Sizing and Performance of Safety Valve Relief Systems for Two-Phase Flow
By H. Kuhn (Grant Holder)* S.D. Morris

Abstract
This report describes a steady-state Homogeneous Equilibrium Model (HEM) that can be
applied to the design of emergency pressure relief systems involving compressible flashing
flows. The relief system may comprise an inlet nozzle (between vessel and vent-pipe inlet)* an
inlet pipe with various fittings (bends.etc)* a safety valve and a tailpipe with fittings including
area changes. Multiple choking may occur in such systems and the model includes a procedure
for dealing with this situation.
The equations of the model have been assembled into a computer program called VLINE and
this program is applied to a practical relief system to illustrate its usefulness in design.

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