scope:

The aim of this Technical Specification is to describe a calculation method dedicated to Bolted Flange Connections (BFC) with metal to metal contact (MMC). It is dedicated to BFC where MMC occurs in a region between the outside diameter of the gasket and the inside diameter of the bolt hole region. For MMC inside the gasket and for MMC outside the bolt hole region, the present method is not appropriate. The calculation method proposed in this Technical Specification is mainly based on the method described in EN 1591-1, dedicated to floating type BFC. The behaviour of the complete flanges-bolts-gasket system is considered. In assembly condition as well as for all the subsequent load conditions, the BFC components are maintained together by internal forces. This leads to deformations and forces balances (see Annex F) which gives the basic relations between the forces variations in the BFC. The calculation of BFC with MMC leads to the consideration of an additional force compared to the EN 1591-1 calculation method: the reaction force in the MMC area. It explains why two compliance equations are required in this Technical Specification (in the EN 1591-1 calculation method just one compliance equation is needed to determine the internal forces in all the load conditions). Unlike EN 1591-1 where the internal forces variations are determined with the compliance relation between the assembly and the considered load condition, here, the internal forces variations are determined by using the compliance relations between two consecutive load conditions. This method does not treat non-gasketed pipe joints.