Safety valve inlet and outlet pipe grades
Thread Content
May I ask, if the grade of the inlet pipe for the safety valve is 300#, why can the grade of the outlet pipe be 150# (since the outlet is used to release air)? When the safety valve opens, isn’t the inlet pressure approximately equal to the outlet pressure? Is there only a pressure drop from the safety valve in the middle? Seeking advice.
It is precisely because of the pressure drop across the safety valve, and this drop is quite significant, that the pressure levels at the inlet and outlet are different
The outlet pressure rating of a safety valve is generally lower than that of the inlet, and the diameter of the outlet pipe is usually larger than that of the inlet pipe. Back pressure is taken into account when designing safety valves; for specific details, one can check the pressure ratings of the inlet and outlet flanges of the safety valve or the manual.
If air is discharged between them, an outlet pressure of 10% of the inlet pressure is considered sufficient