High pressure sealing characteristics of combined structure based on flexible graphite rings

Seal components made of flexible graphite have excellent resistance to temperature, while sealing of high pressure fluids is unsatisfactory. The sealing behavior of flexible graphite rings is characterized by the ratio of the contact pressure to the axial pressure. The FEA results show that the lateral pressure decreases roughly linearly along the direction of the sealing path, and the lateral pressure coefficient increases with increasing axial pressure. We design a combined seal structure based on flexible graphite rings, and extract the contact pressure along two sealing paths. The results imply that the self-sealing effect is more favorable when the pressure of the sealing fluid is increased. The effect of the friction coefficient on the contact pressure is not significant, except at the beginning of the sealing path. Sealing effects are tested under the coupling condition of 350°C and 50 MPa, which verify the sealing performance under high temperature and high pressure. The comparison of the test results of “kf” (the product of lateral pressure coefficient and friction coefficient) with those of the FEA validates the rationality of the analytical approach. The comprehensive coefficient “kf” can be easily obtained by testing, and can be used as a key parameter for seal design.