Pressure Relief Valve Sizing Equations Basis

AIChE Webinar
Originally delivered Mar 14, 2012

For sizing pressure relief valves, many turn to the guidelines and practices of ASME and API that present specific sizing equations given a required relief rate and basic fluid properties. Application of these sizing equations is fairly straightforward for idealized systems (nonflashing liquids or ideal gases), but increase in complexity for non-idealized systems. In some cases, there are no sizing equations presented, leaving the engineer to wonder if some simplifying assumptions can be made to allow the use of idealized equations or if further analysis needs to be done. A fundamental understanding of the basis for the relief valve sizing equations, which is founded on isentropic nozzle flow, will allow one to view the sizing equations as part of a unified mathematical approach, to determine the applicability and limits of the idealized assumptions, and to have a general alternative for use in any fluid regime.

In this webinar, engineers who are responsible for the sizing of pressure relief valves and would like a more in-depth understanding of the mathematical basis for the sizing equations learn:

  1. the basis for the sizing equations as the isentropic nozzle mass flux integration
  2. the effects that the idealized assumptions have on the mass flux integration to yield the common sizing equations
  3. how to apply a numerical integration to size a pressure relief valve for any fluid
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