Finite element analysis of the lens gasket seal The working state of the 18-inch lens gasket seal and the mating flange is simulated by the finite element method, and the stress distribution of the two is analyzed. Since the flange-seal ring system is a strictly axisymmetric structure, and at the same time it is mirror-symmetrical about the middle surface of the seal ring, the finite element analysis can only be performed on the 1/2 radial section, as shown in Figure 2. While improving the efficiency of modeling, it also greatly saves time. The mesh size specified in the model adopts the mapping method, and the mesh is encrypted near the contact surface. Table 2 Parameter Symbol Notes Table Symbol Notes di The inner diameter of the flange or flange surface dD The design value of the sealing ring diameter of the bearing model d′D The intermediate calculated value of the sealing ring diameter d1 The inner diameter of the sealing ring d2 The outer diameter of the sealing ring d5 The outer flange inner slope Diameter h1 The height of the sealing ring at d1 hD The height of the sealing ring at dD h2 The height of the sealing ring at d2 x the distance between the end faces of the two flanges r The rounded value of the spherical radius of the sealing ring r′ The calculated value of the spherical radius of the sealing ring . The working principle of the metal seal determines that the hardness of the sealing ring should be slightly lower than that of the flange, so the lens pad and flange materials are respectively 316 stainless steel and 12Cr2Mo1 [4-5]. The elastic modulus of 316 stainless steel is (2.0×105) MPa; 12Cr2Mo1 is a low-alloy hot-strength steel, and the elastic modulus is (2.06×105) MPa; the yield strength of both is 310 MPa. When creating a sealing surface contact pair, use CONTA172 unit for the contact surface on the lens pad and TARGE169 unit for the target surface on the flange. The internal pressure of the model is 34.5MP, which acts on the inner surface of the sealing ring, the inner surface of the flange and the contact point between the two. An axial concentrated load of 6210kN is applied to the inclined shoulder of the flange. This working preload is calculated according to the relevant regulations of ASME [6]. In view of the mirror symmetry of the model, the vertical displacement of the center line of the seal ring is limited. Model loading and boundary conditions are shown in Figure 3. The stress distribution of the 18-inch lens pad is shown in Figure 4. The maximum equivalent stress value is 241.5MP, which is now near the contact point. The size of the contact pressure determines the final sealing effect. In theory, when the contact pressure is greater than the pressure that needs to be sealed, a safe seal can be formed. The contact pressure between the flange and the sealing ring is 383.0MP, as shown in Figure 5.