Automatic Submerged Arc Welding System in Heavy-Wall Pressure Vessel Fabrication

Abstract When submerged arc welding (hereinafter referred to as “SAW”) is used for welding the longitudinal and circumferential joints of the cylindrical shell of a heavy-wall pressure vessel, its operator is required to be highly trained in terms of skills such as setting welding conditions, determining the number of welding passes per layer, and adjusting the wire aiming position and welding conditions according to changes in the groove shape. In addition, after welding, it is also necessary for the operator to carry out supplementary work such as slag removal, flux supply, and wire cutting to prepare for the next welding operation. Therefore, at present, one welding operator cannot weld multiple joints simultaneously, working on one joint at a time. Furthermore, in welding the outer groove for circumferential joints, the operator must ascend and descend from a work platform installed on the upper part of a cylindrical body 2 meters or higher, which requires physical strength and consideration of operator safety. To solve these issues, we devised an automatic SAW system. Through application of this system, even a less experienced welding operator would be able to perform SAW, which requires a high degree of skill on the part of the operator. Furthermore, the system enables one operator to simultaneously work on two joints, improving productivity. In addition, remote control and monitoring functions are provided to reduce workloads and enhance safety. The integrated system includes an automatic sensing method, an automatic welding operation algorithm, automatic supplementary work units, and a remote control and monitoring unit. We applied the developed system in welding operation of longitudinal joints of the cylindrical shell of a heavy-wall pressure vessel, demonstrating that one operator could simultaneously weld two joints without relying on the skill level of the operator. In addition, for welding circumferential joints, the system enabled a welding operator on the ground to remotely control and monitor the welding. Application of this system is expected to improve welding quality and shorten the process for welding in longitudinal and circumferential joints of cylindrical shells of heavy-wall pressure vessels.