Normal operating bearing sound

①If the bearing is in good continuous running condition, it will emit a low moaning or buzzing sound. If sharp hissing, creaking, and other irregular sounds are emitted, it often indicates that the bearing is in poor continuous running condition. Sharp squeaking noise may be caused by improper lubrication. Improper bearing clearance can also cause metallic noise.

Abnormal bearing noise

► Large metal noise

Reason 1: Abnormal load, countermeasures: Correct the fit, study the bearing clearance, adjust the load, and correct the position of the housing shoulder.

Reason 2: Poor installation, countermeasures: The machining accuracy of the shaft and casing, improvement of installation accuracy, and installation methods.

Reason 3: Insufficient or unsuitable lubricant, countermeasure: Supplement lubricant and choose appropriate lubricant.

Reason 4: There is contact between rotating parts. Countermeasure: Modify the contact part of the curved seal.

► Regular noise

Reason 1: Due to foreign objects causing indentation, rust or scratches on the rolling surface, countermeasures include replacing bearings, cleaning relevant parts, improving sealing devices, and using clean lubricants.

Reason 2: (After carburizing the steel) Surface deformation, countermeasure: Replace the bearing and pay attention to its use.

Reason 3: Stripping of the raceway surface, countermeasure: Replace the bearing.

► Irregular noise

Reason 1: Excessive clearance. Countermeasure: Study the fit and bearing clearance, and modify the preload.

Reason 2: Foreign object intrusion, countermeasures: Research and replace bearings, clean relevant parts, improve sealing devices, and use clean lubricants.

Reason 3: Spherical surface damage and peeling, countermeasure: Replace the bearing.

Detection methods and instruments for abnormal noise in bearings

There are currently two ways to detect abnormal sound in bearings. One is acoustic based noise detection method, and the other is vibration based detection method.

（1） Noise detection method:

It is a direct measurement method for abnormal sound by using high-quality microphones to extract bearing sound pressure signals at a certain distance and direction in a silencing environment with basic noise less than 20dB, and extracting abnormal sound components through certain analysis methods.

（2） Vibration detection method:

It is an indirect detection method for abnormal sound, which can be divided into qualitative detection method and quantitative parameter detection method. Among them, qualitative detection methods are further divided into monitoring abnormal sound methods and observing vibration waveform methods. Quantitative parameter detection method refers to the use of measured parameter values related to abnormal sound in the measured bearing vibration signal, such as the peak value of vibration and wave crest factor, to evaluate the abnormal sound of the bearing.

（3） Measuring instruments for measuring abnormal sound of bearings:

There are many measuring instruments for measuring abnormal sound in bearings, such as the BANT-1 bearing abnormal sound monitor from Hangzhou Bearing Test and Research Center; S092 bearing vibration (abnormal sound) measuring instrument from Shanghai Bearing Technology Research Institute; S0910- III jointly developed by Luoyang Bearing Research Institute and Dalian Bearing Instrument Factory. These bearing measuring instruments can measure the effective value of bearing vibration as well as the peak value, Crest factor and pulse number that reflect the abnormal acoustic parameters of bearings.

1. Keep the original packaging and do not open it arbitrarily. If damage is found to the packaging, it must be carefully cleaned and repackaged with oil.

2. The relative humidity in the storage room should not exceed 60%, and the temperature difference should not be too large. Bearings placed in their original packaging can be stored for several years. Sealed bearings or bearings with dust covers may have reduced lubrication characteristics of the grease filled in the bearings after long-term storage.

3. The storage room should also be resistant to vibration and shaking. Bearings that are not stored in the original packaging should be properly stored. It is strictly prohibited to place bearings with corrosive substances to prevent corrosion and pollution.

4. When storing large rolling bearings, they can only be placed flat, and it is best to have all the sides of the inner and outer rings supported. If stored upright, permanent deformation may occur due to the heavier inner and outer rings and rolling components, while the inner and outer ring walls are relatively thin.

Reasons for Abnormal Bearing Noise

1. Oil contains impurities

2. Insufficient lubrication (oil level too low, improper storage resulting in oil or grease leakage through the seal)

3. The clearance of the bearing is too small or too large (manufacturer issue)

4. Impurities such as sand or carbon particles are mixed in the bearing to act as abrasive agents

5. Dirt such as water, acids, or paint mixed in the bearing can cause corrosion

6. The bearing is clamped flat by the seat hole (the roundness of the seat hole is not good, or the seat hole is twisted unevenly)

7. The pad iron on the bottom surface of the bearing seat is uneven (causing deformation of the seat hole and even cracking of the bearing seat)

8. There are impurities in the bearing seat hole (residual chips, dust particles, etc.)

9. Eccentricity of the sealing ring (rubbing against adjacent parts)

10. The shaft is subjected to additional loads (the shaft is subjected to axial tightness, or there are two fixed end bearings on one shaft)

11. The fit between the bearing and the shaft is too loose (the diameter of the shaft is too small or the locking sleeve is not tightened)

12. The clearance of the bearing is too small and it is too tight when rotating (the tightening sleeve is too tight)