The Kjellberg welding automat KA 4-UPDG was developed for submerged-arc welding with two articulated arms. Two fillet welds can be welded at the same time with high effectiveness. The self-driven welding automat is equipped with a encoder-driven carriage with all-wheel drive. This guarantees a high degree of mobility. The modular design of the KA series allows the flexible adjustment of the KA 4-UPDG to different welding tasks. The pre-selection of nominal values for welding current, arc voltage and welding speed in coordination with the power source as well as the automatic ignition and the automatic burn-free function make it easier to operate the automat. The start-up phase and the end crater filling phase can be adjusted separately. The compact construction of the welding automat with two articulated arms makes it possible to move the KA 4-UPDG directly on the workpiece. It can be guided by means of profile trails.