Glossary

A glossary of terms is listed below. For a complete glossary of terms, please visit the American Gas Association's Web site.

A | B | C | D | E | F | G | H | I | J | K | L | M 

N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Allocation-Capacity
Process by which available pipeline capacity is distributed to parties if requests for volume (i.e., nominations) are in excess of available space. Allocation is typically based on service type, contract type and company's tariff provisions. Also called NOMINATION ALLOCATION

Alternate Fuels
Fuels that can be substituted for the fuel used. With natural gas, the most common alternative fuels are distillate fuel oils, residual fuel oils, coal and wood.

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B

Base Pressure Index
Device that continuously and automatically compensates to correct gas volume at operating pressure to volume at base pressure, without correction for temperature.

Boiler Pressure
Pressure of the steam of water in a boiler, generally expressed in pounds per square inch (psi) and corresponding temperature.

Boiler, High Pressure
Boiler furnishing hot water at pressures in excess of 160 pounds per square inch (psi) and at temperatures in excess of 250°F (121°C) or steam at pressures in excess of 15 psi.

Boiler, Low Pressure
Boiler furnishing hot water at pressures not exceeding 160 pounds per square inch (psi) and at temperatures not more than 250°F (121°C) or steam at pressures not more than 15 psi.

Btu
British thermal unit: Amount of heat needed to raise the temperature of one pound of water one degree Fahrenheit from 58.5°F to 59.5°F under standard pressure of 30 inches of mercury at or near its point of maximum density.

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C

Capacity Release
Mechanism for holders of firm interstate transportation capacity to give their rights to use the firm capacity to other parties 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, Peaking
Capacity of facilities or equipment to supply incremental gas under extreme demand conditions; generally available for a limited number of days at maximum rate.

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.

Ccf
One hundred cubic feet

Confirmed Nomination
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.

Cubic Foot
Most common unit of measurement of gas volume. Amount of gas required to fill a volume of one cubic foot under stated conditions of temperature, pressure, and water vapor.

Customer Imbalance Quantity
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.

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D

Degree Day, Heating
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°F. 

Dekatherm
Unit of heating value equivalent to 10 therms or 1,000,000 Btu.

Design Pressure
Maximum operating pressure permitted by various codes, as determined by the design, material, and location involved.

Differential Pressure
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.

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F

Firm Transportation Service (FTS)
Certified quantity transportation services for which facilities have been designed, installed, and dedicated. Firm transportation service takes priority over interruptible service.

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G

Gas Day
Period of 24 consecutive hours commencing at 10:00 A.M. EST on a calendar day and ending at the same hour on the succeeding calendar day.

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H

Heat factor
Multiplier to convert ccf's to therms based on the measure of heat available or released when one ccf of gas is burned. For example, a heat factor of 1.035 is the multiplier to convert one ccf of gas that contains 1,035 Btu per cubic feet to the equivalent number of therms.

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I

Imbalance
When a party receives or delivers a quantity of natural gas and then delivers or redelivers a larger or smaller quantity of natural gas to another party.

Interruptible Transportation Service (ITS)
Low priority service offered to customers that anticipates and permits interruption on short notice, generally in peak-load seasons, by reason of firm service customers and higher priority users.

Interstate Gas
Gas transported in interstate pipelines that's sold and consumed in states other than the state in which the gas was produced.

Interstate Pipeline
Pipeline that transports natural gas across state lines. Interstate with respect to natural gas companies, the transporting and sale of gas for resale across state lines.

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L

LDC
Local distribution company. A company that receives gas from an interstate pipeline and delivers gas to customers through its own piping.

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M

Marketer (Broker)
Non-regulated buyer and seller of natural gas.

Mcf
One thousand cubic feet

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N

Nominations
Exact listing of the gas quantities 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.

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P

Pipeline Capacity
Maximum amount of gas that can be moved through a pipeline system - based on existing service conditions such as available horsepower, pipeline diameter(s), maintenance schedules, regional demand for natural gas, etc.

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R

Rate Schedule, Transportation
Rate charged to move someone else's gas on a transmission or distribution system. Most transmission companies have many transportation rate schedules based on such factors as mileage, zones, and firm or interruptible.

Regulator, Pressure
Device that maintains pressure in a fluid flow line regardless of the rate of flow in the line or the change in upstream pressure.

Regulator, Relief Pressure
Device for relieving pressures in excess of a predetermined pressure.

Regulator, Service Pressure
Device to reduce and limit the gas pressure at the customer's meter.

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S

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.

System Capacity
Amount of gas that can be transported under specified conditions of pressure, temperature and loading (generally peak-day requirements). The maximum amount of gas that can be delivered during any period of 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.

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T

Tariffs
Tariffs identify all of the terms, conditions, and qualifications upon which service is provided. Click here for specific tariff information.

Therm
Unit of measurement equal to 100,000 Btu (British thermal unit).

Transportation
Act of moving gas from a designated receipt point to a designated delivery point based on the terms of a contract between the transporter and the shipper. Generally it is the shipper's gas that is being moved.

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W

Wellhead Price
Cost of gas as it comes from the well excluding cleaning, compression, transportation, and distribution charges.

Wellhead
Assembly of fittings, valves, and controls located at the surface and connected to the well's flow lines, tubing, and casing that control the flow from the reservoir.

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