Importance of Timken bearing inspection
Importance of Timken bearing inspection
2022年4月16日
Effect of IKO bearing grease on stability
Effect of IKO bearing grease on stability
2022年4月16日

Failure analysis of NSK tapered roller bearing

  • Bearing raceway sound and its control method raceway sound is a smooth and continuous sound made by the rolling body rolling on the raceway surface when the imported bearing is running. It is a unique basic sound that will occur in all rolling bearings. The general bearing sound is the sound of raceway plus other sounds. The raceway sound of ball bearing is irregular, and its frequency is above 1000Hz.Failure analysis of NSK tapered roller bearing
  •  Its main frequency does not change with the speed, but its total sound pressure level increases with the speed. For the bearing with loud raceway sound, the sound pressure level of raceway sound decreases with the increase of viscosity; For bearings with low raceway noise, the sound pressure level changes from decrease to increase when the viscosity increases to more than 20mm2 / s. The greater the rigidity of the bearing pedestal, the lower the total sound pressure level of the raceway sound.Failure analysis of NSK tapered roller bearing
  •  If the radial clearance is too small, the total sound pressure level and dominant frequency of raceway sound will increase sharply with the reduction of radial clearance. The methods to control the sound of raceway are: select low-noise bearings, that is, bearings with small waviness, and carefully select the service conditions. Raceway noise often affects the noise of the whole machinery. Reducing raceway noise can reduce the noise of the whole machinery.Failure analysis of NSK tapered roller bearing
  • Impact sound of rolling element and its control method when the ball bearing or cylindrical roller bearing of larger model runs at low speed under pure radial load, due to the small centrifugal force of the rolling element, the rolling element in the non load area will impact the cage or raceway and make noise. As the speed increases, the sound disappears. The control methods of impact sound of rolling elements are: appropriately reduce the radial clearance, and use the bearing of cage with reasonable structure and flexible material.Failure analysis of NSK tapered roller bearing
  • The rolling sound of imported bearings and its control method rolling sound is the harsh metal friction sound that can occur in cylindrical roller bearings on all occasions. Most of it occurs in larger types of grease lubricated bearings, which is more likely to occur in greases with degraded base oil performance, and almost does not occur in oil lubrication. In addition, it is easy to occur in winter. When bearing pure radial load, it is easy to occur in the case of large radial clearance, and it is easy to occur in a specific speed range with different models and sizes, both continuously and intermittently. Failure analysis of NSK tapered roller bearing
  • Special processing methods for the outer ring raceway can prevent the occurrence of rolling sound. If necessary, this kind of bearing can be selected, or the radial clearance of the bearing can be appropriately reduced, the lubricating grease with excellent performance can be used and the rigidity of the parts matched with the bearing can be improved. Failure analysis of NSK tapered roller bearing
  • When the imported bearing operates under the load of 0.1C, the contact stress between the rolling element and the contact surface of the raceway increases, resulting in the increase of the working temperature of the bearing and the relative deterioration of the performance of the lubricant. Therefore, the limit speed of the bearing will be reduced accordingly.Failure analysis of NSK tapered roller bearing
  • For the range of C / = 10, the reduction of limit speed is very small, so it can be ignored, that is, F1 = 1.
  • For the radial bearing under combined load, due to the increase of the number of rolling elements under load, the increase of friction resistance, the increase of calorific value, the deterioration of lubrication and cooling conditions, and the increase of force acting on the cage, the limit speed of the bearing must be multiplied by a reduction factor F2 according to the bearing type and load angle.Failure analysis of NSK tapered roller bearing
  • If the limit speed of the selected imported bearing cannot meet the use requirements, some improvement technical measures can be adopted to improve it, so as to meet the more satisfactory requirements. Such as improving the bearing tolerance level; Appropriately increase the clearance; Change to special materials and improve the structure of cage; Change the lubrication mode, such as oil-gas, oil mist and jet lubrication; Improve cooling conditions, etc. Regular maintenance of mechanical equipment is very important for production. As a precision accessory of mechanical equipment, the regular inspection of SKF imported bearings is particularly critical. Here is the necessity and key steps of bearing regular inspection.Failure analysis of NSK tapered roller bearing
  • It is important to keep the bearings and lubrication clean
  • Before inspection, clean the surface of the machine, and then remove the parts around the SKF inlet bearing. The oil seal is a very fragile part, so it needs to be disassembled carefully. Do not apply excessive force, and then carefully check the oil seal and its surrounding parts. If there are bad symptoms, be sure to replace it. The bad oil seal will lead to bearing damage and strict equipment shutdown.
  • Check the lubricant of the bearing
  • Rub a little lubricant between your fingers. If there are pollutants, you can feel it, or apply a layer of lubricant on the back of your hand, and then seal it for light inspection.Failure analysis of NSK tapered roller bearing
  • Replace the lubricant of the bearing
  • After draining out the old oil, if possible, refill fresh oil into the oil lubricated bearing and let the machine rotate at low speed for a few minutes. Make the engine oil collect residual pollutants as much as possible, and then drain the engine oil. The engine oil is filtered before use.Failure analysis of NSK tapered roller bearing
  • For grease lubricated bearings, the arbor used when replacing grease should avoid connecting the angle of cotton to any part of the bearing, because these residual fibers may wedge between the rolling parts and cause damage, especially for the application of small bearings.Failure analysis of NSK tapered roller bearing
  • Cover exposed bearings
  • When inspecting bearings, never expose SKF imported bearings to pollutants or moisture. If the work is interrupted, the machine shall be covered with oil paper, plastic sheet or similar materials.Failure analysis of NSK tapered roller bearing
  • If it is possible to clean the naked bearing without disassembly, clean it with a brush coated with white spirit, and then dry it with a piece of lint free cloth or blow dry with compressed air (be careful not to start the rotation of the bearing assembly).Failure analysis of NSK tapered roller bearing
  • Raceway sound of imported bearing and its control method raceway sound is a smooth and continuous sound made by the rolling body rolling on the raceway surface when the shaft is running. It is a unique basic sound that will occur in all rolling bearings. Failure analysis of NSK tapered roller bearing
  • The general bearing sound is the sound of raceway plus other sounds. The raceway sound of ball bearing is irregular, and its frequency is above 1000Hz. Its main frequency does not change with the speed, but its total sound pressure level increases with the speed. For the bearing with loud raceway sound, the sound pressure level of raceway sound decreases with the increase of viscosity; 
  • The sound pressure level of SKF Bearing with low raceway noise changes from decrease to increase when the viscosity increases to more than 20mm2 / s. The greater the rigidity of the bearing pedestal, the lower the total sound pressure level of the raceway sound. Failure analysis of NSK tapered roller bearing
  • If the radial clearance is too small, the total sound pressure level and dominant frequency of raceway sound will increase sharply with the reduction of radial clearance. The methods to control the sound of raceway are: select low-noise bearings, that is, bearings with small waviness, and carefully select the service conditions. Raceway noise often affects the noise of the whole machinery. Reducing raceway noise can reduce the noise of the whole machinery.Failure analysis of NSK tapered roller bearing
  • Impact sound of rolling element and its control method when the ball bearing or cylindrical roller bearing of larger model runs at low speed under pure radial load, due to the small centrifugal force of the rolling element, the rolling element in the non load area will impact the cage or raceway and make noise. As the speed increases, the sound disappears. The control methods of impact sound of rolling elements are: appropriately reduce the radial clearance, and use the bearing of cage with reasonable structure and flexible material.
  • Rolling sound of bearing and its control method rolling sound is the harsh metal friction sound that can occur in cylindrical roller bearings on all occasions. It mostly occurs in grease lubricated larger SKF bearings, but it is more likely to occur in greases with degraded base oil performance, which hardly occurs in oil lubrication. In addition, it is easy to occur in winter. Failure analysis of NSK tapered roller bearing
  • When bearing pure radial load, it is easy to occur in the case of large radial clearance, and it is easy to occur in a specific speed range with different models and sizes, both continuously and intermittently. Special processing methods for the outer ring raceway can prevent the occurrence of rolling sound. If necessary, this kind of bearing can be selected, or the radial clearance of the bearing can be appropriately reduced, the lubricating grease with excellent performance can be used and the rigidity of the parts matched with the bearing can be improved.Failure analysis of NSK tapered roller bearing
  • Bearing lubrication methods can be roughly divided into grease lubrication and oil lubrication. To give full play to the function of bearing, it is important to use reduction and use purpose, and adopt lubrication method. Table 4-2 shows the advantages and disadvantages of grease lubrication and oil lubrication. 3、 Grease is a lubricant composed of base oil, thickener and additives.Failure analysis of NSK tapered roller bearing
  •  When selecting, the lubricating oil that is very suitable for the service conditions of the bearing should be selected. Different trademarks will have great differences in performance. When selecting, attention must be paid to.Failure analysis of NSK tapered roller bearing
  • Common lubricating greases for bearings include calcium base grease, sodium base grease, calcium sodium base grease, lithium base grease, aluminum base grease and molybdenum disulfide grease.Failure analysis of NSK tapered roller bearing
  • The amount of grease filled in SKF Bearing is suitable to fill 1 / 2-1 / 3 of the internal space of the bearing. It should be reduced to 1 / 3 at high speed. Too much grease will increase the temperature rise. 4、 When selecting the working temperature of the lubricating grease, the main indicators should be the drop point, oxidation stability and low-temperature performance.Failure analysis of NSK tapered roller bearing
  •  The drop point can generally be used to evaluate the high-temperature performance, and the actual working temperature of the bearing should be 10-20 ℃ lower than the drop point. The service temperature of synthetic grease shall be 20-30 ℃ lower than the dropping point.
  • When selecting grease for bearing load, select grease with small penetration for heavy load. When working under high pressure, in addition to small penetration, it also has high oil film strength and extreme pressure performance.Failure analysis of NSK tapered roller bearing
  • When choosing grease for environmental conditions, calcium based grease is not easy to dissolve in water and is suitable for dry and less moisture environment. 
Failure analysis of NSK tapered roller bearing

Failure analysis of NSK tapered roller bearing

  • Under high-speed and high-temperature conditions, oil lubrication can be used when grease lubrication is no longer suitable. Lubricating oil circulation can take away a lot of heat. Viscosity is an important characteristic of lubricating oil. The viscosity directly affects the fluidity of lubricating oil and the thickness of oil film formed between friction surfaces. Failure analysis of NSK tapered roller bearing
  • The viscosity of lubricating oil at bearing working temperature is generally 12-15cst. The higher the rotating speed, the lower the viscosity should be selected, and the heavier the load, the higher the viscosity should be selected. Common lubricating oils include machine oil, high-speed machine oil, turbine oil, compressor oil, transformer oil, cylinder oil, etc. For example, the noise of centripetal ball bearing is lower than that of short cylindrical roller bearing, and the noise of short cylindrical roller bearing is lower than that of tapered roller bearing.Failure analysis of NSK tapered roller bearing
  • During the operation of the rolling bearing, it bears a certain load, even static load, but for the steel ball and raceway, its stress is cyclic, and the material will have rolling fatigue, so as to make the imported bearing reach its service life. The phenomenon is that a part of the rolling surface material suddenly falls off like a fish scale. This phenomenon is called fatigue flaking.Failure analysis of NSK tapered roller bearing
  • For the bearing of household appliances, the load borne by the bearing is very small and the service life of the bearing is very long. However, after the shaft rotates for a period of time, it will also produce wear, increased vibration and noise, deterioration of lubricating grease, etc. Due to the strict requirements on the bearing noise of household appliances, when the bearing noise exceeds the allowable range, it is considered that SKF Bearing can no longer be used. The total time of bearing low noise operation is called bearing noise life.Failure analysis of NSK tapered roller bearing
  • The bearings of household appliances are usually grease lubricated sealed bearings without maintenance. Although only a small amount of lubricant is needed for bearing lubrication, the bearing lubrication is poor due to the deterioration and leakage of grease after a long time of operation, resulting in bearing failure. The total operation time of SKF Bearing under good lubrication is called bearing life. In the production of standard SKF bearings, some single row radial ball bearings and short cylindrical roller bearings have low noise types for motor bearings. 
  • The inner diameter of ball bearing φ 2.5mm to φ There are several types of 60mm with three suffixes of ZL, Z2 and Z3, which correspond to three different low-noise requirements respectively. Among the roller bearings, eight models from n309 to n322 are also manufactured according to the low-noise standard. These bearings can be fully applicable to other machines with low noise requirements, and the price is cheap.
  •  If the type and size can meet the requirements, try to use these two types of low noise bearings. In general, Koyo bearing, as a world bearing, will not be excited, but if it is excited, you must check the situation well. Let’s explain the truth of the excitation. Vibration excitation may occur when the bearing is partially damaged. A small number of bearing raceways and rolling elements may be damaged due to incorrect operation or installation. During operation, rolling over damaged bearing parts will produce specific vibration frequency. Vibration frequency analysis can identify damaged bearing components.
  • Vibration excitation may occur when the waviness of Koyo bearing is not necessarily deformed. In the case of close fit between the bearing ring and the bearing seat or transmission shaft, the bearing ring may be deformed by matching with the shape of adjacent components. If deformation occurs, vibration may occur during operation. Therefore, it is important to machine the bearing pedestal and drive shaft to the required tolerances.
  • In addition, the excitation behavior will also occur in applications. In many applications, the stiffness of the bearing is the same as that of the surrounding structure. Because of this feature, as long as the bearing (including preload and clearance) and its configuration in the application are correctly selected, it is possible to reduce the vibration in the application.
  • There is also the excitation generated when the number of loaded rolls changes. When a radial load is loaded on a bearing, the number of rolling elements bearing the load will change slightly during operation, that is, this causes the deviation of the load direction. The resulting vibration is inevitable, but can be reduced by axial preloading, which is applied to all rolling elements (not applicable to cylindrical roller bearings). Let’s introduce three small methods that can reduce the vibration of Koyo bearing. Change the stiffness of the structure, so as to change the critical frequency. Failure analysis of NSK tapered roller bearing
  • Critical excitation vibration is removed from the application. Suppress the critical excitation vibration between the excitation part and the resonance part. The running state of the machine that needs to be checked is the focus of attention in the bearing, and it is becoming more and more important to prepare a thorough inspection scheme.Failure analysis of NSK tapered roller bearing 
  • Because it is an important condition monitoring of all rotating machinery components to prevent Koyo bearing damage and to prevent the early detection of bearing damage during unplanned maintenance equipment shutdown, it is an important part at home.Failure analysis of NSK tapered roller bearing
  • But not all machines are equipped with this advanced equipment. In this case, the machine operator or maintenance engineer must adhere to the Koyo bearing fault signal alarm.
  • The sharp squeaking noise may be caused by the improper clearance of Koyo bearing. Insufficient lubrication can also cause metal sound. Dents in the bearing cup track can cause vibration. As for the noise generated by the equipment caused by knocking scars, this noise has different speed levels of Koyo bearings. If there is intermittent noise, then the rolling part may be damaged. This sound appears. When the surface is damaged, if the bearing hiss “sound pollution often causes serious damage to the bearing and causes irregular and huge noise.
  • However, it is usually unnecessary to replace the Koyo bearing at this time. Therefore, bearing damage, of course, can also be perceived by listening. If better methods are used, such as electronic health monitoring equipment, the operation of bearings before eruption. When the periodic maintenance and operation of IKO bearing equipment and the replacement of peripheral parts are stopped, it is necessary to judge whether the secondary IKO bearing parts can be reused and record the good or bad application conditions.
  • Secondly, check the raceway surface, rolling surface and joint surface of IKO bearing and the wear condition of confrontation frame for damage and abnormal conditions. In particular, check the running track of raceway surface. To judge whether the bearing can be used again, we should think about the level of bearing damage, mechanical function, priority, operation premise, search and inspection cycle, etc.Failure analysis of NSK tapered roller bearing
  • Search and inspection results. If IKO bearing is found damaged and abnormal, please find out the notice and formulate countermeasures according to the phenomenon of bearing damage. In addition, the search and inspection results show that if there are the following defects, the bearing can no longer be used. It is necessary to replace the IKO bearing with a new one. Failure analysis of NSK tapered roller bearing
  • When mass Timken one-way bearing is produced, the adjustment process system such as template, sample, stop and profiling is generally adopted; In single piece small batch production, the scale on the machine tool or gauge block is usually used for adjustment.Failure analysis of NSK tapered roller bearing
  •  The content of adjustment also varies with the complexity of the workpiece. For simple surfaces (such as inner and outer cylindrical surfaces), generally only the position relationship of each forming motion is adjusted; For complex surfaces (such as spiral surface and involute surface), it needs to be adjusted.Failure analysis of NSK tapered roller bearing