Welding Neck Flanges are easy to recognize as the long tapered hub, that goes gradually over to the wall thickness from a pipe or fitting. The long tapered hub provides an important reinforcement for use in several applications involving high pressure, sub-zero and / or elevated temperatures.
A weld neck flange (WN flange) means a flange has a neck for weld with the pipe, it is easily to recognized by their long tapered neck on the flange (The neck is also called hub in the weld neck flange). The tapered neck can supply a high strength reinforcement to support flange and pipe. It means the weld neck flange is suitable to used in high pressure and extremely temperature situation.
The weld neck flange is connected with the pipe from the neck in butt welding method, that means the neck should be have same material and same outer diameter and wall thickness with the pipe. The butt welding joint could provide a strong connection between the pipes and flanges which is better for high pressure application.
With a neck on one side of the flange, the other side of the flange is sealing face, which are between the two flanges joint. WN flange usually supplied with flat face (FF), raised face(RF) and ring type joint (RTJ). The raised face has a height on the flange rather than the flat face, the RTJ face is used to contain the gasket ring which are specially for high pressure application.