Safety and Relief Valves

A safety valve‘s purpose is to exhaust excess and potentially dangerous over-pressure in a system. They are set and sealed at the factory to fully open at a defined pressure to empty the system. In typical operation, the safety valve never operates and only does so in exceptional circumstances. Safety valves are sometimes called SRVs and safety relief valves. Safety valves are generally supplied with a test certificate and should be periodically tested and replaced to ensure that the safety system is ready should over-pressure occur. A typical use is a compressed air reciever, where a safety valve will exhaust pressure should the defined maximum pressure of the tank be exceeded.

Pressure relief valves operate in much the same way as a safety valve however with one main difference. Pressure relief valves have a proportional opening and closing characteristic. They are designed to be activated many times, and will close once the pressure drops to the required pressure. Typically they are supplied at a set pressure, but it can be adjusted as required in service. They are sometimes also called overflow or pressure control valves. They are typically used to protect an existing pump in a closed-circuit from overloading and overheating. The medium can then circulate through the bypass system of the pump or through the piping network.