Strength And Sealing Analysis Of Flange At High Temperature Based On Creep

In this thesis, the oil and gas flange of Aromatics reforming unit in Jin shan Petrochemical Company is researched.The research consists of the temperature distribution of flange, strength and sealing analysis of flange under preload and internal pressure and operating conditons, the change of bolt strss and gasket stress considering the creep of bolt and flange.The temperature distribution of flange is obtained through the steady thermal analysis of flange. Calculated result is compared with the measured result, which shows good coherence. The error is below2%, so the analysis is correct.The smallest preload is obtained through the analysis of preload conditon, considering the gasket nonlinear and contact nonlinear.Under the influence of bolt preload, the flange occurs a certain rotation, which also results in the stress nonuniform distribution of gasket. While the rotation angle is less than the specification of ASME PCC-1, of course, the strength is satisfied.The calculation of internal pressure conditon is based on the preload condition. The results show that gasket stress becomes lower when the internal pressure becomes greater. After assessment, the sealing and strength of flange are satisfied. Under the operating condition, the temperature makes the thermal expansion of bolt and flange different, which results in the gasket stress lower more. After assessment, the strength and sealing of flange are still satisfied.The analysis of creep of flange at high temperature aims at researching the sealing performance of flange for a long time.The results show that: the stress across the section is redistributed because of creep, and the stress of bolt-inside becomes lower and the stress of bolt-outside becomes bigger. The gasket stress becomes lower and lower with the creep time extended, and after10000hours, the flanges can keep seal. The results also show that the greater gasket and bolt stress reduction occur and residue stress of gasket and bolt are bigger when the preloads are bigger.