Which valve re-closes automatically when upstream pressure declines to prevent continued release?

• A. Pressure relief valve
• B. Check valve
• C. Gate valve
• D. Solenoid valve

Answer: (A)

When a system is protected from overpressure, the valve that opens to release excess pressure and then automatically reseats as the pressure falls is a pressure relief valve. It is designed to vent only when the upstream pressure exceeds its set point and to close again once pressure drops back to safe levels, preventing continued release.

A check valve, on the other hand, stops backflow and closes if forward flow stops or reverses, but it doesn’t purposefully vent pressure as part of its normal operation. A gate valve is a manual shutoff that does not respond automatically to pressure changes. A solenoid valve is an electrically actuated valve; it can operate automatically, but its actuation isn’t inherently tied to a pressure-based auto-close in the same way a relief valve is.