How is the throat diameter of a safety valve determined?
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I’m working on a project recently that requires selecting an appropriate safety valve. One of the parameters considered in choosing a safety valve is its throat diameter. So how is this parameter determined? Those who know about it, let’s discuss!
Calculations shall be carried out in accordance with Annex V, Page P97 of the Code for Pressure Vessels, or Appendix B of GB150. Reference can also be made to API520 and HG/T20570.2-95 \"Installation and Selection of Safety Valves\". Just read the book; there are many formulas, and the key is to understand them – the standard approach is simply to apply those formulas.
Calculate the throat diameter of the safety valve based on its discharge volume
According to statistical estimates, the ratio of the throat diameter dt to the nominal diameter DN for fully open safety valves is approximately 0.625, whereas for slightly open safety valves, the ratio of the throat diameter d0 to the nominal diameter DN is approximately 0.8.
There is no national standard; for full opening, the throat diameter is 2 sizes smaller than the nominal diameter, and for partial opening it is 1 size smaller than the nominal diameter