Pump mechanical seal a wide range of different models, but there are five main points of leakage: (l) the seal between the shaft sleeve and the shaft; (2) the seal between the moving ring and the shaft sleeve; (3) ; (4) the seal between the stationary ring and the ring seat; (5) the seal between the seal cap and the pump body. Generally speaking, it is relatively easy to find out and solve the leakage between the extended shaft of the sleeve and the seal cap and the pump body. However, careful observation is required, especially when the working medium is liquefied gas or high pressure, toxic and harmful gas some. The rest of the leakage intuitively difficult to distinguish and judge, to be in the long-term management, maintenance practice, based on the symptoms of leakage observed, analyzed and judged in order to draw the correct conclusion. 1. Leakage during static test. Mechanical seal installation and commissioning is good, the general should be static test, observe the amount of leakage. If the leakage is small, mostly ring or static ring seal problems; leakage is large, then that dynamic and static friction ring there is a problem. In the initial observation of the leakage, to determine the leak site, based on manual observation, if the leakage was no significant changes in the static and dynamic ring seal problems; such as when the crankshaft when there is a significant change in leakage can be concluded that the move, Static friction ring there is a problem; such as the leakage of media along the axial injection, the dynamic ring seal there are many problems, leakage to the surrounding medium jet or water leakage from the hole, the more static ring failure. In addition, the leak channel can exist at the same time, but generally there are major and minor differences, as long as careful observation, familiar with the structure, we must be able to correctly judge. 2. Leakage during commissioning. Pump mechanical seal after static test, the centrifugal force generated by high-speed rotation of the operation, will inhibit the media leakage. Therefore, the test run when the mechanical seal leakage excludes the seal between the shaft and the end cover, basically due to dynamic and static friction ring caused by damage. The main factors that cause the failure of friction seal are: (1) In operation, due to the evacuation, cavitation, pressure and other anomalies, causing greater axial force, so that dynamic and static contact surface separation; (for the installation of mechanical seals (3) the ring seal is too tight, the spring can not adjust the axial displacement of the moving ring; (4) static ring seal is too loose, when the ring (5) There is granular material in the working medium, and it enters the friction pair during operation. The flaw is sealed by dynamic and static inspection. (6) The design and selection are wrong. The ratio of the sealed end surface Low pressure or sealing materials such as larger shrinkage, etc. These phenomena often occur during commissioning, and sometimes can be eliminated by adjusting the static ring seat, etc., but most need to re-disassemble, replace the seal 3. In normal operation suddenly Leakage. A small number of sudden leakage of centrifugal pumps in operation due to normal wear and tear or have reached the service life, and most are due to large changes in operating conditions or improper maintenance caused by (1) pump down, cavitation or longer hold back Pressure, guide (2) the actual output of the pump is too small, a large number of medium pump cycle, heat accumulation, causing gasification of the medium, resulting in seal failure; (3) return flow is too large, resulting in suction tube side of the container (4) for a long time outage, restart without manual turning, friction due to adhesion and tear the sealing surface; (5) the medium corrosive, Polymerization, colloidal substances increased; (6) rapid changes in ambient temperature; (7) frequent changes or adjustments in operating conditions; (8) sudden power outage or downtime, etc. Centrifugal pump in the normal operation of a sudden leak, if not found in time , Often lead to a larger accident or loss, we must pay attention to and take effective measures. 4. The greater the spring compression seal better .In fact not, the spring compression is too large, can lead to rapid wear of the friction pair, instantaneous burning ; Excessive compression of the spring to lose the ability to adjust the end face of the moving ring, resulting in failure of the seal. 5 dynamic ring seal as tight as possible .In fact, the ring seal is too harmful .Improve the seal ring and sleeve Between the wear and tear, premature leakage; the second is to increase the axial movement of the ring, the resistance of the movement in the frequent changes in the conditions can not be adjusted in time; Third, the spring over fatigue vulnerable; Fourth is to move the ring deformation ring , Affect the sealing effect. 6 static ring seal tighter and better static ring seal basic at rest, the relatively tight seal effect will be better, but too tight is also harmful.One is caused by static ring seal due to excessive deformation, Affect the sealing effect; the second is the static ring material to the majority of graphite, generally more brittle, excessive stress can easily cause fragmentation; Third, the installation and removal difficulties, very easy to damage the static ring. Leakage between the sleeve and the shaft (leakage between the shaft) is more common in the seal leakage.It is generally believed that the shaft leakage is the impeller lock is not locked, in fact, there are many factors leading to shaft leakage, such as the shaft pad Failure, offset, there are impurities within the shaft, shaft and sleeve with a larger shape and position of the error, the contact surface damage, there is a gap between the shaft components, shaft thread is too long and so will lead to shaft leakage. Lock over lock only lead to premature failure of the shaft pad, on the contrary, lock the lock body, so that the shaft pad always maintain a certain degree of compression flexibility, in operation, the lock will automatically lock in time, the shaft is always in good Sealed state. 8. New better than the old. Relatively speaking, the use of new mechanical seal effect is better than the old, but the new mechanical seal quality or material selection is not appropriate, with the larger size error will affect the sealing effect; In polymeric and permeability medium, the static ring without excessive Wear, or not replaced as well. Because the static ring in the static ring seat for a long time in a quiescent state, the polymer and impurities deposited as one, played a better seal. 9. Disassembly is better than not demolished. In the event of a mechanical seal leak eager to repair, in fact, sometimes the seal is not damaged, just adjust the condition or adjust the seal to eliminate leakage. This will not only avoid waste but also to verify their ability to judge the fault, accumulate maintenance experience to improve the quality of overhaul