SKF bearing limit speed problem and noise treatment method

(1) Rolling sound of imported bearings and its control method Rolling sound is a kind of slippery continuous sound that the rolling elements roll on the raceway surface when the bearing is running. It is the unique basic of all rolling bearings. sound. The general bearing sound is the rolling sound plus other sounds. The ball bearing's raceway sound is irregular, the frequency is above 1000Hz, its main frequency does not change with the speed, but its total sound pressure level increases with the increase of the speed. For bearings with large rolling sounds, the sound pressure level of the rolling track sound decreases with the increase of viscosity; while for SKF bearings with small rolling sound, the sound pressure level is reduced when the viscosity increases to above 20 mm2/s. Turned to increase. The greater the rigidity of the bearing housing, the lower the total sound pressure level of the raceway sound. If the radial clearance is too small, the total sound pressure level and main frequency of the raceway sound will increase sharply as the radial clearance decreases. The method of controlling the rolling sound is to select a low-noise bearing, that is, a bearing with a small waviness, and carefully select the conditions of use. The raceway sound often affects the noise of the entire machine, and reducing the raceway sound can reduce the noise of the entire machine.

(2) Impact sound of rolling element and its control method When the larger type of ball bearing or cylindrical roller bearing runs at low speed under pure radial load, the rolling element in the non-load area will be small due to the small centrifugal force of the rolling element. Noise is generated by impacting the cage or raceway. But as the speed increases, the sound will disappear. The control methods for the impact sound of the rolling element are: appropriately reducing the radial clearance, and using a bearing having a reasonable structure and a flexible material.

(3) Bearing rolling sound and its control method Rolling sound is a harsh metal friction sound that can occur in cylindrical roller bearings in all occasions, mostly in the grease-lubricated larger type SKF bearing, and in the base oil Greases with degraded performance are more likely to occur and hardly occur when oil is lubricated. In addition, it is more likely to occur in winter. When subjected to pure radial load, it is easy to occur in the case of large radial clearance, and it is easy to occur in a certain speed range depending on the size of the model, and it will occur continuously. It will appear intermittently. Foreign raceway take special processing methods to prevent sound jarring, use this bearing, if necessary or appropriate to reduce the radial bearing clearance, excellent performance and improve the grease to match the mechanical rigidity of the bearing .

Bearing lubrication methods are broadly classified into grease lubrication and oil lubrication. To fully utilize the bearing function, it is important to use the lubrication method for the purpose of reduction and use. Table 4-2 shows the advantages and disadvantages of grease lubrication and oil lubrication. Third, grease lubrication Grease is a lubricant composed of base oil, thickener and additives. When choosing, you should choose the oil that is very suitable for the bearing conditions. The trademarks will be different, and the performance will be very different. When choosing, you must pay attention.

Common greases for bearings include calcium-based greases, sodium-based greases, calcium-sodium-based greases, lithium-based greases, aluminum-based greases, and molybdenum disulfide greases.

The amount of grease filled in the SKF bearing is suitable for filling the inner space of the bearing by 1/2-1/3. It should be reduced to 1/3 at high speed. Excessive grease will increase the temperature rise. Fourth, the choice of grease When the working temperature is selected grease, the main indicators should be the dropping point, oxidation stability and low temperature performance, the dropping point can generally be used to evaluate the high temperature performance, the actual working temperature of the bearing should be lower than the dropping point of 10-20 °C. Synthetic grease should be used at a temperature below the drop point of 20-30 °C.

When selecting the grease for the bearing load, the small grease should be selected for the heavy load. When working under high pressure, in addition to the small penetration, it also has higher oil film strength and extreme pressure performance.

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Analysis of the causes of NSK bearing vibration and noise

Usually when we use imported bearings, the temperature rises after starting to run for a while, but the normal temperature is about 10~40 degrees. It is normal in the range of this value. Some bearings are operated in size and size. Different speeds and lubrication methods result in some bearings heating up slowly.

When the abnormal temperature rises when the NSK bearing does not reach the normal state, the following influencing factors can be considered, and then the rapid shutdown processing will inevitably cause unnecessary loss.

First, the main reason for the abnormal temperature rise of the bearing

Second, the bearing lubricant is too much or too little.

Third, the bearing is not properly installed.

Fourth, the internal clearance of the bearing is too small, or the load is too large.

Fifth, the friction of the bearing seal is too large.

Only if you know the cause of the temperature rise of the bearing clearly can you find a better solution.

Rolling bearings show late fault characteristics to serious faults (generally bearing damage such as axles, burns, sand cracks, raceways, bead wear, etc.) are not more than one week. The larger the equipment capacity, the faster the speed. The shorter the interval. Therefore, in the actual rolling bearing fault diagnosis, once the late fault characteristics are found, the NSK bearing should be judged decisively and the repair should be arranged as soon as possible.

Rolling bearing vibration and noise begin to increase

After a period of motion, the vibration and noise are maintained at a certain level, and the spectrum is very single, only one or two times the frequency. There are very few spectrums above the power frequency, and the bearing status is very stable and enters a stable working period. After continuing to run, the vibration and noise of the rolling bearing begin to increase, and sometimes abnormal sounds appear, but the change of vibration increases slowly. At this time, the bearing kurtness value suddenly reaches a certain value. We believe that the rolling bearing is an initial failure at this time.

NSK bearings are manufactured through multiple processes such as forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of each processing technology will also affect the life of the bearing. Thermal processing and grinding processes that affect the quality of scrap bearings are often more directly related to bearing failure. In recent years, the research on the turbulent layer of the bearing working surface indicates that the grinding process is closely related to the bearing surface quality.

The primary obligation of bearing life analysis is to find out the primary factors that constitute bearing failure based on a large number of configuration data, analysis data and failure mode, so as to propose improvement measures in a targeted manner, delay the decommissioning period of NSK bearings, and avoid bearings. An early failure of a sudden fire.

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