Maintenance of heat conduction oil pump seal
1 pump with a wide variety of mechanical seals, different models, but there are five main leakage points:
(1) the seal between the shaft sleeve and shaft;
(2) the seal between the moving ring and the shaft sleeve
(3) sealing between dynamic and static rings
(4) The seal between the static ring and the static ring seat;
(5) Sealing between the end cover and the pump body.
Generally speaking, the leakage between the shaft sleeve of the thermal oil pump, the sealing end cover and the pump body is easy to find and solve, but it needs careful observation, especially when the working medium is liquefied gas or high pressure, toxic and harmful gas, relatively difficult. The rest of the leakage is difficult to distinguish and judge intuitively. Only by observing, analyzing and judging the symptoms of leakage on the basis of long-term management and maintenance practice can correct conclusions be drawn.
1. Leakage cause analysis and judgment
1. Leakage during installation static test. After the installation and debugging of mechanical seals, static test is generally carried out to observe the amount of leakage. If the leakage is small, most of the problems exist in the moving ring or the static ring seal ring. When the leakage is large, it indicates that there are problems between the friction pairs of the moving and static rings. On the basis of preliminary observation of the leakage and judgment of the leakage position, and then manual observation, if there is no significant change in the leakage, there is a problem with the static and dynamic ring seal ring; If there is a significant change in the amount of leakage during turning, it can be concluded that there are problems with the friction pairs of dynamic and static rings; If the leakage medium is sprayed along the axial direction, there are most problems in the moving ring seal ring. If the leakage medium is sprayed around or leaked from the oil cooling hole, it is mostly the static ring seal ring failure. In addition, leakage channels can also exist at the same time, but generally there are primary and secondary differences, as long as careful observation, familiar with the structure, will be able to correctly judge
2. Leakage during test run. Pump mechanical seal after static test, high-speed rotation of the operation of the separation, the force, will inhibit the leakage of media. Therefore, the mechanical seal leakage during the test run is basically caused by the damage of the friction pair of the dynamic and static rings after the failure of the seal between the shaft and the end cover. The main factors causing the sealing failure of friction pair are:
(1) During operation, due to abnormal phenomena such as vacuation, cavitation and pressure holding, large axial force is caused to separate the contact surface of the moving and static rings
(2) When installing the mechanical seal, the compression is too large, resulting in serious wear and abrasion of the end face of the friction pair
(3) The moving ring seal ring is too tight, and the spring can not adjust the axial floating amount of the moving ring
(4) The static ring seal ring is too loose. When the moving ring floats axially, the static ring breaks away from the static ring seat
(5) There are granular substances in the working medium, friction pair is entered in the operation, and the end faces of the dynamic and static rings are detected
(6) The design and selection is wrong, the specific pressure of sealing end face is low or the cold shrinkage of sealing material is large. The above phenomenon often occurs in the test run, sometimes can be eliminated by appropriate adjustment of the static ring seat, but most need to be re-assembled, replace the seal.
3. Sudden leakage during normal operation. A small number of sudden leakage of centrifugal pump in operation is due to normal wear or has reached the service life, and most of it is caused by large changes in working conditions or improper operation and maintenance.
(1) vacuum, cavitation or longer time pressure, resulting in seal damage
(2) the actual output of the pump is small, a large number of medium pump circulation, heat accumulation, causing the medium gasification, leading to seal failure
(3) The return flow is too large, resulting in the sediment at the bottom of the container (tower, kettle, tank, pool) at the suction pipe side rising, damaging the seal
(4) For a long time outage, restart without manual car, friction pair due to adhesion and tear sealing surface;
(5) Corrosive, cohesive and gelling substances in the medium increase
(6) Rapid change of ambient temperature;
