Creep Relaxation Characteristics in European Standards

Abstract

The European Standards EN 1591-1 which is used for the calculation of bolted flanged joints and EN 13555 in which the determination of the required gasket characteristics are defined were reissued last year. The definition of the creep/relaxation factor in EN 13555 and EN 1591-1 has been modified in these new issues of the standards. Instead of the ratio between the remaining and the initial gasket stress, now the additional gasket deflection due to creep/relaxation effects is considered in the calculation code, and therefore also the evaluation of the corresponding gasket tests has been changed. In this paper the differences in the testing procedure and in the evaluation algorithm are shown, and also a proposal is given to simplify and to reduce the required creep/relaxation testing.