Abstract: The welding procedure specification and the concerned requirement for the shell of f 3 800 mm pressurized gasifier with the advanced －MARK# Ⅳ/4 type is introduced . The test plan is to be determined based on the construction characters. On the basis of test the plan is proven according to the difficulty points in the producing process and find the suitable technology in the manufacturing. While the scientific reasonable welding procedure plan, assure quality of the product and control the deformation caused by the welding by means of a series of technology , narrow gap automatic tracing bead welding is adopted for the longitudinal and girth welding of the shell. The most difficult points are solved for welding the shell of large pressurized gasifier such as assuring the welding quality and controlling the deformation caused by welding, the welding result is satisfied. The success for this term study, valuable experience is accumulated for manufacturing large fatigue vessel and high temperature high pressure mechanical driving equipment.

Key words: Gasifier Shell, Product application, Quality control, Welding procedure specification, asymmetric heat source, dissimilar steels, numerical simulation, Key words：keyhole TIG welding