Has The Motor Bearing Failed? Follow This Method!
1.The reasons for abnormal sound of rolling bearings and treatment methods
1). When the motor is running, a screwdriver can be used with the tip on the bearing outer cover, and the ear is close to the wooden handle of the screwdriver to monitor the sound of the bearing. If there is a faint rolling sound in the inner and outer rings of the rolling body, and the sound is monotonous and uniform, which makes people feel relaxed, it indicates that the bearing is good and the motor is running normally. If you hear an abnormal sound, analyze the cause and handle it.
1.1 The obvious rolling and vibration sound of the rolling element is heard, indicating that the bearing clearance is too large or seriously worn and needs to be replaced.
1.2 The sound of the rolling body is hoarseness and the tone is heavy, indicating that the lubricating oil of the bearing is too dirty, and there are impurities. The bearing needs to be cleaned with kerosene and replaced with new lubricating oil.
1.3 The irregular percussion sound of the rolling element indicates that the bearing has an individual rolling element that is broken and needs to be replaced.
1.4 The sound of an approximate whistle, mixed with the rolling sound of the rolling body, indicates that the bearing lacks lubricating oil or the lubricating oil is improperly selected, and it is necessary to add clean lubricating oil or replace the appropriate lubricating oil.
2, rolling bearing heating causes and treatment methods
2.1 Motor shelving time is too long, lubrication grease deterioration, hardening; New lubricating grease should be replaced.
2.2 Too much or too little lubricating oil in the bearing chamber should be added between 1/3-2/3 of the volume of the bearing chamber; And according to the requirements of the motor instructions, regular quantitative addition of the same type of lubricating oil.
2.3 If there is debris in the bearing room, the bearing should be cleaned with kerosene and replaced with new lubricating oil.
2.4 If the bearing wear is too large or the inner and outer rings are broken, a new bearing of the same type should be replaced.
2.5 Motor running vibration, improper coupling installation, transmission belt is too tight and shaft bending, will cause bearing heat; The cause should be ruled out according to the circumstances.
2.6 If the bearing is not fitted to the shaft shoulder, disassemble the bearing cover, hold the inner ring of the bearing with a copper rod and hammer it in symmetrically.
2.7 If the end cover or bearing cover is not properly assembled, it should be reassembled so that the end cover and the base stop fit well, and the fastening bolts of the bearing cover are tightened diagonally.
2.8 The working performance of the rolling bearing depends not only on the manufacturing accuracy of the bearing itself, but also on the dimensional accuracy of the shaft and hole matched with it, the form and position tolerance and surface roughness, the selection of the fit and the correct installation.
If the inner ring of the bearing is too tight with the shaft, or the outer ring of the bearing is too tight with the inner hole of the end cap bearing, that is, when the male surplus is too large, the bearing clearance will become too small after assembly, and sometimes even close to zero. In this way, the bearing rotation is not flexible, and it will heat up during operation, and even burn out the bearing.
However, if the inner ring of the bearing is too loose with the shaft, or the outer ring of the bearing is too loose with the end cap, the inner ring of the bearing and the shaft, or the outer ring of the bearing and the end cap, will move relative to each other during operation, causing friction and heat, resulting in overheating of the bearing. The suitable interference fit between the inner ring of the rolling bearing and the shaft and the fit between the outer ring of the rolling bearing and the end cap are generally over-fit, and their fit tolerance is shown in the manual or instruction manual.
2.How to clean rolling bearings
Bearings must be carefully cleaned before assembly, and the cleaning agent is generally gasoline or kerosene. The purpose of cleaning is:
1). Wash the anti-rust agent off the bearing.
2). Wash away the stolen goods and debris that may enter the bearing due to carelessness. Bearings with dust caps or sealing rings on both sides have been added with lubricant before leaving the factory, and do not clean them during installation.
The clean bearing should not be placed directly on the work table or in an unclean place, and should be placed under the bearing with a clean cloth or paper. Do not take it directly with your hands, it is best to wear canvas gloves that are not easy to remove hair.
3.How to diagnose whether the rolling bearing is damaged and can continue to use
1). For small motors, move the shaft extension end of the rotor up and down by hand. If the shaft can have a large amount of activity at this time, it indicates that the bearing is seriously worn.
2). Open the end covers at both ends of the motor for inspection. If oil stains are found on the surface of the winding and the core, it indicates that the bearing is leaking oil, the seals are not strict or caused by deformation.
3). After the bearing is removed, wipe the grease in the bearing, and then wash the bearing with gasoline. Then shake the outer ring back and forth relative to the ball by hand, and the clearance of a good bearing is almost imperceptible. If the clearance between the ball and the inner and outer rings is large, the bearing is seriously worn and needs to be replaced with a new one.
4. Correct assembly of rolling bearings
There are two key problems in the assembly of rolling bearings, one is the cleaning method of bearings, and the other is the installation method of bearings. Experience has proved that the cleaning and installation method of bearings has a great impact on the noise and vibration of the motor. Proper cleaning and installation methods can reduce motor vibration and bearing noise. The incorrect cleaning and installation method is often the main reason why the motor produces vibration, noise, the bearing is damaged, or the service life is reduced. Therefore, the cleaning and installation of rolling bearings must be carefully carried out in accordance with the correct method.
1). Preparation before assembly
1.1 The bearing assembly site should be clean to prevent dust or small particles from entering the bearing.
1.2 Check the shape and position tolerance of the shaft, do not meet the requirements, can not be assembled. At the same time, it is also necessary to check the rounded Angle size of the root of the shaft shoulder and the perpendicularity of the shaft shoulder to the shaft. Generally, the radius of the shaft shoulder root should be less than the radius of the bearing inner ring, so that the bearing can be tightened against the shaft shoulder.
1.3 The assembly surface of the parts shall be cleaned with gasoline or kerosene. No rust, spots or solid particles are allowed.
2), bearing set technology
Bearing and shaft assembly methods have two methods: hot sleeve and cold sleeve. However, hot sleeves are generally used, because the bearing inner ring and the journal are generally over-matched, and it is easy to put on after heating.
2.1 Oil heating method
Oil heating method is to put the inner ring of the bearing or separable bearing into the oil tank filled with transformer oil to heat, the temperature of the oil is 80-100℃, and the heating time is 20-40min. In order to prevent the bearing from local heating and precipitate impurities into the bearing, the oil surface should be covered with no bearing, and there should be a wire mesh frame 50-70mm from the bottom of the box, and the bearing is placed on the wire mesh frame. In addition, a thermometer must be hung in the tank to strictly control the temperature of the oil.
When the hot sleeve, take out the heated bearing from the tank, and immediately wipe off the oil stains and attachments attached to the bearing surface with a lineless white cloth, and then pad with the cloth, with both hands flat, align with the rotating shaft, and push it flat to the shaft shoulder. If the sleeve does not go in, it may be too slow, the bearing has cooled, or the hand has not equalized the bearing ends. At this time, the copper sleeve can be used to support the inner ring of the bearing and gently knock it in with a hammer. After the bearing sleeve is good, remove the transformer oil in the bearing, and then add the grease of the motor name label. Generally between 1/3 and 2/3 of the volume of the bearing chamber, it should not be too much or too little. Too much will cause the bearing heat leakage, too little will speed up the bearing wear and emit large noise.
2.2 Cold pressing method of bearing
Cold pressing is to press the bearing to the shaft smoothly at room temperature with a press. When pressing, the center line of the press shaft should be overlapped with the bearing shaft line to prevent the bearing from skewing. And the pressure can only be applied to the inner ring of the bearing, but not on the outer ring or the cage.
5. Failure causes and treatment methods of sliding bearings
1). The reasons and treatment methods of sliding bearing overheating are as follows:
1.1 Oil ring damage causes bearing overheating
The oil ring is often used in the plain bearing to bring the oil into the shaft and the bearing shell, if the oil ring deformation or wear is serious, it will lead to the oil ring does not turn or rotates slowly, so that the oil between the shaft and the bearing shell is reduced, resulting in overheating. Open the bearing housing cover, check the oil ring and replace it in time.
1.2 Bearing overheating due to lubricating oil problems
There are many types of lubricating oil, if the choice is improper, the oil is too dirty, and the oil amount is not enough, it can cause the bearing to overheat. The oil of the plain bearing depends on the power and speed of the motor and other parameters, which can be found in the relevant technical manual.
1.3 Bearing overheat caused by poor machining of bearing bush
Poor scraping of the bearing bush leads to eccentricity of the bearing bush, which makes the part of the bearing bush wear seriously, so that the contact Angle between the rotating shaft and the bearing bush is too large, and the oil wedge cannot be formed, which destroys the friction of the oil body and causes the bearing bush to heat; The bearing bush should be scraped again or replaced with a new one.
1.4 Bearing heating caused by poor cooling
The bearing housing is overheating due to poor heat dissipation caused by oil or the influence of the water temperature and water quantity of the bearing cooling water. The bearing housing should be kept clean and the cooling water pipe unimpeded, and the scale should be removed regularly; And ensure the quality of cooling water and good heat dissipation.
1.5 Oil circulation system failure causes bearing heating
The plain bearing lubricated by pressure oil circulation often suffers from oil shortage and oil cut-off due to oil pipeline blockage or oil pump failure, resulting in bearing heating. In addition, the circulating cooling water temperature of the pressure oil is too high, resulting in high pressure oil temperature; It will also cause the bearing to heat. The tubing should be dredged often and in time, especially in summer, to ensure that the water temperature of circulating cooling water is not high.
2), sliding bearing bearing scraping
2.1 The bushing of the bearing bush generally needs to be scraped. The purpose of scraping is to make the bushing form a certain geometric shape, so that there is a wedge gap between the bushing and the shaft neck, so as to ensure that when the shaft journal rotates, the friction surface can form a wedge oil film, so that the shaft journal rises away from the bushing, and runs under the buoyancy of the oil film, so as to reduce the friction with the bushing and reduce its wear and power consumption.
2.2 The bearing shell shall be inspected by coloring method. When using the coloring method to check, first clean the bearing, check that the bearing should have no cracks, sand holes, peeling and other phenomena. Then evenly apply a thin layer of red lead on the journal, do not apply too thick, that will affect the inspection effect. After the journal is coated with red lead, install the bearing shell and turn twice; Then take out the bearing bush, so that you can see that the protruding part of the bearing bush has red lead color. The distribution of dyeing points requires that there are 2-3 points per square centimeter in the bearing center at an Angle of 60°-70°, and it should not be too much or too little; Otherwise, it needs to be scraped.
2.3 The grinding and scraping of bearing shell adopts the dry grinding method. Use a triangle scraper to first scrape the large points, scrape the dense points thin, and then scrape in one direction in succession, you can scrape twice if necessary. The direction of the knife marks between each pass should intersect to form a network, fish scale. After scraping, clean the tile surface and journal with white cloth stained with alcohol, repeat the above scraping method, so that the dyeing point of the bearing shell is scraped finer and more and more until it meets the requirements.
2.4 No contact points are allowed outside the 70° Angle of the center of the bearing bush. If so, they should be scraped off and the two sides of the bearing bush should be gradually expanded into a wedge gap.
The normal operation of the motor bearing is directly related to the safe and efficient operation of the motor. Only strengthen inspection, correct maintenance of motor bearings; To ensure the safe operation of the motor.
