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Glossary of Gas Terms

Annual Fuel Utilization – Annualized Fuel Utilization Efficiency (AFUE) measures the average annual seasonal efficiency of a gas furnace or boiler and may be expressed as total heating output divided by total energy (fuel) input. AFUEs for furnaces can range from 55% to 97%.

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 caulking, lead, and/or other material in the cast iron pipe annulus.

Bell Hole – A hole dug to allow room for workmen to make a repair or connection in 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.

Block Valve – Main transmission line valve designed to close in or shut down gas flow.

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.

By-Pass – 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 that is by-passed.

Compressor – A mechanical device for increasing the pressure of a gas.

Commodity Cost – The cost of the natural gas or electricity commodity and related charges to deliver it to the marketplace.

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.

Curb Valve – The plug-type valve located in the service line between the main and the building.

Daily Average Send-Out – The total quantity of gas delivered for a period of time divided by the number of days in the period.

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

Demand – 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.

Direct Current (DC) – a fixed polarity power supply with a positive and negative terminal that remains constant.

Distribution –The delivery of natural gas through pipeline systems to an end-user.

Firm Service – Delivery of gas to a customer on a continuous basis with no anticipated interruptions.

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.

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.

Grid – The layout of a gas distribution system in which pipes are laid in both directions in the streets and frequently connected at intersections.

High Voltage Tracing Current – a high voltage DC output applied to a feeder for the purpose of locating a fault.

House Riser, Gas – The principal vertical pipe that conducts the gas from the meter to the different floors of the building.

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.

In Service – a term used to indicate equipment is connected to the system and fulfilling its designated function.

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, due to system supply or capacity limitations that threaten a local distribution company’s ability to continue to serve its firm customers and higher priority users. Customers taking interruptible service generally have alternate energy sources to supply their service, for example, boilers which are capable of consuming fuel oil in additional to natural gas.

Interruption – a cessation of a supply of power to customers.

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.

Live End Cap (LEC) – a sealed housing installed on a primary cable end for the purpose of allowing the cable to be energized after removing defective cable or equipment beyond the live end cap point.

Life Sustaining Equipment (LSE) – any electrically operated equipment that is essential to sustaining the life of the individual user of that equipment. (e.g. iron lung)

Liquefied Natural Gas (LNG) – Natural gas that 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 temperature and pressure.

Load – 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.

Load cycle – the normal pattern of load over a specified time period.

Local Grounds – the protective grounds applied to equipment to be worked upon.

Low Voltage Condition – any voltage that is below the specified parameters for the existing system condition.

Low Voltage Tracing Current – a low voltage DC current applied to a feeder for the purpose of making a positive identification of cable or equipment at the working point.

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.

Odorant – Any material added to natural or LP gas in small concentrations to impart a distinctive odor.

Open-Auto (O/A) – a trip out of a feeder breaker in a substation due to a fault condition or overload on the feeder cable or equipment.

Pipeline – 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.

Plastic Pipe – Pipe made of medium or high-density polyethylene.

Plastic Tubing – Same as plastic pipe except that it is usually of smaller diameter and sized on the same system commonly used for copper tubing.

Pressure Regulator – 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.

Radial – a distribution system with one source of supply only. Also referred to as non-network.

Secondary Network – a system of distribution feeders connected on their secondary side (120/208V). This system allows for a multiple power supply to any given point connected to the secondary grid.

Service (Service Line, Service Pipe) – The pipe that carries gas from the main to the customer's meter.

Service Pressure Regulator – A device designed to reduce and limit the gas pressure at the customer's meter

Storage – The placement of utility-owned gas in underground facilities during the summer, when demand is low, that is withdrawn for the winter when gas consumption is higher.

System Sendout – Total volume of gas delivered from the system in a specified period of time - day, month, year.

System Type - Distribution – Generally mains, services, and equipment that 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:

1. High Pressure: A system that 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.
   
   
2. 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.