Reasons for bearing noise, inspection methods, solutions, and storage methods

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The sound of a properly functioning bearing ❶ If a bearing is in good working condition, it will emit a low humming or buzzing sound. If sharp hissing, squealing noises, and other irregular sounds are heard, it often indicates that the bearings are not functioning properly. The sharp squeaking noise may be caused by improper lubrication. Improper bearing clearance can also cause metallic noise. ❷ Grooves on the outer ring race of the bearing can cause vibration and result in a smooth, crisp sound. ❸ If there is intermittent noise, it indicates that the rolling elements may be damaged. This sound occurs when the damaged surface is rolled over; the presence of contaminants in the bearing often causes a hissing noise. Severe bearing damage can produce irregular and loud noises. ❹ Noise can also be generated by impact marks caused during installation, and this noise varies depending on the speed of rotation of the bearing. Abnormal bearing noise ► Loud metallic noise. Cause 1: Abnormal load. Solutions: Adjust the fit, examine the bearing clearance, adjust it in relation to the load, and correct the position of the housing shoulder. Reason 2: Poor installation. Countermeasure: Improve the machining accuracy of the shaft and housing, as well as the installation accuracy and method. Reason 3: Insufficient or inappropriate lubricant. Countermeasure: Add lubricant and select a suitable one. Reason 4: There is contact between rotating parts. Countermeasure: Modify the contact portion of the labyrinth seal. ►Regulatory noise – Cause 1: Debris causes indentations, rust, or scratches on the rolling surface. Solution: Replace the bearing, clean the relevant parts, improve the sealing mechanism, and use clean lubricant. Reason 2: Surface deformation (after steel carburizing); Solution: Replace the bearing and pay attention to its use. Reason 3: Raceway surface delamination; Solution: Replace the bearing. ►Irregular noise. Cause 1: Excessive clearance; Countermeasure: Study the fit and bearing clearance, and adjust the preload amount. Reason 2: Foreign object intrusion. Countermeasures: Consider replacing the bearings, cleaning the relevant parts, improving the sealing mechanism, and using clean lubricants. Reason 3: Spherical damage, peeling; Solution: Replace the bearing. Detection methods and instruments for abnormal bearing noises. Currently, there are two approaches to detecting abnormal noises in bearings. One is an acoustic-based noise detection method, and the other is a vibration-based detection method. (1) Noise detection method: This is a direct measurement method for abnormal sounds. It involves using a high-quality microphone to capture the sound pressure signals of bearings at a certain distance and direction in a noise-free environment where the background noise level is less than 20 dB. Subsequently, analytical methods are employed to extract any abnormal sound components from these signals. (II) Vibration detection method: It is an indirect method for detecting abnormal noises, and can be further divided into qualitative detection methods and quantitative parameter detection methods. Among them, qualitative detection methods are further divided into the method of listening for abnormal sounds and the method of observing vibration waveforms. The quantitative parameter detection method refers to the use of measured parameter values related to abnormal noises in the vibration signals of the bearing under test, such as the peak value of vibration and the peak factor, to evaluate the abnormal noises of the bearing. (III) Instruments for measuring abnormal noises of bearings: There are many instruments available for measuring abnormal noises of bearings; for example, the BANT-1 bearing abnormal noise monitor developed by the Hangzhou Bearing Testing and Research Center ； S092 bearing vibration (abnormal noise) measuring instrument from Shanghai Bearing Technology Research Institute ； S0910-Ⅲ, jointly developed by the Luoyang Bearing Research Institute and Dalian Bearing Instrument Factory. These bearing measurement instruments can measure the effective value of bearing vibration, as well as parameters reflecting abnormal sounds in bearings, such as peak values, peak factors, and the number of pulses. Proper storage method for bearings: 1. Keep them in their original packaging; do not open it arbitrarily. If the packaging is damaged, it must be opened, thoroughly cleaned, re-oiled, and then repackaged. 2. The relative humidity in the storage area should not exceed 60%, and the temperature difference should not be too large; bearings kept in their original packaging can be stored for several years. In sealed bearings or bearings with dust covers, the lubricating properties of the grease filled inside them may decline after long-term storage. 3. The storage room should also be protected from vibrations and shaking. Bearings that are not stored in their original packaging should be kept properly; it is strictly forbidden to store them alongside corrosive substances to prevent corrosion and contamination. 4. Large rolling bearings should be stored lying flat, with the sides of both the inner and outer rings preferably fully supported. If stored upright, the heavy inner and outer rings as well as the rolling elements, combined with the relatively thin walls of these rings, may cause permanent deformation. Causes of abnormal noises in bearings: 1. Impurities in the lubricant. 2. Insufficient lubrication (too low oil level, or improper storage leading to leakage of oil or grease through seals). 3. The clearance in the bearing is too small or too large (a problem caused by the manufacturer). 4. Impurities such as sand particles or carbon particles are present in the bearing, acting as abrasives. 5. Water, acids, paint, or other contaminants are present in the bearing, causing corrosion. 6. The bearing is compressed by the housing bore (poor roundness of the bore, or the bore being twisted). 7. The shims at the bottom of the bearing housing are not level, resulting in deformation of the bore or even cracks in the housing. 8. There are debris in the bearing bore (residual chips, dust particles, etc.). 9. The seal ring is eccentric, causing it to come into contact with adjacent parts and generate friction. 10. The bearing is subjected to additional loads (axial compression on the bearing, or two fixed-end bearings on the same shaft). 11. The fit between the bearing and the shaft is too loose (the shaft diameter is too small, or the retaining ring is not tightened properly). 12. The clearance in the bearing is too small, resulting in excessive tightness during rotation (the retaining ring is tightened too much)