Preventive measures for bearing running noise and overheating
Preventive measures for bearing running noise and overheating
2022年5月26日
Precautions against bearing running noise and overheating
Precautions against bearing running noise and overheating
2022年5月28日

Vibration and temperature inspection of SKF one-way thrust ball bearing

Temperature of one-way thrust ball bearing

 
  • Vibration of one-way thrust ball bearing is very sensitive to bearing damage, such as spalling, indentation, corrosion, crack, wear, etc., which will be reflected in the vibration measurement of SKF Bearing. Therefore, the vibration can be measured by using a special bearing vibration meter (frequency analyzer, etc.), and the specific abnormal conditions can not be inferred from the frequency analysis.Vibration and temperature inspection of SKF one-way thrust ball bearing
  •  The measured values are different due to the service conditions of the bearing or the installation position of the sensor. Therefore, it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment standard.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • The temperature of the one-way thrust ball bearing can generally be inferred from the temperature outside the bearing chamber. It is more appropriate if the outer ring temperature of the bearing can be directly measured by using the oil hole.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • Generally, the temperature of SKF 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.Vibration and temperature inspection of SKF one-way thrust ball bearing
  •  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.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • 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 accidents.
  • High temperature often indicates that the bearing is in abnormal condition. High temperature is also harmful to the lubricant of SKF bearings. Sometimes bearing overheating can be attributed to the lubricant of the bearing. Vibration and temperature inspection of SKF one-way thrust ball bearing
  • If the temperature of the bearing exceeds 125 ℃ for a long time, the service life of the bearing will be reduced. The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. It contains impurities, excessive load, SKF Bearing Ring damage, insufficient clearance, high friction caused by oil seal, etc.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • Therefore, it is necessary to continuously monitor the SKF Bearing Temperature, whether it is the bearing itself or other important parts. If the operating conditions remain unchanged, any temperature change can indicate that a fault has occurred.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • The periodic measurement of SKF Bearing temperature can be aided by a thermometer, such as a digital thermometer, which can accurately measure the bearing temperature and display it in units of ℃ or Fahrenheit.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • The important SKF Bearing means that when it is damaged, the equipment will be shut down. Therefore, this kind of bearing should be equipped with a temperature detector.Vibration and temperature inspection of SKF one-way thrust ball bearing
Vibration and temperature inspection of SKF one-way thrust ball bearing

Vibration of single direction thrust ball bearing

  • Under normal conditions, SKF bearings will have a natural temperature rise after lubrication or re lubrication and last for one or two days. There are many reasons for the failure of SKF thrust ball bearing. All the influencing factors in the design and manufacturing process are related to the failure of thrust ball bearing, which is difficult to judge by analysis. In general, it can be considered and analyzed from two aspects: use factors and internal factors.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • The use factor mainly refers to whether the installation adjustment, use and maintenance, maintenance and repair meet the technical requirements. The installation condition is one of the primary factors in the use factors. The improper installation of the thrust ball bearing often leads to the change of the stress state between the parts of the whole thrust ball bearing, and the thrust ball bearing operates under abnormal conditions and fails early. Vibration and temperature inspection of SKF one-way thrust ball bearing
  • According to the technical requirements for the installation, use, maintenance and repair of thrust ball bearings, the load, speed, operating temperature, vibration, noise and lubrication conditions borne by the thrust ball bearings in operation shall be monitored and checked.Vibration and temperature inspection of SKF one-way thrust ball bearing
  •  In case of any abnormality, the cause shall be immediately found and adjusted to make them return to normal. In addition, it is also important to analyze and test the quality of lubricating grease and the surrounding medium and atmosphere.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • Internal factors mainly refer to the three major factors that determine the quality of thrust ball bearings, such as structural design, manufacturing process and material quality.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • First of all, long service life of thrust ball bearing can be achieved only when the structure design is reasonable and progressiveness is available. The manufacturing of thrust ball bearings generally involves forging, heat treatment, turning, grinding and assembly. The rationality, progressiveness and stability of each processing technology will also affect the service life of thrust ball bearings. Vibration and temperature inspection of SKF one-way thrust ball bearing
  • The heat treatment and grinding processes that affect the quality of finished thrust ball bearings are often more directly related to the failure of thrust ball bearings. In recent years, the research on the working surface of thrust ball bearings shows that the grinding process is closely related to the surface quality of thrust ball bearings.
  • The metallurgical quality of SKF thrust ball bearing material was once the main factor affecting the early failure of rolling thrust ball bearings. With the development of metallurgical technology, such as vacuum degassing of thrust ball bearing steel, the quality of raw materials has been improved. 
  • The proportion of raw material quality in the failure analysis of thrust ball bearings has decreased significantly, but it is still one of the main factors affecting the failure of thrust ball bearings. Proper material selection is still a factor that must be considered in failure analysis of thrust ball bearings.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • The main task of SKF thrust ball bearing failure analysis is to find out the main factors causing thrust ball bearing failure according to a large number of background materials, analysis data and failure forms, so as to put forward targeted improvement measures, extend the service life of thrust ball bearings and avoid sudden early failure of thrust ball bearings. Vibration and temperature inspection of SKF one-way thrust ball bearing
  • SKF Bearing shows strong regularity and good repeatability in its use. When normal high-quality stainless steel bearings are used at the beginning, the vibration and noise are relatively small, but the frequency spectrum is somewhat scattered and the amplitude is small, which may be caused by some defects in the manufacturing process, such as surface burrs.
  • After a period of movement, the vibration and noise maintain a certain level, and the frequency spectrum is very single, with only one or two times the frequency. The frequency spectrum above three times of power frequency rarely appears. The stainless steel bearing is in a very stable state and enters a stable working period.
  • After continuous operation, the SKF Bearing began to increase in vibration and noise, and sometimes abnormal sound occurred, but the increase in vibration was an initial failure.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • Firstly, the non-ferrous element concentration is abnormal in the bearing spectrum analysis, and many sub micron wear particles of non-ferrous metal components appear in the ferrography; The water content and acid value of lubricating oil exceed the standard, indicating that the pad surface of SKF Bearing is corroded.
  • Secondly, the bearing spectrum analysis found that the iron concentration was abnormal. There were many submicron wear particles in the ferrogram, and the moisture and acid value of the lubricating oil were abnormal, indicating that the back of the bearing was worn due to fretting.
  • Third, there are iron cutting abrasive particles or black oxide particles in the ferrogram of stainless steel bearing, and there is tempering color on the metal surface, indicating that the journal surface of the bearing is strained.
  • Fourthly, cutting abrasive particles are found in the Ferrograph of SKF Bearing, and the abrasive particles are composed of non-ferrous metals, indicating that the surface of the bearing is strained.
  • Fifthly, the bearing spectral analysis found that the iron concentration was abnormal. There were many submicron particles of iron in the ferrogram, and the water content or acid value of the lubricating oil exceeded the standard, indicating that the journal surface of the needle roller bearing was corroded.
  • Now that we know the cause of SKF Bearing Failure, we mainly pay attention to these aspects. The service life of stainless steel bearings will naturally be longer.ball bearing
  • When external hard particles enter the bearing and are pressed between the body and the raceway, an indentation can be formed on the surface. In addition, excessive impact load can also cause local plastic deformation on the contact surface and form pits. When SKF Bearing is stationary, even if the load is very small, evenly distributed pits will be formed on the raceway due to the vibration of the surrounding environment.
  • When SKF Bearing is not well sealed, dust or particulate matter will enter the bearing, or poor lubrication will cause serious scratch or wear on the contact surface, and increase the vibration and noise of stainless steel bearing.

ball bearing structure and service conditions

  • Generally speaking, the correct use of rolling bearings can achieve fatigue life. However, in case of accidental early damage, it can no longer be used. Unlike fatigue life, this early damage is called a failure or accident. Most of them are caused by improper consideration of installation, use and lubrication, foreign matters invading from the outside or insufficient research on shaft and bearing seat.Vibration and temperature inspection of SKF one-way thrust ball bearing
  • The damage state of rolling bearings, such as the scratch of the ring flange of roller bearings, may be caused by insufficient lubricant, improper brand, defective oil supply and drainage structure, foreign matter intrusion, bearing installation error or excessive shaft deflection, or a combination of the above reasons.
  • Therefore, it is difficult to know the real cause of the damage only by investigating the bearing damage. However, if, on the basis of fully understanding the machine, working condition and peripheral structure of the bearing, the situation before and after the failure is clarified, and then combined with the damage of the bearing and a variety of related reasons for analysis, the recurrence of similar failures can be prevented. Representative causes of bearing damage and countermeasures.
  • Even if the advanced manufacturing technology is adopted to process the rolling bearing parts. Observe the change of reading with preload. Pre tightening method has its disadvantages, which are well known. The working surface always has the dial indicator against the bearing end face or the appropriate part of the shaft.
  • Bearing structure and service conditions. Different structures are suitable for different service conditions; The processing technology of automobile bearing parts with different structures will be different, which will affect their quality. 
  • Therefore, we should develop new structural products to adapt to different service conditions, and indicate their suitable service conditions or performance on the instructions for the use of rolling bearings, so as to facilitate the choice of customers.
  • Strengthen process research, improve processing technology, improve processing quality, and reduce the possibility of defects in processing. For example, in terms of heat treatment, for the inner and outer rings of large varieties, try to use the medium and lower quenching and heating temperature to adapt to extending the holding time to improve the alloy concentration and increase the fracture strength of martensite. 
  • On the premise of ensuring the quality, select a higher tempering temperature to enhance the impact toughness of the workpiece.
  • Improve processing monitoring means to promote the improvement of processing quality. Such as improving the monitoring of the curvature position of the flow channel, improving the overall performance of the automobile bearing after assembly, and improving the working condition of the rolling bearing.
  • It is a comprehensive technology to judge and predict the reliability and service performance of the bearing through the fault and deterioration of the bearing and the performance state parameters, identify and judge the position, cause and danger degree of the abnormal situation, and determine the repair and improvement methods. 
  • Therefore, the bearing fault diagnosis technology is not a simple fault detection (or monitoring) technology, nor is it a simple point inspection instrumentation. Correctly, quickly and effectively collect signals, process data, and identify and judge manually or automatically.
  •  In order to determine the scientific repair cycle, necessary tests and estimates of fatigue and wear life should be carried out according to the mechanism of various faults.
  • Bearing fatigue failure is a surface form of failure, which is mainly manifested in the initiation, propagation and fracture process of fatigue cracks, and the long-term impact of load failure under alternate conditions. Cracks are in two aspects:
  • On the surface, this is the effect of external load caused by the plastic deformation on the working surface and the periodic change of contact stress on the strain hardened surface during the rolling contact process of the bearing, and finally the formation of surface cracks between the two from the inner surface of the development of small cracks. Due to the “a” lubricant on the working surface, the open force severely strikes the wall and forces the cracks to move forward;
  • From the surface layer, under repeated pressure, the contact of the surface initially produces cracks at a certain depth at the place where the surface is exposed, and from the angle along the surface direction to a certain depth, from behind the surface of the contact surface, and beyond the surface, and finally forms corrosion stripping, leaving a horse pit.
  • From the bearing surface, or from the cracks in the surface layer, the two objectives (carburization, quenching and other surface heat treatment of parts, if there is uneven hardness, structure, and uneven internal stress and other disadvantages, the contact stress is generally affected by the opposite underground cracks. If the surface quality of parts is poor, there is a defect (oxidation, decarburization), poor friction or lubrication, and from the surface cracks. 
  • The methods to control the sound of the raceway are as follows: select low-noise bearings, i.e. bearings with small waviness, and carefully select the service conditions. Raceway noise often affects the noise of the whole machine. Reducing raceway noise can reduce the noise of the whole machine. Before the bearing is delivered for routine inspection, its oil seal package can be removed, and it can be immersed in washing gasoline or acid free kerosene containing 3% engine oil. 
  • Rotate its outer ring and carefully wash the junction of cage, rolling element and raceway. It is required to thoroughly clean the original oil traces left in any concealed parts. After the bearing is cleaned, the attached cleaning oil shall be drenched and dried on the workbench lined with clean neutral lining paper or slowly dried in the far-infrared oven. The bearing ring, cage or any rolling element shall not be rotated during the whole process from rinsing oil to drying or drying.
  • The bearings that have been dried or dried shall be dripped with lubricating oil as required and immediately delivered for inspection. At this time, there is no oil film protection on the outer surface of the bearing. During the whole inspection process, the operator shall not directly touch the skin of the hands. 
  • The operator shall wear clean gloves or apply antirust agent on his hands. However, the antirust agent on his hands must not be mixed with the rolling surface of the bearing, otherwise the measurement results will be deviated.
  • After the inspection, the bearing shall be immediately delivered for use or treated with anti rust stock. The whole inspection process shall also be completed as soon as possible to avoid corrosion caused by too long. Note that the pure gasoline without engine oil can also cause corrosion.
  • Before inspection, the bearing must be placed on a metal plate in the inspection site together with the gauge block, standard parts and measuring instruments used for inspection, so as to quickly homogenize the temperature of these objects and room temperature.
  • 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 with hands, it should be normal not to feel hot. Otherwise, it indicates that the bearing temperature is too high.
  • The reasons for high bearing temperature include: 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.
  • Bearing noise: the rolling bearing is allowed to have 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 complex, because the mating surfaces of the inner and outer rings of the bearing are worn. Due to this kind of wear, the matching relationship between the bearing and the shell, the bearing and the 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. Insufficient bearing lubrication, dry friction and bearing breakage will produce abnormal sound. After the bearing is worn and loosened, the cage is loose and damaged, which will also produce abnormal noise and bearing damage. During the disassembly and inspection of rolling bearing, the fault and damage cause of bearing can be judged according to the damage of bearing.
  • Metal spalling on the raceway surface: both the bearing rolling element and the inner and outer raceway surfaces are subject to periodic fluctuating loads, resulting in periodic contact stress. When the number of stress cycles reaches a certain value, fatigue spalling will occur on the working surface of the rolling element or the inner and outer race raceways.
  •  If the load of the bearing is too large, the fatigue will be aggravated. In addition, improper bearing installation and shaft bending will also produce the phenomenon of raceway spalling. The fatigue spalling of the bearing raceway will reduce the operating accuracy of the shaft and cause vibration and noise of the mechanism.
  • The causes of bearing fracture include defect and overload. When the external load exceeds the material strength limit, the part fracture is called overload fracture. During the operation of the bearing, defects such as overheating tissue and local burns will also occur, resulting in defect fracture.
  • During the operation of the bearing, sometimes foreign hard particles or hard foreign matters or wear debris on the metal surface will be squeezed between the bearing surfaces, which will cause furrow like abrasion of the bearing. These hard foreign matters enter the bearing through the lubricating medium. With the continuous operation of the bearing, local friction generates heat, which is easy to cause local deformation of the friction surface and friction micro welding, or even local melting, and then cause occlusion.
  • Generally speaking, the bearing itself does not produce noise. The noise we are talking about is actually the sound effect of the bearing directly or indirectly vibrating with the surrounding structure.
  • Excitation caused by the change of the number of loaded rolling elements when a radial load is loaded on a bearing, the number of loaded rolling elements will change slightly during operation, that is, 2-3-2-3 This causes an offset in the direction of the load. The resulting vibration is inevitable, but can be mitigated by axial preloading on all rolling elements (not applicable to cylindrical roller bearings in bearings).
  • When the waviness of components is closely matched between the bearing ring and the bearing seat or the 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.
  • Local damage due to incorrect operation or installation, a small part of the bearing raceway and rolling element may be damaged. During operation, rolling over the damaged bearing parts will produce a specific vibration frequency.
  •  Vibration frequency analysis can identify damaged bearing components. Vibration behavior in applications in many applications, the stiffness of sliding bearings is the same as that of surrounding structures. Because of this feature, as long as the bearings (including preload and clearance) and their configuration in the application are correctly selected, it is possible to reduce the vibration in the application.
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