What do you call devices that shut off the flow in gas pipes or hose lines when breaks occur?

The correct term for devices that shut off the flow in gas pipes or hose lines when breaks occur is "excess flow valves." These valves are specifically designed to detect a sudden increase in flow that typically indicates a leak or break in the line. When such an increase is detected, the excess flow valve automatically closes to stop the flow of gas, thus preventing potential hazards such as explosions or fires due to gas escaping into the environment.

Excess flow valves are crucial for maintaining safety in gas distribution systems, ensuring that the gas can only flow within safe limits. They serve as a protective measure, offering a quick response to emergencies that would otherwise endanger lives and property.

Other devices mentioned have different functions. Flow restrictors are used to limit the amount of fluid that can pass through a system but do not respond to breaks like excess flow valves do. Pressure relief valves are designed to release pressure when it exceeds a certain threshold, protecting systems from overpressure situations, but they do not directly stop flow like an excess flow valve. Gas regulators are primarily used to control the pressure of gas flowing to appliances but do not function to shut off flow in case of a break. Thus, understanding the specific roles of these devices is key in plumbing and gas management practices