A comprehensive study on the mechanical behaviors of pipe flange connections

对管法兰连接的受力性能进行了系统的分析，取得了以下成果。建立了螺旋缠绕垫片和压缩石棉板垫片的高精度本构方程，确定了垫片挠度与接触压力的关系。管法兰连接的最佳紧固程序开发了一个三维有限元程序，用于估算在使用上述三种垫片的情况下，用任意顺序的多个螺栓紧固管法兰连接时螺栓预紧力的分散。还提出了一种有限元程序，它可以提供最优的紧固程序，即在螺栓预紧力中实现较小的散布。为了提高计算精度，还引入了弹性相互作用系数法。分析了采用金属垫片和压缩石棉板垫片的情况下，管法兰连接在内压、拉伸和弯曲作用下，外载荷作用下螺栓预紧力的变化以及垫片轴承面上接触压力分布的变化。对JIS紧固特性和垫圈轴承表面接触压力分布的评论随着管法兰公称尺寸的不同而发生显著变化。因此，建议在相应的JIS中添加适当的注释，以便更好地利用管道法兰连接，参考此处获得的数值结果。

Mechanical behaviors of pipe flange connections have been systematically analyzed and the following results are obtained.1. Formulation of the non-linear relationship between gasket deflection and contact pressure Constitutive equations identifying the relationship between gasket deflection and contact pressure with high precision are proposed for spiral wound gaskets and compressed asbestos sheet gaskets.2. Optimal tightening procedures of pipe flange connections A three-dimensional FEM code has been developed to estimate the scatter in bolt preloads when tightening a pipe flange connection with a number of bolts in any order in case of three types of gaskets stated above being used. Also proposed is a FEM code which can provide optimal tightening procedures, i.e., achieving small amount of the scatter in bolt preloads. Elastic interaction coefficient method is also introduced to improve the computation accuracy.3. Mechanical behaviors of pipe flange connections under external loads Variations of bolt preloads and contact pressure distributions on the gasket bearing surface are analyzed when a pipe flange connection is subjected to inner pressure, tension and bending for the cases of metal gaskets and compressed asbestos sheet gaskets being used.4. Comments on JIS Tightening characteristics and contact pressure distributions on the gasket bearing surface are significantly changed for varying nominal sizes of pipe flanges. It is therefore recommended that proper comments should be added to the corresponding JIS for accomplishing a better use of pipe flange connections referring to the numerical results obtained here.