By design, screwed andsocket-weld fittings cannot be assembled by placing one fitting directly incontact with another fitting. Screwed fittings are manufactured with threads onthe inside of the fitting, and socket-weld fittings have an internal socketthat prevents fitting makeup assembly. To facilitate the assembly of screwedand socket-weld fittings, small lengths of pipe called pipe nipples are used betweenfittings. Pipe nipples can vary in length depending upon the distance requiredto fabricate the pipe configuration. A close nipple is one that provides the minimumlength of pipe between fittings. Remember, screwed and socket-weld fittingshave a certain amount of lost pipe due to thread engagement and socket depth. Therefore, each size pipehas a different minimum length for the dimension of a close nipple. Manycompanies will use 3_ as the standard minimum for pipe nipples.This length will accommodate the amount of pipe lost inside the fitting on eachend as well as provide sufficient wrench clearance during assembly for thelarger screwed and socket-weld pipe sizes.
Swage Swages are functionally similar to reducers, but are specifically designed for screwed and socketweld pipe. Screwed swages have male (external) threads and can be connected to other screwed fittings without the use of a pipe nipple. They are used to make reductions in the line size on a straight run of pipe. Swages, like reducers, are available in either a concentric or eccentric shape.
Swages are unique in that they can be used in screwed,socket-weld, or butt-weld configurations. When used in these configurations, swages will have different end preparations.
Screwed swages will have thread ends (TE),socket-weld swages plain ends (PE), and butt-weld swages have beveled ends (BE). Because socket-weld swages are inserted into mating fittings, many companies allow the substitution of beveled-end swages. Dual purpose fittings like these will make the job of the purchasing group much easier. Swages are also manufactured with different preparations on the two ends. When specifying a swage, use the following abbreviations:
BBE—bevel both ends
TBE—thread both ends
PBE—plain both ends
BLE/TSE—bevel large end/thread small end
PLE/TSE—plain large end/thread small end
