Most fag bearings are damaged for many reasons, such as exceeding the original estimated load, ineffective sealing, too small bearing clearance caused by too tight fit, etc. Any of these factors has its special damage type and will leave special damage traces. Therefore, by examining the damaged bearing, the possible causes can be found in most cases.Bearing maintenance and damage Countermeasures
Generally speaking, one-third of the bearing damage is caused by fatigue damage, the other one-third is caused by poor lubrication, and the other one-third is caused by pollutants entering the bearing or improper installation and treatment. However, these types of damage are also related to industry. For example, the pulp and paper industry is mostly due to bearing damage caused by poor lubrication or pollution, rather than material fatigue.Bearing maintenance and damage Countermeasures
When inspecting the fag bearing removed during the regular maintenance and operation of fag bearing equipment and the replacement of peripheral parts, it is necessary to judge whether the secondary bearing parts can be reused and record the good or bad use. Also carefully investigate and record the appearance of the removed fag bearings. In order to find out and investigate the remaining amount of lubricant, the fag bearing should be well cleaned after sampling.Bearing maintenance and damage Countermeasures
Secondly, check the raceway surface, rolling surface and mating surface of fag bearing and the wear state of cage for damage and abnormalities, especially observe the running track of raceway surface. Judge whether the bearing can be used again after considering the degree of bearing damage, machine performance, importance, operating conditions, inspection cycle, etc.Bearing maintenance and damage Countermeasures
According to the inspection results, if the fag bearing is found to be damaged or abnormal, please find out the causes and formulate countermeasures according to the phenomenon of bearing damage. In addition, according to the inspection results, if there are the following defects, the fag bearing can no longer be used and needs to be replaced with a new bearing. The clearance of rolling bearing is divided into radial clearance and axial clearance. Its function is to ensure the normal operation and lubrication of rolling element and compensate thermal elongation.Bearing maintenance and damage Countermeasures
For Timken bearings with adjustable clearance, due to the positive proportional relationship between axial clearance and radial clearance, the required radial clearance can be obtained as long as the axial clearance is adjusted. However, they are generally used in pairs (i.e. installed at both ends or one end of the shaft). Therefore, it is only necessary to adjust the axial clearance of one Timken bearing. The axial clearance is generally adjusted with gaskets, and some can also be adjusted with screws or thrust rings.Bearing maintenance and damage Countermeasures
For rolling bearings with non adjustable clearance, the radial clearance cannot be adjusted because it has been determined according to the standard during manufacturing. After such Timken bearings are installed on the shaft diameter or in the bearing seat hole, the actual radial clearance is called assembly radial clearance. Bearing maintenance and damage Countermeasures
During assembly, the size of the assembly radial clearance should be just enough to create the necessary working radial clearance during operation, so as to ensure the flexible rotation of the bearing. When this kind of Timken bearing is working, due to the thermal elongation of the shaft when the temperature rises, the inner race is relatively displaced, which reduces the radial clearance of Timken bearing and even makes the rolling element stuck between the inner and outer race.
The above phenomenon can be avoided if an axial clearance is left between one bearing (the other Timken bearing is fixed on the shaft and in the Timken bearing seat) and the side cover in the double support rolling Timken. Incorrect lubricant selection, insufficient lubricant or aging hardening can lead to vibration and noise of INA Bearing, and this noise has no certain law. In this case, only select the appropriate lubricant, adjust the amount of lubricant, prolong the service life of lubricant and reasonably determine the replacement cycle.Bearing maintenance and damage Countermeasures
The raceway sound of INA 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. Bearing maintenance and damage Countermeasures
The general INA 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 INA Bearing with loud raceway sound, the sound pressure level of raceway sound decreases with the increase of viscosity; For ina bearings with low raceway sound, the sound pressure level changes from decrease to increase when the viscosity increases to more than 20mm2 / s. Bearing maintenance and damage Countermeasures
The greater the rigidity of the bearing pedestal, the lower the total sound pressure level of the raceway sound. 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 bearing, that is, INA Bearing 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.Bearing maintenance and damage Countermeasures
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 include: appropriately reducing radial clearance and using INA Bearing with cage with reasonable structure and flexible material.Bearing maintenance and damage Countermeasures
The rolling sound of INA Bearing 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 grease lubricated larger ina 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. Bearing maintenance and damage Countermeasures
Special processing methods for the outer ring raceway can prevent the occurrence of rolling sound. If necessary, this ina 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. Bearing maintenance and damage Countermeasures
When disassembling the lower SKF Bearing for maintenance, first record the appearance of SKF 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.Bearing maintenance and damage Countermeasures
The cleaning of the disassembled imported bearing is divided into coarse cleaning and fine cleaning. Put the metal mesh pad on the bottom of the container respectively, so that the SKF Bearing does not directly contact the dirt of the container. Bearing maintenance and damage Countermeasures
During rough cleaning, if SKF 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.Bearing maintenance and damage Countermeasures
Fine cleaning is to carefully clean the SKF Bearing while rotating in the cleaning oil. In addition, the cleaning oil should always be kept clean.
In order to judge whether the disassembled SKF 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 SKF 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.Bearing maintenance and damage Countermeasures
Tapered roller bearing and split SKF Bearing can inspect the raceway surface of rolling element and outer ring respectively. Since large imported bearings cannot be rotated by hand, pay attention to the appearance of rolling elements, raceways, cages and edge retaining surfaces. The higher the importance of SKF bearings, the more careful the inspection is.Bearing maintenance and damage Countermeasures
Once the final value of the required rated load is determined, you must consider the overall dimensions required for the installation of SKF bearings, including the installation and fixing of SKF bearings considered here. And the size of the shaft matching the bearing with the required load rating. These factors help to determine the bearing structure and size, and some imported bearing types can be excluded. In some cases, due to space constraints, the choice is excluded even before the rated load is determined.Bearing maintenance and damage Countermeasures
For example, if the shape of SKF Bearing is very narrow, ball bearing is the type that can work here. Alternatively, if you have to use a bearing housing with a very small diameter, you need to install two or more roller bearings on the same shaft to achieve sufficient load rating.Bearing maintenance and damage Countermeasures
Another common contradiction arises when the size of the shaft is very different from the required SKF Bearing Load Rating. If the shaft is large but the load is light, even if the required rated load is very small, an expensive and large SKF Bearing with high rated load must be proposed. In this case, contact the bearing manufacturer in order to put forward a cost-effective solution.Bearing maintenance and damage Countermeasures
Basic working conditions. Assuming SKF Bearing is applied to reducer, the inlet bearing must support one end of a shaft with a diameter of about 25mm, and a spur gear is installed on the shaft.Bearing maintenance and damage Countermeasures
Duty cycle and SKF inlet bearing load. The analysis of the gear force and the working cycle of the transmission show that the radial load borne by the bearing is 1780n and the speed is 11000r / min in about 3 / 4 of the time, and the radial load borne by the SKF Bearing is 890n and the speed is 3500r / min in 1 / 4 of the running time. Good positive engagement produces almost no axial force, and there is no oblique engagement or other effective axial component force. It is estimated that the large axial force in both directions is 89n and the large vibration force is 89n.Bearing maintenance and damage Countermeasures
Dimensional limits. Due to the limitation of the internal design of the reducer, the large outer diameter of SKF Bearing is allowed to be 70mm, the large calculated disturbance is 6, and the different axial degrees of large positions are 0 and 0015. Do not require self-aligning bearings.Bearing maintenance and damage Countermeasures
environment The lubrication of SKF bearings is the same as meshing lubrication: oil is injected from a large oil groove, and the high expected temperature is 140 F.Bearing maintenance and damage Countermeasures
Reliability. SKF Bearing must have a good reliability in order to work continuously, with a reliable failure rate of 8%. Vibration is very sensitive to the damage of NSK bearing. Peeling, indentation, corrosion, crack and wear will be reflected in the vibration measurement of NSK bearing.
Therefore, by using a special NSK bearing vibration measuring device (frequency analyzer, etc.), the magnitude of vibration can be measured, and the specific abnormal situation can not be inferred through frequency division. The measured value of NSK of each machine needs to be analyzed in advance due to different installation conditions.Bearing maintenance and damage Countermeasures
Then let’s take a look at the impact of temperature on the bearing. Using high temperature often indicates that NSK bearing has been in abnormal condition. High temperatures are also harmful to NSK bearing lubricants. Sometimes bearing overheating can be attributed to NSK bearing lubricant.
The NSK bearing life is reduced when the bearing temperature exceeds 125 ℃ for a long time. The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. It contains impurities, excessive load, NSK bearing ring damage, insufficient clearance, high friction caused by oil seal, etc.Bearing maintenance and damage Countermeasures
Therefore, it is necessary to continuously monitor NSK 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.
The regular measurement of NSK bearing temperature can be aided by thermometer, such as NSK digital thermometer, which can accurately measure NSK bearing temperature and display it in ℃ or Fahrenheit. Important bearing means that when it is damaged, it will cause equipment shutdown. Therefore, this kind of NSK bearing should be equipped with temperature detector.
Generally, if the bearing is used correctly, it can be used until the fatigue life is reached. However, there will be accidental and premature damage, which is not resistant to use. This early damage, as opposed to fatigue life, limits the use of quality known as failure or accident. Most of them are caused by careless installation, use and lubrication, foreign matters invading from the outside, and insufficient research on the thermal effects of shafts and shells.
As for the damage state of Timken bearing, for example, the clamping damage of the ring retaining edge of roller bearing can be considered as the reason. These reasons also coincide with insufficient lubricant, unsuitable, defects of oil supply and drainage structure, intrusion of foreign matters, bearing installation error and excessive deflection of shaft.Bearing maintenance and damage Countermeasures
Therefore, only investigating the damage of Timken bearing, it is difficult to know the real cause of the damage. However, if we know the use machinery, service conditions, the structure around the bearing, understand the situation before and after the accident, and investigate the damage state of the bearing and several causes, we can prevent the recurrence of similar accidents.
Precautions for the use of Timken bearings are as follows:Bearing maintenance and damage Countermeasures
Keep the bearings clean and tidy
Even small dust that cannot be seen by the eyes will have a bad impact on Timken bearings. Therefore, keep the surroundings clean so that dust will not invade Timken bearings.
Use with care
When Timken bearing is strongly impacted in use, it will produce scars and indentation, which will become the cause of the accident. In serious cases, it will crack and fracture, so we must pay attention to it.
Use appropriate Timken operating tools
Avoid replacing with existing tools and bearing tools, and appropriate tools must be used. We often emphasize the importance of tools because too many customers use the wrong tools in installation, resulting in the damage of Timken bearings.
Pay attention to the corrosion of Timken bearing
When operating Timken bearings, sweat on your hands can be the cause of rust. Pay attention to operate with clean hands and wear gloves as much as possible.