Application of elastic-plastic analysis method in high pressure heater tubesheet design

Abstract

The design method of pressure vessel consists of the elastic analysis method and the elastic-plastic analysis method. The design method based on elastic-plastic theory with more complex computation process contributes to lightweight design, and avoids uncertainty of stress classification in the complex structures. Tubesheet is the main part of high pressure heater, which is very thick based on Chinese code GB151 for the design of heat exchangers. Increased tubesheet with large thermal stress are not conducive to manufacture, heat transmission and detection. The application of limit load method and elastic-plastic method in the analysis and design of high pressure heater tube is to provide direction for the lightweight research of tubesheet. It is shown that high stress appears on the inner wall of jointing of tubesheet with the head due to the original tubesheet owning enough rigidity related to thickness, which should be noted in the design. The limit load method and elastoplastic method could be assessed in the plastic collapse assessment after optimizing the thickness of the tube plate by 5% on the basis of the existing rule design. Compared with the limit load method, the elastic-plastic method could obtain higher limit load due to its higher computational precision. On the other hand, the design method of elastic-plastic analysis method is not required to consider the determination of limit load per ASME VIII-2 judged by its convergence. The elastic-plastic analysis method is worth further study, which is helpful to the revision and improvement of relevant standards in China.