Determination of Pressure Boundary Joint Assembly Bolt Loads
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This WRC Bulletin chronicles the development of the methods detailed in ASME PCC-1-2010 Appendix O “Assembly Bolt Stress Determination”. It includes all the information necessary to enable engineers concerned with sealing reliability to reproduce and build on the work that went into that part of PCC-1. The intent is not to reproduce the method or to include all details of the development of the method. Instead it is to provide references to the documents written during the development of the method and to provide additional details to assist in the understanding and extension of the method in the future. This WRC Bulletin provides references to the historical development articles, an explanation of the basis for the method, a step-by-step guide as to how to apply the ASME code equations to determine flange limits, and a commentary on the Elastic-Plastic Finite Element Analysis (FEA) methods presented therein.
The information presented will assist in developing general limits for acceptable bolt stresses that can be applied to flanged joints without damaging them. This is the case for both standard piping flanges and custom pressure vessel and heat exchanger flanges. By incorporating the equations outlined in this document, not only can the correct assembly bolt load be determined, but the joint can be designed such that it is not possible to over-stress the gasket or flanges. This approach vastly improves the practicality and reliability of the joint. By strictly following these procedures it will not be possible to permanently damage the joint during assembly or operation. The method presented also, enables determining which of a joint’s components are limiting. Absent that knowledge it is not possible to correct the root causes of joint leakage. Finally, the document provides important insight into gasket relaxation factors.