Abstract The purpose of this contribution is to show how methods of structural analysis which have been used for two decades with success in the aerospace industry can be utilised to predict the strength of large, highly stressed (and therefore expensive) components of chemical plants. As an example a large chemical reactor is used, in which extremely thin tube sheets have been installed. For this reactor extensive test results exist, which have been measured during proof testing. The accuracy of the stresses, predicted by the finite element method, is demonstrated by comparising with these experimental results. The method of approach is outlined and the basic assumptions made are compared with those inherent in conventional methods. From this comparison the advantages of the finite element method against conventional methods are deduced.