For the joining of heavy plates, hybrid processes have been established. The presented approach of one side welding of thick metal sheets combines a laser beam and two GMA welding torches in one setup. Using this hybrid process for joining high material thicknesses, manufacturing time can be significantly reduced in comparison to conventional multilayer arc welding processes. Additionally, new construction opportunities allow savings of additive materials. In order to benefit from these economic advantages and to make brilliant high power lasers in pipeline manufacturing useful, this hybrid process needs to run robustly for conventional welding practices as well as for common gap and tolerance ranges. The process time, compared to conventional methods, will be significantly decreased due to the use of disc lasers with a maximum output power of 16 kW combined with two high power GMA sub-processes. For the process development, grade X70 steel sheets with a thickness of 23 mm have already been joined in flat position within a single process step over the whole thickness. Based on these parameter studies, the process limitations have been determined with regard to energy input, gap bridgeability, vertical edge offset and a lateral position deviation of the energy sources from the weld gap. The variable applicability and the robustness of the developed hybrid process have already been approved in application oriented processes.