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 well bore 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 which 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 less charges but is not a measure of actual depreciation.

Acetone test

A process control test for PVC pipe which indicates how well the rigid vinyl compound has been fused together in the extruder. 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


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 less retirements and adjustments of utility plant. It is the net change in utility plant between 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


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.


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 which 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 property or a contract.

Associated Gas


Associated Gas Proration

Restrictions states 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 heat-treating furnace.

Atmospheric Pollution


Atmospheric Pressure



The smallest complete particle of an element which 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


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.

Browse the Glossary