Usage of a weld neck flange
Weld Neck Flanges are flanges that designed to be joined to a piping system by butt welding. the WN Flange is relatively expensive because of its long neck, but is preferred for high stress applications. The neck, or hub, transmits stresses to the pipe, reducing stress concentrations at the base of the Welding-Neck flanges. 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 the Weld-Neck flange matches the bore of the pipe, reducing turbulence and erosion.