Mechanical seals for pumps

Maintenance of pump mechanical seal: There are five main leakage points of pump mechanical seal: (1) The seal between the shaft sleeve and the shaft. (2) The seal between the moving ring and the shaft sleeve. (3) The seal between the dynamic and static rings .(4) The seal between the static ring and the static ring seat. (5) The seal between the seal end cover and the pump body. Generally speaking, the leakage between the shaft overhanging the shaft sleeve and the seal end cover and the pump body is compared It is easy to find and solve, but requires careful observation, especially when the working medium is liquefied gas or high pressure, toxic and harmful gas, it is relatively difficult. The rest of the leakage is difficult to distinguish and judge intuitively, and must be managed and maintained in the long-term. Based on the observation, analysis and judgment of the leakage symptoms, the correct conclusion can be drawn.

Misunderstanding of pump mechanical seal maintenance:

1. The greater the compression of the spring, the better the sealing effect. In fact, if the compression of the spring is too large, it can lead to rapid wear of the friction pair and instant burning. Excessive compression makes the spring lose its ability to adjust the end face of the moving ring, resulting in seal failure.

2. The tighter the sealing ring of the moving ring, the better. In fact, if the sealing ring of the moving ring is too tight, it is harmful and unhelpful. One is to increase the wear between the sealing ring and the shaft sleeve, resulting in premature leakage. When the working conditions change frequently, it cannot be adjusted in time. The third is that the spring is over fatigued and easily damaged. The fourth is that the dynamic ring seal is deformed, which affects the sealing effect.

3. The tighter the static ring sealing ring, the better. The static ring sealing ring 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. The ring material is mostly graphite, which is generally brittle, and excessive force can easily cause cracking. Third, it is difficult to install and disassemble, and it is easy to damage the static ring.

4. The tighter the impeller lock nut, the better. In the leakage of mechanical seals, 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 impeller lock nut is not locked, which actually leads to the leakage between the shafts. There are many factors, such as the failure of the gasket between the shafts, the offset, the impurities in the shaft, the large shape and position error at the joint between the shaft and the shaft sleeve, the damage of the contact surface, the gap between the parts on the shaft, the thread of the shaft head is too large If the lock nut is too long, it will lead to leakage between the shafts. Excessive locking of the lock nut will only lead to premature failure of the inter-shaft pad. On the contrary, properly lock the lock nut so that the inter-shaft pad will always maintain a certain compression elasticity, and the lock nut will automatically lock in a timely manner during operation. tight, so that the shafts are always in a good sealing state.