Pressure relief valve and Safety valve

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

Safety 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 safety valve are semantically related. You can use "Pressure relief valve" instead a noun phrase "Safety valve".