Study on the Standard of Tightening Procedure of Pipe Flange Connections and Evaluation of its Sealing Performance by Computational Mechanics

1.将“弹性相互作用系数法”引入到三维有限元分析中，提出了两种估算任意顺序拧紧夹紧螺栓时螺栓预紧力分散情况的数值方法，并给出了使螺栓最终状态预紧力均匀的最优拧紧顺序。通过将实验得到的石棉连接垫片的应力应变关系纳入有限元分析，系统地分析了最佳拧紧顺序、外载荷作用下的力学行为及其密封性能。3 .管道法兰连接拆卸过程力学性能的阐明利用上述有限元方法系统分析了螺栓夹紧力和垫片界面接触压力分布的变化。4 .为了抑制最终螺栓夹紧力的分散，一种有效的拧紧顺序是将四个螺栓同时夹紧，它们彼此相距90度，然后按顺时针方向简单地拧紧其他螺栓。短螺栓夹紧力对管道法兰连接密封性能的影响研究发现，在20英寸法兰的情况下，缺少两个螺栓会使剩余螺栓产生1.6倍的初始夹紧力。从密封性能的角度看螺栓预紧力中的散射与垫片接触应力的关系转矩控制方法引起的散射比连续拧紧操作引起的螺栓变形的弹性相互作用引起的散射要小得多。基于计算力学的泄漏性能评价方法研究表明，泄漏率可由沿垫片外径方向发生的最大接触应力来估计。这项研究的部分成果已由日本高压研究所（HPI）作为“管道法兰紧固指南”发表。z103tr - 2004”。少

1.Optimal Tightening Procedure of Pipe Flange ConnectionsIntroducing "Elastic Interaction Coefficient Method" into 3-D FEA, two numerical methods have been proposed, which can estimate the scatter of bolt preloads when tightening the clamping bolts with an arbitrary sequence and provide an optimal tightening sequence that gives uniform bolt preloads in the final state.2.Mechanical Behaviors of Pipe Flange Connections using Soft GasketsBy incorporating the stress strain relationship of asbestos joint sheet gasket that were obtained experimentally into FE analysis, an optimal tightening sequence, mechanical behaviors under external loads and its sealing performance have been analyzed systematically.3.Elucidation of Mechanical Properties of the Disassembly Process of Pipe Flange ConnectionsVariations of bolt clamping forces and contact pressure distributions on the gasket interface have been systematically analyzed using FE approach developed above.4.Proposal of a Robust Tightening Proced … More ure of Pipe Flange ConnectionsTo suppress the scatter in final bolt clamping forces, an effective tightening sequence is to clamp the four bolts simultaneously, which are apart ninety degrees each other, and then tighten the other bolts simply in the clockwise pattern.5.Effects of Short Bolt Clamping Force on the Sealing Performance of Pipe Flange ConnectionsIt has been found that the missing of two bolts causes 1.6 times initial clamping force in the remaining bolts in the case of 20 inch flanges.6.Relationship between the scatter in bolt preloads and gasket contact stresses from the view point of sealing performanceThe scatter due to torque control method is found to be fairly smaller than that due to the elastic interaction of bolt deformations caused by the successive tightening operation.7.Evaluation Procedure of Leakage Performance based on Computational MechanicsIt has been shown that the leakage rate can be estimated by means of the maximum contact stress occurred along the outer diameter of gasket.A part of the achievements of this study has been published from High Pressure Institute of Japan (HPI) as "A Guideline for Pipe Flange Tightening. Z103TR-2004". Less