The numerical analysis for the assembly stress in the local short fault of a vessel girth joint

For the appearance of the fault in local girth weld seam of a glycol evaporator, the forced assembly and then welding were carried out, the induced assembly stress was one reason of intergranular stress corrosion crack (IGSCC). Using FEM and based on the theory of thin shell, more effective 3-D models were built and were applied in the assembly stress analysis, varied fault magnitude for the same fault length and varied fault length for the same fault magnitude were all analyzed. The result showed that the maximum stress appeared in the maxi fault field of the girth joint after forced assembly, the stress distribution showed apparent locality and the smaller the fault angle or the bigger the fault magnitude is the higher the peak value of the stress after assembly. For the problem of small fault angle, it is preferred in describing the assembly stress distribution to develop a 3-D analysis model.