The Fea Simulation And Safety Evaluation Of Complex Hydrogen Induced Multi-blister Cracks

In the petrochemical industry,hydrogen damage is easy to occur in hydrotreating unit,which poses a serious treat to the safety of the equipment,such as hydrogen induced blister.Therefore,it is of great significance to study multi-blister in the pressure equipment.In this thesis,the dry gas desulfurization absorption tower is taken as the research object.The cylinder model which contains blisters is simulated with software ABAQUS.Firstly,the model is used to simulate the diffusion of hydrogen in multiple inclusions and cracks based on the coupling of two physics sequences.The results show that the smaller of the distance between blister cracks and the inner wall of the equipment,the higher the hydrogen concentration.The stress accelerates hydrogen diffusion,and the effect of promotion is more obvious with the increase of the stress.Linear-elastic and Elastic-plastic analysis of three-dimensional cylinder models with three or four blister cracks are carried out respectively.The results of LE analysis show that the bulging height of the blister increases with the increase of blisters' size,under the condition of the same hydrogen pressure and crack depth.The depth of a crack in the three blisters becomes smaller,which increases the KI value of the neighboring blister.One crack depth in the four blisters becomes smaller,which reduces the KI value of the diagonal blister.The EP analysis results show that the equivalent plastic strain and displacement of the crack tip increase with the increase of blisters' size,under the condition of the same hydrogen pressure and crack depth.One crack depth of the blisters increased,which makes the stress and J-integral values of all the blisters become smaller,and the self-blister decreases the most.Finally,fitness-for-service is used to evaluate the safety of equipment with multiple blisters.The results of safety assessment are consistent with the results of simulation,and the theory has certain value in engineering practice.The results are of reference value to the study of hydrogen induced multi-blister cracks and safety assessment of equipment.