Effect of Temperature on Bolt Working Load of Pressure Vessels

摘要

The area of sealed flange connections of pressure vessels often encounters critical operating states that are defined by particular load conditions. These loads are exhibited from assembly stage, through pressure testing, to operation of the pressure vessel. The issues arising in assembly conditions alone are complex and significant. However, this article discusses the problematics of flange joints in subsequent conditions. Specifically, it is examining the effect of temperature on the bolt pretension. Stiffness calculations for machine parts which are constantly exposed to high temperatures at continuous exertion of force pose a significant level of complexity even nowadays. For calculations of pre-stressed bolt connections, the computations are even more complicated. This is given by the fact these are highly complex components that are almost always extremely stressed. However, the requirements for critical flange joints are even higher. There are not only bolts strength requirements, but strict leak rate requirements of gasket joint as well. This article provides a basic description of the effect of temperature on bolt pretension. Its theoretical basis is complemented by concrete examples from practice. Subsequently, one of the examples is subjected to FEM analysis. Finally, the possible ways of partial elimination of negative thermal influences on flange connections of pressure vessels are demonstrated.