What is the relationship between the set pressure, back pressure, and operating pressure of a safety valve?
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Last edited by kfz42200 on 2017-3-9 08:48. Model: 3K4, fully open type； Set pressure Mpa(G): 1.6 ； Overpressure: 10% ； Back pressure Mpa(G): 0.4 ； Discharge pressure Mpa: 1.86 ； Emission temperature: 209℃ ； Operating pressure Mpa: 1.4 ； Operating temperature: 198℃ ； Emission capacity Kg/h: 6200 ； Medium: Water vapor ； Medium state: gas phase ； Molecular weight 18 ； Size and nominal pressure inlet/outlet: 3", 300lb/4", 150lb ； Execution standard: API526 and API520 or higher are the standards for safety valves to be purchased. I hadn’t noticed the presence of back pressure before; this time back pressure is present. I’ve asked several people but no one could explain the relationship between them – I’m seeking help from experts! !
This post was last edited by ylb913 on 2017-3-9 12:04: Setting and Selection of Safety Valves HGT 20570.2-95
Selection guidelines for safety valves! It can be used as a reference!
The expert’s explanation is too theoretical; I’m a bit confused now. Can the pressure relationships related to safety valves really be viewed in such a simple way: setting pressure = rated pressure – back pressure?
It mainly depends on the design; back pressure is divided into static back pressure and dynamic back pressure. Based on the data you provided, the starting pressure should be equal to the set pressure minus the back pressure. If the back pressure remains stable at 0.4 MPa or if there is a bellows in place, then this approach can be used