Different sealing surfaces of carbon steel weld neck flanges

　　1. Full Plane Seal Type (FF): It is mostly used for flat weld neck flanges matching in low pressure environment, such as PN1.0.

　　2. Concave and convex sealing surface type (FM): mostly in butt welding and weld neck flanges, not commonly used in the United States, more in the European system, mostly in PN4.0, PN6.4 MPA pressure level, but not conducive to gasket replacement.

　　3. The type of sealing face of convex surface (RF): & nbsp; the weld neck flanges with convex surface has the widest application range, and most of them appear in PN2.0, PN5.0 and PN10.0 MPA pressure grades of American weld neck flanges, and in PN1.6 and PN2.5 MPA pressure grades of European ANSI B16.5 150LBS Carbon Steel Weld Neck Flanges.

　　4. Tenon groove sealing surface type (TG): The use of the same concave and convex surface.

　　5. Ring groove sealing surface type (RJ): It is often used in combination with butt weld connection. It is not used in socket welding. It is mostly used in high temperature, high pressure or both environments. It is also used in PN10.0, PN15.0, PN25.0, PN42.0 MPA pressure grades in American system, and on weld neck flanges with spherical high pressure grades in European system.