
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 difference between PORV and
conventional PRV is that pilot valves use system pressure to seal the valve. A
PRV typically uses a spring to hold the disc or piston on seat. The essential
parts of a PORV 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.
PORV are also called
pilot-operated safety valve...