Leakage Causes and Judgment of Mechanical Seals Used in Chemical Pumps

During the use of chemical pumps, their sealing conditions can directly affect the use of equipment, so in order to ensure the use of equipment, we need to understand the reasons and judgments of the leakage of chemical pump mechanical seals, so as to better use the equipment , improve equipment efficiency.

A. Leakage during installation static test.

After the mechanical seal is installed and debugged, it is generally necessary to conduct a static test to observe the leakage. If the leakage is small, there is a problem with the dynamic ring or the static ring seal ring; if the leakage is large, it indicates that there is a problem between the dynamic and static ring friction pairs. On the basis of preliminary observation of the leakage amount and judgment of the leakage location, and then manual cranking observation, if the leakage amount does not change significantly, there is a problem with the static and dynamic ring seals; if the leakage amount changes significantly during cranking, it can be concluded that it is the dynamic, There is a problem with the friction pair of the static ring; if the leakage medium is sprayed along the axial direction, there are mostly problems with the seal ring of the dynamic ring, and if the leakage medium sprays around or leaks from the water cooling hole, it is mostly due to the failure of the seal ring of the static ring. In addition, leakage channels can also exist at the same time, but generally there are primary and secondary differences. As long as you observe carefully and are familiar with the structure, you will be able to judge correctly.

B. Leakage during test run.

After the pump seal has passed the static test, the centrifugal force generated by high-speed rotation during operation will inhibit the leakage of the medium. Therefore, the leakage of the seal during the test run is basically caused by the damage of the friction pair of the dynamic and static rings after the failure of the seal between the shafts and the end cover is excluded.

C. The main factors causing the failure of the seal of the friction pair are:

1. During operation, due to abnormal phenomena such as evacuation, cavitation, and pressure holding, a large axial force is caused to separate the contact surface of the dynamic and static rings;

2. When the mechanical seal is installed, the compression amount is too large, resulting in severe wear and abrasion on the end face of the friction pair;

3. The sealing ring of the moving ring is too tight, and the spring cannot adjust the axial floating amount of the moving ring;

4. The sealing ring of the static ring is too loose. When the moving ring floats axially, the static ring will break away from the seat of the static ring;

5. There are granular substances in the working medium, which enter the friction pair during operation, and detect the dynamic and static ring sealing end faces;

6. Incorrect design and selection, low specific pressure of the sealing end face or high cold shrinkage of the sealing material, etc. The above phenomenon often occurs during trial operation, and sometimes it can be eliminated by properly adjusting the static ring seat, etc., but most of them need to be disassembled and replaced to replace the seal.

7. Sudden leakage during normal operation. A few of the sudden leakage of the centrifugal pump during operation is due to normal wear or the service life has been reached, but most of them are caused by large changes in working conditions or improper operation and maintenance.

8. Evacuation, cavitation or pressure holding for a long time, resulting in damage to the seal;

9. The actual output of the pump is relatively small, and a large amount of medium circulates in the pump, and the heat accumulates, causing the medium to vaporize and resulting in seal failure;

10. The return flow rate is too large, causing the bottom of the container (tower, kettle, tank, pool) on the side of the suction pipe to have sediment floating and damage the seal;

11. For a longer period of outage, there is no manual cranking when restarting, and the friction pair will tear the sealing surface due to adhesion;

12. Corrosive, polymeric and gelling substances in the medium increase;

13. Rapid changes in ambient temperature;

14. Frequent changes or adjustments in working conditions;

15. Sudden power failure or shutdown due to failure, etc. The centrifugal pump leaks suddenly during normal operation. If it cannot be found in time, it will often lead to major accidents or losses. It must be paid attention to and effective measures should be taken.

The above are the causes and judgments of the leakage of mechanical seals used in chemical pumps. At the same time, based on the above, fault judgments can be made better, so as to quickly restore the use of equipment and avoid serious losses to the enterprise.