TRANSMISSION AND DISTRIBUTION (T&D) SYSTEM EMERGENCIES controlling the Flow of Gas


Other than extinguishment, shutting the flow of the gas is the only offensive action a responder can usually take. In fact, ex- tinguishment should not even be attempted unless the flow can be stopped. Most of the time, all that responders can do is protect the public and/or exposures and let the gas burn. It is imperative that responders know that they are only al- lowed to control the flow at the appliance, service meter, or (in urban areas) curb valve. Closing any other valve in the dis- tribution or transmission lines can lead to disaster. The most common methods for controlling and stopping the flow of gas are limited to a building or a customer.


household appliance Shutoffs FIGURE 4.18 Shutting off a meter.


Each appliance has a shutoff available for routine maintenance and installation. It is usually on or in proximity to the appliance. As with most low-pressure valves, it operates on a quarter turn (90º) in-line valve. This is the valve of choice, if the appliance is the source of the leak. If not, or if the source of the leak cannot be determined, the next choice of control would be at the customer’s service meter.


Meters


Each customer has some form of meter to monitor use and allow for efficient billing. Single-family homes and apartments are supplied by low pressure. Commercial, industrial, and multi-family apartments may have intermedi- ate- or high-pressure meters.


Individual Occupancy Shutoff Valve


pressure Regulator


customer Meter


customer Meter


customer Meter


customer Meter


Main customer Service Shutoff Valve


FIGURE 4.19 Customer service meters at a commercial building with multiple occu- pancy.


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