Safety evaluation of large-scale oil tanks with crack type's defects at lower joint region

At present,techniques for safety assessment of pressure vessels containing defects are fairly mature.But most techniques are for vessels with constant inner pressures,while for large storage tanks,the pressure change with oil level.Whether these large storage tanks can be assessed by the common pressure vessels assessment rules has no final conclusions yet at home and abroad.The major difference between the two kinds of vessels is that pressures are different at defected areas.So this paper focused on the stress analysis of defect areas.A finite element model of lower joint region was set up by ADINA software and a simplified method to calculate stresses at the defected area was put forward through comparison of finite element and theoretical solutions.Based on the above study,safety assessment of large storage tanks can then be conducted according to the code of GB/T 19624-2004,the safety assessment rules of pressure vessels containing defects in service.