Some essential factors concerned with 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:
Set Pressure
A PRV is set to open at the inlet pressure under the specified service conditions.
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 continuous discharge of the fluid through it.
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Full-flow Pressure
The pressure at the inlet of a PRV, when it is passing its rated maximum flow, is called the full-flow pressure.
Pressure Override
The difference between a PRV’s full-flow pressure and cracking pressure is called the pressure override or the pressure build-up over the PRV’s set point.
Closing Pressure
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 firm contact with the seat.
Overpressure
It is the pressure increase above a PRV’s set pressure, expressed in pressure units or as a percentage.
Backpressure
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.
Superimposed Backpressure
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.
Built-Up Backpressure
It is the increase in the pressure in the PRV’s discharge header when fluid flows through it.
Joji Parambath
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Fluid Power Educational Series Books
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