Study On Stress Of Graphene Oxide Asbestos-free Gasket Based On Bolt Flange Device

Due to the advantages of simple structure,good sealing performance,low cost and easy disassembly,the bolted flange device has been widely used in pipeline connections in petroleum,chemical,nuclear,aerospace,automobile,pharmaceutical and other industries.Gasket is a basic component to ensure the safety of mechanical equipment and transmission system in static sealing.The once widely used asbestos gasket is banned because it is harmful to human body.Non-asbestos gasket is used as an alternative to asbestos gasket.With the progress of the times,the structure of machinery and equipment is becoming more and more complex,the working conditions of seals（internal pressure and temperature fluctuation of medium,change of sealing medium,etc.）are becoming more and more complex,and the performance requirements of sealing gaskets are becoming higher and higher.The main work and conclusions of this paper are as follows:（1）The creep relaxation process of non-asbestos gasket under different temperature and different preload was studied by experimental method.Comparing and analyzing the two samples without and with graphene oxide,the results show that the creep relaxation performance of graphene oxide is better than that of non-asbestos gasket without graphene oxide,indicating that the addition of graphene oxide to the formula of non-asbestos gasket can enhance the creep relaxation resistance of gasket under normal temperature and high temperature conditions.（2）The experimental stress values of the gasket without and with graphene oxide non-asbestos gaskets under different temperatures and different preloads are used instead of the working gasket stress,and the calculation method of the leakage rate of the gasket under different temperatures and different preloads is proposed.When the temperature is the same,the leakage rate of gasket decreases with the increase of preload.When the preload is the same,the leakage rate of the gasket increases with the increase of temperature,and the leakage rate of the gasket is less than the leakage rate of the sealing grade T2 of 2×10^-3 mg/s/mm.（3）The finite element model of bolt flange device is established by finite element simulation software,and the reliability of bolt flange device model is verified by experiment and finite element simulation.On this basis,the stress field and leakage rate of the bolt flange device under pre-tightening and pressure-bearing conditions are simulated by finite element simulation software.（4）Through the analysis of the steady-state temperature field of the bolt flange device,the temperature distribution of the flange,bolt and gasket under actual working conditions is simulated.The thermal-structural coupling method is used to simulate the influence of different medium temperatures on the stress of flange,bolt and gasket（from bolt elongation to gasket compression force）and the influence of medium internal pressure fluctuation on gasket stress and leakage rate.The results show that the maximum stress of flange and bolt decreases with the increase of medium temperature.The gasket stress increases from inside to outside along the radial direction.With the increase of medium temperature,the gasket stress decreases and the leakage rate increases.The stress of the gasket is unevenly distributed along the outer circumference,showing a periodic change of 45°;the more the number of internal pressure fluctuations in the medium,the more the stress loss of the inner and outer gaskets,and the worse the gasket sealing effect.（5）Through the transient temperature field analysis of the bolted flange device,the temperature distribution of the gasket is simulated,and the stress and leakage rate of the gasket under different heating rates,temperature fluctuations,and simultaneous fluctuations of the medium internal pressure and temperature are simulated and calculated by using the thermal-structural coupling method.The results show that the faster the heating rate,the greater the reduction of gasket stress and the greater the increase of leakage rate.Temperature fluctuation will lead to the decrease of stress inside and outside the gasket,the increase of gasket leakage rate and the decrease of sealing effect.When the internal pressure and temperature of the medium fluctuate synchronously,the gasket stress is smaller than that when the temperature fluctuates only,and the sealing performance is worse.