Strength And Stability Analysis Of A Super-Large Vacuum Vessel

Vacuum vessels are common used equipment in the petro-chemical industry. Different from vessels under internal pressure loading, vacuum vessels usually fail with the instability which is very sensitive to the geometrical defects. In this paper, finite element method was used to conducte strength and stability analysis for a super-large vacuum vessel and reinforcement measures were proposed based on the numerical results to increase the rigidity of the vessel. In addition, local buckling analysis was also carried out on the tower cylinder under the action of wind loading.First, for the strength analysis, four load cases combined by the external pressure, weight, suspended load, nozzle load, wind load and earthquake load were considered. Stress distribution at the vessel was obtained and strength was checked confirmed to the pressure vessel design standard JB4732-1995 Steel Pressure Vessel - Design by Analysis. Results show that all the strength criteria are satisfied, implying that for a vaccum vessel, strength is not the controlling factor.Secondly, non-linear stability analysis using finite element method was carried out on the super-large vacuum vessels with reinforcement rings and without reinforcement rings. Results show that increasing the thickness of the vessel only cannot effectively increase its anti-instability and on the opposite, the total weight will increase substantially. However, by designing reasonable reinforcement rings, the critical instability pressure of the vessel can be effectively raised and with the weight of the whole vessel decreased and the material degraded, the total cost of the vessel will decrease significantly.Finally, finite element analysis was conducted to study the local buckling in the axial direction of a tower under wind loading. Influences of the roundness of the tower cylinder on the critical instability loading were also investigated. It is found that the form and critical loading of the tower cylinder local instability in the axial direction can be the accurately obtained by performing non-linear buckling analysis, The roundness of the tower cylinder affects the critical loading but has little influence on the critical axial stress. With enough numerical calculations, a formula was regressed to evaluate the critical axial stress.