Bolted flange joints are part of pressure vessel and piping components and are used extensively in the chemical, petrochemical and nuclear power industries. They are simple structures and offer the possibility of disassembly which make them attractive to connect pressurized equipments and piping. In addition of being prone to leakage, they often require maintenance while in operation in which case the bolts are either retightened as in hot torquing or untightened to be replaced. Although costly shutdown are avoided, such a maintenance work exposes the operator to a potential risk because the bolt load alteration can produce a gasket load unbalance which results in a local gasket contact stress to drop below some critical value causing major leak and hence jeopardizing the life of the operator. This paper addresses the issue of the contact stress level unbalance around the flange when the bolts are subjected to bolt-up condition. This study is developed for the purpose of helping limit the degree of load increase in hot torquing or the maximum number of bolts to be replaced at a time and identify those flanges the bolt of which cannot be replaced in service.

This content is only available via PDF.
You do not currently have access to this content.