Which statement correctly identifies the starting point for relief valve operation?

• A. Minimum pressure
• B. Design pressure
• C. Operating pressure
• D. Maximum pressure

Answer: (B)

Relief devices are meant to protect a system by starting to relieve as pressure reaches the point the equipment is designed to handle safely. That point is the design pressure—the maximum safe operating pressure the system is intended to withstand. Setting the relief valve to begin relieving at this pressure ensures pressure won’t climb toward the maximum allowable limit, guarding against overpressure and potential damage.

If the pressure were at a minimum or at the normal operating level, relief wouldn’t be needed or would occur at the wrong time, and relying on the absolute maximum limit would be too late to prevent unsafe conditions. The design pressure defines when relief action should commence to keep the system within safe limits.