Research On High Temperature Thermal Tightness Of Bolt-flange-gasket Connection System

Bolt flange connection is widely used,a considerable part of it is in the state of high temperature operation,with the extension of service life,the seal element rebound ability decreases,the bolt creep deformation,affecting the sealing of the bolt flange connection.The sealing performance of the flange depends on the remaining preload on the gasket under the working condition.When the temperature changes,the remaining preload will change with the change of thermal expansion and elastic modulus,thus affecting the sealing performance of the flange.In engineering,the load loss of bolts is mainly handled by increasing preload and secondary heat load.The research contents of this paper mainly include:(1)the flange design method and the determination of bolt preload are introduced through the theory.Analyze and compare the fastening method of ASME pcc-1 or HPIS Z103 TR,and the fastening steps of a domestic petrochemical company.The thermal compactness in engineering is discussed and the degree of secondary thermal compactness and thermal compactness are determined.(2)the three-dimensional mechanical model of bolt-flange-gasket connection system was established by using simulation software,and the distribution and deformation rules of each stress field were obtained by simulating different working conditions.(3)the three-dimensional heat transfer model of the flange was established,and the steady-state temperature field and the coupling field of the thermal structure were simulated,and the influence of temperature on the bolt-flange-gasket connection system was analyzed.(4)based on the steady-state temperature field and thermal-structure coupling,the numerical simulation calculation of shim at each temperature was carried out.With the increase of temperature,gasket stress distribution is uneven,may cause seal failure.At the same time,the sealing performance of different preload forces at high temperature was studied,and different preload forces of bolts were applied to simulate and analyze at different temperatures,so as to determine whether secondary thermal tightening was needed under this working condition.