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.
Weld neck flanges are the most popular flange type with a neck extension with a weld bevel at the end, this type of flange is designed to butt weld directly to pipe to provide a superior and relatively natural form connection. In larger sizes and higher pressure classes, this is almost exclusively the type of flange connection utilized.
Also known as nozzle flanges or “long neck” flanges, these items were designed with the pressure vessel and tank fabrication industry in mind. They are typically made as a one-piece construction with the intention of replacing a standard weld neck and pipe weld combination. They usually have one straight thru bore with a square cut end (instead of the typical weld neck bevel). The overall length of the nozzle flange is up to the end user, and the body of the nozzle can be modified to some pre-existing sizes or custom sizes for additional reinforcement as required.
Welding Neck Flanges are easy to recognize at the long tapered hub, that goes gradually over to the wall thickness from a pipe or fitting.