superimposed back pressure constant or variable

ProMax currently supports six different sets of Relief Valve Sizing Standards: Alternatively, the EN ISA 4126 standard accounts for thermodynamic non-equilibrium. For instance, API 520, one of the most cited standards, assumes both a mechanical and thermodynamic equilibrium, and constant phase properties during relief. There are many different standards for Relief Valve Sizing, each applying different assumptions, thus giving different results. Any stream in ProMax may have one or more Relief Valve Sizing Analyses added, so multiple cases can be studied in a single stream if desired. The Relief Valve Sizing in ProMax is performed as a stream analysis. The first step in sizing a Relief Valve in ProMax is to determine which scenario you are interested in modeling. In any of these scenarios, the pressure will increase until a predetermined relief pressure is reached, at which point the relief pressure valve will open, decreasing the pressure after the turnaround time. It is generally recommended to perform multiple case studies to find the most conservative sizing. Many scenarios can result in an increased vessel pressure, and each scenario may result in a different valve size. Properly sized relief valves will provide the required protection, while also avoiding issues with excessive flow rates, including: possible valve damage, impaired performance, undersized discharge piping and effluent handling systems, and higher costs. Pressure relief valves are used to protect equipment from excessive overpressure. Pressure Relief Valve Sizing Craig Spears November 10, 2015

Superimposed back pressure constant or variable