Design rules for flat face flanges with metal-to-metal contact beyond the bolt circle are covered by Appendix Y of the ASME Code. These design rules are based on Schneider’s work [1]. The prediction of tightness of these bolted joints relies very much on the level of precision of the O-ring gasket compression during operation. The evaluation of this compression requires a rigorous flexibility analysis of the joint including bolt-flange elastic interaction. This paper analyses flange separation and the bolt load change in flat face bolted joints. It proposes two different analytical approaches capable of predicting flange rotation and bolt load change during operation. The first method is based on beam theory applied to a continuous flange sector. This approach is an improvement of the discrete beam theory used by Schneider [1]. The second method is based on circular plate theory and is developed for the purpose of a more accurate assessment of the load changes. As in the Taylor Forge method, this approach is in general better suited than the beam theory for flat face flanges in particular when the flange width is small. The proposed models are compared to the discrete beam theory and validated using numerical FEA on different flange sizes.

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