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Mechancial Seal MN206, Pump Spare Parts For Power Plants And Mines
MN206 mechanical seal double-elastic, double-end, non-equilibrium structure, the circulating coolant should be kept in the sealed cavity to lubricate the friction pair. Suitable for medium lift slurry pumps.
The change in the density of the medium in the pump chamber of the slurry pump has an effect on the performance of the pump. If the density of the slurry pump transport medium changes, the most important effect on the performance of the slurry pump is the pressure head and shaft power. From the calculation formula of the pressure head P/Pg (p is the density), it can be seen that as the density of the medium increases, the pressure head will decrease, resulting in a decrease in the lift.
When the head of the slurry pump is constant, the density of the medium increases, and the difference between the inlet and outlet pressure heads of the slurry pump will increase. The main phenomenon is that the pump outlet pressure (table pressure) increases. The viscosity of the slurry pump medium has a large effect on the pump. The flow of water is much faster than that of oil, and the flow of hot asphalt and thin paste is more retarded. Viscosity reflects this characteristic of fluid motion. The property of creating internal friction between fluid layers as the fluid moves is referred to as the viscosity of the fluid. The physical quantity indicating the size of the viscosity is called viscosity. The greater the viscosity of the fluid, the lower the pump's lift characteristic curve, and the higher the power as the viscosity increases, so the efficiency will decrease.
There are five main leak points for pump mechanical seals:
(l) a seal between the sleeve and the shaft;
(2) sealing between the moving ring and the sleeve;
(3) Seal between moving and static rings;
(4) sealing between the stationary ring and the stationary ring seat;
(5) Sealing between the sealed end cap and the pump body.
In general, the leakage between the shafts of the bushings, the seal end caps and the pump body is easier to find and solve, but it needs to be carefully observed, especially when the working medium is liquefied gas or high pressure, toxic and harmful gas, it is relatively difficult. some. The remaining leaks are difficult to distinguish and judge intuitively. It is necessary to observe, analyze, and judge the leak symptoms on the basis of long-term management and maintenance practices in order to draw correct conclusions.
1. Leak when installing the static test. After the mechanical seal is installed and debugged, it is generally necessary to perform a static test to observe the amount of leakage. If the leakage is small, there are problems with the moving ring or static ring seal; when the leakage is large, it indicates that there is a problem between the friction pairs of the moving and stationary rings. On the basis of preliminary observation of the leakage amount and judging the leakage location, the vehicle can be manually observed. If there is no significant change in the leakage amount, the static and dynamic ring seals have problems; if there is a significant change in the leakage amount during the cranking, it can be determined that it is moving. There is a problem with the static ring friction pair; if the leakage medium is sprayed in the axial direction, there are many problems with the moving ring seal ring, and the leakage medium is sprayed to the periphery or leaks from the water cooling hole, and the static ring seal ring is mostly invalid. In addition, the leakage channel can also exist at the same time, but there are generally primary and secondary differences. As long as the observation is meticulous and familiar with the structure, it can be judged correctly.
2. Leakage that occurs during commissioning. After the static test of the mechanical seal of the pump, the centrifugal force generated by the high-speed rotation during operation will suppress the leakage of the medium. Therefore, the leakage of the mechanical seal during the test run is basically caused by the failure of the friction pairs of the moving and stationary rings after the failure of the seal between the shafts and the end cap seal. The main factors causing the failure of the friction pair seal are:
(l) During operation, due to abnormal phenomena such as evacuation, cavitation, and rolling, a large axial force is caused to separate the moving and static ring contact surfaces;
(2) The amount of compression of the mechanical seal during installation is too large, resulting in severe wear and abrasion of the end face of the friction pair;
(3) The moving ring seal ring 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 is axially floating, the static ring is separated from the static ring seat;
(5) There are granular materials in the working medium, and the friction pair is entered during operation to detect the moving and static ring sealing end faces;
(6) The design selection is wrong, the sealing end face is lower than the pressure deviation or the sealing material is more cold-shrinkable. The above phenomenon often occurs during trial operation, and can sometimes be eliminated by appropriately adjusting the static ring seat, etc., but most of them need to be reassembled and replaced.
3. Sudden leakage during normal operation. A small amount of sudden leakage of the centrifugal pump during operation is due to normal wear or has reached the service life, and most of them are caused by large changes in working conditions or improper operation and maintenance.
(1) evacuation, cavitation or rolling for a long time, resulting in seal damage;
(2) The actual output of the pump is too small, a large number of medium pumps circulate, heat accumulates, causing gasification of the medium, resulting in seal failure;
(3) The return flow is too large, causing the sediment at the bottom of the suction side container (tower, kettle, tank, pool) to rise and damage the seal;
(4) For a longer period of time, there is no manual turning when restarting, and the friction pair tears the sealing surface due to adhesion;
(5) Increased corrosive, polymerizable, and gelatinous substances in the medium;
(6) The ambient temperature changes drastically;
(7) Frequent changes or adjustments in working conditions;
(8) Sudden power failure or downtime. The centrifugal pump suddenly leaks during normal operation. If it cannot be found in time, it will often cause a big accident or loss. It must be taken seriously and effective measures taken.
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