Several Misunderstandings in Overhauling Mechanical Seals

In the regular maintenance of mechanical seals, many people tend to fall into some misunderstandings, resulting in the use of mechanical seals not as good as before, or failure. Let's take a look at some common misunderstandings.

(1) The greater the spring compression, the better the sealing effect. In fact, otherwise, the excessive compression of the spring can lead to rapid wear of the friction pair and instant burning; excessive compression makes the spring lose the ability to adjust the end face of the moving ring, resulting in the failure of the mechanical seal.

(2) The tighter the static ring seal, 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; the second is that the material of the static ring is mostly graphite, which is generally brittle, and excessive stress is easy to cause fragmentation; the third is that it is difficult to install and disassemble, and the static ring is easily damaged.

(3) The tighter the sealing ring of the moving ring, 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 axially, and it 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.

(4) The tighter the impeller lock nut, the better. Among the mechanical seal leakage, 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 cause the leakage between the shafts, such as failure of the gasket between the shafts, offset, impurities in the shaft, and a large shape at the joint between the shaft and the shaft sleeve. Position errors, damage to the contact surface, gaps between components on the shaft, and excessively long threads on the shaft head will cause leakage between shafts. Excessive locking of the lock nut will only lead to premature failure of the inter-shaft pads. On the contrary, moderately lock the lock nut so that the inter-shaft pad will always maintain a certain compression elasticity. During operation, the lock nut will be automatically locked in a timely manner, so that the shafts are always in good condition. sealed state.

(5) The new one is better than the old one. Relatively speaking, the effect of using the new mechanical seal is better than that of the old one. In polymeric and permeable media, if the static ring is not excessively worn, it is better not to replace it. 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.

Therefore, when overhauling the mechanical seal, the operator is required to have certain professional knowledge and practical experience, so as to better judge the problem of the mechanical seal and make a reasonable solution.