In flange connection, convex flange needs to cooperate with concave flange, commonly known as "one male and one female", while convex flange should cooperate with convex flange. In general, raised face flange should also be a kind of plane flange, code name is RF, and raised face flange code name is m.

Please refer to hg20592-2009 for details. RF face can only be connected with RF face, m face flange needs to be connected with FM face. The compression of M / FM surface is better than that of RF surface.

Often in the actual procurement process, many people think that the two are the same, resulting in the loss of order. The following picture can be more vivid to let you see the difference between the two