Stress Distribution in the Bolted Flange Connection with Gasket Subjected to Cyclic Loading Condition

The flange connections are commonly designed for design and hydrostatic loads, which are assumed to be constant with time. But under operating condition, the loads acting on the flange connection including the fluid temperature and pressure vary with respect to time in a periodic manner. The spiral wound gasket is a semi metallic gasket with stainless steel rings and graphite filler rings wounded simultaneously in the radial direction. In the present work, 3D finite element model of the flange connection is developed and the behavior is analyzed for loading conditions varying with respect to time. The gasket is modeled through micromechanical approach, considering the individual elasto-plastic behavior of stainless steel and graphite filler rings. The time independent plastic behavior of the structural components in flange connection along with stainless steel in SPWG is modelled using Chaboche kinematic hardening model. This modeling helps in computing the behavior of the stress distribution in flange connection subjected to varying working cycle. The leakage characteristic of the connection is controlled by the contact stress distribution in the gasket material. Under cyclic working condition, the contact stress exerted on the gasket material also depends on the plastic behavior of other members like flanges and bolts in the connection. A realistic contact stress distribution in gasket under varying working cycle is obtained using the micromechanical approach. The effective gasket width, contributing to the sealing behavior in the radial direction is observed to reduce under cyclic working loads due to accumulated deformation.