Application research on water diversion bearing of large vertical water pump oil bearing
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Abstract This paper analyzes the structure and principle of the guide tube with clean water lubrication and compares it with the traditional water lubricated bearings. The application of the tubeless water lubrication guide bearing in place of the oil bearing in the large vertical water pump is introduced, and the water lubrication Bearings for large vertical pumps should pay attention to the problem. Key Large Vertical Water Pumps Water Lubrication Guide Bearings Applications and Study on Water Lubricating Pilot Bearings in Large Vertical Water Pumps Qiu Baoyun et al Abstract: Oil 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 pumps.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. Keywords: large vertical water pumps, water lubrication pilot bearings, application1 The problems raised Vertical water pump unit, due to the structure, manufacture, installation error, incoming and other reasons, the operation of the spindle and impeller radial force, water pump guide bearing steady pump shaft and impeller Role. 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 Comparison of two kinds of water lubrication bearing structure 2.1 rubber seal water lubrication guide bearings Traditional rubber seal water lubrication guide bearings taking into account the river water lubrication sediment more serious, at the top of the bearing 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 the bushing 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 seal water lubrication guide bearing 2.2 pipe-type water lubricated bearings Housui water-lubricated bearings, retaining the oil bearing guide vane water guide cone and pump shaft protection tube, the pump body at the upper end of the tube with the pump shaft Between the additional dynamic water sealing device, through the blade embedded in the pipe or guide the upper guide bearing water, the pressure is greater than the pump body of water, water along the bearing wall sink downward flow, the formation of 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 Care-type clear water lubrication guide bearing 3 oil bearing into 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 Set, pump impeller diameter D = 2.0m, design head 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 bearing, 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 operating for 15 years and had an operating hour of 50000h and an overhaul cycle of more than 7 to 10 years. During this period, the pump was in a good working condition (the other pump oil bearing had an average of 2 to 3 service intervals over a 15-year period) 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 should be noted that the main problems Impeller diameter more than 2m vertical water pump oil lubricated bearings to water, with good reliability, low cost, easy installation and maintenance advantages. 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 The use of pipe protection water lubrication structure Practice has proved that the pipe protection 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 of 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 to reduce the guide bearing load pump unit manufacturing and installation of mass error and the structure is caused by the pump bearing the root cause of 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 use of large-scale vertical water pump protection of water-lubricated bearings, which can stop the pump pumping water sediment into the bearings, which not only has the advantages of investment and maintenance convenience and reliability, 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.