Bolted flanged connections are used extensively in the petrochemical and nuclear industries. Under high temperatures, their leakage tightness behavior is compromised due to the loss of load as a result of creep of not only the gasket material but also the bolt and the flange materials. The relaxation of the bolt load and the corresponding loss of the gasket contact stress are not easy to assess analytically and consequently there is no established design calculation procedure. The objective of this paper is to present an analytical method that is part of the SuperFlange program [1] and is capable of predicting the load relaxation in a bolted joint when subjected to flange, bolt and gasket creep. The proposed method is validated by comparison with 3D FE models of different size flanges. In some cases, the relaxation caused by the flange and bolt materials is shown to be significant.

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