Creep Analysis of Combined Bolted Flange Joints under High Temperature

The tightness of bolted flange joints will weaken due to the loss of bolt load as a result of creep under high temperature. There exists no mature calculation procedure that can accounts for creep. Based on the finite element simulation of a combined flanged joint under four various conditions, the strength integrity and sealing performance of it are evaluated according to the code JB4732-2005. The results show that the integrity and tightness of the combined flanged joint under pre-loading condition, pressure condition and operating condition (except local film stress) meet requirements. However, more than 50% of the bolt load relaxation is found due to creep, part of the gasket residual stress is lower than the required minimum sealing pressure. It can lead to leakage. Bigger bolt pre-tightening force, materials with good creep relaxation resistance and hot-tighting method are recommended to reduce the influence of creep.