Flat welded flange(PL）:The application range of flat welded flange is increased from the old PN25 to the phenomenon standard PN40, which has lower cost but poor rigidity. It is not recommended to use in conditions with high requirements such as flammable and explosive and toxic and harmful media. The sealing surface has a sudden surface and a full plane.

Flat welded flange with neck(SO):The neck height of flat welded flange with neck is lower, compared with flat welded flange with plate, its stiffness and bearing capacity are improved. Compared with the butt welding flange, the welding workload is large, the welding rod consumption is high, can not withstand high temperature and pressure and repeated bending and temperature fluctuations, but the ready-made installation is more convenient, and the welding seam detection process can be omitted, and it is more popular. The sealing surface has the form of plane, protruding surface, concave and convex surface, mortise and groove surface.

Flange with neck butt welding(WN):Also called high neck flange, the flange is not easy to deform, sealing performance number, and the price is relatively moderate. It is suitable for high pressure, high temperature and large pipe diameter. The sealing surface has the form of plane, protruding surface, concave and convex surface, tenon and groove surface and ring connection surface.