Troubleshooting and maintenance of bearing damage
Troubleshooting and maintenance of bearing damage
2022年5月20日
Four major causes of vibration damage of IKO imported bearing
Four major causes of vibration damage of IKO imported bearing
2022年5月22日

Troubleshooting of bearing sealing fault

Trouble shooting of bearing sealing fault

  • In order to maintain the original performance of the bearing in good condition for as long as possible, it is necessary to maintain and repair in order to prevent accidents, ensure the reliability of operation and improve productivity and economy. Troubleshooting of bearing sealing fault
  • Maintain the operation standard of corresponding mechanical operation conditions and carry out it regularly. The contents include monitoring the operation status, replenishing or changing the lubricant, and regular disassembly inspection. As maintenance items in operation, there are bearing rotation sound, vibration, temperature, lubricant state, etc.Troubleshooting of bearing sealing fault
  • Bearing cleaning: when disassembling the lower bearing for maintenance, first record the appearance of the bearing, confirm the residual amount of lubricant, and wash the bearing after sampling the lubricant for inspection. As a cleaning agent, gasoline and kerosene are commonly used.Troubleshooting of bearing sealing fault
  • The cleaning of the removed bearing is divided into coarse cleaning and fine cleaning. They are placed in the container respectively. First, put the metal mesh bottom so that the bearing does not directly contact the dirt of the container. Troubleshooting of bearing sealing fault
  • During rough cleaning, if the bearing rotates with dirt, it will damage the rolling surface of the bearing, which should be paid attention to. In the coarse cleaning oil, use a brush to remove the grease and adhesion. After it is roughly clean, turn to fine cleaning.
  • According to the load acting on the bearing and the rotation condition of the ferrule, the load borne by the ferrule can be divided into three types: fixed load, rotating load and back and forth shaking load.Troubleshooting of bearing sealing fault
  • Fixed load
  • The resultant radial load is borne by part of the region of the ferrule raceway and transmitted to the corresponding part of the region of the appropriate surface of the shaft or shell. This load is called fixed bearing load.Troubleshooting of bearing sealing fault
  • The unique feature of the fixed load is that the synthetic radial load is relatively static with the ferrule. Generally, loose ferrules can be used to bear fixed load.Troubleshooting of bearing sealing fault
  • Load shedding
  • The synthetic radial load vector acting on the bearing ring rotates along the circumferential direction of the raceway, is successively borne by each part of the raceway, and is transmitted to each part of the outer surface of the shaft housing hole accordingly. This kind of load is called off load, also known as cyclic load.Troubleshooting of bearing sealing fault
  • The unique feature of load shedding is that the synthetic radial load vector rotates relative to the ferrule. The ferrule bearing the transfer load and the shaft or shell hole shall be suitable for filtering or interference. If you think it is appropriate to use the gap and install it properly, there will be slip between you and me, which will cause friction damage and friction heating of the contact surface, rapidly increase the temperature and quickly destroy the bearing. Troubleshooting of bearing sealing fault
  • The volume of the desired interference is determined according to the operating conditions, and the principle is that when the bearing is working under the load effect, it will not cause the “crawling” phenomenon of the actuating ferrule on the appropriate surface in the shaft or housing hole.Troubleshooting of bearing sealing fault
  • The synthetic radial load vector acting on the bearing ring relatively swings back and forth within a certain area of the ring raceway, which is borne by a certain area of the raceway and transmitted to a certain area on the surface of the shaft or shell hole, or the load acting on the bearing is impact load and oscillation load, and its load direction or number often changes. This load is called swing load, also known as non directional load.Troubleshooting of bearing sealing fault
Troubleshooting of bearing sealing fault

There are great differences bearing sealing fault

  • When the bearing bears back and forth shaking load, especially when bearing heavy load, the inner and outer rings should be considered appropriate and the interference should be used appropriately. When the inner ring swings and rotates back and forth, it is generally considered appropriate by the inner ring, but it is appropriate to use it when the transfer load is removed. 
  • However, sometimes the outer ring must be able to swim towards the bearing outside the housing or when its load is light, it can be considered appropriate to use a slightly looser outer ring than the rotating load. Troubleshooting of bearing sealing fault
  • There are great differences between the working surface and the core of bearing parts in terms of state, structure and performance requirements, but the overall heat treatment often makes it impossible to take into account, and the potential of materials can not be brought into full play. Troubleshooting of bearing sealing fault
  • The application of material surface strengthening technology can not only better solve the differences in structure and requirements between the surface and the core, but also further make the surface obtain some special working properties to meet the requirements of the bearing working under specific conditions.Troubleshooting of bearing sealing fault
  •  This is of great significance in the development of science and technology. The traditional surface strengthening method belongs to the category of heat treatment. The surface strengthening methods such as laser, electron beam and ion beam developed in modern times not only apply some high and new technologies to the surface strengthening of materials, but also go beyond the scope of traditional heat treatment and form a new technical field. Troubleshooting of bearing sealing fault
  • Therefore, the current surface strengthening technology can form a variety of classification methods from different angles. According to the physical and chemical process of surface strengthening technology, it can be roughly divided into five categories: Troubleshooting of bearing sealing fault
  • surface deformation strengthening, surface heat treatment strengthening, chemical heat treatment strengthening, surface metallurgy strengthening and surface film strengthening.Troubleshooting of bearing sealing fault
  • The metal surface layer is plastically deformed by mechanical methods to form a hardened layer with high hardness and high strength. This surface strengthening method is called surface deformation strengthening, also known as work hardening. Including shot blasting, sand blasting, cold extrusion, rolling, cold rolling and impact, explosion impact strengthening, etc. 
  • The characteristics of these methods are: the strengthening layer dislocation density increases and the sub crystal structure is refined, so as to improve its hardness and strength and reduce the surface roughness value, which can significantly improve the surface fatigue strength of parts and reduce the sensitivity of fatigue notch. This strengthening method has the advantages of simple process and remarkable effect. Troubleshooting of bearing sealing fault
  • There is no obvious boundary between the hardened layer and the matrix, the structure is coherent, and it is not easy to fall off in use. Most of its methods have been applied in the bearing industry: the surface impact strengthening of rolling element is the application of this kind of method, and precision rolling has become a new ferrule processing and strengthening method.Troubleshooting of bearing sealing fault
  • Quenching the surface layer of parts by means of solid-state phase transformation and rapid heating is called surface heat treatment, commonly known as surface quenching. Including flame heating quenching, high (medium) frequency induction heating quenching, laser heating or electron beam heating quenching, etc. The characteristics of these methods are: local heating and quenching of the surface, small deformation of the workpiece; Fast heating speed and high production efficiency; The heating time is short, and the surface oxidation decarburization is very slight.Troubleshooting of bearing sealing fault
  • Selection and control of shaft and bearing housing tolerance: the bearing shall rotate flexibly without blocking feeling after being pressed in. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large and the tolerance should be reduced. Troubleshooting of bearing sealing fault
  • If there is an obvious “rusty” feeling when the tapered roller bearing is rotated by hand after being pressed into the shaft, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good. Therefore, when controlling the tolerance of shaft and bearing chamber, it is also necessary to control the roundness. At present, many domestic manufacturers only control the tolerance, not the roundness.Troubleshooting of bearing sealing fault
  • Bearing assembly method: because the bearing is a high-precision product, if it is not assembled properly, it is easy to damage the tapered roller bearing channel, resulting in bearing damage. The bearing shall be equipped with a special mold during assembly, which cannot be knocked at will. Troubleshooting of bearing sealing fault
  • When pressing the shaft, only the small ring can be stressed, and when pressing the large ring, only the large ring can be stressed. Air pressure or hydraulic pressure is required during assembly. During press assembly, the upper and lower touch shall be outside the horizontal state. If there is inclination, the bearing channel will be damaged due to stress and the bearing will produce conduction sound.Troubleshooting of bearing sealing fault
  • Prevention of assembly foreign matters: when the tapered roller bearing is installed on the rotor for dynamic balance, it is easy to put the iron filings generated during dynamic balance into the bearing, so it is necessary to perform dynamic balance before installing the bearing. Troubleshooting of bearing sealing fault
  • In order to facilitate assembly, some manufacturers apply some oil or grease in the bearing chamber for lubrication effect during assembly, but it is often difficult for operators to control the amount. If more oil or grease is accumulated in the bearing chamber, it is easy to enter the bearing along the shaft when the bearing rotates. The bearing chamber shall not be coated with oil or grease. If it must be coated, it shall be controlled and there shall be no accumulation in the bearing chamber.Troubleshooting of bearing sealing fault
  • Prevention of paint rust: paint rust is often found in sealed motors. The sound of the motor is very good during assembly, but after being placed in the warehouse for some time, the abnormal sound of the motor becomes very large, and there is serious rust when removing the tapered roller bearing. In the past, many manufacturers thought it was the bearing problem. Troubleshooting of bearing sealing fault
  • After our continuous publicity, now the motor factory has realized that the main problem is the insulating paint. This problem is mainly because the acidic substances volatilized from the insulating paint form corrosive substances at a certain temperature and humidity, which corrodes the bearing channel and leads to bearing damage. At present, only good insulating paint can be selected and assembled after drying and ventilation for a period of time.Troubleshooting of bearing sealing fault

When the engine speed changes from

  • After the bearing is pressed into the bearing, it shall rotate flexibly without blocking feeling. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large and the tolerance should be reduced. If the thrust cylindrical roller bearing rotates by hand after being pressed into the shaft, there is an obvious “rusty” feeling, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good. 
  • Therefore, when controlling the tolerance of shaft and bearing chamber, it is also necessary to control the roundness. At present, many domestic manufacturers only control the tolerance, not the roundness.
  • Because the bearing is a high-precision product, if it is not assembled properly, it is easy to damage the bearing channel, resulting in bearing damage. The thrust cylindrical roller bearing shall be equipped with a special mold during assembly, and can not be knocked at will. 
  • When pressing the shaft, it can only be stressed by a small ring, and when pressing a large ring, it can only be stressed by a large ring. Pneumatic or hydraulic pressure is required during assembly. During press assembly, the upper and lower molds shall be outside the horizontal state. If there is inclination, the bearing channel will be damaged due to stress and the bearing will make a guide sound. fatigue pitting
  • When the rolling bearing is loaded Contact stress will be generated on the contact surface between the rolling element and the inner and outer rings Because the inner ring, outer ring and rolling element have relative rotational motion during operation, the contact stress changes in a pulsating cycle. 
  • When the contact stress exceeds the limit value, fatigue cracks will appear under the surface layer and gradually expand to the surface, so as to form fatigue pitting corrosion on the surface of the rolling element of the inner and outer race raceway, make the rolling bearing lose the rotation accuracy and produce noise, impact and vibration. Therefore, pitting corrosion is one of the failure forms of rolling bearing
  • Plastic deformation
  • When the rotational speed of the rolling bearing is very low or only swings, excessive opening load or impact load will cause large local deformation at the contact between the bearing raceway and the rolling element, which will exceed the yield limit of the material, and large plastic deformation will occur if the deformation exceeds a certain range The bearings will not work properly. Therefore, plastic deformation is another failure form of rolling bearing.
  • In order to judge whether the disassembled bearing can be reused, it is necessary to check after the bearing is cleaned, and carefully check the state of raceway surface, rolling surface and mating surface, the wear of cage, the increase of bearing clearance and whether there are damages and abnormalities related to the decline of dimensional accuracy. For non separable small ball bearing, support the inner ring horizontally with one hand and rotate the outer ring to confirm whether it is smooth.
  • diagnosis:
  • When the engine speed changes from idle speed to medium speed, the sound is clear. As the speed increases, the sound becomes more prominent, which is the sound of the bearing.
  • Conduct a fire cut-off test on a cylinder, and the sound is weakened or disappears, which is the bearing sound of the cylinder.
  • The bearing alloy is ablated if the sound is made regardless of the speed and temperature, and the engine vibrates, and the sound does not change during the fire break test.
  • The bearing shows a strong regularity in its use process, and the repeatability is very good. When the normal high-quality bearing (linear bearing) is used at the beginning, the vibration and noise are relatively small, but the spectrum is a little messy and the amplitude is small, which may be caused by some defects in the manufacturing process, such as surface burrs.
  • After moving for a period of time, the vibration and noise maintain a certain level, and the spectrum is very single, with only one or two times the frequency. The frequency spectrum of more than three times of power frequency rarely appears, and the bearing state is very undisturbed, so it enters the undisturbed working period.
  • In the later stage of operation, the vibration and noise of the bearing begin to increase, sometimes with abnormal sound, but the change of vibration increase is slow. At this time, the kurtosis value of the bearing suddenly reaches a certain value. We believe that at this time, the bearing shows initial failure.
  • In order to maintain the original function of the bearing in good condition for as long as possible, it is necessary to maintain and inspect it in order to prevent accidents, ensure the reliability of operation and improve productivity and economy. Maintain the scale of corresponding machinery operation premise on schedule. The contents include supervising the operation status, adding or changing lubricants, and inspecting the disassembly on schedule. As the inspection items in operation, there are bearing rotation sound, vibration, temperature, lubricant state, etc.
  • Bearing cleaning: when disassembling the lower bearing for inspection, first record the appearance of the bearing, confirm the residual amount of lubricant, and wash the bearing after sampling the lubricant for inspection. As a cleaning agent, gasoline and kerosene are commonly used.
  • The cleaning of the removed bearing is divided into coarse cleaning and fine cleaning. They are placed in the container respectively. First, put the metal mesh bottom so that the bearing does not directly contact the dirt of the container. 
  • During rough cleaning, if the bearing rotates with dirt, it will damage the moving surface of the bearing, which should be paid attention to. In the coarse cleaning oil, use a brush to remove the grease and adhesion. After it is roughly clean, turn to fine cleaning.
  • Fine cleaning is to carefully clean the bearing while rotating in the cleaning oil. In addition, the cleaning oil should always be kept clean.
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