Dynamic and static methods were previously developed for the modeling of spring loaded pressure relief valve stability in Parts 1 through 7 of this white paper series. We extend those methods to pilot operated pressure relief valves in this 8th installment. Pilot operated pressure relief valves can be modeled dynamically using either a dual degree of freedom (DDOF) model or a lumped single degree of freedom (SDOF) model.
This paper provides guidance on how to select parameters for both DDOF and SDOF models for use with Process Safety Office® SuperChems® Expert.
Pilot Operated Pressure Relief Valves (POPRV) consist of two major components, (a) the "pilot" valve, and (b) the "main" valve. This is shown in Figure 1.
Both the pilot valve and the main valve are spring loaded. The pilot valve, also called the "pilot", is the control unit of the POPRV. It controls the function and behavior of the main valve.
The pilot valve directs the main valve to open or close by allowing the fluid to enter or exit the dome of the main valve. The main valve action follows the pilot valve action but can lag the pilot valve action by 10 to 20 milliseconds.
Watch the presentation on Analysis of PRV Stability In Relief Systems Part VIII by Georges A. Melhem, Ph.D., FAIChE, on Process Safety tv®.
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