Pressure relief valve and Relief valve

Relief valve and pressure relief valve are semantically related. In some cases you can use "Relief valve" instead a noun "Pressure relief valve".

Relief valve noun - A valve in a container in which pressure can build up (as a steam boiler); it opens automatically when the pressure reaches a dangerous level.

Pressure relief valve and relief valve are semantically related. You can use "Pressure relief valve" instead a noun phrase "Relief valve".