What happens when excess flow occurs in a liquid service valve?

When excess flow occurs in a liquid service valve, the mechanism is designed to close automatically if the outflow exceeds a safe rate. This is a crucial safety feature to prevent potential hazards that could arise from excessive flow, such as leaks or system failures. The correct answer highlights the importance of controlling flow to maintain safety standards in systems using liquid propane gas.

In this scenario, if the flow rate becomes too high, the valve’s automatic closure is a protective response that helps to minimize risks associated with leaks and pressure build-up. This safety response ensures that the system can operate without posing danger to people or property. The other options do not accurately describe the function of an excess flow valve in this situation. For instance, simply allowing gas flow in one direction or having all flow uninterrupted does not address the need for safety controls during excess flow conditions.