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What Will Lead To Mechanical Seal Leakage?
Mar 22, 2018

Mechanical seal leakage analysis

1. Installation of static test leakage. After the installation and debugging of mechanical seals, static test should be conducted to observe the leakage. If the leakage volume is small, there are problems in the ring or ring sealing ring. When the leakage volume is large, it indicates that there is a problem between the dynamic and static friction pairs. On the basis of preliminary observation of leakage and judging the leakage location, the manual disc car is observed. If there is no obvious change in the leakage volume, there is a problem in the static and dynamic ring sealing ring. If there is a significant change in the leakage volume of the car, it can be concluded that there is a problem with the friction of the stationary ring. The axial injection, such as medium leak, ring seal problems, leakage of medium around jet or leak from the water cooling hole, more for static seal failure, in addition, the leakage channels can also exist, but generally speaking, there are difference between primary and secondary, as long as observe carefully, be familiar with the structure, must be able to correctly judge [2].

2. Leakage during test run. Mechanical seal of pump after static test, the centrifugal force generated by high-speed rotation during operation can suppress leakage of media. Therefore, the mechanical seal leakage during the test run is mainly caused by the damage of the friction pair of the stationary ring and the static ring. The main factors that cause the failure of friction secondary seal are:

(l) in the operation, due to the abnormal phenomena such as evacuation, cavitation and pressure, the large axial force is caused, and the contact surface of the moving and stationary rings is separated.

(2) the mechanical seal compression amount is too large for installation, causing serious wear and abrasion of the friction side face;

(3) the ring seal is too tight, and the spring cannot adjust the axial float of the moving ring;

(4) the static ring sealing ring is too loose, when the moving ring axis is floating, the static ring is separated from the static ring seat;

(5) in the working medium, there are granular materials, and in the operation, the friction pair, flaw detector and static ring seal face;

(6) the design selection is wrong, the sealing end face is lower than the pressure or the sealing material has a large shrinkage. The above phenomena often appear in the trial operation, and can be eliminated by proper adjustment of static ring seats, but most of them need to be reassembled and sealed.

3. A sudden leak in normal operation. The sudden leakage of the centrifugal pump in operation is due to normal wear or service life, and most of it is caused by the large change of operating conditions or improper operation and maintenance.

(1) vacuum, cavitation or prolonged holding pressure, leading to sealing failure;

(2) the actual output volume of the pump is small, and the inner circulation of a large number of medium pumps, the heat accumulation, causes the media to vaporize, leading to the sealing failure;

(3) the return flow is too large, causing the bottom sediment of the suction tube side container (tower, kettle, tank and pool) to rise at the bottom and damage the seal;

(4) for a long time outage, no manual drive is provided for the restart, and the friction pair is torn by adhesion;

(5) the corrosive, polymerizing and gelatinous substances in the medium are increased;

(6) drastic changes in environmental temperature;

(7) frequent changes or adjustments in the working conditions;

(8) sudden power failure or downtime, etc. When the centrifugal pump suddenly leaks in the normal operation, if it can not be found in time, it usually leads to a large accident or loss, which must be taken seriously and taken effective measures.

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