In order to understand the behavior of bolted joints and select a right size, type and gasket load combination, a detailed analysis tool is very helpful. However, the modeling and analysis of a bolted joint connection is a complicated, complex process; particularly if multiple parts are considered in the Finite Element (FE) modeling. Analysis results are often sensitive to bolt pre-torque, gasket type, gasket thickness and other challenges of Finite Element (FE) modeling. In addition, often credible and reliable gasket deflection-load data are not readily available. The bolted joint under study was a double-gasket joint with inner gasket leakoff. The joint has leaked on several occasions, sometimes after several years of service due to warmup/cooldown cycling and sometimes immediately after installation and pressurization. A 3-D FE model was developed for assembly of tubesheet, bolt, two inner and outer gaskets, and vessel cover. Different cases were studied by changing gasket load-deflections for different gasket materials, gasket thicknesses and bolt loads. The outcome of the analyses was used to predict the behavior of bolted joints and understand the root cause of leakage. The results provided guidance for choosing the right combination of bolt pre-torque and gasket type.
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