Technical requirements of mechanical seals and key points of use of seals

The mechanical seal is a high-precision mechanical component, and its correct installation and operation have a great impact on its service life. We generally follow the standards set by the Ministry of Petrochemicals. The technical requirements for the matching part of the pump with the mechanical seal and the mechanical seal are as follows: The mechanical seal is a high-precision mechanical component, and its correct installation and operation have a great impact on its service life. We generally follow the standards set by the Ministry of Petrochemicals. The technical requirements for the matching part of the pump with the mechanical seal and the mechanical seal are as follows: 1. Shaft curvature: the maximum is not more than 0.05 mm; 2. Rotor vibration: the vicinity of the shaft sleeve at the moving ring seal is not more than 0.06 mm; 3. Shaft The axial movement of the shaft is not allowed to exceed ±0.5 mm. If there is a shaft sleeve, the shaft sleeve is not allowed to be loose; 4. The alignment error of the coupling: for the gear coupling, it is not more than 0.08 ~ 0.10 mm (P2008C), For the elastic coupling, it is not more than 0.05-0.06 mm; (the customary practice is that the end jump is less than 0.05, and the radial jump is less than 0.10) 5. The concentricity tolerance between the gland (static ring seat) and the seal matching stop to the shaft centerline is 0.05 mm , the verticality value of the plane in contact with the gasket to the center line is 0.03 ~ 0.05 mm, if it does not meet the requirements, the sealing cavity should be processed; 6. Install the shaft sleeve end of the dynamic ring seal, and install the static ring The end of the gland (or housing) of the sealing ring should be chamfered and smoothed. 7. Be careful when installing and disassembling the mechanical seal. It is strictly forbidden to use a hand hammer and a flat shovel to avoid damage to the sealing element. If the scale cannot be removed, it should be cleaned and then removed. 8. If mechanical seals are used at both ends of the pump, take care of each other during assembly and disassembly to prevent one from neglecting the other. 9. For the mechanical seal that has been run, if the gland is loose and the seal moves, the dynamic and static ring parts must be replaced, and should not be re-tightened to continue use. Because the original running track of the friction pair will change after loosening, the sealing performance of the contact surface is easily damaged. Use points of seals Seals are materials or parts that prevent fluid or solid particles from leaking from adjacent joint surfaces and prevent external impurities such as dust and moisture from invading the internal parts of the machine and equipment (1) Select the appropriate seal material and Hydraulic oil, as well as adaptability to operating temperature, compatibility with oil. (2) The geometric position accuracy (concentricity) of the sliding parts relative to the seal is high, the material is good (such as hard chrome plating) and the surface roughness is fine, which can prolong the service life. ① For oil seals used in hydraulic pumps and motor journals, not only the roughness of the sliding surface is required to be within Ra of 0.25m, but also the surface is required to be plated with hard chrome, and the diameter of the oil seal lip needs to be appropriately adjusted according to the specific situation. Adjust the spring force to make it tight enough, and use a mounting sleeve or a thin gasket to protect the sealing ring during installation to prevent the lip from rolling and twisting, causing the spring to slip out. ②The inner surface of the hydraulic cylinder is usually processed by rolling, which not only improves the surface roughness, but also makes the surface hardened by cold work, which is beneficial to prolong the service life of the sealing ring. In addition, the pressure used, the length and type of the sliding surface also have a great influence on the service life. Therefore, the regular inspection time should be determined according to these conditions.