Performance of Koyo bearing material after heat treatment
Performance of Koyo bearing material after heat treatment
2022年5月5日
Impact of vibration on imported Koyo bearings
Impact of vibration on imported Koyo bearings
2022年5月7日

Key points and fault causes of fag bearing operation inspection

  • After fag bearing installation, in order to check whether the installation is correct, operation inspection shall be carried out. Small machinery can be rotated by hand to confirm whether it rotates smoothly. The inspection items include poor operation caused by foreign matters, scars and indentation, unstable torque caused by poor installation and poor processing of mounting base, excessive torque caused by too small clearance, installation error and sealing friction, etc. If there is no abnormality, the power operation can be started.Key points and fault causes of fag bearing operation inspection
  • Large machinery cannot rotate manually, so the power shall be cut off immediately after no-load start, and the machinery idles. Check whether there is vibration, noise, contact of rotating parts, etc. after confirming that there is no abnormality, enter the power operation.Key points and fault causes of fag bearing operation inspection
  • Power operation, starting from no-load and low speed, slowly increase to the rated operation under the specified conditions. During the test run, the inspection items are whether there is abnormal sound, FAG bearing temperature change, lubricant leakage or discoloration, etc. If any abnormality is found, stop the operation immediately, check the machinery, and remove the bearing for inspection if necessary.Key points and fault causes of fag bearing operation inspection
  • Fag bearing temperature can generally be inferred from the external temperature of bearing pedestal. However, it is more accurate to directly measure the temperature of the bearing outer ring by using the oil hole. The bearing temperature rises gradually from the beginning of operation, and the temperature is usually stable after 1 ~ 2 hours. If the bearing is not installed properly, the temperature will rise sharply, resulting in abnormal high temperature. Key points and fault causes of fag bearing operation inspection
  • The reasons are too much lubricant, too small bearing clearance, poor installation, excessive friction of sealing device, etc. In the case of high-speed rotation, the wrong selection of fag imported bearing structure and lubrication mode is also the reason.Key points and fault causes of fag bearing operation inspection
  • The rotating sound of fag bearing is checked with stethoscope, and there are strong metal noise, abnormal sound, irregular sound and other indications of abnormality. The reasons are poor lubrication, poor accuracy of shaft or bearing seat, bearing damage, foreign matter intrusion, etc.Key points and fault causes of fag bearing operation inspection

Common faults of fag bearing are as follows:Key points and fault causes of fag bearing operation inspection

  • Tile surface corrosion: abnormal concentration of non-ferrous metal elements is found by spectral analysis; Submicron wear particles with many non-ferrous metal components appear in ferrography; The water content and acid value of lubricating oil exceed the standard.Key points and fault causes of fag bearing operation inspection
  • Journal surface strain: there are ferrous cutting abrasive particles or black oxide particles in the ferrogram, and there is tempering color on the metal surface.Key points and fault causes of fag bearing operation inspection
  • Journal surface corrosion: the spectral analysis found that the concentration of iron was abnormal. There were many submicron particles of iron in the ferrogram, and the water content or acid value of lubricating oil exceeded the standard.Key points and fault causes of fag bearing operation inspection
  • Surface strain: cutting abrasive particles are found in the Ferrograph, and the abrasive particles are composed of non-ferrous metals.Key points and fault causes of fag bearing operation inspection
  • Fretting wear of tile back: abnormal iron concentration is found by spectral analysis. There are many iron components, submicron wear particles, abnormal moisture and acid value of lubricating oil in the ferrogram.Key points and fault causes of fag bearing operation inspection
  • Under the condition of liquid lubrication, the sliding surface is separated by the lubricating oil without direct contact, which can also greatly reduce the friction loss and surface wear, and the oil film also has a certain vibration absorption ability

Bearing maintenance is a necessary condition for fag bearing operation inspection 

  • The common maintenance is for bearing lubrication. After reading how to select the lubrication mode of bearing and understanding the lubrication mode of bearing, it is also necessary to understand the maintenance of bearing system. Let’s see how to carry out SKF Bearing Lubrication and maintenance.Key points and fault causes of fag bearing operation inspection
  • Keep the bearings lubricated clean
  • Before inspecting the SKF Bearing, the surface of the bearing shall be cleaned first, and then the oil seal of the bearing and its surrounding parts shall be carefully inspected. If there are bad symptoms, it must be replaced. The bad oil seal will cause damage, make the cloud shape of the bearing abnormal and cause the shutdown of the equipment.Key points and fault causes of fag bearing operation inspection
  • Take care to cover exposed bearings
  • When inspecting the bearing, do not 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. If it is possible to clean the naked bearing without disassembly, clean it with a brush coated with petroleum solvent, and then wipe it dry with a piece of lint free cloth or blow it dry with compressed air (be careful not to start the rotation of the bearing assembly). Key points and fault causes of fag bearing operation inspection
  • Use a small mirror and a probe similar to that used by dentists to check the track surface, retainer and beads of the bearing. Do not clean the sealed cover or dust-proof bearing; 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.Key points and fault causes of fag bearing operation inspection
  • Check the lubricant of the bearing
  • Lubricants are important not only for bearings, but also for all SKF bearings. However, please note that Japanese bearings should not add too much grease. Then it’s time to change the lubricant of the 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. Key points and fault causes of fag bearing operation inspection
  • Make the oil collect residual pollutants as much as possible, and then drain the oil. When replacing the grease of the bearing lubricated with grease, the Joe remover used shall avoid the contact of cotton with any part of the bearing. Because these residual fibers may wedge between rolling parts and cause damage, especially in bearing applications.Key points and fault causes of fag bearing operation inspection
  • Through these three steps, you can well maintain your bearing, greatly increase its service life and save your operation cost.
  • Not only the surface quality of SKF Bearing workpiece is poor, but also the crystal corrosion resistance of the workpiece is reduced. When the SKF Bearing workpiece is seriously overheated, it will produce coarse grains and increase the amount of 8 iron cable in the steel, which is easy to deteriorate the hot working performance of the workpiece. When the stainless steel box or flange is overheated, it is easy to produce orange peel surface defects.fag bearing operation inspection

 

Key points and fault causes of fag bearing operation inspection

It contains impurities, excessive load imported bearing

  • The use factors of NSK imported bearings mainly refer to whether the installation, adjustment, use and maintenance, maintenance and repair meet the technical requirements. According to the technical requirements of bearing installation, use, maintenance and repair, monitor and inspect the load, speed, working temperature, vibration, noise and lubrication conditions borne by the running bearing, find out the cause immediately and adjust it to make it return to normal.
  •  The installation condition is one of the primary factors in the use factors. The improper installation of the bearing often leads to the change of the stress state between the parts of the whole set of NSK imported bearing. The bearing operates in an abnormal state and ends its service life early. The internal factors mainly refer to the three factors that determine the quality of NSK imported bearing, such as structural design, manufacturing process and material quality.
  • The metallurgical quality of NSK imported bearing materials was once the main factor affecting the early failure of rolling bearings. With the progress of Metallurgical Technology (such as vacuum degassing of bearing steel), the quality of raw materials has been improved. 
  • The proportion of raw material quality factor in bearing failure analysis has decreased significantly, but it is still one of the main influencing factors of bearing failure. Proper material selection is still a factor that must be considered in the failure analysis of NSK imported bearings.
  • NSK imported bearings are generally manufactured through forging, heat treatment, turning, grinding and assembly. The rationality, progressiveness and stability of each processing technology will also affect the service life of the bearing. 
  • Among them, the heat treatment and grinding processes that affect the quality of finished NSK imported bearings are often more directly related to the failure of bearings. In recent years, the research on the metamorphic layer on the working surface of NSK imported bearings shows that the grinding process is closely related to the surface quality of NSK imported bearings.
  • The main task of service life analysis of NSK imported bearings is to find out the main factors causing bearing failure 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 NSK imported bearings and avoid sudden early failure of bearings.

Fag bearing operation inspection

  • To this end, the following preventive measures are proposed:Key points and fault causes of fag bearing operation inspection
  • The heating temperature of the stainless steel box and the heating time of the forged parts shall be strictly controlled to prevent overheating of the workpiece.Key points and fault causes of fag bearing operation inspection
  • In the production of workpiece forging, if the forging ratio is too small and the final forging temperature is too high, it is also easy to have coarse-grained structure defects. The forging ratio of workpiece should be appropriate and sufficient and the final forging temperature should be moderate.Key points and fault causes of fag bearing operation inspection
  • The solution treatment temperature of SKF Bearing workpiece should not be too high, the holding time should not be too long, the heating temperature should not be higher than 1150 “C, and the holding time should be calculated as 1-l_5min / mm.Key points and fault causes of fag bearing operation inspection
  • For the coarse workpiece with overheated structure, the method of forging and refining grain can be used to eliminate the defects, prevent the orange peel surface defects of the workpiece during cold deformation, and improve the surface quality of the workpiece.Key points and fault causes of fag bearing operation inspection

Contact fag bearing operation inspection

  • Contact fatigue failure refers to the failure of fag bearing working surface caused by alternating stress. Contact fatigue spalling occurs on the working surface of fag bearing, which 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. 
  • Due to the gradual expansion of the spalling surface, it often expands to the deep layer, forming deep spalling. Deep spalling is the fatigue source of contact fatigue failure.Key points and fault causes of fag bearing operation inspection
  • Wear failure
  • 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 fag bearing parts to be damaged gradually, and eventually lead to the loss of dimensional accuracy of fag bearing 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 fag bearing loses its rotation accuracy and even cannot operate normally. Wear failure is one of the common failure modes of various bearings. According to the wear form, it can be divided into common abrasive wear and adhesive wear.
  • Abrasive wear refers to the wear caused by the relative movement of the contact surface due to the extrusion of foreign hard particles or hard foreign matters or wear debris on the metal surface between the working surfaces of fag bearings, which often causes furrow like scratches on the working surfaces of bearings. Hard particles or foreign matters may come from the inside of the host machine or from other adjacent parts of the host system, and are sent into the fag bearing by the lubricating medium. 
  • Knowledge of fag bearing accuracy error.

  • Adhesive wear refers to the uneven stress on the friction surface due to the micro bulge or foreign matter on the friction surface. When the lubrication conditions are seriously deteriorated, the local deformation and friction micro welding of the friction surface are easy to be caused due to the heat generated by local friction. 
  • In serious cases, the surface metal may be locally melted, and the force on the contact surface will tear the local friction welding point from the substrate and increase the plastic deformation. This cycle of adhesion tear adhesion constitutes adhesive wear. Generally speaking, slight adhesive wear is called scratch and severe adhesive wear is called bite.
  • Fracture failure
  • The main causes of fag bearing fracture failure are defect and overload. When the external load exceeds the material strength limit and causes the part to break, it is called overload fracture. The main cause of overload is the sudden failure or improper installation of the host. Defects such as microcracks, shrinkage cavities, bubbles, large foreign objects, overheated tissue and local burns of bearing parts will also cause fracture at the defect during impact overload or violent vibration, which is called defect fracture. 
  • It should be pointed out that in the manufacturing process of fag bearing, the presence of the above defects can be correctly analyzed through instruments in the factory re inspection of raw materials, quality control of forging and heat treatment and processing process control, and the control must be strengthened in the future. But generally speaking, most of the fag bearing fracture failures are overload failures.
  • Clearance change failure
  • Fag bearing in operation, due to the influence of external or internal factors, the original matching clearance changes, the accuracy decreases, and even causes “bite” called clearance change failure. External factors such as excessive interference, improper installation, expansion caused by temperature rise, instantaneous overload, etc., and internal factors such as residual austenite and residual stress in an unstable state are the main reasons for the change and failure of clearance.
  • If fag bearing is well lubricated and properly blocked from sundries and moisture, it means that the oil seal should not be worn However, when opening the bearing housing, check the bearing and regularly check the oil seal Check the condition of oil seals near the bearing to ensure that they are sufficient to prevent hot liquid or corrosive liquid or gas from penetrating into the bearing along the axis. If the oil seal is worn, replace it as soon as possible
  • High temperature often indicates that fag bearing is in abnormal condition High temperatures are also harmful to lubricants in bearings Sometimes fag bearing overheating can be attributed to the lubricant of the bearing If the bearing operates for a long time at a temperature of more than 125 ℃, the service life of fag bearing will be reduced
  • The causes of high temperature fag bearing include insufficient or over lubrication, magazine in lubricant, excessive load, FAG bearing damage, insufficient clearance, high temperature friction caused by oil seal, etc
  • Check the condition of the running machine and monitor it to avoid equipment shutdown