How to divide the pressure rating of common flange?

In the domestic and international standards, there are clear requirements for the compression resistance of large stainless steel flange. Large stainless steel flange is generally divided into PN25, pn6, PN10, PN16, PN25, PN40, etc. PN10 and PN16 are commonly used.

As an example, the design pressure of flange of internal pressure vessel with safety valve shall be determined according to the opening pressure of safety valve. The design pressure is equal to or slightly greater than the opening pressure of the safety valve, and the opening pressure of the safety valve is 1.05 ~ 1.1 times of the working pressure.

BS 4504 ASTM A105 PN16 raised face slip on flanges

Given that the working pressure is 0.8MPa, the opening pressure of the safety valve can be taken as 0.88mpa, so the design pressure can be taken as 0.9mpa. In this way, it is reasonable to choose a high allowable working pressure of 0.9mpa (1.0MPa level flange) for 1C4 material of vessel pipe flange at 50 ℃.