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1. Relief valve opening is directly proportional to thepressure rise.Safety valve opening will happen at after reaching the setpressure.2. Safety valve can be operated manually with use of easinggear (as in boilers) whereas Relief valve can not.3. Safety valve is set at 3% above the working pressureRelief valve is set at 10% above working pressure.4. Safety valve is used in a vapour or steam system, whereasRelief valve can be used in Fluid or compressed air system.
Relief valves are normally installed on water boilers and other systems with internal (usually air) pressure to emitt off some of that pressure when it reaches a designed level. They are usaully built with the spring inside that is compressed under pressure. Unlike relief valves, safety valves are operated manually by turning on or off the during emergecy situation such as a house that is flooding.
Relief Valve is to release the air pressure from the system and the Safety Valve is to stop or to close the flow from the system.
A safety valve is used at applications requiring immediate relief of excess pressure and opens instantly.
A relief valves open gruadually after the set point value and closes and open intermittently as per the difference in excess pressure.
Pressure Relief Valve - is the term used to describe relief device on a liquid filled vessel. For such a valve the opening is proportional to increase in the vessel pressure. Hence the opening of valve is not sudden, but gradual if the pressure is increased gradually.
Pressure Safety Valve - is the term used to describe relief device on a compressible fluid or gas filled vessel. For such a valve the opening is sudden. When the set pressure of the valve is reached, the valve opens almost fully.
