Causes and Countermeasures of Periodic Leakage of Mechanical Seals

The leakage rate of mechanical seal accounts for more than 50% of all maintenance pumps. The operation of mechanical seal directly affects the normal operation of the pump.


Periodic leakage

(1) The axial displacement of the pump rotor is large and the interference between the auxiliary seal and the shaft is also large, so that the moving ring cannot move flexibly on the shaft. After the pump turns over and the dynamic and static rings are worn, the compensation displacement can not be obtained.

Countermeasures: when assembling the mechanical seal, the axial displacement of the shaft should be less than 0.1mm and the interference between the auxiliary seal and the shaft should be moderate. While ensuring the radial seal, the movable ring should be able to move flexibly on the shaft after assembly (the pressing spring of the movable ring can spring back freely).

(2) Insufficient lubricating oil on the sealing surface causes dry friction or roughening of the sealing surface.

Countermeasures: the height of the lubricating oil surface in the oil chamber should be higher than the sealing surface of the dynamic and static rings.

(3) Periodic vibration of rotor. The reason is that the stator is not aligned with the upper and lower covers, or the impeller and the main shaft are unbalanced, cavitation or bearing damage (wear), which will shorten the seal life and generate leakage.

Countermeasures: the above problems can be corrected according to the maintenance standards.


According to JB4127.1-1999 Technical Conditions of Mechanical Seal, the service life of mechanical seal should not be less than 1 year when the sealed medium is water, oil and similar medium under the condition of reasonable selection and correct installation and use. When the sealed medium is corrosive medium, the service life of mechanical seal is generally 6 months to 1 year. However, it is not subject to this restriction when the use conditions are harsh. " In the sealing test, the average leakage should not exceed 5ml/h when the outer diameter of shaft (or shaft sleeve) is greater than 50mm, and it should not exceed 3ml/h when the outer diameter of shaft (or shaft sleeve) is not greater than 50mm.

The above data are for your reference only, especially in some special working conditions, the service life and leakage rate of the machine seal are generally not suitable for making a clear commitment, besides, long-term storage after delivery is also unreasonable.





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