If you have ever simply clicked the "Depressuring" button in HYSYS, set a valve diameter, and reported the result, you are leaving money (and safety margin) on the table.
HYSYS defaults to "All Flow Regimes." For backpressure > 50% of upstream pressure, switch to "Subcritical only." Otherwise, your valve will be undersized.
Target Audience: Process Engineers, Safety Engineers, Senior Students. Software: Aspen HYSYS V12+ (Concepts apply to V10–V14)