**Abstract:**
This article provides a comprehensive overview of the most common causes of mechanical seal failure. A mechanical seal is a high-precision component that requires careful design, precise machining, and accurate assembly. When used in pumps, it must be tailored to meet various technical specifications, media conditions, and lubrication requirements to ensure long-term and reliable sealing performance. Understanding these factors is essential for maintaining optimal operation and minimizing downtime.
**Keywords:** Mechanical seal leakage, pump maintenance, sealing failure
A mechanical seal, also known as an end face seal, consists of two mating surfaces perpendicular to the shaft axis. These surfaces are subjected to fluid pressure and external spring force, allowing them to maintain contact and prevent leakage through the use of auxiliary seals.
**Common Leakage Phenomena**
Mechanical seal failures account for over 50% of all pump maintenance issues, directly affecting the normal operation of the equipment. The following are the most frequently encountered problems:
**1. Periodic Leakage**
(1) Excessive axial movement of the pump rotor can cause interference between the auxiliary seal and the shaft, preventing the rotating ring from moving freely. This leads to wear on both the rotating and stationary rings, reducing their ability to compensate for displacement.
**Solution:** During installation, the axial movement of the shaft should not exceed 0.1 mm, and the interference between the auxiliary seal and the shaft should be moderate. Ensure the rotating ring moves freely and the spring can rebound without restriction.
(2) Inadequate lubrication on the sealing surface may result in dry friction or incomplete sealing.
**Solution:** Maintain sufficient lubricating oil in the oil chamber to cover the sealing surfaces of the rotating and stationary rings.
(3) Periodic vibration of the rotor, often due to misalignment of the stator or imbalance between the impeller and the main shaft, can lead to shortened seal life and eventual leakage.
**Solution:** Follow standard maintenance procedures to correct misalignment, imbalance, cavitation, or bearing damage.
**2. Seal Failure Due to Shaft Wear (Grinding Shaft)**
Small submersible sewage pumps, especially those below 715 kW, often experience seal failure due to grinding shafts. Common locations include the auxiliary seal of the rotating ring, the static ring, and occasionally the spring.
The primary causes include:
â‘ Poor working conditions in double mechanical seals, where particles and impurities can enter the sealing surface, leading to failure.
â‘¡ The upper sealing surface may lack proper lubrication, causing higher friction between the static and rotating rings than between the rubber bellows and the shaft, resulting in relative rotation.
â‘¢ Corrosion from weak acids and bases in the sewage can cause the rubber components to lose elasticity or degrade, leading to grinding shafts.
**Solutions:**
â‘ Ensure cleanliness in the lower end cap and oil chamber, and avoid using contaminated lubricants.
â‘¡ Position the oil chamber cavity above the sealing surfaces of the rotating and stationary rings.
â‘¢ Use appropriate mechanical seal structures based on the medium. For high-lift pumps, consider redesigning the seal structure. For corrosive media, use fluorine rubber resistant to weak acids and bases. Adding anti-pinning rings can also help.
**3. Leakage Caused by Pressure**
(1) High pressure or pressure waves can cause excessive force on the sealing faces, making it difficult to form a liquid film and increasing wear and heat, which may lead to thermal deformation.
**Solution:** Follow specified spring compression during installation. Avoid excessive or insufficient compression. In high-pressure environments, use materials like cemented carbide or ceramics and enhance cooling and lubrication.
(2) Vacuum conditions during pump startup or shutdown can create dry friction, leading to leaks in built-in mechanical seals.
**Solution:** Use double-sided mechanical seals to improve lubrication and sealing performance.
**4. Leakage Due to Media Characteristics**
Most submersible sewage pump seal failures occur when the static and dynamic ring seals become inelastic or decayed due to corrosion from weak acids and bases in the wastewater. Nitrile rubber seals are particularly vulnerable under such conditions.
**Solution:** Use high-temperature, acid and alkali-resistant fluorine rubber for corrosive media.
**5. Leakage Caused by Solid Particles**
Solid particles entering the sealing face can scratch or accelerate wear. Accumulated scale or grease on the shaft may exceed the wear rate of the friction pair, preventing the rotating ring from compensating for displacement.
**Solution:** In areas with high solid content, use tungsten carbide friction pairs for better durability.
**6. Other Issues Leading to Leakage**
Design, selection, and installation errors can also cause mechanical seal failure. For example, improper spring compression (within ±2 mm) can either increase end pressure too much, causing overheating and deformation, or reduce sealing effectiveness if too low.
Additionally, the shaft or sleeve surface where the rotating ring is installed, and the seal gland where the stationary ring is mounted, should be chamfered and smoothed to prevent damage during assembly.
**Conclusion**
This article outlines the most common causes of mechanical seal leakage. As a high-precision component, mechanical seals require strict attention to design, manufacturing, and assembly. Proper analysis of pump requirements, media properties, and lubrication conditions is crucial for ensuring long-term, reliable sealing performance.
PU Resin For PVC Leather
PU resin, also known as polyurethane resin, is widely used in the production of synthetic leather. Synthetic leather, also referred to as faux leather or artificial leather, is a man-made fabric that imitates the appearance and feel of genuine leather. PU resin is a key component in the manufacturing process of synthetic leather, as it provides the material with its durability, flexibility, and water resistance.
The process of producing synthetic leather involves coating a fabric substrate, such as polyester or nylon, with a layer of PU resin. This resin is typically applied in liquid form and then undergoes a curing process to solidify and bond with the fabric. The resulting material has a leather-like texture and appearance.
PU resin offers several advantages for synthetic leather production. It has excellent abrasion resistance, making the synthetic leather more durable and long-lasting. It also provides flexibility, allowing the material to be easily shaped and molded into different forms. Additionally, PU resin offers good water resistance, preventing the synthetic leather from absorbing moisture and becoming damaged.
Moreover, PU resin can be customized to achieve different finishes and textures, such as smooth, grainy, or embossed patterns, depending on the desired aesthetic. It can also be colored in various shades to mimic different types of leather. This versatility makes PU resin a popular choice for synthetic leather manufacturers.
Overall, PU resin plays a crucial role in the production of synthetic leather, providing the material with its desirable qualities of durability, flexibility, and water resistance.
Polyurethane Raw Chemical,Pu Resin For Pvc Leather,Adhesive Pvc Leathere Pu Resin,Tpu Raw Chemical Material
XUCHUAN CHEMICAL(SUZHOU) CO., LTD , https://www.xuchuanchem.com