There are various types of sealing surfaces for stamped flanges, including convex surface (RF), concave surface (FM), concave convex surface (MFM), tenon groove surface (TG), full plane (FF), ring connecting surface (RJ), etc. The national standard flange is divided into two major systems, namely the European system and the American system.

There are currently four flange standards in China, namely:

The flange standards for the mechanical industry are JB/T74-86. 2——1994；

Petrochemical industry flange standard SH3406-1996;

Chemical industry flange standard HG20592-20635-1997;

Flange standard GB/T9112-9124-2000.

So, how to choose a flange? There are several basis points as follows:

The properties of the conveying medium include general medium, medium, toxic medium, flammable and explosive medium,

Determine flange specifications based on the connection object.

Determine the connection method and sealing surface form between the flange and the pipe based on the usage location and connection conditions.

Based on the parameters of the medium, working pressure, and working temperature, the nominal pressure PN of the flange is determined according to the working temperature and pressure of the medium when the medium is determined.