Mechanical seal oil leakage can be roughly divided into the following situations: I hope to help you: one is to aggravate the wear between the sealing ring and the shaft sleeve, premature leakage; Second, it increases the resistance of axial adjustment and movement of the moving ring, so it cannot be adjusted timely when the working condition changes frequently. Three is the spring overfatigue easy to damage; Fourth, the moving ring sealing ring deformation, affect the sealing effect. Such as small leakage, mostly moving ring or static ring sealing ring problems; When the amount of leakage is large, it indicates that there is a problem between the friction pairs of dynamic and static rings.
1. It's better to tear it down than not to tear it down. In this way, it can not only avoid waste but also verify their fault judgment ability, accumulate maintenance experience and improve maintenance quality. When the gear oil pump static ring seal ring is basically in a static state, the relatively tight sealing effect will be better, but too tight is also harmful. Because the static ring is in a static state for a long time in the static ring seat, the polymer and impurity deposition as a whole, has a better sealing effect.
2. The tighter the moving ring seal, the better.
(1) there are granular substances in the working medium, friction pair is entered in the operation, and the end faces of dynamic and static rings are tested;
(2) The seal ring of the static ring is too loose, and when the moving ring floats axially, the static ring breaks away from the static ring seat;
(3) the sealing ring of the moving ring is too tight, and the spring cannot adjust the axial floating amount of the moving ring;
(4) The compression amount of mechanical seal installation is too large, resulting in serious wear and abrasion of the end face of the friction pair;
(5) During operation, large axial force is caused by abnormal phenomena such as vacuation, cavitation and pressure holding, so that the contact surfaces of the moving and static rings are separated;
2. Leakage occurred during test run.
3. The tighter the static ring seal, the better. 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. After the installation and debugging of mechanical seals, static test is generally carried out to observe the amount of leakage. One is caused by excessive deformation of static ring seal, affecting the sealing effect; Second, static ring material with graphite in the majority, generally more brittle, excessive stress is easy to cause fragmentation; Third, it is difficult to install and disassemble, and easy to damage the static ring. It is generally believed that the leakage between the shafts is that the impeller lock is not locked. In fact, there are many factors leading to the leakage between the shafts, such as the failure of the inter-shaft pad, deviation, impurities between the shafts, the shaft and the shaft sleeve with larger shape and position errors, contact surface damage, the clearance between the shaft components, the shaft head thread is too long, etc., will lead to the leakage between the shafts. 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.
Two, several misunderstandings in the maintenance of mechanical seal with pump
(1) Sudden power failure or fault shutdown. 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 many problems in the moving ring seal ring, and the leakage medium is sprayed around or leaked from the water cooling hole, it is mostly the static ring seal ring failure. Mechanical seal leakage, the leakage between the shaft sleeve and shaft (shaft leakage) is more common. 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.
2. New is better than old. Sudden leakage of centrifugal oil pump in normal operation, if not found in time, will often lead to a large accident or loss, attention should be paid and effective measures should be taken. Once there is mechanical seal leakage, it is urgent to disassemble and repair. In fact, sometimes the seal is not damaged, and the leakage can be eliminated only by adjusting the working condition or properly adjusting the seal.
Iii. Leakage cause analysis and judgment
Generally speaking, the leakage between the shaft sleeve extension, the sealing end cover and the pump body is easier 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 main factors causing the sealing failure of friction pair are:
1. Leakage during static test of installation.
2. The greater the compression of the spring, the better the sealing effect. Relatively speaking, the effect of using the new mechanical seal is better than the old, but the quality or material selection of the new mechanical seal is not correct, and the size error will affect the sealing effect. In cohesive and permeable media, it is better not to replace the static ring if there is no excessive wear. 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. Excessive locking of the lock mother will only lead to premature failure of the inter-shaft gasket, on the contrary, properly locking the lock mother, so that the inter-shaft gasket always maintain a certain compression elasticity, in the operation of the lock mother will automatically timely locking, so that the shaft is always in a good sealing state.
(1) The design and selection is wrong, the specific pressure of sealing end face is low or the cold shrinkage of sealing material is large.
(2) The seal between the static ring and the static ring seat;
(3) sealing between dynamic and static rings;
(4) the seal between the moving ring and the shaft sleeve;
(5) the seal between the shaft sleeve and shaft;
There are many kinds of mechanical seals for pumps, different models, but there are five main leakage points:
(6) Sealing between the end cover and the pump body.
3. The tighter the impeller lock, the better. After static test of mechanical seal pump, centrifugal force generated by high-speed rotation during operation will inhibit the leakage of media. In fact, moving ring seal ring too tight harmful. In fact, the spring compression is too large, can lead to rapid wear of the friction pair, instant burning; Excessive compression causes the spring to lose its ability to adjust the end face of the moving ring, resulting in seal failure. The sudden leakage of explosion-proof pumping pump in operation is caused by normal wear and tear or has reached the service life, but most of them are caused by the large change of working conditions or improper operation and maintenance.
(1) The working condition changes or adjusts frequently;
(2) Rapid change of ambient temperature;
(3) corrosive, cohesive and gelling substances in the medium increase;
(4) For a long time outage, restart without manual car, friction pair due to adhesion and tear sealing surface;
(5) The return flow is too large, resulting in the sediment at the bottom of the suction tube side container (tower, kettle, tank, pool) rising, damaging the seal;
(6) the actual output of the pump is small, a large number of medium pump circulation, heat accumulation, causing the medium gasification, resulting in seal failure;
(7) vacuum, cavitation or longer time pressure, resulting in seal damage;
4. Sudden leakage during normal operation.
Author: Berthed oil pump
