There is a real difference between PSV and PRV based on how they operate, and although a PRV is a type of safety valve (PSV) it should be not be confused with a standard PSV. PRV open based on proportional pressure that they are exposed to, once above the set pressure. This is why they are used mainly for hydraulic systems (limited stored energy). While PSV simply dumps all the pressure once it isexposed the its set pressure, and for this reason it is mainly used for gas (high stored energy).
another difference between prv and psv is that, prv operates normally by controlling the system, whereas once the psv is operated, the device should be taken out of system and then needs to be sent to the maintenance warehouse to for calibration purposes
