A comprehensive study on the mechanical behaviors of pipe flange connections

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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.