Residual Stress Research Of The Laminates Of Integral Multilayer-Wrapped Pressure Vessel

In China there are two blasting accidents of traditional multilayer-wrapped urea synthesizer in 1995 and in 2005, the cause of the latter accident is thought of the laminate cracking, and the existence of its deep girth weld is a major unsafety factor. The integral multi-layer wrapped pressure vessel, involved in this text, has no deep longitudinal and girth welds in the laminates,so it is more safe.Because of welding without testing on the laminates, although this could save costs and production time,the integrally wrapped cylindrical vessel has a certain insecurity, specially the vessels with large-scale.Based on original blind holes method, its strain release factors are corrected, so that higher accuracy can be got when measuring welding residual stress. With selecting corresponding parameters, ANSYS, the finite element analysis software, can analyze calibration tests. And the results of the finite element analysis are in accordance with the actual calibration test.Compared with the measured residual stress values, the mechanical model with friction between layers is relatively correct in the area away from the weld, and the residual stress is related to r and 0. However, in the area affected by weld this model can not reflect the distribution of welding residual stress.And the residual stress distribution is similar to the butt plate of the welding residual stress. Therefore, in the area affected by weld, the formula is fitted by actual measued data, which can provide certain support to manufacturing of the large diameter, thick integrally multi-layer wrapped pressure vessel. The residual stresses were measured in three welds, which are the longitudinal weld, the girth weld and the intersection of longitudinal and girth welds.Through the comparison, it is found that residual stress in the intersection of the longitudinal and girth welds is relatively small, and that the maximum residual stress values appears at the central of the fusion Zone.It is recommended that the welds of multilayer-wrapped layers need an appropriate local annealing.