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The Ultimate Guide:What a Bad Bearing Sounds like
Bearings are key components of mechanical equipment and automobiles, ensuring smooth operation and reducing friction between moving parts. During use, rolling bearings will change their load capacity, rotation accuracy, and friction performance due to their own quality and external conditions. When the performance indicators of a bearing are lower than the use requirements and it cannot work normally, it is called bearing damage or failure. Once a bearing is damaged or in an unexpected situation, various abnormal phenomena will occur, such as the machine or equipment stopping and the function being damaged. This blog aims to explore what a bad bearing sounds like, including the classification of bearing noise, the reasons for the noise, and how to deal with it. This is one of the important manifestations of bearing damage, and I hope to provide you with constructive suggestions for judging bearing failure.
If the bearing is in good rotation condition, it will sound a low humming or buzzing sound. If it sounds a sharp hissing sound, squeaking sound and other irregular sounds, it often indicates that the bearing is in poor condition. Sharp squeaking noises may be caused by improper lubrication. Improper bearing clearance can also cause sharp noises. Based on many years of bearing manufacturing experience, Aubearing has summarized the types of noises when poor bearings are running.
Noise description | Characteristics | Cause analysis |
ZA-ZA | Sound quality does not change with rotation speed (dust/foreign matter) | Dust/foreign matter |
GA-GA | Sound quality changes with rotation speed (scratches) | Track surface, ball, roller surface roughness |
CI-LA | Small bearings | Track surface, ball, roller surface roughness |
CI-LA | it happens intermittently and regularly. | Contact with the sealing ring part |
Contact with retainer and sealing cover | ||
WU-WU | Due to changes in rotation speed, the size and height change. The sound gets louder as it rotates at a certain speed. There are also times when it sounds like an alarm or a whistle. | Resonance, poor fit (poor shaft shape) |
DI-DI | Track surface deformation | |
Roar | Track surface, balls, and roller corrugations (if there is slight noise in large bearings, it is normal) | |
GA-ZI | Crunchy feeling when rotating manually | Track surface scratches (regular) |
Balls, roller scratches (irregularities) | ||
Dust/foreign matter, track surface deformation (some gaps are negative)… | ||
Rumble | Large bearings, small bearings with continuous sound at high speeds | Track surface, ball, roller surface scratches |
ZI-LA | Irregular occurrence (not caused by changes in rotation speed),Mainly small bearings | Mixed with dust/foreign matter |
Jingle Jingle Jingle | Tapered roller bearings: Regular and high-speed continuous tone large bearings small bearings | If the sound from the retainer is clear, it is normal. |
If the grease changes from uncomfortable to soft at low temperatures, it is considered good. | ||
Operation due to internal wear of the cage, insufficient lubrication, and insufficient bearing load. | ||
Hua La Hua La | Continuous sound at high speed | Impact sound inside the retainer, insufficient lubrication. The abnormal sound disappears after reducing the internal gap or preloading. |
In the case of all rollers, impact sounds between rollers will occur. | ||
Bang Bang | Loud metal impact sound,Low-speed thin-section large bearings (TTB), etc. | Rail wheel deformation |
Guang-Guang | The main reason is that the cylindrical roller bearing changes due to changes in rotation speed, and metallic sound can be heard when the sound is loud. After replenishing lubricant, it will stop for a while. | Lubricating oil is too thick |
Radial internal clearance is too large | ||
Not enough lubricant | ||
Qiang-Qiang | Metal-to-metal gnashing, sharp sound | Roller and rib bite of roller bearings |
Internal clearance is too small | ||
Not enough lubricant | ||
KA-PA | Irregular squeaking noise | Slippage of mating parts |
Squeaking noise from the mounting surface | ||
The squeak of keys etc. |
Detection method of abnormal bearing noise
There are currently two ways to detect abnormal bearing noise: one is based on acoustic noise detection, and the other is based on vibration detection.
Noise detection method
In an environment where the basic noise is less than 20db, a high-quality microphone is used to extract the bearing sound pressure signal at a certain distance and direction, and the abnormal sound components are extracted through a certain analysis method. This is a direct measurement method for abnormal sound. The auscultation method is used to monitor rolling bearings by contacting the outer shell of the measured bearing with one end of a tool such as a stethoscope, and placing the other end in the ear hole of the inspector to listen to the sound inside the bearing to determine the condition of the bearing. The commonly used tools for monitoring the working status of rolling bearings using the stethoscope method are stethoscopes or long screwdrivers with wooden handles, and hard plastic tubes with an outer diameter of about φ20mm can also be used.
Vibration detection method
The vibration detection method is an indirect detection method for abnormal sound, which can be divided into qualitative detection method and quantitative parameter detection method. Among them, the qualitative detection method is further divided into abnormal sound monitoring method and vibration waveform observation method. The quantitative parameter detection method refers to the use of the measured parameter values related to the abnormal sound in the vibration signal of the tested bearing, such as: the peak value of vibration, the crest factor to evaluate the abnormal sound of the bearing.
Symptoms of abnormal bearing noise
(1) The bearing emits a uniform and continuous “hissing” sound. This sound is generated by the rolling elements rotating in the inner and outer rings, and includes irregular metal vibration sounds that are unrelated to the speed. This generally indicates that the amount of grease added to the bearing is insufficient and should be replenished. If the equipment is shut down for too long, especially in low temperatures in winter, the bearing may sometimes make a “SISI-SASA” sound during operation. This is related to the reduction in the radial clearance of the bearing and the reduction in the working penetration of the grease. The bearing clearance should be adjusted appropriately and a new grease with a lower viscosity should be replaced.
(2) The bearing makes a uniform periodic sound in a continuous “HUA-HUA” sound. This sound is caused by scratches, grooves, and rust spots on the rolling elements and the inner and outer ring raceways. The period of the sound is proportional to the speed of the bearing. The bearing should be replaced.
(3) The bearing makes a discontinuous “GENG-GENG” sound. This sound is caused by the cracks in the retainer or the inner and outer rings. The bearing must be stopped immediately and replaced.
(4) The bearing makes an irregular and uneven “CA-CA” sound. This sound is caused by impurities such as iron filings and sand falling into the bearing. The sound intensity is low and has nothing to do with the speed. The bearing should be cleaned, re-greased or replaced.
(5) The bearing makes a continuous and irregular “SA-SA” sound. This sound is generally related to the loose fit between the inner ring of the bearing and the shaft or the loose fit between the outer ring and the bearing hole. When the sound intensity is high, the matching relationship of the bearing should be checked and repaired in time if problems are found.
(6) The bearing emits a continuous shrill whistling sound. This sound is caused by friction caused by poor bearing lubrication or lack of oil, or excessive contact of the rolling elements, such as deviation of the inner and outer ring raceways, or excessive fit of the inner and outer rings of the bearing. The bearing should be inspected in time to find out the problem and deal with it accordingly.
30 Causes of Bad Bearing Noise
1. Grease contains impurities;
2. Insufficient lubrication (the oil level is too low, improper storage causes oil or grease to leak through the seal);
3. The bearing clearance is too small or too large;
4. Impurities such as sand or carbon particles are mixed into the bearing, which acts as a grinder;
5. Water, acid or paint and other contaminants are mixed into the bearing, which will cause corrosion;
6. The bearing is pinched flat by the seat hole (the roundness of the seat hole is not good, or the seat hole is twisted and not straight);
7. The pad iron on the bottom surface of the bearing seat is uneven (leading to deformation of the seat hole or even cracks in the bearing seat);
8. There are debris in the bearing seat hole (remaining chips, dust particles, etc.);
9. The sealing ring is eccentric (hits adjacent parts and causes friction);
10. The bearing is subject to additional load (the bearing is axially tightened, 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 adapter sleeve is not tightened);
12. The clearance of the bearing is too small and it is too tight when rotating (the adapter sleeve is too tight);
13. The bearing has noise (caused by the end face of the roller or the steel ball slipping);
14. The thermal elongation of the shaft is too large (the bearing is subject to statically indefinite additional axial load);
15. The shaft shoulder is too large (hits the bearing seal and causes friction);
16. The shoulder of the seat hole is too large (distorting the seal of the bearing);
17. The gap of the labyrinth seal ring is too small (friction occurs with the shaft);
18. The teeth of the lock washer are bent (hit the bearing and cause friction);
19. The position of the oil slinger is inappropriate (hits the flange cover and causes friction);
20. There are pressure pits on the steel balls or rollers (caused by hitting the bearings with a hammer during installation);
21. The bearing has noise (interference from external vibration source);
22. The bearing changes color and deforms when heated (caused by using a spray gun to heat and disassemble the bearing);
23. The shaft is too thick and the actual fit is too tight (causing the bearing temperature to be too high or making noise);
24. The diameter of the seat hole is too small (causing the bearing temperature to be too high);
25. The diameter of the bearing seat hole is too large and the actual fit is too loose (the bearing temperature is too high – the outer ring slips);
26. The bearing seat hole becomes enlarged (the bearing seat hole of non-ferrous metal is enlarged or enlarged due to thermal expansion);
27. The cage is broken.
28. The bearing raceway is rusty.
29. Steel balls and raceways are worn (the grinding process is unqualified or the product is bruised).
30. The ferrule raceway is unqualified.
Bearing damage analysis and solutions
Bearing damage is related to many factors such as the power of the equipment, selection, design, manufacturing and installation quality, as well as operation mode and inspection and maintenance. They often interact with each other at the same time, and it is difficult to determine the cause. It is even difficult to solve. But there are still certain rules to follow. As long as we grasp the phenomena and causes of problems, there will be ways to solve them. Based on specific problem phenomena, sum up experience, analyze and propose targeted measures and countermeasures to solve the problem, so as to extend the life of the equipment and reduce workload and maintenance costs.
According to the analysis results of the cause of the problem, there are generally the following approaches: (1) Re-study and calculate the design, selection and bearing model of the wheel hub bearing according to the size of the load; (2) Clean the oil tank during maintenance and improve the installation process, lubrication method, Select the type of grease and other means; (3) The size of the operating load is affected by the impact force to determine the starting and stopping method. (4) Check the shaft bending, swing and hub sway, and improve the alignment accuracy to slow down the axial and radial impact forces. (5) Check the strength of the bearing box and its bottom corner bolts to prevent impact fatigue damage caused by vibration. (6) Choose different hub forms to slow down the axial and radial impact forces and increase the life of the hub and bearings. (7) Improve the shaft end sealing device to prevent water corrosion of the wheel hub bearing, and take measures such as drainage and oil change after shutdown.