Analytical Modeling of Flat Face Flanges With Metal-to-Metal Contact Beyond the Bolt Circle

Design rules for flat face flanges with metal-to-metal contact beyond the bolt circle are covered by Appendix Y of the American Society of Mechanical Engineers Code. These design rules are based on Schneider’s work (1968, “Flat Faces Flanges With Metal-to-Metal Contact Beyond the Bolt Circle,” ASME J. Eng. Power, 90(1), pp. 82–88). The prediction of tightness of these bolted joints relies very much on the level of precision of the self-sealing 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 the beam theory applied to a continuous flange sector. This approach is an improvement of the discrete beam theory used in the Schneider model. The second method is based on the 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 with the discrete beam theory and validated using numerical finite element analysis on different flange sizes.