API-RP-576

4.2 Pressure-relief Valve
A pressure-relief valve is designed to open for the relief of excess pressure and reclose
thereby preventing further flow of fluid after normal conditions have been restored. A
pressure-relief valve opens when its upstream pressure reaches the opening pressure. It
then allows fluid to flow until its upstream pressure falls to the closing pressure. It then
closes, preventing further flow.
Examples of specific types of pressure-relief valves include:
• safety valve,
• relief valve,
• conventional safety-relief valve,
• balanced safety-relief valve, and
• pilot-operated pressure-relief valve.
Fion Zhnag/ Charlie Chong