... surface: flat, raised face,male and female, tongue and groove, rubber ring joint face, the lens surface and the diaphragm welded surfacee ... flange c, Loose flange, Butt weld ring with loose with neck flange, Butt weld ring with loose with plate flange. d, ... sealing surface: flat, raised face, convex face, tongue and groove, ring joint faceFlange production standard Chinese Standard:GB/T9112-2000(GB9113 ...