Relaxation behavior of flanged joints consisting of 9% Cr-steels

Flanged joints form an integral part in the construction of modern power plants. They serve as detachable connections for piping sections. Hanged joints are exposed to high and complex loading. The loading reduces the flanges ability to seal, therefore costly maintenance work is necessary to retighten the flange bolts. Up to now these facts have only partly been considered in current computational models. In the present work the experimental relaxation characteristics of various flanged joints consisting of 9 % chromium steels is investigated. The possibilities of numerical simulation of the relaxation characteristics of flanged joints and the optimisation of inspection intervals are examined by applying an inelastic finite-element (FE) analyses. As a result of this work a reliable tool for predicting the long term-relaxation behavior of flanged joints is available. Additionally the results can be used to optimise inspection intervals and to determine the design of flanged joints. (author)