Study On Axial Sealing Performance Of Graphite Ring

With the development of the petroleum industry,people put forward more stringent requirements for sealing in exploration and transportation of oil and gas.The sealing performance is good or bad,which directly affects the success or failure of the entire oil and gas operation.Flexible graphite materials have gradually become the first choice for nonmetallic sealing materials due to their excellent mechanical properties,sealing properties and stability properties.Therefore,the research on the axial sealing performance of graphite ring has important practical significance for expanding the application range of graphite material sealing in oil casing annulus and underwater pipeline connection,and promoting the research and development of graphite gasket.Based on the characteristics of axial seals,the main test fixtures were designed and processed in the paper.The compression resilience performance of the graphite ring of three molding methods in different radial gaps was studied,and the graphite ring forming method suitable for axial sealing was screened.Compression resilience,radial contact stress and axial sealing performance of graphite packing rings of different densities were researched by testing;Based on the testing results of compression rebound and radial contact stress measurement,correction functions with linear variation of radial gap amount were introduced.The ANSYS was used to investigate the influence of structural parameters and medium pressure on the sealing performance of graphite ring.According to the theory of porous media,a graphite ring axial leakage model was established and study the influence of external working conditions on leakage mode was studied.Research shows: The graphite packing ring has good resilience performance,and is insensitive to radial clearance compared to the other two types of graphite rings,and is suitable for annulus sealing;And the radial contact stress on the pipe wall is linearly positively correlated with the axial load,and decreases with the increase of the radial clearance.The decreasing trend increases with the increase of the clearance amount,and is not affected by the density of the graphite packing ring.In terms of sealing performance,The leak rate increases with the increase of the medium pressure to satisfy the constant term is zero,and the quadratic function changes.and the leak rate decreases with the increase of the axial load to satisfy power function changes.The results of finite element analysis show that the radial contact stress of the outer ring surface of the graphite ring decreases with the increase of the axial height,increases with the increase of the aspect ratio,and decreases slightly with the increase of the medium pressure.At the same time,due to the increase of the gap amount,the influence of the medium pressure on the contact stress is slightly improved.The regression coefficients AL and AM which characterize the number and diameter of the leakage channels in the leakage model decrease with the increase of the density of the graphite ring,and the sealing performance is improved;The increase of the medium pressure causes the leakage rate to increase,and also changes the proportion of the leakage rate of the two parts.Among them,the ratio of laminar leakage rate increases,and the proportion of molecular leakage rate decreases.The increase of the gasket stress causes the leakage rate to decrease,and the proportion of the laminar leakage rate to the total leakage rate is also decreased,and the proportion of the molecular leakage rate to the total leakage rate is increased.