Matters needing attention in analyzing load failure of outer spherical bearing
Matters needing attention in analyzing load failure of outer spherical bearing
2022年4月14日
Precautions to avoid Timken bearing failure
Precautions to avoid Timken bearing failure
2022年4月14日

What should be paid attention to in order to prolong the life cycle of outer spherical bearing

  • Lubrication is very important, not only for Timken bearings, but also for all bearings. However, please note that the bearing should not add too much grease. Then it’s time to change the lubricant of the bearing. 

What should be paid attention to in order to prolong the life cycle of outer spherical bearing

  • After draining the old engine oil, if possible, the bearings lubricated with engine oil should be filled with fresh engine oil and let the machine rotate at low speed for a few minutes. Make the oil collect residual pollutants as much as possible, and then drain the oil.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  •  When replacing the grease of the bearing lubricated with grease, the Joe remover used should avoid the contact of cotton with any part of the outer spherical bearing. Because these residual fibers may wedge between rolling parts and cause damage, especially in the application of small bearings.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • When inspecting the bearing, never expose the bearing to pollutants or moisture. If the work is interrupted, the machine shall be covered with oil paper, plastic sheet or similar materials. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • If the Timken bearing without cover can be cleaned without disassembly and inspection, it shall be cleaned with a brush coated with petroleum solvent, and then wiped dry with a piece of lint free cloth or blown dry with compressed air (be careful not to start the rotation of the bearing assembly). 
  • Use a small mirror and a probe similar to that used by dentists to check the track surface, retainer and beads of the bearing. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Do not clean Timken bearings with encrypted cover or dust-proof; Just wipe the outer surface. If the bearing is damaged, it needs to be replaced. It is much more economical to replace the bearing during the regular shutdown and maintenance period than the loss of sudden shutdown due to the damage of the array bearing.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Contact fatigue failure refers to the failure of bearing working surface caused by alternating stress. Contact fatigue spalling occurs on the working surface of the bearing and is often accompanied by fatigue cracks. It first occurs from the large alternating shear stress below the contact surface, and then extends to the surface to form different spalling shapes, such as pitting or pitting spalling, which is called shallow spalling.
  • Wear failure refers to the failure caused by the continuous wear of the metal on the working surface caused by the relative sliding friction between the surfaces. Continuous wear will cause gradual damage to bearing parts, and eventually lead to the loss of bearing dimensional accuracy and other related problems. 
  • Wear may affect the change of shape, the increase of fit clearance and the change of working surface morphology, may affect the lubricant or make it polluted to a certain extent, resulting in the complete loss of lubrication function, so that the outer spherical bearing loses the rotation accuracy and even can not operate normally. 
  • Wear failure is one of the common failure modes of all kinds of Timken bearings. According to the wear form, it can be divided into common abrasive wear and adhesive wear.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The friction of the roller will make the speed of the roller drop more slowly, so that the user will not find that the friction of the roller will consume enough time before it is completely damaged. If the roughness of the surface is slight and the lubricating oil film has an appropriate thickness, the probability of surface stress generation is quite low, which is why it is necessary to properly select the appropriate engine oil for lubrication. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • However, if the pressure load exceeds the Pu value of the oil film (fatigue load limit value, such as too high speed and too high pressure impact), the fatigue of the material will come sooner or later.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The metallurgical quality of cylindrical roller bearing data was once the primary factor affecting the early failure of Timken bearing. With the improvement of metallurgical skills (such as vacuum degassing of bearing steel), the quality of raw materials has been improved. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The proportion of raw material quality factors in the analysis of bearing failure has obviously decreased, but it is still one of the primary influencing factors of bearing failure.
What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Whether the material selection is appropriate or not is still the factor that must be considered in the analysis of bearing failure.
  • The primary obligation of failure analysis of cylindrical roller bearings is to find out the primary elements of bearing failure according to a lot of setting data, analysis data and failure modes, so as to put forward targeted improvement methods, extend the service life of bearings and prevent sudden early failure of bearings.
  • There are many factors affecting the fatigue life of cylindrical roller bearings, which can not be fully estimated or eliminated through the premise of standardized experiments, resulting in the great discreteness of bearing practice fatigue life. Therefore, the expression parameter of bearing fatigue life is additional life L10. The meaning of L10 in ISO recommendation specification r281 is clear as follows:What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • “For a sufficient number of the same batch of bearings, the extra life L10 is revealed by the number of revolutions (or hours when the speed remains unchanged). 90% of the bearings in this batch can reach or exceed this number of revolutions (or hours) before the occurrence of fatigue exploitation”. So far, all countries in the world have obeyed the above rules.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • In some countries such as the United States, the concept of median life expectancy is also used. Median life LM refers to the median life of a batch of the same cylindrical roller bearings, that is, 50% of the bearings can reach or exceed the total number of revolutions or the number of tasks at a certain speed before they peel off.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  •  The median life LM is not the arithmetic mean value of the life of a batch of bearings. The average median life LM is about 5 times of the additional life.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The concept of extra life is only applicable to a sufficient number of bearings, not to a single bearing.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • For example, if 40 sets of 6204 bearings have an additional life of 1000h without fatigue damage according to their application strips, the other four sets can show fatigue failure in less than 1000h. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The significance of the additional fatigue life represents the life that can be expected when these cylindrical roller bearings normally develop their data potential. Therefore, in most cases, when selecting cylindrical roller bearings, users still calculate the fatigue life first, and then check it according to the practical failure category, such as wear life check. Take the smaller value in the accounting consequences as the bearing accounting life.What should be paid attention to in order to prolong the life cycle of outer spherical bearing

Causes of early damage of cylindrical roller bearing (improper lubrication)

  • Although “maintenance free” rubber sealed bearings can be installed, 36% of the bearings that failed early are still caused by incorrect application of grease technology.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Any cylindrical roller bearing with improper lubrication will inevitably fail in advance. Since Timken bearing is the part in the flower drum where the rubber is not easy to assemble and disassemble, it is congenital to use incorrect grease, and the grease is not replaced in the later use, or it is not replaced in time after the grease is carbonized, deteriorated and contaminated, then it is difficult for your flower drum to have long enough service life and good lubrication.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Are there any requirements for the installation surface and installation site? yes. It is assumed that there are iron filings, burrs, dust and other foreign matters in Timken bearing, which will make the bearing produce noise and vibration during operation, and even damage the raceway and rolling element. Therefore, before installing the bearing, you must ensure that the installation surface and installation condition are clean.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Must the bearing be cleaned before installation? The surface of the joint bearing is coated with antirust oil. You must carefully clean it with clean gasoline or oil, and then apply clean, high-quality or high-speed and high-temperature lubricating grease before installation and application. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The influence of cleanliness on bearing life and vibration noise is often large. However, we would like to remind you that there is no need to clean and refuel the fully sealed bearing.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The bearing temperature can generally be estimated according to the external temperature of the bearing seat. However, it is more accurate to directly measure the temperature of the bearing outer ring with the oil hole. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The bearing temperature rises gradually from the beginning of operation, and the temperature is usually stable after 1 ~ 2 hours. If Timken bearing device is poor, the temperature will rise sharply, showing abnormal high temperature. The reasons are such as too much smoothing agent, too small bearing clearance, poor device, excessive seal installation friction and so on.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The rotating sound of the bearing is checked with a stethoscope, and there are strong metal noise, abnormal sound, irregular sound and other abnormalities. The reasons are poor smoothness, poor accuracy of sWhat should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Selection and control of tolerance of shaft and bearing chamber: Timken bearing is pressed into the bearing chamber and rotates by hand. If there is an obvious “rusty” feeling, it may be that the tolerance of shaft is too large or the roundness of shaft is not good.
  •  If the bearing is pressed into the bearing chamber, 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.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  •  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.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Prevention of assembly foreign matters: when the articulated 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. What should be paid attention to in order to prolong the life cycle of outer spherical 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.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  •  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.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Bearing assembly method: because the bearing is a high-precision product, if it is not assembled properly, it is easy to damage the joint bearing channel, resulting in bearing damage. The bearing shall be equipped with a special mold during assembly, which cannot be knocked at will. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • When pressing the shaft, only the small ring can be stressed, and when pressing the large ring, only the large ring can be stressed. Pneumatic or hydraulic pressure is required during assembly. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • 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 Timken bearing will produce conduction sound.
  • 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 noise of the motor becomes very large, and there is serious rust when removing the bearing. 
  • In the past, many manufacturers thought it was the bearing problem. 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 joint bearing channel and leads to the damage of Timken bearing. At present, the problem can only be to select good insulating paint and assemble after drying and ventilation for a period of time.
  • “Listening”: listen to the abnormal sound of wheel vibration and the friction sound of thrust ball bearing when the train enters the station. Careful train arrival inspection is the primary link for early detection of bearing failure. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • At present, the vehicles in use have many defects, such as tread peeling, local scratch and so on, resulting in excessive vibration of wheels in use, which has a very harmful impact on bearings and parts. Therefore, when the train arrives at the station for inspection, we should concentrate on the detailed inspection of the rolling bearing with large vibration, so as to find the hot shaft fault as soon as possible.
  • In “look”: appearance fault characteristics of thrust ball bearing. All bearings that fail will be reflected from the appearance. Different faults reflect different characteristics. These features are no more than the following:
  • Large clearance between thrust ball bearing jacket and sealing cover, grease overflow, discoloration, bearing outward movement, crack damage, corrosion, etc. Once the appearance fault features are found during the inspection, it is necessary to make careful judgment and determine the exact location of the fault. 
  • The clearance between the outer ring of the shaft end and the two sealing covers is too large. Check the 197726 bearing vehicle and find that the clearance between the front and rear ends of the bearing outer ring and the sealing cover is too large, and there is more grease overflow, which is the collapse of the bearing outer ring.
  • Oil rejection of the sealing covers at both ends of the thrust ball bearing is a common bearing surface fault. If it is found that the sealing cover is not loose due to oil throwing, it can continue to be assembled and used after wiping off the oil dirt. However, it must be noted that if there is oil leakage due to cracks at the mouth of the outer ring, it shall be returned and scrapped.
  • This is also a common fault. If it is only found that the steel wire is broken and the lead seal is lost, and the locking lug of the locking piece is still tightly attached to the six aspects of the front cover bolt, it proves that the bolt is not loose, it is necessary to confirm whether the thrust ball bearing moves outward. If it is found that the bearing moves outward, it should be demounted if the axial clearance is too large.
  • This kind of fault is relatively rare. If the outer ring of the bearing is seriously rusted and covered with corrosion pits during operation inspection, it shall be returned and disassembled. Electric corrosion of bearing. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The electric corrosion of thrust ball bearing is caused by the current passing through the bearing during the electric welding operation on the bogie or the upper part of the vehicle body. Therefore, during the electric welding operation on the bogie or the upper part of the vehicle body, electric corrosion caused by current passing through the bearing shall be prevented. What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • During operation, if it is found that there is a molten pit damaged by electric spark on the tread of the same section where the wheel of the wheel set contacts with the steel rail and on the outside of the rim, the thrust ball bearing shall be disassembled and inspected.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • Timken bearing grease is usually expressed by apparent viscosity or similar viscosity. When describing the viscosity of grease, the temperature and shear speed must be indicated. Similar viscosity indexes can be used to control its low-temperature fluidity and pumpability.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • One of the important indexes to measure the low-temperature performance of thrust ball bearing grease is the low-temperature torque, that is, the degree to which the grease blocks the rotation of low-speed flow bearing at low temperature (below – 20 ° C). The Low-Temperature Torque of grease is expressed by the average value of starting torque and torque after rotating for 60mm.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  • The evaporation (degree) of Timken bearing grease indicates the degree of volatilization of grease oil when the grease is used for a long time under high temperature conditions. The smaller the evaporation, the better. The evaporation of grease mainly depends on the properties and fraction composition of lubricating oil.
  • Oxidation stability refers to the ability of lubricating grease to resist the action of heat and oxygen and keep its properties from permanent change when it is stored for a long time or used at high temperature for a long time.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
  •  Due to oxidation, the content of free alkali is often reduced or the content of free organic acid is increased, the dropping point is reduced, the appearance color is darker, there is a strange odor, the consistency, strength limit and similar viscosity are reduced, and corrosive products and substances that destroy the structure of lubricating grease are generated, resulting in the separation of soap and oil. 
  • Therefore, in the long-term storage of lubricating grease, it should be stored in a dry and ventilated environment to prevent exposure to the sun, and the changes of free alkali or free organic acid, corrosivity and other items should be regularly checked to ensure its quality and performance.What should be paid attention to in order to prolong the life cycle of outer spherical bearing
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