Abstract: An automatic welder is used in an internal welder unit which travels along the interior of a pipeline and welds the abutting ends of the pipe segments together. The automatic welder has a carriage assembly that contains a laser source for producing a laser beam, first and second line-up clamp assemblies for aligning the respective abutting ends of the pipe segments together, at least one laser beam conductor, or alternatively a reflecting surface positioned between said first and second line-up clamp assemblies along the axis of said beam, for directing said beam to the abutting ends of said first and second pipe segments, and a drive for rotating the reflecting surface around the axis of said beam to direct the beam to the abutting ends of said pipe segments for welding said pipe segments together. The automatic welder can also be configured as an external welder in which the automatic welder carrying a laser source is carried on a track mounted on the outside of the pipeline.

Abstract: An automatic welder is used in an internal welder unit which travels along the interior of a pipeline and provides the interior weld passes at the junction of abutting pipe joints. The internal welder unit has an electronic control system which includes a plurality of microprocessor control units, each of which performs specific functional operations for the internal welder unit. The microprocessor control units are interconnected by a serial communication link which permits the transmission of commands and data between all of the microprocessor control units. The control system includes a back end control unit positioned in the internal welder unit, a front end control unit with a panel in the weld unit, a reach rod control unit at the end of a reach rod and a power supply control unit adjacent the arc power supply. The control system directs the operation of orbiting internal welders to have a zero or slow travel speed at a start point to ensure a high reliablity of arc initiation.