Some essential factors concerned about the operation of hydraulic pressure regulators are its set pressure, cracking pressure, full-flow pressure, pressure-override, closing pressure, overpressure, blowdown, and backpressure. These useful terms are defined in the following sections:
It is the inlet pressure, under the specified service conditions, at which a PRV is set to open.
Cracking (Opening) Pressure
It is the value of increasing the inlet pressure of a PRV at which there is a measurable lift of its poppet, and there is a continuous discharge of the fluid through it.
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The pressure at the inlet of a PRV, when it is passing its rated maximum flow, is called the full-flow pressure.
The difference between the full-flow pressure and the cracking pressure of a PRV is called the pressure-override or the pressure build-up over the set point of the PRV.
It is also known as ‘reseat’ pressure. The closing pressure of a PRV is the value of decreasing inlet pressure at which the poppet of the PRV re-establishes a firm contact with the seat.
It is the pressure increase above the set pressure of a PRV, expressed in pressure units or as a percentage.
It is the pressure that exists at the outlet of a PRV as a result of the pressure in the discharge system. It may be subdivided into superimposed and built-up backpressures.
This is the backpressure acting on the outlet of a closed PRV. It is the effect of the pressure in the discharge system coming from multiple sources.
It is the increase in the pressure in the PRV’s discharge header when the fluid is flowing through the PRV.
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