Which type of valve must have a closing flow greater than the maximum system design flow rate?

The type of valve that must have a closing flow greater than the maximum system design flow rate is the excess-flow check valve. This valve is designed to automatically close if the flow exceeds a predetermined level, which is set to be higher than the system's maximum design flow rate. This feature is critical for safety; it helps prevent potential leaks or over-pressurization in the system by stopping the flow in the event of a rupture or significant leakage downstream.

In CNG applications, if a pipeline fails or a fitting comes loose, the excess-flow check valve will quickly shut off the flow, thus minimizing the potential for dangerous situations, such as gas escaping into the atmosphere. The design ensures that normal operations are unimpeded while providing a reliable safeguard against flow rates that exceed system capacities.

Other valve types, such as pressure relief valves, backflow check valves, and manual valves, serve different functions and do not necessarily require the same flow specifications as the excess-flow check valve. Pressure relief valves are designed to vent excess pressure and protect against over-pressurization rather than controlling flow rate. Backflow check valves prevent the reverse flow of gas, ensuring that it flows in one direction, while manual valves are operated by hand and do not automatically react to