Weld Neck Flange is flanges that designed to be joined to a piping system by butt welding. This kind of flange include lots of specification,Weld neck Flange is expensive because of its long neck and cost of people for contact WN flange with pipeline or fitting, but is preferred for high stress applications. The necks, or hubs, transmits stresses to the pipeline. The gradual transition of thickness from the base of the hub to the wall thickness at the butt weld provides important reinforcement of the Weld Neck flange. The bore of Weld-Neck flange matches bore of the pipeline, reducing turbulence and erosion.