Mechanical seals, also known as end face seals, consist of a pair of sealing faces that are perpendicular to the axis of rotation. These faces rely on the interaction between the auxiliary seal and external forces—such as fluid pressure and mechanical spring force—to maintain tight contact with the opposing face while allowing relative sliding, thus preventing fluid leakage. One common issue is periodic leakage, which can occur due to several reasons: 1. Excessive axial movement of the pump rotor may cause high friction between the auxiliary seal and the shaft, limiting the flexibility of the moving ring. This can lead to wear during operation without proper compensation. **Solution:** During assembly, ensure the axial play of the shaft is less than 0.1 mm, and the interference fit between the auxiliary seal and the shaft should be moderate. The moving ring must be able to move freely on the shaft after installation, and the spring should be able to rebound properly. 2. Insufficient lubrication on the sealing surface can result in dry friction or damage to the sealing faces. **Solution:** Ensure the oil level in the lubrication chamber is above the dynamic and static ring sealing surfaces to maintain proper lubrication. 3. Periodic vibration caused by misalignment of the stator with the end caps, unbalanced impeller, cavitation, or damaged bearings can also contribute to leakage. Another type of leakage occurs under high-pressure conditions: 1. High pressure or pressure fluctuations can cause excessive spring force, making it difficult for a liquid film to form on the sealing faces. This leads to increased wear and thermal deformation. **Solution:** Follow the recommended spring compression during assembly. For high-pressure applications, use materials like tungsten carbide or ceramics, and improve cooling and lubrication to reduce heat buildup. 2. Vacuum conditions during pump startup or shutdown can create negative pressure in the sealing chamber, leading to dry friction. **Solution:** Use dual mechanical seals to enhance lubrication and sealing performance, especially in vacuum environments. Leakage can also occur due to the properties of the medium itself: 1. Particles and impurities in the fluid can damage the sealing faces, while weak acids or bases in the medium can degrade the auxiliary seals. **Solution:** Maintain cleanliness in the lower cover and oil chamber, avoid using contaminated lubricants, and ensure the oil level in the seal chamber is above the sealing surface. Choose appropriate mechanical seal designs based on the medium—such as fluororubber for corrosive environments, and tungsten carbide-to-tungsten carbide pairs where solids are present. Other causes include improper design, selection, or installation of the mechanical seal: **Solution:** Ensure the spring compression error is within -2 mm to +2 mm. Too much compression increases face pressure, leading to excessive heat and thermal deformation. Too little compression reduces sealing effectiveness. Chamfer and polish the sealing gland to prevent damage during assembly. In summary, mechanical seals are precision components that require careful consideration of operating conditions, media properties, and proper installation. By addressing these factors, mechanical seals can perform reliably over long periods, ensuring efficient and safe pump operation.

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