The main types of flanges are welding neck, long welding neck, lap joint, threaded and blind flange, sliding sleeve, socket welding, in addition to these standard flanges, there are some special flanges, rotating flanges, expansion/deceleration Device flange and hole flange.
The type of flange used in piping applications mainly depends on the required strength of the flange joint. The use of flanges or welded connections can simplify operation and maintenance (flange connections can be quickly and easily removed).
The welding flange ("WN") adopts a long tapered hub, which can be welded to the pipeline. This type of flange is usually used for high pressure and high temperature/low temperature applications. These applications require the unrestricted flow of the fluid conveyed by the piping system (the flange hole matches the pipe hole), no pressure drop can prevent negative effects, and the metal near the flange joint will cause turbulence and corrosion. The tapered hub allows the mechanical stress to be smoothly distributed between the pipe and the welding neck flange, and facilitates radiographic inspections to detect possible leaks and welding defects. The size of the flange (NPS and pipe table) should be consistent with the size of the connecting pipe.