How to divide the pressure class of flange

　　Common flange is used in different places, so the pressure level is different to a certain extent. For example, large stainless steel flange is mainly used in chemical engineering high temperature pipeline, so it has high requirements for its material pressure bearing function.

　　As a result, customers often require forging flange, because the data through forging to improve the arrangement density, and also enhance its ability to bear pressure. In the domestic and world standards, there are clear requirements for the pressure resistance of large stainless steel flange. Large stainless steel flange is generally divided into: PN25, pn6, PN10, PN16, PN25, PN40, etc. Among them, PN10 and PN16 are the most commonly used.

　　The design pressure of flange of internal pressure vessel with safety valve should be judged 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.

　　If the working pressure is 0.8MPa, the opening pressure of 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 select the maximum allowable working pressure of 0.9mpa (1.0MPa class flange) at 50 ℃.