The issue of the pipe diameter downstream of the safety valve
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I would like to ask the experienced experts on this forum: what are the requirements regarding pipe diameter for the pipelines downstream of the safety valve, whether they are used for venting to the atmosphere or for flare discharge, and whether the venting is done separately or together? I saw the following explanation on Baidu Tieba: For the pressure relief pipe of a single safety valve, the back pressure should be no more than 10% of the pressure released by that valve, but it should not be smaller than the diameter of the safety valve’s outlet pipe ； 2. The discharge pipe connecting multiple safety valves shall be designed such that the back pressure generated when all safety valves discharge simultaneously is not greater than 10% of the discharge pressure of any single safety valve, and the cross-sectional area of the discharge pipe shall not be smaller than the sum of the cross-sectional areas of all the branch pipes.
The requirement for the diameter of the pipe downstream of the safety valve is primarily determined such that the back pressure does not exceed 10% of the safety valve’s discharge pressure. For the pressure relief pipe of a single safety valve, its diameter should not be smaller than the outlet diameter of the safety valve. If it is a drain pipe connecting multiple safety valves, it is necessary to ensure that the back pressure generated when all safety valves discharge simultaneously does not exceed 10% of the discharge pressure of any single safety valve; moreover, the cross-sectional area of the drain pipe should be no smaller than the sum of the cross-sectional areas of all the individual branches. This design is intended to ensure that the safety valve can properly release pressure, thereby preventing safety issues caused by excessive backpressure. .
During expert inspections, we have encountered such problems; for safe discharge, safety valves are sometimes used as backups for one another. Indeed, the cross-sectional area of the discharge pipe should be no smaller than the sum of the cross-sectional areas of all the branch pipes. It also depends on the design – namely, how many safety valves will be discharging simultaneously. Being pressed isn’t counted: L
Same question: additionally, how is the pressure drop in the pipeline leading to the safe import calculated? If there are experts in this field, please share your opinions or provide various calculation formulas. Thank you!