Socket Welded Fittings are used in sizes 1-1/2″ (or 2″) and smaller. Welded fittings are specified the same as the pipe, by weight, schedule or wall thickness. These fittings are specified per the pressure class. Socket-weld fittings include a deep socket into which the pipe slips and aligns itself. The weld is then made on the outer surface of the pipe and fitting, which eliminate the need for or use of special clamps or tack welding for alignment prior to the final fit-up welding. These fittings are provided with a bell-shaped end that is internally machined to encompass the external diameter of the pipe that fits. Socket welded fittings are preferred in areas of high vibration.
Socket welded flanges are commonly used for small-bore piping. The socket-welded flange is susceptible to crevice corrosion, wherein the gap at the pipe to socket interface is a crevice exposed to the process fluid. The socket weld flange is bored to the ID of the pipe and counter bored is slightly larger than the pipe to allow the pipe to be inserted and welded in place. They allow a pipe to fit inside a machined socket of a flange prior to welding. The pipe slips in upto the end of the socket and is welded on the outside with a fillet weld. This flange pipe fits into the recess to allow smooth flow through the flange. They are ideal for small diameter high-pressure applications.