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.