One length of pipe may be joined to another by composition flanges as shown in Fig. 255 or in a permanently brazed cup joint as shown in Fig. 256.

The flange joint may be readily taken apart by removing the bolts. Flanges are standardized in all their dimensions and in com-position. Each length of pipe is permanently connected to its flange by beading at the end, as at b, into a recess in the flange, and by brazing around the groove c made for holding the brazing metal after it melts. A flange is brazed on while the pipe rests vertically, and frequently a ring of plastic fire clay is built around the joint on the flange shoulder d to keep the brazing metal on the joint while molten.

The lap of a cup joint is about equal to the diameter of the pipe. The cupped portion b is expanded by an expander, the bell-mouth c is flared by the collar hammer, and when the two lengths of pipe are cleaned for brazing and fitted together, the fillet d is closed against the inner pipe by the drift set. After brazing, the joint is smoothed by filing. The flared ring c assists to stiffen the pipe.

Fig. 257. - Preparing a Branch Joint Opening.