Which valve automatically releases excess pressure to protect the system?

• A. Relief valve
• B. Check valve
• C. Block valve
• D. Throttle valve

Answer: (A)

The essential idea is automatic protection against overpressure. A relief valve is designed to open on its own when system pressure reaches a preset limit, venting fluid out of the circuit to prevent components from being damaged. Once the pressure drops below the set point, it closes again. This automatic venting is what keeps the system within safe pressure levels.

Other valves don’t perform this automatic safety function. A check valve prevents backflow but doesn’t relieve excess pressure. A block valve is a shutoff device used to isolate parts of the system and does not automatically release pressure. A throttle valve restricts flow to control rate, not to relieve pressure automatically.

So the valve that automatically releases excess pressure to protect the system is the relief valve.