Abstract: The volume of the LNG storage tanks built in China has developed from 160,000 m3 to 270,000 m3. So the welding workload of the storage tank is large, especially the welding of the 9% Ni steel inner tank, which is the key link in the construction of the LNG storage tanks and the requirements for welding quality are also very high. At present, the annular seam adopts submerged arc automatic welding, which realized the mechanization of welding, yet the longitudinal seam adopts electrode arc welding, which not only has high labor intensity, but also has low welding efficiency. Therefore, it is an inevitable trend to develop efficient and stable longitudinal seam automatic welding process technology. This paper presents the longitudinal seam automatic welding technology of LNG storage tank from the aspects of welding method selection, welding equipment development, welding groove design, welding performance test, engineering application and so forth. This can provide reference for the technicians engaged in LNG storage tank welding.

Key words: LNG storage tank, longitudinal seam of the inner tank, automatic welding process