Reasons and Measures for Wear of Sliding Bearing of Mine Hoist
Abstract: Based on the effective work practice, combined with the wear problem of the sliding bearing of the coal mine hoist, this paper actively expounds the causes and measures, hoping that the analysis can further ensure the production efficiency of the coal mine hoist.
Keywords: mine hoist; Sliding bearing; Wear; strategy
Among the various parts of the coal mine hoist, the sliding bearing is the most critical part. Exploring the wear problem of the sliding bearing of the coal mine hoist can ensure the safe operation of the hoist, reduce the probability of failure, increase the startup rate, and reduce the cost of maintenance, thus providing an effective guarantee for related work.
1.Reasons for wear of sliding bearing of coal mine hoist
1.1 Bearing defects
The defects of the bearing itself accelerated the wear of the sliding bearing, mainly including: first, poor tin coating quality and failure to accurately grasp the temperature of the bearing pad and babbitt alloy led to poor bonding of the bearing pad back layer and lining layer; Second, when casting the bearing pads, the temperature is not enough or the preheating is not enough, resulting in the presence of gas in the hanging pads; Third, low curing temperature and large grain size of Sn Sb alloy lead to uneven internal grains of Babbitt alloy.
1.2 Non standard assembly
Non standard assembly will also lead to wear problems, and non-standard assembly will aggravate the wear of bearings. The main reasons include: First, the centerline of the bearing and the centerline of the bearing seat are not coincident, resulting in early fatigue and failure of the alloy layer. Second, the bearing pedestal does not match the bearing, resulting in a sliding hazard. Third, uneven bearing clearance or excessive bearing clearance.
1.3 Improper use of bearings
Improper use of the bearing will also cause the sliding bearing to bear wear. Common improper operations include: first, foreign particles enter the bearing, causing bearing scratches; Second, when using lubricating oil additives, oxidation will produce acidic substances, which will cause corrosion to the bearing; Third, the lack of effective lubrication viscosity has greatly reduced the bearing capacity, resulting in bearing wear.
2. Measures to prevent wear of sliding bearing of coal mine hoist
2.1 Control the clearance of sliding bearing
In order to improve the smooth operation of the bearing, a certain distance of radial clearance should be set in the sliding bearing to ensure that the journal can accurately butt with the bearing and improve the accuracy of operation. The axial clearance is set to ensure the effective length expansion and contraction while increasing the journal temperature.
2.1.1 Determination of clearance
Generally, the radial clearance shall be determined according to the design and assembly properties of the sliding bearing, and it is generally specified that the middle side clearance is half of the top clearance. When setting the radial clearance of sliding bearing shaft, the clearance size shall be determined according to different structural forms, usually not more than 2mm, but the clearance shall also be controlled to exceed the extreme value of expansion during the expansion process of journal.
2.1.2 Measurement and adjustment of sliding bearing clearance
When determining the clearance of the sliding bearing, the range of the best clearance of the journal shall prevail. The journal at the extreme position shall be measured with a feeler gauge, a dial indicator, etc., and the data at the two extreme positions shall be superimposed to obtain the perimeter clearance range standard. The side clearance of the sliding bearing can be measured with a feeler gauge, which should normally be inserted into a 30 ° arc. Use feeler gauge and lead wire to measure the top clearance, of which the lead wire is the most accurate method. At this time, it shall be ensured that the radius of the lead wire is 2~3 times of the top clearance value, and the length is controlled within 15mm~20mm. It is not allowed to select too hard lead wire.
2.1.3 Clearance adjustment
When the range of the top clearance of the sliding bearing exceeds the limit value, it is necessary to reduce the force to adjust the pad mouth properly. In addition, the contact angle of the journal and the lower end of the bearing shall be checked to ensure that the contact angle is controlled within 120 °.
2.2 Timely inspection and maintenance of sliding bearing
2.2.1 External inspection
(1) The main contents of the external inspection are to check the lubrication and temperature conditions, check the starting and stopping changes, running vibration, shifting sound, etc., so as to judge and analyze the bearing status. However, under some conditions, small gaps are difficult to find.
(2) Monitoring the temperature of the bearing line: in the main shaft sliding bearing of the coal mine hoist, common problems such as slow speed, large load, long maintenance interval, etc. make it difficult to find the internal problems in time. Therefore, it is necessary to monitor the bearing bush specifically. Usually, the bearing pad temperature sensor is used for monitoring. When the temperature exceeds the standard, it can automatically alarm, so that bearing faults can be found and handled in time, effectively avoiding the problem of bearing burning.
(3) Monitoring oil sample: running problems can be found in the lubricating oil of sliding bearing, and whether there is alloy falling off can be judged by observing the oil return. Usually, samples are taken from the oil return port, and observe whether there is any flash in the oil under the sun, such as the severity, so as to judge the wear of bearing pads. In addition, the oil samples shall be regularly tested and analyzed. For example, according to ferrography analysis technology, the operation status of sliding bearings shall be truthfully mastered, and the maintenance measures and time shall be scientifically determined to ensure the scientific maintenance of mechanical equipment.
2.2.2 Disassembly inspection
During the disassembly inspection, determine whether it is necessary to replace the bearing bush by judging the specific defects. If it is not necessary to replace, effective measures can be taken to eliminate the defects in the disassembly inspection to improve the wear condition of the bearing.
Main inspection contents: (1) Check the position and size of the contact area between the bearing pad and journal and the wear condition of the bearing pad end. Is the inspection acceptable? The clearance is at the joint edge of bearing bush and bushing. Check the bushing and judge whether there is separation according to the hoarseness. (2) Measure and record the top clearance, side clearance and axial clearance of bearing pads.
3. Treatment of sliding bearing wear failure
3.1 Repair of lining
(1) When the pad lining is worn and the top clearance increases, there are two common treatment methods:
First, if conditions permit, adjust the clearance by removing the pad and reducing the pad thickness.
When the pad liner is worn normally and the clearance increases, two phenomena may occur: one is the contact between the pad liner and the journal, the other is the contact between the pad liner and the journal? enlarge; The other is that the bearing liner and journal have good running in in the contact area, the surface is flat and smooth, and the lubricating oil is difficult to enter the contact area. At this time, the bearing bush shall be repaired and scraped in time to ensure uniform distribution of lapping points on the surface of the contact area, and then the pad shall be removed.
Second, when there is no pad to remove and the shaft position has changed greatly beyond the allowable range, it is necessary to replace the pad lining as soon as possible and repair the contact area.
(2) When the bushing is seriously bitten and the journal is glued, stop the operation immediately and replace the bushing to handle the journal.
(3) When the bearing wear is caused by the separation of the bearing alloy layer from the bearing pad, or the occurrence of air holes, peeling, pitting, etc., in addition to replacing the pad lining, repair welding shall be carried out according to the standard requirements.
3.2 Repair of sliding bearing
When the sliding bearing has problems, it will also lead to increased bearing wear. The common bearing repair methods are rough scraping, fine scraping, fine scraping, scraping oil points, etc.
(1) Rough scraping: When there are obvious machining marks, repair marks, strain and wear marks on the surface of the workpiece, rough scraping shall be carried out first. Select a longer tool mark, and use a scraper to scrape at the large radius arc at the large front corner, so as to increase the scraping area and improve the scraping speed. After mastering the effective operation, the process can be transited from rough scraping to fine scraping.
(2) Fine scraping: after the rough scraping is completed, use the scraper to fine scrape at an included angle less than the rough scraping angle, shorten the knife trace, and combine the position with the smaller arc radius of the scraper to fine scrape, constantly change the scraping direction, and ensure that the scraping pattern is 45 °~60 °.
(3) Fine scraping: On the basis of fine scraping, reduce the rake angle of the scraper, which is negative if necessary, and shorten the knife trace again to ensure the scraping accuracy and prevent dents. For fine scraping, gently drop the knife, quickly lift the knife, and grind each knife to avoid repeated scraping and crossing forward. During fine scraping, the largest and brightest grinding point shall be scraped. Scrape off the top of the medium lapping point, without thinning the small lapping point.
Regardless of the scraping method, the force shall be equal, the display agent shall be evenly applied, the pressure shall be stable, and the axial movement shall be avoided with false points. For the relevant bearing pads, different scraping schemes shall be considered according to the specific conditions.
3.3 Adjustment and measurement of bearing clearance
In order to prevent bearing wear, it is necessary to add lubricating oil appropriately. In addition, the rationality of bearing clearance is an important factor to ensure the rotation accuracy and meet the requirements of rotation speed. The common clearance processing method is to use feeler gauge to measure and press lead wire to determine the clearance data, and then select shims to adjust the bearing clearance at the split or directly repair and scrape the pad surface to reduce the bearing wear.
In a word, the use of the coal mine hoist has greatly improved the production efficiency of the coal mine. As a technician, it is necessary to study the wear of the sliding bearing of the coal mine hoist. Through the above analysis and discussion of the sliding bearing of the coal mine hoist, the basic method to solve the damage of the sliding bearing of the coal mine hoist is obtained, hoping to achieve the purpose of extending the service life of the sliding bearing of the hoist.
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