FEM Analysis and Preload Evaluation of Bolted Joints Subject to Low Temperature

Bolted joints are broadly used in various industrial products. Especially in chemical engineering, the reliability of bolted joints can have a significant influence on the safety of chemical systems. In some fields, such as liquefied natural gas (LNG) industry, equipment usually works in low temperature (−162°C). Different materials with various thermal expansion rates are usually used in bolted joints; Therefore the preload and stress distribution of bolted joints in low temperature can change apparently due to the different axial and radial thermal deformation. If the preload design in normal temperature is inappropriate, the bolted joints may either encounter relaxation or over-tightening in working temperature. In this study, a theoretical analysis is proposed in order to evaluate the appropriate preload selection of bolted joints work in low temperature. FE analysis is made to examine the accuracy of the theoretical formula. The result shows that the error is less than 10% in most cases. The stress distribution on the bolt thread region is studied and the result shows that the maximum tensile stress on the bolt thread region is much higher than in non-thread region. Availability and safety should be both considered in preload selection of bolted joints working in low temperature. Finally the effect of radial thermal deformation difference is discussed when the thermal expansion rate difference is high. The effect of radial thermal deformation difference should not be neglected in some cases.