Welding tank wall, can't be first girth welding, according to your description, should be a large storage tank, to vertical group, the girth welding first it's hard to achieve, the first is the circular seam group of difficulties, the second is the girth welding can lead to serious deformation of longitudinal seam, and thus affect the group of the longitudinal seam welding, moreover, the first longitudinal seam welding, longitudinal seam free shrinkage, the girth doesn't really matter, and girth welding first, due to the longitudinal seam is fixed at one end, cause not free shrinkage, residual stress and the deformation and stress will increase greatly.Welding short weld is first in order to reduce welding deformation and welding long short was first fixed, unable to free shrinkage, will lead to deformation is large, will ultimately affect the floor with cylinder group to, and even whole unqualified (floor deformation regulations within 50), in the same way, welding short to long weld first little influence, and can get good welding quality.In addition, if the welding seam is long, it is recommended to adopt the method of segmenting backwelding from the middle to both sides to control the welding deformation to the minimum.