Failure Causes of Mechanical Seal of Slurry Pump 

Slurry pump refers to a device that converts electrical energy into kinetic energy and potential energy of a medium by increasing the energy of the solid and liquid mixed medium through the action of centrifugal force (the rotation of the impeller of the pump). It has the advantages of small leakage, low energy consumption, long life and wide range of use. In recent years, it has been widely used in some fields such as mines and power plants.

Many processes, such as the slurry pumps used in flue gas desulfurization systems, generally use mechanical seals and have a more complex structure. The mechanical seal is suitable for harsh working conditions with high solid particle content and high corrosion and abrasion. Therefore, the failure rate of the slurry pump equipment caused by the mechanical seal is very high. Once the mechanical seal fails, it will cause the whole machine to stop working. The centrifugal slurry pump supplier talks about the reasons for the failure of the mechanical seal of the slurry pump.

Failure causes of mechanical seal of centrifugal slurry pump:

1. Leakage during assembly

The mechanical seal is very prone to problems during installation. The mating surfaces of the dynamic and static ring friction pairs may have been deformed, scratched or cracked before or during the installation. The end faces are mixed with dirt or impurities, and the uneven spring force causes the unequal end faces Will cause the mechanical seal to fail.

Under normal circumstances, after installation and commissioning of the mechanical seal, a static pressure test should be conducted to observe the leakage of the mechanical seal. If the amount of leakage is small, it is mostly because there is a problem with the moving ring or static ring sealing ring. If the amount of 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 volume and judgment of the leakage location, and then manually cranking, if there is no obvious change in the leakage, there is a problem with the static and dynamic ring seals. 1. There is a problem with the static ring friction pair.

If the leaking medium is sprayed in the axial direction, there are many problems with the moving ring seal ring. If the leaking medium is sprayed around or leaks from the water cooling hole, the static ring seal ring is mostly invalid. In addition, leakage channels can also exist at the same time, but there are generally major and minor differences. As long as the observation is meticulous and familiar with the structure, it can be judged correctly.

2. A leak during trial operation

The centrifugal force generated by the high-speed rotation of the mechanical seal of the slurry pump after the static pressure test will inhibit the leakage of the medium. Therefore, the mechanical seal leakage during the trial operation is basically due to the damage of the dynamic and static ring friction pairs after eliminating the failure between the shaft and the end cover seal.

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

1) During operation, due to abnormal phenomena such as evacuation, cavitation, and pressure suppression, a large axial force is caused to separate the contact surfaces of the dynamic and static rings; (2) When the mechanical seal is installed, the amount of compression is too large, resulting in the frictional end face Severe wear and bruise;

(3) The moving ring seal 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 floats axially, the static ring is separated from the static ring seat;

(5) There is particulate matter in the working medium, which enters the friction pair during operation, damaging the end faces of the dynamic and static ring seals.

The above phenomenon often occurs during the trial operation, and sometimes it can be eliminated by properly adjusting the static ring seat, etc., but most of them need to be reassembled and replaced, and the seal replaced.

3. Leakage during normal operation

Centrifugal slurry pumps suddenly leak during operation, a few are due to normal wear or have reached the service life, and most are caused by large changes in working conditions or improper operation and maintenance. :

(1) Evacuation, cavitation, or holding back for a long time, leading to seal damage;

(2) The actual output of the pump is too small, a large amount of media circulates in the pump, heat accumulates, causing vaporization of the media, resulting in seal failure;

(3) Sealed cooling water is interrupted;

(4) For a long period of shutdown, there is no manual cranking when restarting, and the friction pair seal tears the sealing surface due to adhesion;

(5) Increased corrosive, polymerizable and gelling substances in the medium;

(6) The environmental temperature changes rapidly;

(7) The operating conditions are frequently changed or adjusted.

The slurry pump expeller's mechanical seal usually needs to be connected to the cooling water. Before using the slurry pump, the shaft seal water must be turned on. After stopping the pump for five minutes, it can be turned off because the cooling water is interrupted and the machine is burned Sealed accidents often occur and require special attention.

The slurry pump is frequently started or the power is suddenly turned off to cause the slurry in the pipeline to be backfilled. The pressure in the pump chamber increases sharply, which causes the dynamic and static ring of the mechanical seal to open, thereby invalidating the mechanical seal. If the pump is shut down for a long time, the pump cavity and mechanical seal must be cleaned with clean water before shutting down. When restarting, the crank should be manually cranked to ensure that the friction pair seal is not stuck.

4. Wear and corrosion failure

Due to the presence of abrasive particulate media in the slurry transported by the slurry pump, it will have the following effects on the mechanical seal used:

(1) Increased wear of the sealing end face: Between the sealing faces, particles leak into the end face, which acts as an abrasive and accelerates the wear of the sealing face;

(2) Blockage of particles on the medium side: due to the accumulation of particles and bridging, the movement of the spring, pin, and auxiliary seal ring is hindered, which leads to a decrease in the followability and floatability of the compensation ring;

(3) Atmospheric-side particle clogging: Due to the small gap between the inner diameter of the sealing surface and the shaft (or shaft sleeve), the leaked solid particles cannot be discharged in time, which is easy to accumulate and block, which hinders the movement of the auxiliary seal ring, resulting in sealing Fail

(4) Abrasion: refers to the local biting and tearing caused by the abrasive particles on the surface of the sealing element, which occurs more seriously in the presence of granular media;

(5) Abrasion of transmission elements: Because the transmission pins are in granular media, the abrasion of the elements themselves is exacerbated by the abrasive action of the particles during movement.

When selecting the model, the mechanical seal product should be avoided as far as possible, so as not to cause the above failure. The mechanical seal has two major ways to solve the problem of the role of the granular medium: First, set some additional internal structure or take auxiliary measures to the mechanical seal Such as screw seal, sealing liquid, flushing water, water tank or oil tank to establish liquid barriers to prevent particle accumulation, etc.), try to avoid the above five kinds of failures, so that the mechanical seal is in good working condition.

The correct analysis of the various reasons for the failure of the mechanical seal of the slurry pump for metallurgical can take corresponding correct countermeasures to ensure the reliability of the mechanical seal. In use, we should strictly abide by the requirements for the use of mechanical seals, so that the mechanical seals can effectively operate for a long time, reduce the number of unnecessary replacements, and reduce cost investment.

We are a slurry pump, FGD pump, sump pump and froth pulp pump supplier in China, Our products are mainly used for transport of solid particles with a strong abrasive, high-concentration slurry.

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