Finite Element Stress Analysis Of The High Pressure Vessel Flat Cover

High pressure vessel always works under high pressure and temperature conditions in some cases, and the consequence of its failure is very serious. Therefore, the security problem of high pressure vessel draws more and more attention in the fields of science and engineering. In the conventional design, the corresponding formulas are used in strength calculation of high pressure vessel components, and the high safety factor is selected to ensure the safety of high pressure vessel, which may lead to enormous waste of materials.Finite element analysis (FEA) is developed in the design of the high pressure vessel, which brings new conception and method. In this paper, FEA and ANSYS12.1 are used to study the flat cover of high pressure vessel. The main work and result are shown as follows:(1) The flat cover of ammonia converter are taken as an example in the paper, and through definition of material properties, three-dimensional finite element modeling, meshing, applying the load, computing and checking the results of analysis, it finishes the design by analysis of the flat cover. The results show that the bigger concentrated stress is located in the structural discontinuity of the openings and grooves in the flat cover, where the stress values are great. And much of stress focusing on one plane will lead to the occurrence of dangerous sections, which can firstly cause the failure of the flat cover.(2) The displacement field, temperature field and thermal—structural coupled field are established respectively on the flat cover of ammonia converter. And through the comparison of analysis results in two kinds of situation, that are pure pressure loads and the action of pressure loads and temperature loads, it concludes that the stress values obtained in thermal—structural coupled field have the increase of different level than that obtained in displacement field and the maximum stress value increase 97%. But the stress values of flat cover are still less than the values of design stress intensity, which shows the design of flat cover with the conventional design method is partial to safety.(3) Two improvement schemes are proposed based on the unreasonable phenomena in the above results. The one scheme is that change the opening position in the flat cover, through the comparison of the path calculating results in thermal—structural coupled field, it obtains that reducing the structure discontinuous area in dangerous sections can improve force-bearing conditions. And the other scheme is that reduce the thickness by 55mm and the weight by 12% on the basis of changing the opening position in the flat cover, it shows that the check results in thermal - structural coupled field still meet the strength requirements, which indicates that the improvement is successful and embodies the superiority of the design by analysis.