Several Misunderstandings in the Maintenance of Pump Mechanical Seals

At present, under the requirements of production safety and environmental protection of mechanical seals, the use of mechanical seals has become more and more extensive, and industrial and enterprise power equipment uses mechanical seals to ensure no leakage between dynamic and static sealing surfaces. There are many types of mechanical seals for industrial pumps and chemical pumps, and the models are also different, but there are mainly five leakage points: the seal between the shaft sleeve and the shaft; the seal between the moving ring and the shaft sleeve; the seal between the dynamic and static rings; The seal between the static ring and the static ring seat; the seal between the sealing end cover and the pump body.

Generally speaking, the leakage between the overhanging shaft of the shaft sleeve, the sealing end cover and the pump body is relatively easy to find and solve, but careful observation is required, especially when the working medium of the mechanical seal is liquefied gas or high pressure, toxic and harmful gas, relatively difficult. The rest of the leakage is difficult to identify and judge intuitively. It is necessary to observe, analyze, and judge the leakage symptoms on the basis of long-term management and maintenance practice, in order to draw correct conclusions, use and maintain them correctly.

1. The greater the compression of the mechanical seal spring for the pump, the better the sealing effect

In fact, the compression of the spring is too large, which can lead to rapid wear of the friction pair and instant burning; the excessive compression of the mechanical seal for pump makes the spring lose its ability to adjust the end face of the moving ring, resulting in seal failure.

2. The tighter the seal diagram of the mechanical seal for pump, the better

In fact, too tight of the moving ring seal is harmful and unhelpful. One is to intensify the wear between the sealing ring and the shaft sleeve, resulting in premature leakage; the other is to increase the resistance of the moving ring to adjust and move in the axial direction, which cannot be adjusted in time when the working conditions change frequently; the third is that the spring is over fatigued and easily damaged; four It is to deform the moving ring sealing ring and affect the sealing effect.

3. The tighter the static ring seal of the mechanical seal for pump, the better

The static ring seal is basically in a static state, and the sealing effect will be better if it is relatively tight, but it is also harmful if it is too tight. One is the excessive deformation of the static ring seal, which affects the sealing effect; the second is that the material of the static ring is mostly graphite, which is generally brittle, and excessive stress can easily cause cracking; the third is that it is difficult to install and disassemble, and it is easy to damage the static ring.

4. The tighter the impeller lock nut of the mechanical seal for pump, the better

In the leakage of mechanical seals for pumps, the leakage between the shaft sleeve and the shaft (inter-shaft leakage) is relatively common. It is generally believed that the leakage between the shafts means that the lock nut of the impeller is not locked. In fact, there are many factors that lead to the leakage between the shafts, such as the failure of the gasket between the shafts, the offset, the impurities in the shaft, and the large shape of the shaft and the shaft sleeve. Position errors, damage to the contact surface, gaps between the components on the shaft, and excessively long threads on the shaft head will lead to leakage between shafts. Excessive locking of the lock nut will only lead to premature failure of the inter-shaft pads. On the contrary, properly lock the lock nut to keep the inter-shaft pads with a certain compression elasticity. During operation, the lock nut will automatically lock in a timely manner, so that the shafts are always in good sealed state.

5. The new mechanical seal for pump is better than the old one

Relatively speaking, the effect of using the new mechanical seal is better than that of the old one, but when the quality or material of the new mechanical seal is not selected properly, the larger error in the fit size will affect the sealing effect; in the polymeric and permeable media, if the static ring is not excessive It is better not to replace if worn out. Because the static ring is in a static state for a long time in the static ring seat, the polymer and impurities are deposited as a whole, which plays a better sealing effect.

6. It is better to dismantle and repair the mechanical seal of the pump than not to dismantle it

Once the mechanical seal of the pump leaks, it is urgent to dismantle and repair. In fact, sometimes the seal is not damaged, and the leakage can be eliminated by adjusting the working conditions or properly adjusting the seal. This not only avoids waste, but also can verify its own fault judgment ability, and accumulate maintenance experience to improve the quality of maintenance.