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    Pump mechanical seal leakage causes and overhaul misunderstanding

    Author: Release:2012-10-07
    Generally, the shaft extending outside the sleeve, the leak between the seal cover and the pump housing is relatively easy to find and solve, but need careful observation relatively difficult, especially when the working medium is a liquefied gas or high pressure, toxic or harmful gases, more. Difficult to discern on the rest of the leakage intuitive judgment shall be leak symptoms were observed on the basis of the long-term management and maintenance practices, analysis, study them, in order to draw the right conclusions.
    Types of pump mechanical seal range of different models, but the leakage point five:

    (L) a seal between the sleeve and the shaft;

    (2) moving the seal between the ring and the sleeve;

    (3) dynamic and static ring seal;

    (4) the seal between the stationary ring and stationary ring seat;

    (5) a seal between the seal cover and the pump housing.

    A leakage analysis and judgment

    Install static test leak. Mechanical seal installation and commissioning, to carry out the static test, observe the amount of leakage. Small amount of leakage, snap ring or stationary ring seal problems; leak is large, it indicates that moving and stationary ring problems between the friction pair. Observed on the basis of preliminary observations leakage to determine the leaking part, and then manually turning leakage no significant changes in the static and dynamic ring seal problem; Barring a significant change in the amount of leakage can be concluded that dynamic the stationary ring friction pairs exist; such as the leakage of medium along the axial injection, the majority of problems ring seals, leaking medium spray or leakage from the water cooling holes around the stationary ring seal failure. In addition, leakage channels can simultaneously exist, but generally the major and minor distinction, as long as careful observation, familiar with the structure will be able to correctly judge.

    2 the leakage test operation. Pump mechanical seal after a static test, the high speed operation is generated by rotation of the centrifugal force, will inhibit the leakage of the medium. Therefore, commissioning mechanical seal leakage exclude shaft and end cap seal failure, basically due to dynamic friction pair of stationary ring caused by the destruction. The main factors causing friction pair of seal failure:

    (L) operation, due to the time of cavitation pressureout abnormal phenomenon, caused by the large axial force, so moving, stationary ring contact surface separation;

    (2) installation of mechanical seals and compression excessive friction pair the end face serious wear, abrasions;

    (3) ring seals tight, the spring axial float ring can not be adjusted;

    (4) The stationary ring seal is too loose, when the snap ring axial float, static ring from the stationary ring seat;

    (5) working medium granular material, running into the friction pair testing dynamic and static ring seal faces;

    (6) Design and Selection, the seal faces pressure is low or sealing material Lengsu sexual large. The above-mentioned phenomena often appear in the commissioning, by appropriate adjustment of the static ring seat can sometimes be eliminated, but most need to be re-disassembly, replace the seal.

    Normal operation, a sudden leak. Centrifugal pumps in operation in a few due to normal wear and tear or has reached the end of its life, and most of the operating conditions change or operation, improper maintenance caused a sudden leak.

    (1) the time of cavitation or longer time pressureout seal damage;

    (2) the actual output of the pump is small, a large number of medium pump for circulating the heat accumulation causing media vaporized, resulting in seal failure;

    (3) The return flow is too large, resulting in the suction tube side of the container (tower, kettle, cans, pool) dregs at the bottom of the damage to the seal;

    (4) for a long time to shutdown, restart manually turning the friction pair due to adhesions tearing the sealing surface;

    (5) medium corrosive, increased polymerizable gumming substance;

    (6) The ambient temperature is rapidly changing;

    (7) Case frequent changes or adjustments;

    (8) a sudden power outage or downtime. In normal operation, the centrifugal pump suddenly leak, and if they can not find that tend to result from the a larger accident or loss, attention has to be paid, and to take effective measures.

    Pump a few errors in the maintenance of the mechanical seal

    The greater the amount of compression spring seal the better. In fact, the compression spring excessive, can lead to rapid wear and friction pair instantly burning; excessive compression of the spring to lose the ability to adjust automatically ring face seal failure.

    2 snap ring seal Figure as tight as possible. In fact, ring seals tight harm than good. One intensified between the seals and bushings wear, premature leaks; increases the axial adjustment of the snap ring the mobile resistance, when the operating conditions change frequently unable to make timely adjustments; the spring fatigue fragile; four the ring seal deformation, affecting the sealing effect.

    Stationary ring seal as tight as possible. Stationary ring seal in a quiescent state basic, relatively tightly sealing effect would have been better, but too tight is also harmful. One cause static ring seals due to excessive deformation, affecting the sealing effect; stationary ring made from graphite majority, are generally more brittle, excessive force can easily cause fragmentation; Third, install, difficult to remove, easy to damage the stationary ring.

    4. Impeller lock nut as tight as possible. Mechanical seal leaks, the leakage between the sleeve and the shaft (shaft leakage) is more common. Is generally believed that the axis between the leak did not lock the impeller lock nut, in fact lead to shaft leak by many factors, such as pad failure, offset shaft axis between impurities, with the Department of the shaft and sleeve larger shaped bit error, the contact surface damage between the various components of the shaft gap, shaft head thread too long will result in leakage between the shafts. Locking excessive can only lead to premature failure of the shaft between pad lock mother, opposite lock moderate furrowed mother, so always maintain a certain compression elastic shaft between pad lock master automatically timely locking operation, the shaft is always in good a sealed state.

    5 new better than the old one. In contrast, the effect of using the new mechanical seal better than the old, but the quality of the new mechanical seal or material selection is not that time, the larger with the size of the error will affect the sealing effect; polymerization and permeability media, such as non-excessive static ring wear, or not replaced as well. Because the stationary ring in the stationary ring seat in a quiescent state for a long period of time, the polymer and impurities deposited as one played a better seal.

    Overhaul is better than not demolished. In fact, sometimes the seal is not damaged, simply adjust the working conditions or the appropriate adjustments to seal leakage can be eliminated once the mechanical seal leakage would rush to overhaul. This not only avoids the wasteful and can verify their own fault judgment, the accumulation of maintenance experience to improve the maintenance quality.

    Copyright | Binzhou City Oasis sealed Products Co., Ltd. Technical Support: Ocean Technolog

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