Mechanical seal operation precautions

Mechanical seals are one type of seals. They are generally used for dynamic sealing of rotating parts. By fitting a proper flushing scheme, a small amount of leakage or zero leakage of the medium can be achieved (the gas/liquid will enter the medium). Mechanical seal The mechanical seal is formed by at least one pair of end faces perpendicular to the axis of rotation, which are held under the action of the fluid pressure and the elastic force (or magnetic force) of the compensating mechanism and the auxiliary seal. A device that prevents fluid leakage.

Causes and judgments of leakage of mechanical seals for chemical pumps

A. Leak when installing the static test.

After the mechanical seal is installed and debugged, it is generally necessary to perform a static test to observe the amount of leakage. If the leakage is small, there are problems with the moving ring or static ring seal; when the leakage is large, it indicates that there is a problem between the friction pairs of the moving and stationary rings. On the basis of preliminary observation of the leakage amount and judging the leakage location, the vehicle can be manually observed. If there is no significant change in the leakage amount, the static and dynamic ring seals have problems; if there is a significant change in the leakage amount during the cranking, it can be determined that it is moving. There is a problem with the static ring friction pair; if the leakage medium is sprayed in the axial direction, there are many problems with the moving ring seal ring, and the leakage medium is sprayed to the periphery or leaks from the water cooling hole, and the static ring seal ring is mostly invalid. In addition, the leakage channel can also exist at the same time, but there are generally primary and secondary differences. As long as the observation is meticulous and familiar with the structure, it can be judged correctly.

B. Leakage during test operation.

After the static test of the mechanical seal of the pump, the centrifugal force generated by the high-speed rotation during operation will suppress the leakage of the medium. Therefore, the leakage of the mechanical seal during the test run is basically caused by the failure of the friction pairs of the moving and stationary rings after the failure of the seal between the shafts and the end cap seal.

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

1. During operation, due to abnormal phenomena such as evacuation, cavitation and rolling, a large axial force is caused to separate the moving and static ring contact surfaces;

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

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

4. The static ring seal ring is too loose. When the moving ring is axially floating, the static ring is separated from the static ring seat;

5. There are granular materials in the working medium, and the friction pair is entered during operation to detect the moving and static ring sealing end faces;

6, the design selection is wrong, the sealing end face is lower than the pressure or the sealing material is more cold shrinkage. The above phenomenon often occurs during trial operation. Sanchang Pump Industry can sometimes be eliminated by properly adjusting the static ring seat, but most of them need to be disassembled and replaced.

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

8. Evacuation, cavitation or rolling for a long time, resulting in seal damage;

9. The actual output of the pump is too small, a large number of medium pumps circulate inside, heat accumulates, causing gasification of the medium, resulting in seal failure;

10. The return flow is too large, causing the bottom of the suction side container (tower, kettle, tank, pool) to rise and damage the seal;

11. For a longer period of time, there is no manual turning when restarting, and the friction pair tears the sealing surface due to adhesion;

12. Increased corrosive, polymerizable and gelatinous substances in the medium;

13. The ambient temperature changes drastically;

14 working conditions are frequently changed or adjusted;

15 sudden power failure or downtime. The centrifugal pump suddenly leaks during normal operation. If it cannot be found in time, it will often cause a big accident or loss. It must be taken seriously and effective measures taken.

Note: How to extend the service life?

In order to make the pump work normally, it is necessary to develop good habits every day - inspection and maintenance, which can avoid a lot of troubles, and also improve work efficiency, so daily inspection and maintenance is very important, we can not ignore it.

Environmental Quality

Although China's operating environment for pumps is constantly improving and improving, there are still some people who put the pumps in a poor environment, but if they are placed in poor conditions, they should be cleaned frequently. In this case, everyone should check and maintain it frequently.

Daily inspection

In daily inspections, we must take full control of the chemical pump and test the instrument, but also play a subjective role. Check whether the pressure, current, voltage, flow and temperature indicated by each part of the instrument are normal, whether there are any deformations, variations, and whether there are any leaks or blockages. Listen to the sound of any part, such as impact sound, breakage. Sound, friction, etc., but also pay attention to the vibration of the chemical pump is not very large.

Number of inspections

In order to ensure the efficiency of the use of chemical pumps, we must check at least twice a day, even if the pump is more automated, it needs to be checked regularly.