An Evaluation of the ASME Flange Design Method for Large Diameter Bolted Joints

Abstract Poor industry experience with large diameter flanges has led to a perception that existing design methods may be inadequate to account for the actual stresses and displacements that occur in service or during hydrostatic testing. The ASME method for design of tapered hub flanges with gaskets located inside the bolt circle, as found in Section VIII Div. 1 Appendix 2 and Div. 2 4.16, does not place any limit on the diameter of the flange which may be designed, nor does it make any adjustments for diameter as found in PD5500. The ASME Method, commonly called the Taylor Forge Method, makes certain simplifications in the solution of the relevant differential equations, in the interest of practical computation. Past studies have identified problems related to these simplifications, resulting in inadequate analysis of the response of the structure to internal pressure loading. In this work, a parametric study is performed on a large number of randomly generated flange geometries. Flange stresses calculated using the ASME method are compared to more accurate methods, and the resulting dataset analyzed for correlation between the diameter and inaccuracy in the ASME method. The influence of mechanical interaction (accounting for the pressure-ballooning of the attached pipe or shell) is also investigated as an enhancement to the ASME method. The study does not find a fundamental problem with the ASME method as flange diameter increases. However, the study does identify certain pitfalls in practical design of large diameter flanges and makes recommendations for improving these designs.