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Slurry pump mechanical seal failure cause analysis land solutions

Time : 2019-07-26 Hits : 309
Mechanical seal with less leakage, low energy consumption, long life and other advantages, the use of a wide range, in recent years has been widely used in pump shaft seals and other equipment, mechanical seal technology continues to improve, more and more also has a high reliability, Improve the power, metallurgy, mineral processing and other users of the use of mechanical seal experience and confidence, so that the application in the pulp pump continue to be promoted. However, because the slurry pump has a mechanical seal structure is complex, requiring high precision machining, installation technology, etc., due to the use of harsh working conditions, containing solid particles, corrosion and wear, so the slurry pump mechanical seal caused by the equipment failure rate is very high, Once the mechanical seal fails, it will cause the machine to stop working. Comprehensive analysis and machine seal failure causes correct and timely take appropriate precautions  and corrective measures accurate troubleshooting is the key and reliable operation of the slurry pump.
Second, assembly leakage fault:
Mechanical seal installation problems, dynamic, static ring face shall not have deformation, cracks, scratches, dust or impurities friction with the surface before installation or installation process, balance spring force to face inequality can lead to mechanical seal failure, good mechanical seal installation, the general to carry out static pressure test. Observation of leakage. Such as small leakage, the greater the dynamic or static, the leakage of the sealing ring, indicating that the dynamic and static ring friction problems. In the preliminary observation, judgment, leakage, observation of manual turning, for if leakage, no significant changes in C, statistical dynamic sealing problems, such as leakage has obvious changes, the conclusion can be drawn that is dynamic and static direction injection of leakage of the friction pair, the annular sealing ring problems from the surrounding water, jet cooling holes or leakage of the leakage of the medium, more static seal failure. In addition, the leakage channel can also exist at the same time, but generally speaking, there are primary and secondary differences, as long as careful observation, familiar with its structure, can correctly judge.
Mechanical seals assembly should pay attention to the following three problems:
1) amount of spring compression, moderate, large compression spring can lead to rapid wear friction and excessive compression spring instantaneous loss lose the ability to adjust ring face, resulting in seal failure, excessive amount of spring compression will lead to fatigue failure, the deformation of the sealing ring, sealing effects.
(2) seal tight ring seal ring too loose or too tight, will aggravate the wear between the sealing ring and the shaft sleeve, the early leak, will also increase the axial adjustment, when moving ring resistance changes, the state can not be timely adjustment.
(3) to avoid static sealing too tight, static ring seal is basically in a static state, the difference is relatively tight, the sealing effect will be better.
Static ring is too large, easy to cause static seal ring deformation is too large, affect the static ring material for silicon carbide sealing effect,
Generally brittle, too much stress is easy to cause fracture, static ring is too tight, will cause difficulties in installation and disassembly, easy to damage the static ring.
Third, test run leakage:
Slurry pump mechanical seals, after static test, the operation of high-speed rotating centrifugal force, will inhibit the leakage of media. Therefore, the mechanical seal leaks during the test run, and the sealing failure of the end cover of the shaft is largely due to the failure of the friction joint due to the damage of the dynamic and static friction ring. Mainly include:
(1) when operating, at this time, cavitation and pressure anomalies, such as large axial forces, are caused by static and dynamic ring contact surfaces.
(2) when the mechanical seal is installed, it causes a large amount of compression on the ends of the friction pairs, causing severe wear and tear.
(3) ring too loose or too tight, the number of spring can not adjust the axial floating ring.
(4) when the static ring is loose, the axial floating ring and the static ring ring remain.
(5) in the working medium, there are granular materials, into the friction pairs, destruction of moving ring and static ring seal.
6 design selection, sealing surface pressure is low or cold sealing material is larger.
The above phenomenon often occurs in the trial operation, and sometimes can be adjusted by appropriate static ring elimination, but most need to disassemble, replace the seals.
Fourth, in normal operation, the sudden leakage of fault
The mud pump leaks suddenly during operation. A few of them are caused by normal abrasion or service life, but mainly due to the change of their working conditions or improper operation. The main reasons are as follows:
(1) time, cavitation or longer pressure output, resulting in sealing damage.
(2) the actual pump output is too small, a large number of media in the pump cycle, heat accumulation, resulting in medium vaporization, leading to sealing failure.
(3) sealed cooling water.
(4) long-term shut down and restart without manual turning, the sealing surface friction due to adhesion and pull bad.
(5) moderately corrosive, polymerizable and colloidal substances increased.
6. Sharp changes in ambient temperature.
All landlord conditions are constantly changed or adjusted.
Today, a sudden power outage or shutdown, etc..
In normal operation, the sudden leakage of centrifugal pumps, if not found in time, often have greater accidents or losses, should be paid attention to, and take effective measures. The cooling water to satisfy the mechanical seal of the mud pump, often the pump before use, you must first open the seal water after 5 minutes, stop the pump, can be closed, because the cooling water and the engine combustion accidents often occur, users need to pay special attention to. The pump caused by frequent start or sudden loss of power line in the mud flow, pump pressure increased sharply, resulting in the mechanical seal ring opening, so that the mechanical seal failure, the mechanical seal mechanical seal factory design, fully considered by these factors, to avoid the blackout. The pump must be shut down for a long time, the seal cavity and machine cleaning with water pump should be started before the shutdown, manual turning, confirming that no adhesion friction.
Five, wear corrosion failure
As a result of the presence of abrasive particles in the slurry pump, the mechanical seal is generally used in the slurry medium as follows
Risk type:
(1) wear of seal. As the particle surface penetrated into the end surface, the abrasive effect was produced, and the wear of the sealing surface was accelerated.
(2) the side that the particle of the medium is blocked. Because of the accumulation of particles, the bridge blocks the movement of the springs, pins and auxiliary seals, resulting in a decrease in the floatability of the tracking and compensating loops.