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Mechanical Seal Selection Guide
by：Lepu Seal
2022-09-07
Mechanical Seal Selection Guide
Each type of mechanical seal can only be used effectively within the specified range. Improper selection of mechanical seals will lead to significant reduction in sealing performance, shortened life, and even failure. The following is the selection guide for mechanical seals: steps/methods Seal chamber medium pressure P P≤0.8MPa, choose unbalanced type, P≥0.5MPa, choose balanced type of mechanical seal. Mechanical seal selection guide Line speed V The line speed should be combined with pressure, temperature, medium characteristics, etc. to determine the spring form. The PcV value relates to the stability (vaporization) of the fluid film between the sealing surfaces and the wear resistance of the friction pair. In the absence of external cooling, the maximum operating temperature of the mechanical seal generally depends on the safe operating temperature of the auxiliary sealing material. The particularity of the medium Some mediums will have special requirements for auxiliary seals, such as solvents and other media can not use fluorine rubber, mineral oil can not use EPDM rubber, users should pay special attention. 1) Balanced type should be used for low-viscosity medium that is prone to dry friction; forced transmission structure should be used for high-viscosity medium. 2) Strong corrosion should be sealed with externally mounted PTFE bellows. Matters needing attention 1. The radial runout of the main shaft where the seal is installed should be ≤0.04mm (0.06mm), and the axial movement amount should be ≤0.3mm, and the corresponding parts of the shaft and the static ring seat should be processed according to the requirements of the figure. 2. The parts of the sealing chamber, shaft and mechanical seal should be cleaned, and there should be no pollution, bumps, scratches, and especially to prevent impurities, dust and particles from being brought into the sealing chamber. 3. It is strictly forbidden to collide and beat violently during installation, and the surface of the friction pair should be absolutely clean. 4. The static ring gland must have sufficient strength, and the screws should be tightened evenly during installation to ensure that its end face is perpendicular to the axis. 5. After installation, lightly press the moving ring by hand, it should be flexible and have a certain elasticity; manual cranking, it should run freely. 6. Carry out a static pressure test to observe whether there is leakage. 7. Start the test run, pay attention to whether there is any abnormal sound. 8. When the operating temperature exceeds 80°C, forced circulation should be adopted to cool the seal. 9. The sealed pipeline must be kept unobstructed; dry friction is strictly prohibited.
Each type of mechanical seal can only be used effectively within the specified range. Improper selection of mechanical seals will lead to significant reduction in sealing performance, shortened life, and even failure. The following is the selection guide for mechanical seals: steps/methods Seal chamber medium pressure P P≤0.8MPa, choose unbalanced type, P≥0.5MPa, choose balanced type of mechanical seal. Mechanical seal selection guide Line speed V The line speed should be combined with pressure, temperature, medium characteristics, etc. to determine the spring form. The PcV value relates to the stability (vaporization) of the fluid film between the sealing surfaces and the wear resistance of the friction pair. In the absence of external cooling, the maximum operating temperature of the mechanical seal generally depends on the safe operating temperature of the auxiliary sealing material. The particularity of the medium Some mediums will have special requirements for auxiliary seals, such as solvents and other media can not use fluorine rubber, mineral oil can not use EPDM rubber, users should pay special attention. 1) Balanced type should be used for low-viscosity medium that is prone to dry friction; forced transmission structure should be used for high-viscosity medium. 2) Strong corrosion should be sealed with externally mounted PTFE bellows. Matters needing attention 1. The radial runout of the main shaft where the seal is installed should be ≤0.04mm (0.06mm), and the axial movement amount should be ≤0.3mm, and the corresponding parts of the shaft and the static ring seat should be processed according to the requirements of the figure. 2. The parts of the sealing chamber, shaft and mechanical seal should be cleaned, and there should be no pollution, bumps, scratches, and especially to prevent impurities, dust and particles from being brought into the sealing chamber. 3. It is strictly forbidden to collide and beat violently during installation, and the surface of the friction pair should be absolutely clean. 4. The static ring gland must have sufficient strength, and the screws should be tightened evenly during installation to ensure that its end face is perpendicular to the axis. 5. After installation, lightly press the moving ring by hand, it should be flexible and have a certain elasticity; manual cranking, it should run freely. 6. Carry out a static pressure test to observe whether there is leakage. 7. Start the test run, pay attention to whether there is any abnormal sound. 8. When the operating temperature exceeds 80°C, forced circulation should be adopted to cool the seal. 9. The sealed pipeline must be kept unobstructed; dry friction is strictly prohibited.
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