Key words 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

lubricating pilot bearings are poor in reliability and a new type of clear water lubricating pilot bearings with shaft enclosing tubes found successful application in large vertical water pumpss.Compared with old type of bearings, strucural principles of the new ones ware briefly analysized. Put forward were the points which should be paid attention to in uses of the barings.

vertical water pumps, water lubricating pilot bearings, application

1 The question is raised

Vertical water pump unit, due to the structure, manufacture, installation error, incoming flow and other reasons, the operation of the spindle and impeller by the radial force, the water pump guide bearing plays a role in stabilizing the pump shaft and impeller. Guide bearing the earliest use of rubber materials, water lubrication. As the pump to large-scale development, the rotating part of the unbalanced radial force increases, although later the use of better wear resistance of polyurethane and other materials, and the use of water lubrication, but the effect is not good, the bearing material pole Easy to wear, poor running water quality when the river only hundreds of hours. Check found that the inner wall of the bearing was frayed with a large number of sand, indicating that water seal sealing effect is not good, the river sediment will still enter the bearings. Therefore, later widely used in large vertical pumps oil-lubricated Babbitt bearings, to increase its bearing capacity of anti-wear. However, the structure of the oil bearing complex, high cost, fatal drawback is that the following water seal unreliable, often fail a lot of water leakage, and bearing damage caused by flooding. Taking into account the water lubrication guide bearing, as long as sediment does not enter the river to ensure that its operational life may be greatly extended. Analyze its problems, improve its structure, the oil bearing to water bearing.

2 two kinds of water lubrication bearing structure comparison

2.1 rubber seal water lubrication guide bearing

The traditional rubber seal seal water lubrication guide bearings take into account the river water lubrication sediment more serious, the top of the bearing is provided with a water tank for pressure water lubrication (Figure 1). This structure in multi-silt pumping station effect is still not satisfactory, the pump body in the river of sediment will still enter the bearings, damage to bushings and journal. The reason is that after the water flows out from the lower part through the guide vane slot, the overcurrent section suddenly expands to form a recirculation zone at the top of the clear water tank, the water flow velocity slows down and the sediment in the water is deposited by gravity and falls into the clear water tank through the rubber plate sealing gap And the bearing clearance, bearing damage from abrasion.

Figure 1 rubber seal water lubrication guide bearing

2.2 tube type water lubrication bearings

Housings water lubrication bearings, retaining the oil bearing guide vane pump guide Cone and pump shaft protection tube, the pump body and the shaft at the upper end of the additional dynamic water seal device, through the blade embedded in the pipe or tube Upper guide bearing for water, the pressure is greater than the pump body water, water along the bearing wall sink down, forming lubrication (Figure 2). This structure compared with the traditional rubber seal sealed water lubrication structure, the upper part of the bearing is completely isolated from the water inside the pump, to ensure that the river sediment will not enter the bearing, the bearing has good lubrication conditions. This is in line with the literature [1] introduced a small vertical guide vane pump silt water pumping protection measures exactly the same.

Figure 2 tube clear water lubricating guide bearing

3 oil bearing to water bearing application examples

3.1 application background

Jiangsu Jiangdu third pumping station installed ZL13.5-8 large vertical pump supporting 1600kW vertical reversible variable pole motor 10 sets, the pump impeller diameter D = 2.0m, design lift 8m, design flow 13.5m3s. The pump adopts double Biyou tube type oil lubricated alloy bearing, the bearing is arranged in the guide vane body hub, the lower part of the hub adopts the comb-tooth labyrinth ring sealing device, the upper part of the hub is connected with the split-type rear water taper and the fixed protective tube, Outside the pump shaft and out of the pump cover, between the outer wall of the protective tube and the pump cover is provided with a static seal, the inner side of the protective tube and the pump shaft communicating with the atmosphere [2] , prevent the pump body of water into the guide vane body hub cavity damage oil bearings.

This bearing often fails during the application process, mainly as follows: (1) Since the cycle of circulating tube Pitot often break, the bottom of the bearing body rotating oil pan oil can not reach the tank, bearing and journal dry friction and damage; (2) the lower part of the bearing seal labyrinth ring seal leakage, less than water leakage, guide vane hub leakage of water level rise, exceeding the maximum allowable bearing damage caused by water bearing. Each pump has occurred such failures, an average of about 4 times per occurrence, up to more than 10 times, and often occurs in the drainage drought drought stage, had to repair the replacement of bearings, and sometimes the unit must be all open, hanging out Because of short time, tight manpower and poor environment (the other units are still running), the quality of the repaired units is hard to be guaranteed, which often results in continuous failures, which seriously affect the reliability of the units and the equipment is in good condition Rate, increase maintenance costs and labor intensity.

In view of the above, after the 3 #, 8 # pump oil lubricated bearings to water lubricated bearings before and after 1972, respectively, in 1996 and 1997 to conduct a comprehensive disintegration inspection, periodic overhaul. At that time, the pump had been running for 15 years and had an operating hour of 50000h and an overhaul cycle of more than 7 to 10 years. In the meantime, the working condition of the pump had been good (other pump oil bearing averaged 2 ~ 3 times overhaul during 15 years) Wear only 1mm, unit reliability and pump bearing life are greatly increased, saving maintenance costs, and achieved good economic returns.

In contrast, the fourth pumping station a bearing oil lubrication into a water-lubricated pump, in just over a year time, the bearing failure occurred three times overhaul, the most serious is the flood in 1991 during the flood tensions, bearing wear To the bearing body, the bearing body in turn pulled out the pump shaft pits 1 ~ 2mm deep dent, and the occurrence of blade husks. The reason why this happens, mainly to remove the shaft protection, the use of river water lubrication, and the larger the river sediment. In addition, the larger pump (D = 3.1m), the bearing radial force is also greater, is another cause of bearing damage.

4 large vertical water pump bearing water lubrication should be noted that the main problems

Vertical impeller pump diameter of 2m or more to use water-lubricated bearing lubrication, with good reliability, low cost, easy installation and maintenance. The bearing is also suitable for newly designed and manufactured large vertical pumps. However, because of the unbalanced radial force of rotating parts, the bearing capacity of non-metallic materials used in water-lubricated bearings is relatively poor compared with that of babbitt. The abrasion resistance and water quality of lubricants are very important. The following problems should be paid attention to when using them.

4.1 using protective water lubrication structure

Practice has proved that the pipe-type water lubrication bearings can effectively prevent sediment into the bearings, using this structure, lubrication of water must have sufficient flow and pressure to ensure clean water lubrication. Hydrodynamic seal is set between the protective tube outside the pump body and the pump shaft. The concentricity of the pump shaft and the inner side of the protective tube with the pump shaft shall meet the requirements. Otherwise, the pump shaft sealing effect is not good, a lot of lubrication water leaks, and caused by water pressure can not be formed, and a large number of leaking can cause drainage, environmental problems, and even the effusion of water endanger the motor above.

4.2 Reasonable design bearings

To design a reasonable bearing, we must first determine a reasonable bearing design load. The actual load of the water pump guide bearing is composed of electromagnetic imbalance force of the supporting motor, mechanical unbalance force of rotating components of the unit and hydraulic imbalance force of the pump [3] . Through a comprehensive analysis of the factors affecting the bearing load, the author puts forward the method of determining the design load. Design load is determined, the choice of bearing and wear resistance of non-metallic bearing materials, bearing structure, especially the size of lubrication sink, to meet the pressure bearing area and bearing capacity of both the requirements.

4.3 reduce the guide bearing load

The quality of the pump unit assembly and installation of the error and the structure is caused by the pump bearing the root cause of the load. The way to reduce the bearing load is as follows: to improve symmetry uniformity of motor air gap: to reduce the eccentric mass of the rotating parts; to set the pump shaft protection tube while eliminating the flow resistance of the pump shaft; to measure and adjust the blade angles to reduce the angle error; High-quality inlet channels reduce impeller flow non-axisymmetric. Especially when the unit is installed, the installation error should be reduced as much as possible. Attention should be paid to control the installation error direction so that the sub-loads acting on the bearings will be opposite in direction and offset each other, which can greatly reduce the actual working load of the bearing and prolong the service life of the bearing.

5 Conclusion

Compared with the bearing, the large vertical water pump uses the pipe-type clear water lubricating bearing, which can prevent the pump to draw water and sediment into the bearing, thus not only has the advantages of investment saving and convenient maintenance, but also has good reliability and long working life. As long as the design is reasonable, to ensure the quality of lubrication water quality, pressure and flow, improve the quality of the installation, reduce the bearing working load, to ensure that the sealing performance between the pipe and the shaft seal, water pipe lubrication bearings in the low lift large vertical pump Promote the use of value.

About the author: Qiu Baoyun, male, 38 years old, master of engineering, associate professor, master of fluid machinery and engineering tutor, mainly engaged in water pump unit structure, installation, flow characteristics and other aspects of research and teaching work, published more than 50 papers by Jiangsu Provincial outstanding water science and technology papers first prize, water conservancy science and technology progress prize two and many other awards. Address: 225009 Yangzhou University, Yangzhou University, School of Hydraulic Engineering.

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, edited by Shen Rimai. Jiangdu irrigation and drainage station. Water Power Press, 1986: 293 ~ 312
3, off wake Van, Yao Zhaosheng compilation. Pump parts strength calculation. Machinery Industry Press, 1981: 342 ~ 343

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