Safety valves nominal pressure, the opening pressure, the emissions pressure, returns to the place pressure, to open shuts the differential pressure concept

Safety valve's nominal pressure expression safety valve's under normal temperature condition highest allowable pressure, the high temperature equipment uses the safety valve should not consider under the high temperature material allowable stress reduction. The safety valve is carries on the design manufacture according to the nominal pressure standard.
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　　 Opening pressure: Is also called the set pressure, is the safety valve valve petal starts under the operating condition to raise the time medium pressure.
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　　 Emissions pressure: The valve petal achieves when the stipulation opening altitude imports the side the pressure. >z-_PX 0$
　　 Returns to the place pressure: After safety valve emissions, the valve petal contracts the valve seat, the medium stop discharges when the inlet pressure. Returns to the place pressure is attributes the safety valve service performance a key parameter, generally requests it at least for the working pressure 80%, the upper limit take does not have the valve petal frequent beat as suitable.
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　　 Opens shuts the differential pressure: The opening pressure and returns to difference of the place pressure.
　　 Is as follows to the boiler boiler barrel and the superheater safety valve's opening pressure stipulation:
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　　 when (1) the fixed steam pressure is smaller than 1.27MPa, opening pressure respectively be working pressure +0.02MPa and working pressure +0.04MPa;
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　　 (2) the fixed steam pressure is bigger than 1.27MPa, but is smaller than time 3.82MPa, the opening pressure respectively is 1.04 time of working pressures and 1.06 time of working pressures;
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　　 when (3) the fixed steam pressure is bigger than 3.82MPa, the opening pressure respectively is 1.05 time of working pressures and 1.08 time of working pressures.
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　　 Economizer safety valve's opening pressure for economizer working pressure 1.5 times.
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　　 The pressure vessel safety valve's opening pressure do not surpass pressure vessel's design pressure.