Analysis Of Flange Connection Tightness Under High Temperature

The study of the flange sealing is the key part of the joint for the vessel and pipe. Working under high temperature and high pressure flange connection system, gasket in high yield stress state,the long-term service will make the material degradation and the decrease of mechanical performance,leakage occurred easy in the connected joints,lead to seal failure.So the study of the tightness analysis under high temperature and pressure flange joint is one of the current research focus.In this paper,through numerical simulation method of high temperature and stress of flange connection under steady state is analyzed,the change of the sealing perfomance is discussed in diffrernt working condition of temperature and pressure fluctuations,and to evaluate its sealing performance. Including:(1) The flange system as a whole is based on the flange deformation of structure simplification and assumption,and carried on the detailed load-deformation analysis,obtained the torque balance equation and deformation coordination equation.(2) Considering the octagonal gasket nonlinear contact problem,a three-dimensional mechanical model of flanged connection system is established by using the finite element software ANSYS.The stress distribution and deformation is obtained through the finite element pre tightening and confined condition analysis.The result under pressure on the gasket stress is reduced, the circumferential stress distribution is more uniform, radial stress is uneven.(3) Flange three dimensional heat transfer model is established based on heat transfer theory, then carried on the steady temperature field and thermal structure coupling field of finite element calculation.The temperature field distribution was obtained and the steady state thermal stress distribution under high temperature.Analyzed performance of the flanges, gaskets and bolts under high temperatures, each flange fitting stress increased generally in the coupling field.(4) Stiffness analysis was carried out on the flange connection system, it is concluded that the changing rule of the flange displacement and deflection under different temperature, and the steady temperature field under high temperature and pressure in the flange joint tightness assessment. It is obtained that in the steady state temperature field in the flange joint sealing is reliable, octagon gasket is in high yield condition, long-term working can make the gasket material degradation which can lead to seal failure, working for the long-term under high temperature and high pressure flange connection system failure reason to provide reliable basis.