he nominal diameter of the flange is denoted by DN

　　The nominal diameter of the flange is denoted by DN, which is the common caliber of various steel pipe and Stainless Steel Socket Weld Flange. The same nominal diameter of the steel pipe and pipe fittings are not necessarily connected with each other, not necessarily interchangeable, flange nominal diameter is not a practical sense of the outer diameter or inner diameter, the value is close to the inner diameter.