1¡¢The greater the spring compression, the better the sealing.
This is not true. Excessive spring compression can cause rapid wear of the friction pair and even instantaneous burning. Over-compression also reduces the spring¡¯s ability to adjust the rotating ring face, leading to seal failure.
2¡¢The tighter the rotating ring seal, the better.
An overly tight rotating ring seal does more harm than good. First, it accelerates wear between the seal ring and the shaft sleeve, causing premature leakage. Second, it increases the resistance to axial adjustment and movement of the rotating ring, making it difficult to adapt when operating conditions change frequently. Third, the mechanical seal spring may become excessively fatigued and fail more easily. Fourth, the rotating ring seal may deform, reducing sealing performance.
3¡¢The tighter the stationary ring seal, the better.
The stationary ring seal is basically in a stationary state, so a relatively tighter fit may improve sealing. However, excessive tightness is also harmful. First, it can cause excessive deformation of the stationary ring seal and impair sealing. Second, stationary rings are often made of graphite, which is relatively brittle and can easily crack under excessive force. Third, installation and removal become difficult, and the stationary ring is easily damaged.
4¡¢The tighter the impeller lock nut, the better.
Leakage between the shaft sleeve and the shaft is a common source of mechanical seal leakage. It is often assumed that such leakage in fluoroplastic chemical pumps is caused by a loose impeller lock nut. In fact, many factors can cause shaft leakage, such as failure or misalignment of the shaft gasket, impurities in the shaft clearance, excessive dimensional and geometric errors between the shaft and shaft sleeve, damage to the contact surface, clearance between components on the shaft, and an excessively long shaft thread. Over-tightening the lock nut will only cause premature failure of the shaft gasket. Proper tightening allows the shaft gasket to maintain a certain compressive elasticity, so that the lock nut can self-adjust during operation and keep the shaft area properly sealed.
5¡¢New mechanical seals are always better than old ones.
Generally, new mechanical seals perform better than used ones. However, if the quality or material selection is improper, or if the mating dimensions have large errors, sealing performance may be affected. In polymerizing or permeable media, it is often better not to replace the stationary ring if it shows no excessive wear. Because the stationary ring remains stationary in its seat for a long time, polymers and impurities tend to deposit and form a stable sealing layer.
6¡¢Disassembly and repair are always better than leaving the seal as is.
When mechanical seal leakage occurs, it is not always necessary to disassemble and repair immediately. In some cases, the seal is not damaged, and the leakage can be eliminated by adjusting operating conditions or making proper seal adjustments. This approach avoids unnecessary waste and also helps verify fault diagnosis, accumulate maintenance experience, and improve overhaul quality.