Preparatory to welding a pair of pipe lengths to one another it is conventional to arrange the confronting ends of two pipe lengths adjacent one another substantially in the position in which they are to be welded together. It is more common than not for discrepancies to exist between the configurations of the pipes. That is, the end of one pipe may be more or less round than the other. Thus, if the confronting ends of the pipe lengths are to conform to one another, they must be reshaped or reformed.
Reformation of the confronting ends of pipe sections may be complicated due to differences in wall thickness between the adjacent pipes. For example, the wall of one pipe section having a specified internal or external diameter may be substantially thicker or thinner than the wall of an adjacent pipe section having the same internal or external diameter. For a proper joint to be formed between the two sections, the differences in wall thickness should be compensated for as uniformly as possible around the circumference of the pipe sections.
Following the positioning and reformation of two pipe sections that are to be welded together, it is conventional to tack weld the sections together at circumferentially spaced zones while the pipe sections remain clamped. The tack welding zones should be distributed as evenly as possible over the circumference of the pipe sections so that, when the clamp is removed to complete the welding operation, the tendency of reformed pipes to revert to their original configurations does not result in mismatching of the confronting ends or undue stressing of the tack weldment.
Apparatus constructed in accordance with the invention facilitates the clamping, reformation, and tack welding of pipe sections to one another.