According to Section VIII, what is the maximum set pressure for safety valves?

• A. Relieving pressure
• B. MAWP
• C. Set pressure
• D. Piping maximum relief pressure

Answer: (B)

The key idea is that safety devices must be set so the system never exceeds what the vessel is designed to safely handle. In ASME Section VIII, the maximum pressure a vessel may operate under in normal service is the MAWP (maximum allowable working pressure). The safety valve is supposed to start relieving at a pressure that prevents the vessel from reaching that limit. Therefore, the set pressure of a safety valve must be no higher than the MAWP, making MAWP the maximum permissible set pressure. This keeps overpressure from occurring and protects the vessel from unsafe conditions.

Relieving pressure and piping maximum relief pressure are related concepts, but they describe different aspects of the protection system. The set pressure is specifically the pressure at which the valve begins to open, and the allowable ceiling for that set pressure is the MAWP.