Question regarding the maximum discharge pressure of safety valves per HG/T20570
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For HG/T20570, is the maximum discharge pressure of a safety valve calculated based on the design gauge pressure or absolute pressure multiplied by a coefficient? If the design pressure is 3.0 Mpa (G), then is the maximum discharge pressure of the fire safety valve 3.0*121%, or 3.1*121%?
Is there no standard for this? It can be checked
In HG/T 20570, the calculation coefficient for the maximum relief pressure is generally determined based on the design pressure of the equipment (gauge pressure). In other words, if the design pressure of the equipment is 3.0 MPa(G), then the maximum discharge pressure of the safety valve under fire conditions should be calculated in gauge pressure: Maximum discharge pressure = 3.0 MPa(G) × 121% = 3.63 MPa(G). There is no need to convert this value to absolute pressure (3.1 MPa) for calculation. .
GB150 provides detailed criteria for selection.