ChinaFlatFlangeFactory The main characteristics of the flange are the connection mode and sealing form. The main influencing parameter is the pipe pressure (different media affect the selection of materials). Generally speaking: Low pressure system (pn<2.5mpa) adopts flat welding or plate flange; Common raised face (RF) seal, medium pressure system (2.5-64mpa) adopts butt welding flange; RF or concave convex surface (fm/m) seal, high-pressure system (above 10.0MPa), usually adopts butt welding flange and ladder groove (RJ) seal;http://www.sy-exports.net/flat-flange/