Pressure Release Valves (PRV)

A pressure relief valve is a safety device that relieves overpressure in a vessel or piping. The generic terms are pressure relief valves (PRV) or pressure safety valves (PSV). They are a subset of pressure relieving devices (PRD), which include devices that are not valves, such as vacuum breakers and rupture disks.

Main types of pressure relief valves include:

• Relief valve (RV) - an automatic system that relieves liquid pressure above a pre-set limit.

• Safety valve (SV) - an automatic system that relieves gas pressure above a pre-set limit (e.g., safety valves on pressure cookers release pressure caused by steam expansion due to the application of heat).

• Safety relief valve (SRV) - an automatic system that relieves gas and liquid pressure.

(RV, SV and SRV are spring operated/loaded. LPSV and VPSV are spring operated or weight loaded. )

• Pilot operated safety relief valve (POSRV) - an automatic system that relieves pressure from a remote command from a pilot on which the static pressure (from equipment to protect) is connected.

• Low pressure safety valve (LPSV) - an automatic system that relieves low levels of gas pressure.

• Vacuum pressure safety valve (VPSV) - an automatic system that relieves static pressure on a gas. The pressure is small, negative and near the atmospheric pressure.

• Low and vacuum pressure safety valve (LVPSV) - an automatic system that relieves static pressure on a gas. The pressure is small, negative or positive and near the atmospheric pressure.