Vibration and temperature inspection of SKF one-way thrust ball bearing
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Precautions against bearing running noise and overheating

The application of material surface bearing running

  • There are great differences between the working surface and the center of bearing parts in terms of state, structure and performance requirements. However, the overall heat treatment often fails to take into account, and the potential of materials cannot be brought into full play. 
  • The application of material surface strengthening technology can not only better solve the differences between the surface and the center in terms of structure and requirements, but also further enable the surface to obtain some special working properties, so as to meet the working surface performance requirements of bearings working under specific conditions. 
  • This is of great significance in the development of modern science and technology. The traditional surface strengthening method belongs to the category of heat treatment. The surface strengthening methods developed in modern times, such as laser, electron beam and ion beam, not only apply some high and new technologies to the surface strengthening of materials, but also go beyond the traditional heat treatment in technology and form a new technical field. 
  • Therefore, the current surface strengthening technology can form a variety of classification methods from different angles. According to the physical and chemical processes of surface strengthening technology, it can be roughly divided into five categories: surface deformation strengthening, surface heat treatment strengthening, chemical heat treatment strengthening, surface metallurgy strengthening and surface film strengthening.Precautions against bearing running noise and overheating
  • The metal surface layer is plastically deformed by mechanical methods to form a hardened layer with high hardness and strength. This surface strengthening method is called surface deformation strengthening, also known as work hardening. Including shot blasting, sand blasting, cold extrusion, rolling, cold rolling and impact, explosion impact strengthening, etc.Precautions against bearing running noise and overheating
  •  The characteristics of these methods are: the strengthened layer dislocation density is increased, the sub crystal structure is refined, so that the hardness and strength are improved, and the surface roughness value is reduced, which can significantly improve the surface fatigue strength of parts and reduce the sensitivity of fatigue notch. This strengthening method has the advantages of simple process and remarkable effect. Precautions against bearing running noise and overheating
  • There is no obvious boundary between the hardened layer and the matrix, the structure is coherent, and it is not easy to fall off in use. Most of these methods have been applied in the bearing industry: the surface impact strengthening of rolling elements is the application of these methods, and precision rolling has become a new ring processing and strengthening method.Precautions against bearing running noise and overheating
  • Quenching the surface layer of parts by means of solid phase transformation and rapid heating is called surface heat treatment, commonly known as surface quenching. It includes flame heating quenching, high (medium) frequency induction heating quenching, laser heating or electron beam heating quenching, etc.Precautions against bearing running noise and overheating
  •  The characteristics of these methods are: the surface is locally heated and quenched, and the workpiece deformation is small; Fast heating speed and high production efficiency; The heating time is short, and the surface oxidation decarburization is very slight.Precautions against bearing running noise and overheating
  • Continuous vacuum dryer, this model is a comprehensive development of structural spray drying and freeze drying. The working process is carried out in a low-temperature environment. The dry environment should be kept in a low-temperature state.Precautions against bearing running noise and overheating
  •  First, the equipment itself should be equipped with high-performance cooling components. Second, the heat dissipation performance of the equipment itself is better. This requires that the performance of the bearing must meet the requirements of low-temperature resistance and high heat dissipation.Precautions against bearing running noise and overheating
  • Vacuum disc continuous dryer is mainly used to dry heat sensitive materials, and its drying process is carried out under negative pressure. In the process of machining, due to the different space pressure, the equipment may have a small amount of expansion and contraction changes, which will have a great impact on the equipment components for a long time.Precautions against bearing running noise and overheating
  •  This requires that the bearing has higher toughness and the clearance can be adjusted freely in a small range. To ensure that the above performance bearing products are purchased, it is necessary to further understand the bearing code interpretation.Precautions against bearing running noise and overheating
  • Double cone rotary vacuum dryer is mainly used to dry powder, granular and fibrous materials. According to these dry materials, it can be judged that the working environment is dirty and there is a lot of floating dust, which requires high dust-proof performance of the bearing. Precautions against bearing running noise and overheating
  • Another is the mechanism of the equipment itself. This model adopts two-stage belt / chain elastic connection, so the equipment operates stably. To achieve high-speed and stable operation of the equipment, the rotating parts are bearings.Precautions against bearing running noise and overheating
  • When the grease performance of the bearing is poor under the radial load, the “click, click” noise will be heard at the initial stage of operation. This is mainly due to the noise generated by the sudden acceleration of the rolling element and its collision with the cage after the rolling element leaves the load area. This kind of impact sound is inevitable but will disappear after a period of operation.Precautions against bearing running noise and overheating
  • Measures to prevent cage noise are as follows:Precautions against bearing running noise and overheating
  • In order to make the cage rotate stably, the ring type should be adopted as far as possible and the surface should be fully lubricated. The structure of tapered roller bearing under high-speed working conditions should be improved. The L-shaped cage of roller should be changed into the Z-shaped cage with ring edge.Precautions against bearing running noise and overheating
Precautions against bearing running noise and overheating

Pay attention bearing running

  • The bearing shall rotate flexibly without blockage after being pressed into the bearing. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large, and the tolerance should be adjusted. If the thrust cylindrical roller bearing rotates by hand after being pressed into the shaft, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good.Precautions against bearing running noise and overheating
  • Therefore, the roundness should also be controlled when controlling the shaft and bearing housing tolerances. At present, many domestic manufacturers only control the tolerances, but do not control the roundness.Precautions against bearing running noise and overheating
  • Because the bearing is a high-precision product, it is easy to damage the bearing channel if it is improperly assembled, resulting in bearing damage. The thrust cylindrical roller bearing shall be equipped with a special mold during assembly, and can not be knocked at will. Precautions against bearing running noise and overheating
  • When pressing the shaft, only a small circle can be stressed, and when pressing a large circle, only a large circle can be stressed. Pneumatic or hydraulic pressure is required during assembly. The upper and lower moulds shall be outside the horizontal state during press assembly. If there is inclination, the bearing channel will be damaged due to stress and the bearing will make a guide sound.Precautions against bearing running noise and overheating
  • What should be done when the bearing temperature rises:Precautions against bearing running noise and overheating
  • When the bearing temperature rises, first judge whether there is misoperation. If it does rise, the following measures shall be taken:
  • Check whether the oil level of the oil indicator is normal. If not, check whether the oil drain valve of the oil tank is tightly closed. If it has been closed tightly, it shall be filled with oil. If it is leakage of sealant gasket, it shall be shut down for treatment.Precautions against bearing running noise and overheating
  • Take an oil sample to observe whether the oil color has changed, and conduct laboratory test to see whether it has deteriorated. If the deterioration is confirmed, stop the machine and replace the oil.Precautions against bearing running noise and overheating
  • Check whether the bearing has abnormal sound and whether the bearing swing is abnormal.Precautions against bearing running noise and overheating
  • Check the oil pressure of the governor. If the oil pressure is low, the cooling water hydraulic valve may be closed.
  • Check whether the cooling water pressure, water flow and pipeline system are normal. If the filter is blocked due to low water pressure and cannot be handled in time, it can be shut down for treatment. When it is confirmed that it can work, it can be put into use.Precautions against bearing running noise and overheating
  • First, let’s take a look at the reasons for the bearing temperature rise:Precautions against bearing running noise and overheating
  • It may be that the oil quality of the bearing is deteriorated, the oil itself is not clean, or the oil is deteriorated during operation. For example, the increase of water in the oil will increase the acidity of the oil, reduce the lubricating effect of the oil, cause the bearing bush to be corroded, and cause the bearing temperature to rise.Precautions against bearing running noise and overheating
  • It may be caused by the interruption of cooling water of the bearing.Precautions against bearing running noise and overheating
  • The bearing shows strong regularity and good repeatability during its use. When the normal high-quality bearing (linear bearing) is used at the beginning, the vibration and noise are relatively small, but the frequency spectrum is somewhat messy 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 of the frequency. The frequency spectrum above three times of the power frequency rarely appears, and the bearing state is very undisturbed, entering the undisturbed working period.Precautions against bearing running noise and overheating
  • At the later stage of operation, the vibration and noise of the bearing began to increase, sometimes with abnormal sound, but the vibration increased slowly. At this time, the kurtosis value of the bearing began to suddenly reach a certain value. We believe that at this time, the bearing shows initial failure.Precautions against bearing running noise and overheating
  • In order to maintain the original function of the bearing in good condition for as long as possible, it is necessary to maintain, inspect and prevent accidents, ensure the reliability of operation and improve productivity and economy. Precautions against bearing running noise and overheating
  • Maintain the scale of corresponding machinery operation premise on schedule. The contents include supervision of operation status, supplement or change of lubricant, and inspection of regular disassembly. As inspection items during operation, there are rotating sound, vibration, temperature, lubricant state, etc. of the bearing.
  • Bearing cleaning: when disassembling the lower bearing for inspection, first record the appearance of the bearing, confirm the residual amount of lubricant, and then clean the bearing after sampling the lubricant for inspection. As a cleaning agent, gasoline and kerosene are commonly used.Precautions against bearing running noise and overheating
  • The removed bearings shall be cleaned in coarse cleaning and fine cleaning. They shall be placed in the container respectively. The metal mesh pad shall be placed at the bottom first so that the bearings do not directly contact the dirt in the container. Precautions against bearing running noise and overheating
  • During rough cleaning, if the bearing rotates with dirt, it will damage the moving 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.Precautions against bearing running noise and overheating
  • Fine cleaning means that the bearing is carefully cleaned while rotating in the cleaning oil. In addition, the cleaning oil should always be kept clean.Precautions against bearing running noise and overheating

Measures to prevent cage noise are as follows bearing running overheating

  • When the bearing rotates at high speed, the vibration amplitude of the cage of the bearing with large pocket clearance is much larger than that of the cage with small pocket clearance, so the value of the pocket clearance is particularly important.Precautions against bearing running noise and overheating
  • Improve the manufacturing accuracy of the cage as much as possible, improve the surface quality of the cage, and reduce the noise caused by the collision or friction between the rolling element and the cage.Precautions against bearing running noise and overheating
  • Actively adopt advanced cleaning technology to effectively and thoroughly clean spare parts and assembled products to improve the cleanliness of bearings.
  • Selection and control of shaft and bearing housing tolerance: the bearing shall rotate flexibly without blocking feeling after being pressed in. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large, and the tolerance should be adjusted. 
  • If the tapered roller bearing rotates by hand after being pressed into the shaft, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good. Therefore, the roundness should also be controlled when controlling the shaft and bearing housing tolerances. At present, many domestic manufacturers only control the tolerances, but do not control the roundness.Precautions against bearing running noise and overheating
  • Assembly method of bearing: because the bearing is a high-precision product, if it is improperly assembled, it is easy to damage the groove of tapered roller bearing, resulting in bearing damage. The bearing shall be equipped with a special mold during assembly, and can not be knocked at will.Precautions against bearing running noise and overheating
  •  When pressing the shaft, only the small circle can be stressed, and when pressing the large circle, only the large circle can be stressed. Pneumatic or hydraulic pressure is required during assembly. During press assembly, the upper and lower touch shall be outside the horizontal state. If there is inclination, the bearing channel will be damaged due to stress, and the bearing will produce conducting sound.Precautions against bearing running noise and overheating
  • Prevention of assembly foreign matters: when the tapered roller bearing is installed on the rotor for dynamic balancing, it is easy to put the iron filings generated during dynamic balancing into the bearing, so it is necessary to perform dynamic balancing before installing the bearing. Precautions against bearing running noise and overheating
  • In order to facilitate assembly, some manufacturers apply some oil or grease in the bearing chamber for lubrication, but it is often difficult for operators to control the amount. If there is a large amount of oil or grease in the bearing chamber, it is easy to enter the bearing along the shaft when the bearing rotates.
  •  The bearing chamber shall not be coated with oil or grease. If it must be coated, it shall be controlled that there shall be no accumulation in the bearing chamber.Precautions against bearing running noise and overheating
  • Prevention of paint rust: paint rust is often found in sealed motors. The sound of the motor is very good during assembly, but after it has been stored in the warehouse for some time, the abnormal noise of the motor becomes very large, and there is serious rust when the tapered roller bearing is removed. In the past, many manufacturers thought it was the bearing problem. Precautions against bearing running noise and overheating
  • After our continuous publicity, the motor factory has realized that the main problem is the insulation paint. The main reason for this problem is that the acid substances volatilized from the insulating paint form corrosive substances at a certain temperature and humidity, which corrode the bearing channel and cause bearing damage. At present, only good insulating paint can be selected and assembled after drying and ventilation for a period of time.
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