Socket Welding Flange, a popular type of pipe flange, was initially developed for use on small-sized high- pressure piping. The fabrication of this type of flange is similar to that of a slip-on flange. However, the internal pocket of a socket weld flange allows for a smooth bore and better fluid flow. When provided with an internal weld, the static strength of this flange is equal to slip-on flange, but the fatigue strength is 50% greater than double welding slip-on flanges. Smooth bore conditions in such a flange can easily be attained without having to bevel the flange face and, after welding, to reface the socket weld flange as would be required with slip-on flanges. For this reason, the internally welded flange is popular in chemical process piping.