Numerical Simulation and the Improved Welding of Storage Tank Heads with Respect to Minimised Welding Strains

The article presents results of Sysweld software programme-based tests involving the use of numerical simulation in the improvement of the welding of a storage tank head with respect to the minimisation of welding strains (distortions). The development of CAD models and mock-ups used in the FEM analysis was based on drawing documentation. The numerical simulation concerning the distribution of the field of displacements in the storage tank head was performed for four models, involving various welding sequences and directions. Related analyses involved the initial model applied in the technology currently used in the fabrication of storage tank heads as well as three new models (of welding sequences and directions). The comparative analysis, involving the initial model and the three new models, was concerned with different values of displacements in all directions (X, Y and Z) and at all characteristic points of the storage tank head. The simulation results revealed the existence of correlations between welding sequence and directions and varied distributions of fields of displacements (strains/distortions). Post-weld distributions of fields of displacements in the initial model and models 2-4 were characterised by varied values of displacements, yet also by the similar nature of tank head stress-triggered distortions. Dimensionally relevant displacements (distortions) of the storage tank head were observed in direction Z (i.e. direction perpendicular to the surface). In all the models subjected to analysis, the greatest displacements were identified in the areas of storage tank head nodes. Selected welding stages in the initial model were characterised by greater displacements than those observed in models 2-4. In line 1, higher values were observed at stages 8-10, 12 and 13. In turn, in line 2, higher values were observed at stages 8-10. In addition, in line 2, stages 11-14 were characterised by greater displacements in the initial model if compared with those identified in models 3 and 4. The FEM-based analysis of the tank head enabled the qualitative verification of tank-related welding schemes in terms of welding strains.