Analysis of causes affecting NTN bearing failure
Analysis of causes affecting NTN bearing failure
2022-04-24
Purpose and principle of preloading NSK imported bearings
Purpose and principle of preloading NSK imported bearings
2022-04-24

Precautions for SKF Bearing in use

  • Although the quality of SKF bearings and other aspects are relatively good, SKF rolling bearings are precision components, and their use must be carried out with corresponding caution. No matter how high-performance SKF bearings are used, if they are not used properly, they will not get the expected high performance. There are the following precautions for the use of SKF bearings:Precautions for SKF Bearing in use
  • Keep SKF bearings and their surroundings clean.Precautions for SKF Bearing in use
  • Even small dust that cannot be seen by the eyes will have a bad impact on SKF bearings. Therefore, keep the surroundings clean so that dust will not invade the SKF Bearing.Precautions for SKF Bearing in use
  • Use with care.Precautions for SKF Bearing in use
  • Strong impact on SKF Bearing in use 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.Precautions for SKF Bearing in use
  • Use appropriate operating tools.Precautions for SKF Bearing in use
  • Avoid replacing with existing tools, and appropriate tools must be used.Precautions for SKF Bearing in use
  • Pay attention to the corrosion of SKF Bearing.Precautions for SKF Bearing in use
  • When operating SKF bearings, sweat on your hands can be the cause of rust. Pay attention to operate with clean hands and try to wear gloves. Size, direction and nature of NTN imported bearing load [the load capacity of the bearing is expressed by the basic rated load, and its value is contained in the bearing size table] the bearing load is rich in changes, such as the size of the load, whether there is only radial load, whether the axial load is unidirectional or bidirectional, the degree of vibration or impact, etc. After considering these factors, we can choose the appropriate bearing type.Precautions for SKF Bearing in use
  • Generally speaking, the radial load capacity of NTN imported bearings with the same inner diameter increases in the following order: deep groove ball bearing < angular contact ball bearing < cylindrical roller bearing < tapered roller bearing < self-aligning roller bearing
  • The analysis of the relative inclination between the inner ring and the outer ring is the factor that causes the relative inclination between the inner ring and the outer ring of the bearing (such as the deflection of the shaft caused by the load, the poor accuracy of the shaft and housing or installation error), and select the bearing type that can adapt to this service condition. If the relative inclination between the inner ring and the outer ring is too large, the bearing will be damaged due to internal load. Therefore, the type of bearing that can withstand this inclination should be selected.Precautions for SKF Bearing in use
  • Generally speaking, the allowable inclination angle (or centering angle) increases in the following order:
  • Cylindrical roller bearing, tapered roller bearing, deep groove ball bearing (angular contact ball bearing) and self-aligning roller (ball) bearing are NTN imported bearing types whose rigidity can meet the rigidity required by the mechanical shaft system [when the bearing bears load, the contact part between the rolling element and the raceway will produce elastic deformation. “High rigidity” refers to the small amount of deformation of this elastic deformation]. In the main shaft of machine tool and the final reducer of automobile, while improving the rigidity of the shaft, The rigidity of the bearing must also be improved.Precautions for SKF Bearing in use
  • The deformation of roller bearing under load is smaller than that of ball bearing. Applying preload (negative clearance) to the bearing can improve the rigidity. This method is suitable for angular contact ball bearings and tapered roller bearings.Precautions for SKF Bearing in use
  • The installation space of NTN imported bearing can be accommodated in the bearing installation space. Since the rigidity and strength of the shaft are paid attention to in the design of the shaft system, the shaft diameter, i.e. the inner diameter of the bearing, is generally determined first. However, rolling bearings have a variety of size series and types, and the appropriate bearing type should be selected from them.Precautions for SKF Bearing in use
  • The following bearings are generally used:Precautions for SKF Bearing in use
  • Deep groove ball bearing, contact ball bearing, cylindrical roller bearing
  • Rotation accuracy the type of bearing with the required rotation accuracy [the dimensional accuracy and rotation accuracy of the bearing have been standardized by GB according to the bearing type]? The spindle of machine tool, gas turbine and control machine require high rotation accuracy, high speed and low friction respectively. At this time, bearings with accuracy above grade 5 should be used.Precautions for SKF Bearing in use
  • The installation and disassembly frequency and methods of regular inspection of installation and disassembly. When the installation and disassembly are frequent, the cylindrical roller bearing with separable inner ring and outer ring, needle roller bearing and tapered roller bearing are more convenient.Precautions for SKF Bearing in use
Precautions for SKF Bearing in use

Precautions for SKF Bearing in use

  • The speed can adapt to the NTN imported bearing type of mechanical speed [the limit value benchmark of bearing speed is expressed by the limit speed, and its value is contained in the bearing size table] the limit speed of bearing is not only taken from the bearing type, but also limited to the bearing size, cage type, accuracy grade, load conditions and lubrication mode. Precautions for SKF Bearing in use
  • Therefore, these factors must be considered in the selection. Ina bearing temperature is too high: when the mechanism is running, the part where the bearing is installed is allowed to have a certain temperature. When touching the mechanism shell by hand, it should be normal not to feel hot. Otherwise, it indicates that the bearing temperature is too high.Precautions for SKF Bearing in use
  • The reasons for the high temperature of INA Bearing are: the quality of lubricating oil does not meet the requirements or deteriorates, and the viscosity of lubricating oil is too high; The mechanism assembly is too tight (insufficient clearance); The bearing assembly is too tight; The bearing race rotates on the shaft or in the shell; Excessive load; Broken bearing cage or rolling element, etc.Precautions for SKF Bearing in use
  • INA Bearing Noise: the rolling bearing is allowed to make slight running noise during operation. If the noise is too loud or there is abnormal noise or impact sound, it indicates that the bearing is faulty. The reason for the noise of rolling bearing: it is more complex. It is the wear of the mating surfaces of the inner and outer rings of the bearing. Due to this kind of wear, the matching relationship between INA Bearing and shell, bearing and shaft is damaged, resulting in the axis deviation from the correct position and abnormal noise when the shaft moves at high speed. When the bearing is tired, the metal on its surface will peel off, which will also increase the radial clearance of the bearing and produce abnormal noise.Precautions for SKF Bearing in use
  • Insufficient bearing lubrication, dry friction and bearing breakage will produce abnormal sound. 3) After the bearing is worn and shaken, the cage is loose and damaged, which will also produce abnormal noise and damage to the bearing. During the disassembly and inspection of rolling bearing, the fault and damage cause of bearing can be judged according to the damage of bearing.Precautions for SKF Bearing in use
  • Metal spalling on the raceway surface: the rolling element of INA Bearing and the raceway surfaces of inner and outer rings are subjected to periodic pulsating load, resulting in periodic contact stress. When the number of stress cycles reaches a certain value, it will be produced on the working surface of rolling element or inner and outer race raceway.Precautions for SKF Bearing in use
  • Fatigue peeling. If the load of ina bearing is too large, this fatigue will be exacerbated. In addition, improper bearing installation and shaft bending will also produce raceway spalling. The fatigue spalling of bearing raceway will reduce the operation accuracy of shaft and cause vibration and noise of mechanism.Precautions for SKF Bearing in use
  • INA Bearing burn: the burned bearing has a return fire color on its raceway and rolling element. The causes of burns are generally insufficient lubrication, unqualified or deteriorated lubricating oil quality, and tight assembly of ina bearings.Precautions for SKF Bearing in use
  • Plastic deformation: uneven pits appear on the contact surface between raceway and roller of INA Bearing, indicating plastic deformation of bearing. The reason is that under the action of large static load or impact load, the local stress on the working surface of the bearing exceeds the yield limit of the material, which generally occurs on ina bearings rotating at low speed.Precautions for SKF Bearing in use
  • INA Bearing Race crack: the crack of bearing race may be caused by too tight bearing fit, loose bearing or inner ring, deformation of INA Bearing containing parts, poor surface processing of ina bearing installation, etc. In order to ensure the performance of rolling bearings and maintain long-term use under good conditions, NTN imported bearings must be inspected and maintained. Precautions for SKF Bearing in use
  • This inspection and maintenance is very important to prevent faults in advance. It is hoped that regular inspection and maintenance can be carried out according to the operation standards suitable for the operating conditions of the machine. Generally, the following methods are adopted: the inspection under the operating state is based on the rolling sound, vibration Check the temperature and the nature of the lubricant, and judge the supplement or replacement time of the lubricant.Precautions for SKF Bearing in use
  • NTN imported bearing inspection: fully observe the bearings removed due to the regular inspection and replacement of the machine, and check the condition of the raceway surface, whether there is damage and whether it can be reused. Due to the clearance of NSK imported bearing, the inner and outer rings will move relatively under the action of load, which will reduce the stiffness of NSK imported bearing, cause the radial and axial vibration of the shaft, and affect the working accuracy and service life of the machine.Precautions for SKF Bearing in use
  •  In order to reduce this vibration, for high-precision and high-speed mechanical equipment, the preloading method is often adopted when installing NSK imported bearing, that is, a certain load (radial or axial) is given to NSK imported bearing in advance during installation to eliminate its original clearance, and make NSK imported bearing body and inner and outer rings produce elastic deformation, so as to prevent relative movement between inner and outer rings during operation.Precautions for SKF Bearing in use
  • Preventive measures: improve the lubrication system and supplement or replace the lubricant regularly and properly
  • Non standard bearing operation:
  • Improper installation, operation or disassembly of the bearing may cause deformation or damage to the cage
  • Preventive measures: use proper operation, installation and disassembly tools, and use Beijing deruimei genuine NTN bearings.
  • Bearing rust and corrosion:
  • Contact with water may cause corrosion and rust of bearing elements. Rusted and damaged bearings may cause spalling during operation
  • Preventive measures: check the sealing regularly to ensure good sealing effect and store NTN bearings correctly
  • Bearing current:
  • Energizing the bearing while it is rotating may cause grooves or nicks. When the bearing is stationary, improper grounding of electrical operation will cause slight burns
  • Precautions: before welding components other than NTN bearings, reduce or avoid current through the bearings through appropriate grounding connections
  • Bearing external material:
  • Abrasive particle contamination and debris intrusion can cause wear, scratches and dents on the working surface of NTN bearings
  • Precautions: remove invading particles and debris, change lubricant and check sealing system
  • Bearing eccentricity:
  • Eccentricity, inclination or excessive load may lead to geometric stress concentration or surface spalling
  • Precautions: use accurately machined NTN bearing pedestal and shoulder
  • 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. High temperature often indicates that the bearing is in an abnormal condition. High temperature is also harmful to the lubricant of the bearing. Sometimes bearing overheating can be attributed to the lubricant of the bearing. If the bearing temperature exceeds 125 ℃ for a long time, the bearing life will be reduced. The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. The oil seal contains excessive clearance, insufficient friction, etc.
  • Therefore, it is necessary to continuously monitor the bearing temperature. NTN bearing is used to measure the bearing itself or other important parts. If the operating conditions remain unchanged, any temperature change can indicate that a fault has occurred. The periodic measurement of bearing temperature can be aided by thermometer, such as digital thermometer, which can accurately measure the bearing temperature and display it in ℃ or Fahrenheit.
  • Generally, the temperature of the bearing can be inferred from the temperature outside the bearing chamber. If the oil hole can be used to directly measure the temperature of the outer ring of the bearing, NTN bearing is more suitable. Usually, the temperature of the 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. NTN bearing is a precision part of imported bearings. The system realizes the optimization of workshop asset efficiency and maintenance work for the decision support of mechanical service, preventive maintenance means, condition monitoring and a series of maintenance work. Therefore, bearing plays a vital role in some industries. 
  • The shaft parts of machine tools, especially the spindle, are generally assembled with NSK Bearings or sliding bearings and rotate at a high speed, sometimes generating high heat. If this phenomenon is not eliminated in time, it will lead to overheating of the bearing and increase the temperature of the corresponding parts of the machine tool, resulting in thermal deformation.
  •  In serious cases, the height of the spindle and tailstock will be unequal, which will not only affect the accuracy and machining accuracy of the machine tool itself, but also burn out the bearing. The causes of main shaft bearing heating and its troubleshooting are shown in Table 1. In order to ensure the working condition of NTN bearing, it is necessary to avoid damage as much as possible. What should we do?
  • 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 can not be resistant to use. This early damage, as opposed to fatigue life, is called the quality service limit of 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 NTN bearing, for example, the clamping damage of the ring retaining edge of roller bearing can be considered as the reason. These reasons can 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.
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