Cause analysis of common bearing quality faults
Cause analysis of common bearing quality faults
2022年5月25日
Vibration and temperature inspection of SKF one-way thrust ball bearing
Vibration and temperature inspection of SKF one-way thrust ball bearing
2022年5月27日

Preventive measures for bearing running noise and overheating

The measures to prevent cage noise are as follows:bearing running

  • When the grease performance of the bearing is poor under radial load, the noise of “click, click” will be heard at the beginning of operation, which is mainly due to the noise caused by the sudden acceleration of the rolling element and its collision with the cage after leaving the load area. This impact sound is inevitable, but will disappear after a period of operation.Preventive measures for bearing running noise and overheating
  • In order to stabilize the rotation movement of the cage, the ring mode should be adopted as far as possible and the surface should be fully lubricated. The structure of tapered roller bearing under high-speed working conditions should be improved. The L-shaped cage of the roller should be changed into the Z-shaped cage with ring retaining edge.Preventive measures for bearing running noise and overheating
  • When the bearing rotates at high speed, the vibration amplitude of the cage of the bearing with large pocket clearance is much larger than that of the cage with small pocket clearance, so the value of pocket clearance is particularly important.Preventive measures for bearing running noise and overheating
  • Pay attention to reducing the radial clearance as much as possible.Preventive measures for bearing running noise and overheating
  • Try to improve the manufacturing accuracy of the cage and improve the surface quality of the cage, which is conducive to reducing the noise caused by the collision or friction between the rolling element and the cage.
  • Actively adopt advanced cleaning technology to effectively and thoroughly clean spare parts and products after assembly, so as to improve the cleanliness of bearings.Preventive measures for bearing running noise and overheating
  • 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. Preventive measures for bearing running noise and overheating
  • 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.Preventive measures for bearing running noise and overheating
  • 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. When pressing the shaft, only the small ring can be stressed, and when pressing the large ring, only the large ring can be stressed.Preventive measures for bearing running noise and overheating
  •  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.Preventive measures for bearing running noise and overheating
  • 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. 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.Preventive measures for bearing running noise and overheating
  • 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. Preventive measures for bearing running noise and overheating
  • 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, the problem can only be to select good insulating paint and assemble after drying and ventilation for a period of time.Preventive measures for bearing running noise and overheating
  • Vibration of one-way thrust ball bearing
  • The vibration of one-way thrust ball bearing is very sensitive to the damage of the bearing, such as peeling, indentation, corrosion, crack and wear, which will be reflected in the vibration measurement of SKF Bearing. Therefore, the vibration can be measured by using a special bearing vibration meter (frequency analyzer, etc.), and the specific abnormal situation can not be inferred by frequency division. Preventive measures for bearing running noise and overheating
  • The measured values are different due to the service conditions of the bearing or the installation position of the sensor, so the temperature of the unidirectional thrust ball bearing needs to be measured in advance
  • The temperature of one-way thrust ball bearing can be inferred from the temperature outside the bearing chamber. It is more appropriate if the oil hole can be used to directly measure the temperature of the outer ring of the bearing.Preventive measures for bearing running noise and overheating
  • Generally, the temperature of SKF Bearing starts to rise slowly with the operation of the bearing, and reaches a stable state after 1-2 hours. The normal temperature of the bearing varies with the heat capacity, heat dissipation, speed and load of the machine. 
  • If the lubrication and installation parts are appropriate, the bearing temperature will rise sharply and abnormal high temperature will occur. At this time, the operation must be stopped and necessary preventive measures must be taken.Preventive measures for bearing running noise and overheating
  • The thermal sensor can monitor the working temperature of the bearing at any time, and automatically alarm or stop when the temperature exceeds the specified value to prevent the occurrence of combustion shaft accident.Preventive measures for bearing running noise and overheating
  • High temperature often indicates that the bearing is in an abnormal condition. High temperatures are also harmful to SKF Bearing Lubricants. Sometimes bearing overheating can be attributed to the lubricant of the bearing. Preventive measures for bearing running noise and overheating
  • If the temperature of the bearing exceeds 125 ℃ for a long time, the service life of the bearing will be reduced. The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. It contains impurities, excessive load, SKF Bearing Ring damage, insufficient clearance, high friction caused by oil seal, etc.
  • Therefore, it is necessary to continuously monitor SKF Bearing Temperature, whether it is measuring the bearing itself or other important parts. If the operating conditions remain unchanged, any temperature change can indicate that a fault has occurred.Preventive measures for bearing running noise and overheating
  • The periodic measurement of SKF Bearing temperature can be aided by a thermometer, such as a digital thermometer, which can accurately measure the bearing temperature and display it according to the unit of ℃ or Fahrenheit.Preventive measures for bearing running noise and overheating
  • SKF Bearing of importance means that when it is damaged, it will cause equipment shutdown. Therefore, this kind of bearing should be equipped with temperature detector.Preventive measures for bearing running noise and overheating
  • Under normal circumstances, SKF bearings will have a natural temperature rise after just lubrication or re lubrication and last for one or two days. There are many reasons for the failure of SKF thrust ball bearing. All influencing factors in the design and manufacturing process will be related to the failure of thrust ball bearing, which is difficult to judge by analysis. In general, it can be considered and analyzed from two aspects: use factors and internal factors.Preventive measures for bearing running noise and overheating
  • Use factors mainly refer to whether the installation, adjustment, use and maintenance, maintenance and repair meet the technical requirements. The installation condition is one of the primary factors in the use factors. The improper installation of the thrust ball bearing often leads to the change of the stress state between the parts of the whole set of thrust ball bearing, and the thrust ball bearing operates in an abnormal state and fails early. Preventive measures for bearing running noise and overheating
  • According to the technical requirements for the installation, use, maintenance and repair of the thrust ball bearing, the load, speed, working temperature, vibration, noise and lubrication conditions of the thrust ball bearing in operation shall be monitored and inspected.Preventive measures for bearing running noise and overheating
  •  If any abnormality is found, the cause shall be found immediately and adjusted to make it return to normal. In addition, it is also important to analyze and test the quality of grease and the surrounding medium and atmosphere.Preventive measures for bearing running noise and overheating
  • Internal factors mainly refer to the three factors that determine the quality of thrust ball bearings, such as structural design, manufacturing process and material quality.Preventive measures for bearing running noise and overheating
  • First of all, long service life of thrust ball bearing can be achieved only when the structure design is reasonable and progressiveness is available. The manufacturing of thrust ball bearing generally goes through many processing procedures, such as forging, heat treatment, turning, grinding and assembly. The rationality, progressiveness and stability of each processing technology will also affect the service life of thrust ball bearings. Preventive measures for bearing running noise and overheating
Preventive measures for bearing running noise and overheating

The main task of failure analysis of bearing running

  • Among them, the heat treatment and grinding processes that affect the quality of finished thrust ball bearings are often more directly related to the failure of thrust ball bearings. In recent years, the research on the metamorphic layer on the working surface of thrust ball bearing shows that the grinding process is closely related to the surface quality of thrust ball bearing.Preventive measures for bearing running noise and overheating
  • The metallurgical quality of SKF thrust ball bearing material was once the main factor affecting the early failure of rolling thrust ball bearing. With the progress of Metallurgical Technology (such as vacuum degassing of thrust ball bearing steel), the quality of raw materials has been improved. Preventive measures for bearing running noise and overheating
  • The proportion of raw material quality factor in the failure analysis of thrust ball bearing has decreased significantly, but it is still one of the main influencing factors of thrust ball bearing failure. Proper material selection is still a factor that must be considered in the failure analysis of thrust ball bearing.Preventive measures for bearing running noise and overheating
  • The main task of failure analysis of SKF thrust ball bearing is to find out the main factors causing the failure of thrust ball bearing according to a large number of background materials, analysis data and failure forms, so as to put forward targeted improvement measures, prolong the service life of thrust ball bearing and avoid sudden early failure of thrust ball bearing. Preventive measures for bearing running noise and overheating
  • During the operation of fag bearing, except for some inherent movements between high-temperature bearing parts and required by function, all other movements that deviate from the ideal position are called bearing vibration. The vibration generated by fag bearing movement is a very complex random vibration, which can not be completely described by a specific motion equation at present. Preventive measures for bearing running noise and overheating
  • The factors affecting fag bearing vibration are very complex. The vibration of fag bearing will be affected by the corrugation, roughness, surface quality, the size difference of rolling element, the structural type of imported bearing, assembly clearance, working conditions and so on.Preventive measures for bearing running noise and overheating
  • Research work at home and abroad has shown that bearing noise and vibration are the reflection of two different sides of the same thing. They are intrinsically related. Fag bearing vibration is the source of noise. Noise and vibration are produced when high-temperature bearings operate, so their measurement methods must have commonality. Therefore, the purpose of controlling bearing noise by controlling bearing vibration can be achieved in a certain range and degree.Preventive measures for bearing running noise and overheating
  • The impact sound of the moving projectile and its control method. When the larger ball bearing or fag bearing is running at low speed under pure radial load, due to the small centrifugal force of the moving projectile, the moving projectile in the non load area will impact the connecting frame or raceway and make noise. But with the advance of the speed, that kind of sound will disappear. Preventive measures for bearing running noise and overheating
  • The control method of the impact sound of moving projectile is not: properly reduce the radial clearance, and use the imported bearing of the connecting frame without reasonable layout and material.Preventive measures for bearing running noise and overheating
  • The rolling sound of fag bearing and its control method rolling sound is the harsh metal friction sound that can occur in no place of high-temperature bearing. Most of it occurs outside the larger model bearing lubricated with grease, but it is more difficult to occur outside the grease with degraded base oil function, and it hardly occurs when it is lubricated with oil. 
  • SKF Bearing shows strong regularity and good repeatability in its use. When the normal high-quality stainless steel bearing is put into use, the vibration and noise are relatively small, but the spectrum is scattered 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 above three times of power frequency rarely appears, and the stainless steel bearing is in a very stable state and enters a stable working period.Preventive measures for bearing running noise and overheating
  • After continuous operation and entering the later stage of use, the vibration and noise of SKF Bearing begin to increase, and sometimes abnormal sound occurs, but the increase of vibration is an initial failure.
  • Firstly, the spectral analysis of bearing shows that the concentration of nonferrous metals is abnormal, and many submicron wear particles of nonferrous metals appear in the ferrography; The water content and acid value of lubricating oil exceed the standard, indicating that the pad surface of SKF Bearing is corroded.
  • Second, the spectral analysis of the bearing found that the iron concentration was abnormal. There were many iron components, submicron wear particles, and abnormal moisture and acid value of the lubricating oil, indicating that the back of the bearing was worn due to fretting.
  • Third, there are iron cutting abrasive particles or black oxide particles in the ferrogram of stainless steel bearing, and there is tempering color on the metal surface, indicating that the journal surface of the bearing is strained.
  • Fourth, cutting abrasive particles are found in the Ferrograph of SKF Bearing, and the abrasive particles are composed of non-ferrous metals, indicating that the surface of the bearing is strained.Preventive measures for bearing running noise and overheating
  • Fifthly, the bearing spectral analysis found that the concentration of iron was abnormal. There were many submicron particles of iron in the ferrogram, and the moisture or acid value of lubricating oil exceeded the standard, indicating that the journal surface of needle roller bearing was corroded.Preventive measures for bearing running noise and overheating
  • Now that we know the cause of SKF Bearing Failure, we mainly pay attention to these aspects, and the service life of stainless steel bearing will naturally be long.Preventive measures for bearing running noise and overheating
  • When external hard particles enter the bearing and are pressed between the body and the raceway, indentation can be formed on the surface. In addition, excessive impact load can also make the contact surface produce local plastic deformation and form pits. When SKF Bearing is stationary, even if the load is very small, evenly distributed pits will be formed on the raceway due to the vibration of the surrounding environment.
  • When SKF Bearing is not well sealed, dust or particulate matter enters the bearing, or poor lubrication will cause serious scratch or wear on the contact surface, and increase the vibration and noise of stainless steel bearing. Generally speaking, the correct use of rolling bearings can achieve fatigue life. Preventive measures for bearing running noise and overheating

Allowable inclination angle: bearing running

  • However, in case of accidental early damage, it can no longer be used. Unlike fatigue life, this early damage is called a failure or accident. Most of them are caused by poor consideration of installation, use and lubrication, foreign matters invading from the outside or insufficient research on shaft and bearing seat.Preventive measures for bearing running noise and overheating
  • The damage state of rolling bearing, such as the scratch of the ring retaining edge of roller bearing, may be caused by insufficient lubricant, improper brand, defective oil supply and drainage structure, intrusion of foreign matters, bearing installation error or excessive deflection of shaft, or a combination of the above reasons.Preventive measures for bearing running noise and overheating
  • Therefore, only investigating the bearing damage, it is difficult to know the real cause of the damage. However, if we fully understand the machine, working condition and peripheral structure of the bearing, understand the situation before and after the fault, and then analyze the damage of the bearing and various related reasons, we can prevent the recurrence of similar faults. Representative causes and Countermeasures of bearing damage.
  • Even if the advanced manufacturing technology is adopted to process rolling bearing parts. Observe the change of reading with preload. Preloading method has its disadvantages, which are well known. The working surface will always keep the dial indicator against the appropriate part of the bearing end face or shaft.
  • Bearing structure and service conditions. Different structures are suitable for different service conditions; The processing technology of automobile bearing parts with different structure will be different, which will affect their quality. Therefore, we should develop new structural products to adapt to different service conditions, and indicate their suitable service conditions or performance in the instructions for the use of rolling bearings, so as to facilitate the selection of customers.Preventive measures for bearing running noise and overheating
  • Strengthen process research, improve processing technology, improve processing quality and reduce the possibility of defects in processing. For example, in terms of heat treatment, for the inner and outer rings of larger varieties, try to use the medium and lower limit quenching heating temperature to adapt to prolonging the holding time to improve the alloy concentration and increase the fracture strength of martensite. On the premise of ensuring the quality, select a higher tempering temperature to enhance the impact toughness of the workpiece.Preventive measures for bearing running noise and overheating
  • Improve processing monitoring means and promote the improvement of processing quality. For example, improve the monitoring of the curvature position of the flow channel, improve the overall performance of the automobile bearing after assembly, and improve the working condition of the rolling bearing. Preventive measures for bearing running noise and overheating
  • Service environment of NTN bearing: select the specification, size and accuracy according to the service position, service conditions and environmental conditions. Matching appropriate bearings is the premise to ensure the service life and reliability of angular contact ball bearings.
  • Application position: angular contact ball bearing is suitable for bearing the combined radial and axial load dominated by radial load. It is usually used in pairs with two sets of NTN bearings. It is mainly used in the transmission parts of automobile, such as front and rear hubs, driving bevel gears, differential, reducer and so on.Preventive measures for bearing running noise and overheating
  • Allowable speed: under the condition of correct installation and good lubrication, the allowable speed is 0.3-0.5 times of the bearing limit speed. Under normal conditions, it is appropriate to use 0.2 times of the limit speed.
  • Allowable inclination angle: tapered roller bearings generally do not allow the shaft to be inclined relative to the shell hole. If there is an inclination, the inclination shall not exceed 2 ‘.Preventive measures for bearing running noise and overheating
  • Allowable temperature: under the condition of bearing normal load, high temperature resistance of lubricant and sufficient lubrication, the general angular contact ball bearing is allowed to work at the ambient temperature of – 30 ℃ – 150 ℃.Preventive measures for bearing running noise and overheating
  • First of all, check the vibration of angular contact ball bearing during operation. Peeling, indentation, corrosion, crack and wear will be reflected in the vibration measurement of bearing. NTN bearing vibration is very sensitive to the damage of plastic bearing. Therefore, the vibration can be measured by using special bearing vibration measuring instrument (frequency analyzer, etc.).Preventive measures for bearing running noise and overheating
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