.

    Wet Gas


    Weymouth Formula

    A formula for calculating gas flow in large diameter pipelines. Compare PANHANDLE FORMULA.


    The transportation of customer-owned gas by a transmission company for the customer at a pre-determined cost to the customer.


    A long, steel casing that uses an inclined plane to deflect the drill bit for the control in directional drilling.


    One who drills wells in the hope of finding gas or oil in territory not known to be a gas or oil field.

    Wind Chill Factor

    The equivalent temperature resulting from the combined effect of wind and temperature. For example: At 10 degrees Fahrenheit above 0 with a 20-mile per hour wind, the effect is the same as 24 degrees Fahrenheit below 0 without wind. See also CHILL FACTOR.

    Wind Load Rating

    A specification used to indicate the resistance of a derrick to the force of the wind. The wind load rating is calculated according to formulas incorporated in API specifications. Typical wind resistance of derricks is 75 miles per hour with pipe standing in the derrick and 115 miles per hour and more with no pipe standing in the derrick.

    Withdrawn Gas


    Wobbe Index

    A number that indicates the interchangeability of fuel gases and is obtained by dividing the heating value of gas by the square root of its specific gravity.


    To perform one or more of a variety of remedial operations on a producing well with the hope of restoring or increasing production.

    Working (Operating) Interest

    The interest in a mineral property entitles the owner to the production from the property, usually subject to a royalty and sometimes to other nonoperating interests. A working interest permits the owner to explore, develop, and operate the property.

    Working Capital

    Money necessarily invested in the business to carry on the day-to-day operations. Working capital includes 1) Cash working capital requirements; 2) Average monthly balances of: a) materials and supplies (inventory) b) prepayments (i.e., taxes, rents, insurance) c) gas held in storage for current use (inventory) d) advance payments on gas purchases. The Natural Gas Act permits the recognition of a working capital allowance in the rate base.

    Working Capital

    The amount of cash or other liquid assets that a company must have on hand to meet the current costs of operations until such a time as it is reimbursed by its customers. Sometimes it is used in the narrow sense to mean the difference between current and accrued assets and current and accrued liabilities.

    Working Gas

    Gas in an underground storage field that is available for the market. See STORAGE, UNDERGROUND.

  • Y & Z

    Yield Point

    The stress at which a material exceeds its elastic limit. Below this stress, the material will recover its original size on the removal of the stress. Above this stress, it will not.

    Zero Gas

    Gas at atmospheric pressure.

    Zero Gas Governor


    Zero, Absolute


    Zinc Oxide

    An infusible white solid used in the preparation of synthetic natural gas to absorb sulfur from naphtha.


    A geographical area. A geological zone, however, means an interval of strata of the geologic column that has distinguishing characteristics from surrounding strata. Also, a space or group of spaces within a building with heating and/or cooling requirements sufficiently similar so that comfort conditions can be maintained by a single controlling device.

    Zone Heat

    Central heating and/or cooling system which is arranged so that different temperatures can be maintained in two or more areas of the building being heated or cooled or simultaneously heated or cooled.

    Zone Rate

    See RATE, ZONES.

    Zone, Storage


    Zone-Gate Method

    A method of developing zoned rates. This method involves first segregating costs by zone as if each zone were a separate entity, then developing the unit costs of gas flowing through each zone. The customers in downstream zones pay the costs associated with their gas flowing through the upstream zones.