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Application Of Large Horizontal Axial Flow Pump Water Guide Bearing

Application Of Large Horizontal Axial Flow Pump Water Guide Bearing

NSK Bearing

1. Overview

The water guide bearing is the key part of the large water pump, which plays a role in bearing the radial force of the pump rotating part and stabilizing the impeller rotation. If the water guide bearing wear is too large or damaged, it will cause the unit axis oscillation increase, vibration intensified, and even the occurrence of blade collision accident. According to the investigation, most of the pump operation failure is water guide bearing fault. Therefore, the water guide bearing is the main control factor of the pump reliability, Operation life and planned overhaul cycle.

Jiangsu Province Qinhuai Sluice Management pumping Station (hereinafter referred to as "Xinhe Pump Station") was completed in 1982, as a building station nearly 30 years old station, in the horizontal axial flow pump water guide bearing the use of accumulated a lot of experience.

2. Characteristics of water Guide bearing

For horizontal or oblique pump units, water guide bearings are subjected to the weight of the rotating components. As the bearing is immersed in a certain pressure under the water, the use of turbine oil or water lubrication of the guide bearings, not only requires a good bearing wear resistance, but also to ensure that the lubrication conditions, there is a need to set up water seal and drainage leakage device to prevent the pump containing sediment and other impurities in the water body into the bearing. Once the water containing sediment enters the oil lubricated bearing, it will destroy the lubricating condition, damage the bearing and cause the bearing to fail in a short period of time.

3, water Guide bearing requirements

The pump guide bearing requirements have good reliability and durability. The main factors affecting the performance of water guide bearing are: Radial unbalance force of pump rotation, bearing structure, material and lubricating condition, etc. The reliability of water guide bearings is defined under the operating conditions and operating time, the bearing does not occur sudden failure or failure to stop the nature of the work, which requires that the bearing has sufficient bearing capacity, sealing leakage device reliable. With the increase of running time, the wear of bearing material and axle neck increases, some non-metallic materials will gradually occur hardening, crack and other aging phenomenon. Bearing durability is mainly defined under the conditions of use, bearing material anti-wear (wear amount within the allowable range), anti-aging ability.

4, the type of water guide bearing

4.1 Water-lubricated non-metallic bearings

① Rubber Bearing

Rubber bearings are generally used for vertical pump water guide bearings, in the horizontal pump, because of the need to carry the weight of the rotor components and a certain radial load, it is not only to aggravate the rubber bearing the lower part of the serious eccentric wear, and its wear resistance is far from meeting the operational requirements, but also due to the bearing and the rubber bearing parts deformation, Make the pump run with additional vibration, affecting the steady operation of the pump.

②P23 Bearing

P23 bearing is a kind of bakelite bearing, this kind of material brittleness is big, fragile, and its debris is hard, once the debris falls off, will accelerate the wear and nap with the big shaft bearing gear that match.

③F102 Bearing

Compared with P23 bearing, F102 bearing has high bearing capacity, good toughness, ability of impact load, high compressive strength, no debris accelerated wear, good abrasion resistance. However, as with P23 bearings, the application of the bearing material, molding process and the surface treatment of the pump shaft must have strict requirements.

④ Dragon Bearing

Dragon bearing self-recovery and excellent elasticity, it is capable of impact, and easy to process, resistant to sewage, wear resistance, but dragon bearings are used for vertical axial flow pump, in the horizontal axial flow pump water Guide bearing application has its limitations.

4.2 Oil-lubricated metal bearings

① Metal sliding Bearing

Horizontal pump metal sliding water guide bearings are generally used in the Babbitt alloy material, grease lubrication and dilute oil lubrication of two lubrication methods. The metal sliding bearing is suitable for the operating condition of low speed, heavy duty and higher pressure. Grease lubricated metal plain bearings have high maintenance and management requirements, and are not easy to realize automatic control and management. Thin oil lubricated bearings require a thin oil lubrication station or gravity tank in the pump set, which increases the configuration parts of the pump set. Metal sliding bearing has the possibility of polluting the water quality environment after oil dripping, which requires extremely reliable sealing, but with self-tuning function, it can eliminate defects such as shaft alignment, so its running reliability is high, especially for pumping stations with continuous operation and long running time (over 5000h).

② Rolling Bearings

Rolling bearing bearing capacity, high reliability, long service life, generally with dilute oil lubrication, but because it changes the pump over-flow section area, it is to carry out a large number of pre-hydraulic research. In addition, according to the current bearing technology rolling bearing can not do the composition of the semi-structure, but also to the maintenance of great inconvenience.

Application of 5 Water guide bearing in Xinhe pumping station

5.1 Selection of water guide bearings

Construction station of the newly river Pumping station five units used is rubber bearings, due to serious wear, after the change in 1995 as polyurethane rubber bearings, although the annual operating time is not long, but the water guide bearing wear and deformation problems are still quite prominent. With the start of the 2002 strengthening and Rebuilding project, the Xinhe pump station is very cautious in the selection of water guide bearings, and through the collection of data, two kinds of schemes are determined after analysis and comparison:

(1) Based on the reliability of the water guide bearing, the thin oil lubricated metal bearing is similar to the 4.1m inclined pump of the Taipu River Pump station. The disadvantage of the structure is: the structure is complex, because the bearing material using Babbitt alloy, in the installation of the need for scraping tile, the installation of high-technology requirements; bearing lubrication using high gravity tank oil lubrication, operation and maintenance management is more complex.

(2) from the maintenance and management of convenient, economic point of view, the use of water turbine has long been the application of mature technology-elastic metal plastic tile (PTFE plastic tile). Its friction coefficient with the mirror plate is only the 35%~50% of the Babbitt alloy, which not only makes the car easy and labor-saving, but also does not need to scratch, thereby reducing the labor intensity and shortening the maintenance period; Moreover, the structure can be used to lubricate and cool the water medium directly, and the auxiliary equipment is less. The only regret is that the structure has never been used in the pump industry before.

After repeated demonstration of the above scheme, from the benefit of the horizontal Unit water guide bearing selection of the same conditions of operation comparison, and easy to summarize, improve and choose, the final decision after the transformation of the Xinhe pumping Station 5 two-way horizontal Unit 4 units using thin oil lubricated metal bearings, 1 units using elastic metal plastic water guide bearings.

5.2 Technical Analysis

Xinhe Pumping Station horizontal unit of the journal is 240mm, bearing the diameter of Shangliyo 3100kg, if the effective length of the bearing is 400mm, then the pressure is 3.29 kg/cm, whether the use of thin oil lubrication metal bearings, or elastic metal plastic tile bearings, design to ensure its reliability, And consider the future of the general purpose of spare parts, in addition to the bearing material, the two materials of the water guide bearing the structural dimensions must be consistent (that is, to ensure that the two materials are interchangeable bearings). In addition, the following aspects are noted in the design:

(1) The bearing shell is designed as a sphere to increase the function of automatic centering. Bearings and housings with spherical contact, bearing in the housing can be flexible rotation along the axis (axial rotation range of 1°30′), so that the bearing can be balanced, to eliminate the shaft system due to the bad and the operation of the unbalanced force caused by the local force overload of the bearing.

(2) Each bearing in the structure of all parts are used along the center of the shaft half-structure, thin oil-lubricated metal bearing skeleton oil seal using the British Walker Company's products, but also for the semi-structure, in order to install, overhaul.

(3) Thin oil lubricated metal bearing lubrication using high gravity tank oil lubrication, bearings are equipped with inlet and outlet tubing, can be replaced at any time the lubricant in the bearing.

(4) Thin oil lubricated metal bearings sealed with three skeleton oil seal, inside two skeleton oil seal open Inward seal oil, outside a skeleton oil seal opening outward seal water, in seal oil skeleton oil seal and seal water Skeleton oil seal set a return oil (water) ring, the skeleton oil seal leakage of oil or infiltration into the water, through the return oil (water) tube timely out of the pump, This ensures that the oil leaking from the skeleton oil seal will not enter the water, and that the water seeping from the skeleton oil seal will not enter the bearing.

(5) Pump shaft neck, the use of mature hardfacing cemented carbide processing technology to improve the surface hardness and roughness of the friction site.

The main advantages of the thin oil lubricated metal bearing and the elastic metal plastic Water guide bearing are: can withstand the large radial load, also can withstand the radial pulsating load (that is, the impact performance is strong), this is at present domestic similar unit water guide bearing cannot realize, is also very suitable the actual working condition; the lubrication system is simple, reliable and long service life.

5.3 Actual use of the situation

After the renovation of the New River Pumping Station unit in June 2003 trial operation, 2005 also for the improvement of Nanjing water environment and the municipal government co-operation as the "River Diversion" project of the main work-water diversion, so the annual operating time of the hundreds of units from the transformation before the increase to the present 3000 units, And most of the time is the ultra-head operation, so that the test of the Unit water guide bearing is self-evident. Of course, the bearing performance of the two structures is also different:

Up to 2006 years, 5 units of the guide bearing operation is basically stable, water-lubricated bearing wear is very small, and oil-lubricated 4 units in addition to the slight water seepage operation is normal.

To 2006, 4 units of oil lubricated bearings have different degrees of water seepage phenomenon, lubricating oil emulsion, which more serious must be through continuous replenishment, oil change to maintain the operation. Xinhe pumping station combined with major overhaul on the 4# and

After the unit was dismantled, two units were found to have the same problem: the short shaft in contact with the three rubber seal ring in the place of the obvious grinding groove, the analysis should be due to the water pressure of sediment with the water infiltration into the sealing device, some sediment will stay on the surface of the sealing ring caused by the surface of the short shaft wear, So that more river water into the bearings. In order to save the maintenance time and cost, adopt the method of stagger the sealing ring and wear surface by adding washer, make the sealing device to restore the effect, after two years the operation effect is good, but in 2009, the same situation re-appeared, the demolition found on the short shaft in addition to the original three groove and added three grooves.

The water-lubricated water-guide bearing of the # Unit has remained stable, with 2003 years, 2005 and 2010 of three demolition found bearing only minor wear, still in normal range.

Considering the reasons for stability, coupled with environmental factors, water lubrication will also become a trend of development, and further test the use of elastic metal plastic in large horizontal axial flow pump, 2010 Xin River Pump Station will be the water guide bearing of the water lubricated elastic metal plastic bearings, the use of temperature stability, flow inspection is not abnormal , the wear condition is to be viewed at the time of disassembly.

6. Conclusion

The lean oil lubricated Babbitt water guide bearing is relatively stable when used, but it needs scraping during installation, high installation process requirements, and the need to set up a thin oil lubrication station or gravity tank in the pump set, which increases the configuration parts of the pump set. Metal sliding bearing has the possibility of polluting the water environment after oil dripping, which requires a very reliable seal, but long-term use, seepage leakage of the situation is difficult to avoid, maintenance cycle longer, and easily pollute the environment.

Water has the advantages of pollution-free, wide-ranging, safe and flame-retardant, it can be used instead of oil in many occasions, it is a kind of lubricating medium with broad development prospect. Before the elastic metal plastic, although not used in large pumping stations, but the successful use of water turbine motor is obvious to all, in the actual operation of the river pump station, this kind of material is the most stable in operation, saving a lot of maintenance costs and manpower, it is worth promoting vigorously.

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