INFLUENCE OF TOLERANCES on weld formation and quality of laser-GMA-hybrid girth welded pipe joints

The mechanized GMAW process is currently the most widely used welding process for transmission pipelines and represents the benchmark against which other welding processes have been assessed. Although there have been a number of recent welding procedure developments like twin-wire or double-torch welding that have improved its productivity, the potential for a further increase of its efficiency is exhausted. Alternatively, the Laser-GMA-Hybrid welding of the first pass, offers new possibilities to reduce the number of filler pass welding runs and the necessary equipment substantially. This paper will give an overview about the latest results of the development to qualify the Laser-GMAW hybrid process for pipeline girth welding. The approach of this work was extensive and included the equipment, the edge preparation and the welding process in several positions. Finally, the results were tested under near realistic conditions. Compared to advanced GMAW procedures with a minimum of four runs to complete an 11,7 mm (0,460") wall thickness, the number of runs was reduced to one, by combining the hybrid first pass with a single GMAW filler pass weld in the same run.