First, about the service life
In mechanical seals, the main wear part is the end face of the sealing friction pair, because the wear amount of the seal end face is not large under normal working conditions, such as the balance coefficient of 0.75 graphite friction pair, the wear amount per hour in water and oil is about 0.1 micron, that is to say, the wear amount of 10,000 hours of continuous operation is about 1 mm. It can be seen that the wear of the friction pair generally does not affect the seal life. Mechanical seals can generally be used continuously for 1 to 2 years, and there is no problem in individual cases for 5 to 10 years. The above life premise is that the mechanical seal runs under the allowed working conditions, such as the movement of the shaft, beating, medium particle concentration, temperature, corrosion and other factors.
External factors affecting the life of mechanical seals:
1. The pump shaft has large channeling momentum
2. The axial force is too large
3. The disturbance of the pump shaft is too large
4. The auxiliary flushing system is unreasonable
2. Standards for leakage
China's JB4127.1-1999 "Mechanical seal Technical conditions" stipulates: "In the case of reasonable selection, installation and correct use, when the sealed medium is water, oil and similar media, the use of mechanical seals is generally not less than 1 year. When the sealed medium is a corrosive medium, the service life of the mechanical seal is generally 6 months to 1 year. However, when the conditions of use are harsh, this limitation shall not apply." Sealing test, the average leakage of the shaft (or sleeve) outer diameter greater than 50mm does not exceed 5mL/h, the shaft (or sleeve) outer diameter is not greater than 50mm leakage is not greater than 3mL/h