Abstract: An expandable band is employed to provide a mold on the interior of the joint into which the weld puddle is flowed which may be made of any appropriate material, but preferably is copper. The back-up band is carried on a set of rounding jacks which engage the facing pipe ends and exert a circumferentially uniform radial force on the pipes. This serves to round the ends equally and bring them into coaxial alignment with each other in the vicinity of the joint. The back-up band bridges the joint and expands to form a closed or semi-sealed chamber around the joint.

Abstract: A pair of pipe ends are first prepared prior to welding to provide highly accurate guide surfaces. Secondly, a welding torch carriage arrangement is provided which engages the exterior surfaces of the abutting pipe ends to be welded, which carriage is guided around the circumference of the pipe ends in conjunction with the guide surfaces provided thereon. Thirdly, a back-up band arrangement is provided interiorly of the joint to be welded.An expandable band is employed to provide a mold on the interior of the joint into which the weld puddle is flowed which may be made of any appropriate material, but preferably is copper. The back-up band is carried on a set of rounding jacks which engage the facing pipe ends and exert a circumferentially uniform radial force on the pipes. This serves to round the ends equally and bring them into coaxial alignment with each other in the vicinity of the joint. The back-up band bridges the joint and expands to form a closed or semi-sealed chamber around the joint.