(a) Silver brazing. (1) Circumferential pipe joints may be either of the socket or butt type. When butt joints are employed the edges to be joined must be cut or machined square and the edges must be held closely together to insure a satisfactory joint.

(b) Copper-alloy brazing. (1) Copper-alloy brazing may be employed to join pipe, valves, and fittings. Circumferential joints may be either of the butt or socket type. Where butt joints are employed, the included angle must be not less than 90° where the wall thickness is three-sixteenths of an inch or greater. The annular clearance of socket joints must be held to small clearances.

(2) Copper pipe fabricated with longitudinal joints for pressures not exceeding that permitted by the regulations in this subchapter may have butt, lapped, or scarfed joints. If of the latter type, the kerf of the material must be not less than 60°.

(c) Brazing, general. (1) Heat must be applied evenly and uniformly to all parts of the joint in order to prevent local overheating.

(2) The members to be joined must be held firmly in place until the brazing alloy has set so as to prevent any strain on the joint until the brazing alloy has thoroughly solidified. The brazing must be done by placing the flux and brazing material on one side of the joint and applying heat until the brazing material flows entirely through the lap and shows uniformly along the seam on the other side of the joint. Sufficient flux must be used to cause the brazing material to appear promptly after reaching the brazing temperature.