The Structure And The Sealing Performance Research Of The Expanded Graphite Composite Gasket

Expanded graphite was made of natural graphite through physical or chemical method.With the special porous structure, expanded graphite had so many excellent characteristics that it was widely used in lots of filed,such as environmental protection, medical health, petroleum, chemical industry and military industry and other departments, played a very important role in the industrial manufacture. Especially as a new type of sealing material, expanded graphite was increasingly used to replace the traditional metal sealing material and the poison asbestos material,and had been applied to the dynamic and static sealing system in many equipments, so studying the structure and properties of sealing components which were made of this kind of material had highly interested researchers who were engaged in this sealing filed and had achieved many significant results.In this paper,the structure characteristics,basic characteristics, preparing methods of expanded graphite materials and the research characteristics of composite materials was briefly introduced.Meanwhile the sealing mechanism,failure analysis,deformation coordination equations of flange connection system and a new design method was analyzed. ANSYS numerical analysis method and conclusion of expanded graphite composite gasket was mainly introduced and the structure of Metal corrugated flexible graphite composite gasket was optimized.First of all, on the premise of experimental study which was made by Gao Zhongbai et al,the leakage rate of expanded graphite wound gasket under the condition of normal temperature was made a simulation analysis,a specially used for gasket calculation meshing method was cited and the bolt pre-tightening unit was adopted to simulated the pre-loaded effect of bolt.Several unit types and meshing methods were introduced.Study shows that with the internal pressure of medium elevating,leakage rate of the gasket will increase,and with the increase of bolt pretensioning forces,leakage rate of the gasket will decrease.But an impact that was caused by the width of winding belt and acted on the leakage rate of gasket was not significant.Those influence of these results were consistent with experimental results,so the reliability of the simulation method was manifested.Then the leakage rate of gasket under different temperature was simulated.Results show that the medium temperature had a great influence on the leakage rate of gasket structure,and with the increase of temperature, the gasket leakage rate increased obviously.Secondly, expanded graphite metal corrugated composite gasket which was the most concern material had been carried on the numerical analysis in this paper.2-D modeling method was chose to establish geometric model of gaskets.How the pitch, tooth number of the metal frame and the thickness of expanded graphite coating would influence on the gasket compression resilience was studied.Meanwhile the gasket stress correspond to various geometric sizes and deformation value was input to the origin software for processing,the corresponding pressure closed curve was achieved.At last,the closure stress values which was got by these simulation results was used as the gasket material characteristics and put into the stress analysis of the bolted flange connection structure simulation analysis.According to the numerical simulation method that was introduced in this paper,the seal characteristics of expanded graphite metal corrugated composite gasket was simulated.The simulation results showed that the standard metal flexible graphite composite gasket which was set by chemical industry standard HG/T20623-2009was not the best.When other conditions remain unchanged,the pitch of the metal frame was1.2mm, the teeth number of the metal frame was10,and the thickness of expanded graphite coating was0.5mm or the pitch of the metal frame was1.0mm, the teeth number of the metal frame was12,and the thickness of expanded graphite coating was0.4mm,those sealing performance of the composite gaskets which were designed by these two structure was better than the standard gasket’s sealing performance,and all gasket leakage rate that were calculated by the simulation method were maintained at10-4～10-3cm3/s range,conformed to the leakage rate requirements based on the tightness design method and achieved the optimization design of the gasket structure.The most important was this paper provided a correct numerical simulation method for the gasket performance and some reference data.All in all, the study method was introduced in this article plays a important role in the further research for the features of gasket.