This paper presents a detailed analysis of the structure and function of protective tube water-lubricated guide bearings, comparing them with traditional water-lubricated bearings. It explores the application of these bearings in large vertical pumps and highlights key considerations for their effective use. The study emphasizes the advantages of modern water-lubricated bearings, such as improved reliability, reduced maintenance, and better performance under challenging conditions.
**Keywords:** Large vertical water pump, lubrication, guide bearing, application
**Application and Study on Water Lubricating Pilot Bearings in Large Vertical Water Pumps**
By Qiu Baoyun et al.
Water-lubricated pilot bearings have traditionally suffered from poor reliability. However, a new type of clear water-lubricated bearings with shaft-enclosing tubes has been successfully applied in large vertical pumps. Compared to older models, the structural principles of these new bearings are briefly analyzed, and important points for their proper use are discussed.
**Keywords:** Vertical water pumps, water lubricating pilot bearings, application
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**1. Introduction**
Large vertical pump units often experience radial forces acting on the shaft and impeller due to structural design, manufacturing errors, or flow conditions. Guide bearings play a critical role in stabilizing the pump shaft and impeller. Initially, rubber-based bearings were used with water lubrication. As pump sizes increased, the radial forces grew, leading to the use of more wear-resistant materials like polyurethane. However, even with these improvements, the performance remained unsatisfactory, especially in environments with high sediment content.
The inner walls of the bearings showed signs of abrasion, with sand accumulation indicating poor sealing. This led to the widespread adoption of oil-lubricated Babbitt bearings, which offered better load capacity and wear resistance. However, these bearings had complex structures, high costs, and a major drawback: unreliable water seals that often resulted in leakage and damage from flooding. To address these issues, researchers focused on improving water-lubricated bearings, aiming to extend their service life by preventing sediment from entering.
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**2. Comparison of Two Types of Water-Lubricated Bearings**
**2.1 Rubber Seal Water-Lubricated Guide Bearings**
Traditional rubber-sealed water-lubricated guide bearings rely on a water tank at the top for pressure lubrication. However, this design is ineffective in high-sediment environments. Sediment can still enter the bearing through gaps, causing wear and damage. The flow pattern inside the bearing creates a recirculation zone, where particles settle and eventually reach the bearing clearance, accelerating wear.
**2.2 Tube-Type Water-Lubricated Bearings**
Tube-type water-lubricated bearings retain the oil-bearing structure but incorporate a protective tube around the pump shaft. A dynamic water seal is added at the top, ensuring that clean water flows down the bearing surface, providing effective lubrication. This design isolates the bearing from the pump's internal water, significantly reducing the risk of sediment intrusion and extending the bearing’s lifespan.
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**3. Case Study: Transition from Oil to Water Lubrication**
At the Jiangsu Jiangdu Third Pumping Station, 10 large vertical pumps (ZL13.5-8) were equipped with double biyou tube-type oil-lubricated alloy bearings. These bearings faced frequent failures, including dry friction due to oil circulation issues and water leakage from labyrinth seals. Each pump required multiple overhauls annually, increasing maintenance costs and reducing operational efficiency.
After replacing the oil-lubricated bearings with water-lubricated ones, the system showed significant improvements. One pump operated for 15 years with over 50,000 hours of operation, requiring only one overhaul during that period. In contrast, another station experienced repeated failures within a year, highlighting the importance of proper design and maintenance.
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**4. Key Considerations for Using Water-Lubricated Bearings in Large Vertical Pumps**
While water-lubricated bearings offer many advantages—such as low cost, ease of installation, and good reliability—they also require careful attention to several factors:
**4.1 Proper Protective Water Lubrication Structure**
To ensure effective lubrication, the water must have sufficient flow and pressure. A hydrodynamic seal between the protective tube and the pump shaft is essential. Misalignment can lead to leaks, reducing the effectiveness of the system and potentially damaging the motor.
**4.2 Rational Bearing Design**
Designing a suitable bearing requires determining the appropriate load based on electromagnetic, mechanical, and hydraulic imbalances. Material selection, especially non-metallic options, must balance wear resistance with adequate bearing capacity.
**4.3 Reducing Bearing Load**
Installation accuracy and pump assembly quality directly affect bearing load. Techniques such as balancing the motor air gap, reducing eccentric mass, and optimizing blade angles help minimize the load on the bearings, thus extending their service life.
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**5. Conclusion**
The use of tube-type water-lubricated bearings in large vertical pumps offers significant benefits, including reduced maintenance, improved reliability, and longer service life. With proper design, quality control of lubrication water, and accurate installation, these bearings can be effectively used in low-head large vertical pumps. Their successful application demonstrates the potential for broader adoption in the industry.
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**About the Author:**
Qiu Baoyun, male, 38 years old, holds a Master’s degree in Engineering and is an associate professor. He specializes in the research and teaching of water pump unit structure, installation, and flow characteristics. He has published over 50 papers and received multiple awards for his contributions to water science and technology.
**Authors:**
Qiu Baoyun (Yangzhou University)
Huang Haitian (Jiangsu Province Jiangdu Water Conservancy Project Management Office)
Wei Qiang Lin (Jiangsu Province Jiangdu Water Conservancy Project Management Office)
Tang Zhengjun (Jiangsu Province Jiangdu Water Conservancy Project Management Office)
**References:**
1. Wu Binghong. Vertical shaft guide vane pumping silt water protection measures. Irrigation and drainage machinery, 1985; (1): 63
2. Shen Rimai (Ed.). Jiangdu irrigation and drainage station. Water Power Press, 1986: 293–312
3. Van Off Wake, Yao Zhaosheng (Comp.). Pump parts strength calculation. Machinery Industry Press, 1981: 342–343
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