Page 411 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 7 .11 Lube, Seal and Control Oil System Best Practices
The function of a relief valve as a protection device is to limit
B.P. 7.11. Supporting Material
pump discharge pressure and horsepower to a specified value
without generating any valve instabilities. While the function of
Relief valves for positive displacement a relief valve is simple enough, valve chatter (instability) and
pumps failure to positively reseat can cause the shutdown of the critical
equipment. Relief valve chatter can cause high pressure pulses
Since positive displacement pumps are not self-limiting, i.e., that will activate shutdown pressure switches and damage valve
they can produce increasing pressure if sufficient driver power is seats and plugs.
available, hence a device to limit pump pressure and horsepower The inability to reseat properly will introduce an ‘equivalent
is required. orifice’ into the system that will reduce or totally eliminate the
system flow to the critical system components.

Fig 7.11.1 Modulating relief valve (Courtesy of Fulflow Specialties Co. Inc.)

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