Stress distribution and performance of threaded bolts in gasketed flange joints

Abstract

AbstractThe performance of the flange joint depends on the relaxation of load in bolts. This in turn affects the gasket stress and control of leakage. A finite element model of flange joint with threaded bolt‐nut fastener having zero helix angle is developed and analyzed for stress distribution in the threaded bolt. The stress concentration factor at the thread root region is observed to be non‐uniform along the circumference due to the bending behavior of the bolt in the flange joint. The maximum stress is observed in the first engaged thread. The variation in bolt load due to internal fluid, thermal and external loads are also investigated for both single and twin‐gaskets (two concentric half‐sized single gaskets). The gasket material and gasket configuration are observed to be potential factors causing variation in the distribution of load in the flange joint. In a flange joint subjected to external bending load, the maximum stress concentration in the bolt is observed to be in the first thread, instead of the first engaged thread. Under external bending load, the flange joint loses its structural integrity before the traces of leakage occur in the joint.