Pilot Operated Pressure Relief Valve

Like other Pressure Relief Valves (PRV), Pilot Operated Relief Valves (PORV) are used for emergency relief during overpressure events (e.g. a tank gets too hot and the expanding fluid increases the pressure to dangerous levels). The distinction between Pilot Operated Relief Valves and conventional Pressure Relief Valves is that pilot valves use system pressure to seal the valve. A Pressure relief valves typically uses a spring to hold the disc or piston on seat. The essential parts of Pilot Operated Relief Valve are a pilot valve (or control pilot), a main valve, a Pitot tube, the dome, a disc or piston, and a seat. The volume above the piston is called the dome. THe Pilot Operated Relief Valve also called Pilot Operated Safety Valve, POPRV (Pilot Operated Pressure Relief Valve), or POSRV (Pilot Operated Safety Relief Valve), depending on the manufacturer and the application. Technically POPRV is the most generic term, but PORV is often used generically (as in this article) even though it should refer to valves in liquid service

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