Valves are required along the gas delivery system so that sections of the system can be isolated and shut down in the event of a leak or other emergency, or for controlling flow or performing maintenance.
Valve applications include:
- Mainline valves shut off main flow stream.
- Tap valves shut off deliveries at offline delivery points.
- Blowdown valves release gas to de-energize a piping system.
- Station valves isolate compressor stations, pressure limiting stations, and metering stations.
- Emergency valves isolate pipeline sections or a facility in an emergency.
- MAOP valves isolate sections of system where maximum allowable operating pressures (MAOPs) are different.
- Therm billing area (TBA) valves isolate sections of system where gas Btu content is different.
- Relief valves release gas to atmosphere if pressure exceeds a set point.
- Excess flow valves automatically close if excess flow is sensed.
- Service valves shut off flow of gas to customer at the meter.
- Curb valves, located in the street or sidewalk, shut off services between the main and a customer meter (used when a service value at the meter might be inaccessible to a crew).
Most values are operated manually by a crew member, but some values are automated and may operate on their own given certain conditions or may be able to be operated remotely via electronic signal.