... flat, raised face,male and female, tongue and groove, rubber ring joint face, the lens surface and the diaphragm welded surfacee, ... d, Flange sealing surface: raised face, male and female, tongue and groove, metal rings connected surface 3, Chinese steel pipe ... sealing surface: flat, raised face, convex face, tongue and groove, ring joint faceFlange production standard Chinese Standard:GB/T9112-2000 ...