This paper presents an in-depth analysis of the structural design of water-lubricated guide bearings with protective tubes, and compares them with traditional water-lubricated bearings. It introduces the application of protective tube water-lubricated guide bearings in large vertical pumps, highlighting important considerations for their proper use. The study emphasizes the advantages of this new type of bearing, particularly in terms of reliability, maintenance, and longevity.
**Keywords**: Large vertical water pump, lubrication, guide bearing, application
**Application and Study on Water Lubricating Pilot Bearings in Large Vertical Water Pumps**
Qiu Baoyun et al.
Water-lubricated pilot bearings have historically suffered from poor reliability. A new type of clear water-lubricated pilot bearing with a shaft-enclosing tube has been successfully applied in large vertical pumps. Compared to older models, the structural principles of these new bearings are briefly analyzed, and key points for their proper use are discussed.
**Keywords**: vertical water pumps, water lubricating pilot bearings, application
**1. The Problem Arises**
Vertical water pump units, due to structural design, manufacturing, and installation errors, as well as flow conditions, experience radial forces on the shaft and impeller. The guide bearing plays a critical role in stabilizing the pump shaft and impeller. Initially, rubber materials were used for guide bearings with water lubrication. As pump sizes increased, the unbalanced radial forces also grew, leading to the use of more wear-resistant materials like polyurethane. However, the performance remained unsatisfactory, with frequent wear and short operational life, especially when water quality was poor. Inspections revealed that sand had entered the bearings through the sealing gaps, causing damage. This led to the widespread use of oil-lubricated Babbitt bearings, which improved load capacity and wear resistance. However, these bearings have complex structures, high costs, and a major drawback: unreliable water seals that often result in leakage and subsequent damage. To address this, researchers explored the potential of water-lubricated bearings, which can significantly extend service life if sediment is prevented from entering.
**2. Comparison of Two Types of Water-Lubricated Bearings**
**2.1 Rubber Seal Water-Lubricated Guide Bearings**
Traditional rubber-sealed water-lubricated guide bearings were designed to handle sediment-laden water. A water tank was installed at the top of the bearing for pressure lubrication. However, this structure still failed to prevent sediment from entering the bearing, leading to wear and damage. The reason was that after water flowed out through the guide vane slots, it created a recirculation zone at the top of the water tank, where sediment settled and entered the bearing clearance through the rubber seal gap.
**2.2 Tube-Type Water-Lubricated Bearings**
Tube-type water-lubricated bearings retain the oil-bearing guide vane cone and pump shaft protection tube. A dynamic water seal device is added at the upper end of the pump body and shaft. Water flows under pressure along the bearing wall, providing effective lubrication. This structure isolates the bearing from the water inside the pump, preventing sediment from entering and ensuring better lubrication conditions. This approach aligns with the silt protection measures described in literature [1].
**3. Case Study: Transition from Oil to Water Lubrication**
At the Jiangsu Jiangdu Third Pumping Station, 10 ZL13.5-8 large vertical pumps were equipped with double Biyou tube-type oil-lubricated alloy bearings. These bearings experienced frequent failures, such as dry friction due to oil circulation issues and water leakage from the labyrinth seal, leading to damage. After replacing oil-lubricated bearings with water-lubricated ones, the pumps operated reliably for over 50,000 hours, with minimal maintenance. In contrast, another pumping station faced repeated failures due to inadequate protection against sediment and higher radial forces.
**4. Key Considerations for Water-Lubricated Bearings in Large Vertical Pumps**
While water-lubricated bearings offer cost savings, ease of maintenance, and good reliability, several factors must be addressed:
**4.1 Protective Water-Lubrication Structure**
The tube-type structure effectively prevents sediment from entering the bearing. Sufficient water flow and pressure are essential for clean lubrication. A hydrodynamic seal between the protective tube and the pump shaft is crucial. Proper alignment is required to ensure effective sealing and avoid water leakage, which could lead to environmental and mechanical issues.
**4.2 Reasonable Bearing Design**
Designing a suitable bearing requires determining an appropriate load. Factors such as electromagnetic imbalance, mechanical unbalance, and hydraulic imbalance contribute to the actual load. Based on these, the bearing material, size, and lubrication system must be carefully selected to meet both pressure and load requirements.
**4.3 Reducing the Load on the Guide Bearing**
Installation errors and imbalances in rotating components are primary causes of bearing overload. Steps to reduce this include improving motor air gap symmetry, reducing eccentric mass, optimizing pump shaft design, and ensuring accurate blade angles. Proper installation and error control can significantly reduce the working load on the bearing, extending its lifespan.
**5. Conclusion**
Compared to traditional bearings, the use of tube-type water-lubricated bearings in large vertical pumps offers significant advantages, including reduced maintenance costs, longer service life, and improved reliability. With proper design, high-quality water supply, and careful installation, these bearings can be widely adopted in low-head large vertical pumps.
**About the Author:**
Qiu Baoyun, male, 38 years old, Master of Engineering, Associate Professor, and tutor in fluid machinery and engineering. His research focuses on the structure, installation, and flow characteristics of water pump units. He has published over 50 papers and received multiple awards, including the First Prize for Outstanding Water Science and Technology Papers in Jiangsu Province.
**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 (compiled). Pump Parts Strength Calculation. Machinery Industry Press, 1981: 342–343
Electronic Red Dot Sights,Good Quality Red Dot Sights,Is Red Dot Sights Accurate,Laser Red Dot Sights
Nantong Dinggo Optical Instrument Co.,Ltd , https://www.riflescopeofficial.com