The large thick wall equipment tube（52 mm at the thinnest part of the plate） was affected by constraints and environment during the construction process

and the traditional technology method and Fangfashigong caused cracks in the weld seam. In this paper

we describe the cracks in three stages of welding

bottom beating and post-welding heat treatment during the construction of large thick wall equipment

analyze the environmental factors

construction technology and Shigongfangfa

and formulate effective improvement measures. The method of increasing the density of positioning welding

the thickness of positioning welding

the slow cooling after welding

and adjusting the process control of the number of segmental heat treatment are used to avoid the crack defects again. It can avoid the crack defects in the subsequent welding activities of the equipment cylinder

and it can provide effective experience for the subsequent assembly activities of the similar thick wall equipment

and ensure the smooth completion of the welding energy and quality of the large thick wall weld group in the relevant fields.