Pump mechanical seal is a precision, mechanical basic element of a more complex structure, is a key component of pump machinery. Sealing performance and service life depends on many factors, such as the accuracy of selection, the machine, proper installation, use and so on.

A member from outside the pump; the pump to deliver a more fluid medium, with horizontally mounted, high speed, high pressure, with solid particles, corrosion resistance and other characteristics, so the main pump mechanical seal materials often need to withstand the impact of solid particles erosion The sealing surface erosion caused by high temperature and high speed, high pressure seal parameter instability brought about by corrosion and other adverse factors matrix structures, mechanical seals Sealing material higher, generally sealing surface friction materials are optional nickel-based alloy, cobalt-based alloy, sintered silicon carbide, reaction bonded silicon carbide, metal impregnation graphite, graphite-filled PTFE, Teflon filled with glass fiber, aluminum oxide ceramic, and so special ; matrix material optionally 2Cr13 stainless iron, 301 stainless steel, 304 stainless steel, 316 stainless steel, 316L stainless steel, 904L stainless steel, Teflon and the like; spring compensators made of Hastelloy optional, 1Cr18Ni9Ti, 3Cr13 and so on;

Unlike kettle mechanical seal, pump mechanical seal sealing medium mostly liquid, solid-liquid mixture and atmospheric gases; and kettle mechanical seal used for sealing a high pressure gas or gas-liquid mixture, disclosure of environmental and biological cause serious threats.

Pump mechanical seal is a precision, mechanical basic element of a more complex structure, is a key component of pump machinery. Sealing performance and service life depends on many factors, such as the accuracy of selection, the machine, proper installation, use and so on. Pump mechanical seal variety. Different models, its maintenance is very difficult to discern and judge.

Pump mechanical seal leakage points have major five places:

(1) The seal between the sleeve and the shaft.

(2) Dynamic seal between the ring and the sleeve.

(3) The line between the static ring seal.

(4) On the stationary ring seal between the stationary ring seat.

(5) The seal between the seal cover and the pump.

Generally, between bushes overhanging shaft seal leakage between the cover and the pump is relatively easy to find and solve, but need careful observation, especially when the working medium is liquefied gases or high pressure, toxic gases, relatively difficult more. The rest of the leak is difficult to discern intuition and judgment shall be on the basis of long-term management and maintenance practice, leak symptoms were observed, analyzed, judged, in order to draw the right conclusion.

Leakage reason analysis and judgment

1. When the installation of static leak test. After installation of mechanical seals, generally the static test, observe leakage. The leak was smaller, mostly stationary ring seal ring or problems; leakage is large, then the move, there is a problem of friction between the stationary ring. Preliminary observation leakage in judgment on the basis of the leak point, and then manually jigger observed no significant changes in the amount of leakage if the static and dynamic ring seal in question; if Barring significant changes in the amount of leakage can be judged to be moving, static ring friction problem; as media leaks along the jet axis, the ring seal problems mostly media leaks to the surrounding water spray or leak from the cooling holes, then mostly stationary ring seal failure. In addition, the leak paths can also exist, but generally there are differences between primary and secondary, as long as careful observation, familiar with the structure, we will be able to judge correctly.

2. Leakage occurs when commissioning. Pump mechanical seal after the static test, the high-speed rotation of the centrifugal force generated when the operation would inhibit media leaks. Therefore, the exclusion of commissioning mechanical seal leakage between the shaft and cover seal failure after, basically due to the dynamic and static ring friction caused by sabotage. Factors causing friction seal failure are:

(1) Operation, because the evacuation, cavitation, hold pressure and abnormal, causing large axial force, so dynamic and static ring contact surface separation;

(2) When installing the mechanical seal compression is too large, resulting in serious vice Friction wear, abrasion;

(3) Tight ring seals, spring can not adjust the axial float ring of the amount;

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

(5) Working medium is particulate matter, running into friction, testing dynamic and static ring seal faces;

(6) The design selection is incorrect, the sealing face pressure is low or the sealing of large and other materials expand and contract. The above phenomenon often appear in commissioning, and sometimes can be adjusted to eliminate the stationary ring seat, etc., but most need to re-disassembly, replace the seal.

3. Normal operation sudden leak. Centrifugal pumps in operation suddenly leaking a few are due to normal wear and tear or end of life, but mostly due to large changes or operating conditions, caused by improper maintenance.

(1) Evacuated, cavitation or longer hold back pressure, resulting in seal damage;

(2) The actual pump output is too small, a lot of media in the pump cycle, heat build-up, causing the media gasification, resulting in seal failure;

(3) The return flow is too large, leading to inhalation tube side of the container (tower, kettle, tank, pool) at the bottom of the dregs, damage to the seal;

(4) For a long time outage, no manual re-start when the disk drive, friction due to adhesions and tearing the sealing surface;

(5) Medium corrosive, polymerizing, gumming substances increased;

(6) Environmental drastic changes in temperature;

(7) The condition frequently changes or adjustments;

(8) A sudden power failure or downtime and so on. Centrifugal sudden leak in normal operation, if not in time, tend to lead to more accidents or loss shall be seriously and take effective measures.

Pump mechanical seal repair errors

1. The greater the amount of spring compression seal better. In fact, spring compression excessive friction can cause rapid wear, instantly burning; excessive compression of the spring to lose the ability to regulate the end face of the ring, resulting in seal failure.

2. Ring seals tight as possible. In fact, ring seals tight harm than good. First, the increased wear and tear between the seal and the sleeve, premature leakage; the second is to increase the axial adjustment ring, the resistance movement can not be properly adjusted when conditions change frequently; three spring fatigue easily damaged; four It is to make the ring seal deformation, affecting the sealing effect.

3. Stationary ring seal tight as possible. Stationary ring seal basically at a standstill, a relatively tight seal effect will be better, but too tight is harmful. One cause static ring seal due to excessive deformation, affect the sealing effect; the second is mostly static ring material with graphite, are generally more brittle, excessive force can easily cause fragmentation; third is to install, difficult to remove, easy to damage the stationary ring.

4. The impeller locknut tight as possible. Mechanical seal leak, the leak between the sleeve and the shaft (intermediate shaft leakage) is more common. Generally it believed that between the impeller shaft leakage is not locking the lock master, in fact, among the factors leading to the shaft leaks more, such as inter-axle pad failure, the offset between the axis of the inner impurities, the shaft and the sleeve with a larger form at bit error, the contact surface damage, there is a gap between the components on the shaft, the shaft head screw is too long, and this will lead to inter-axial leakage. Lock master lock over only lead to premature failure of inter-axle pad, contrary moderately lock locked mother, so that inter-axial compression pad always maintain a certain flexibility in the operation of the lock master lock automatically in due course, so intermediate shaft is always in good The sealed.

5. The new is better than old. In contrast, the use of new mechanical seals better than the old, but the new mechanical seal of quality or choice of material is not the time, with the larger size of the error will affect the sealing effect; and permeability in the polymerization medium, such as a stationary ring without undue wear, or not replaced at all. Because static ring in the stationary ring seat for a long time at rest, the polymer and impurities deposited as a whole, played a good seal.

6. Overhaul is better than not split well. Once the mechanical seal leakage will appear eager to overhaul, in fact, sometimes sealed and not damaged, just adjust the working conditions or the appropriate adjustments to seal leaks can be eliminated. In this way, you can avoid wasting verify your fault judgment, the accumulation of experience in maintenance to improve repair quality

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