Bolted flanged joint assemblies may begin to leak some time following a successful hydrostatic test.One of the reasons is that the gasket experiences a drop in its initial compressive stress due to creep,thermal dilatation and thermal degradation.The need to pay attention to the relaxation behaviour of bolted joints for high temperature applications is recognized by the ASME Code,but no specific guidelines are given to help engineers neither at the design nor maintenance levels.
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