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When an imported bearing rotates, the free vibration of the cage and its impact with the rolling elements or raceways cause noise.
This noise can occur in various bearings, but it has a low sound pressure level and is low-frequency. Its characteristics are:
a. This noise can occur with both stamped and plastic cages.
b. This noise occurs with both oil and grease lubrication.
c. This noise is most likely to occur when the outer ring is subjected to bending moment.
d. This noise is more likely to occur when the radial clearance is large.
Since cage pocket clearance and cage-race clearance are unavoidable in finished bearings, completely eliminating cage noise is very difficult. However, it can be improved by reducing assembly errors and optimizing appropriate clearances and cage runout.
Another type of cage noise is the loud noise generated by the self-excited vibration of the cage caused by friction between the cage and the guide surfaces of other bearing components. Imported bearings often have thinner stamped cages with lower bending stiffness in both the radial and axial planes, resulting in poor overall stability. During high-speed rotation, this bending deformation can cause self-excited vibration, producing a "buzzing" sound.
When the bearing is under radial load and the grease performance is poor, a "clicking" noise may be heard during the initial operation. This is mainly due to the rolling elements suddenly accelerating after leaving the load area and colliding with the cage, causing noise. This impact sound is unavoidable, but it will gradually disappear with increased operating time.
The following three methods can be used to solve the problem of noise from imported bearings caused by improper lubrication:
Choose the correct lubricant;
Add lubricant according to the specified amount;
Replace the lubricant regularly to prevent it from aging and hardening.
If the bearing is making noise due to improper lubrication, there is no need to worry excessively, as this problem can be effectively solved. If the bearing surface is damaged or dust has entered, there is also no need to worry, as there are corresponding solutions.
Cleaning
First, the bearing needs to be disassembled for inspection, and its appearance should be recorded. Simultaneously, the amount of remaining lubricant inside the bearing must be determined and sampled before cleaning the bearing.
Cleaning can be divided into two steps: rough cleaning and fine cleaning. Neutral, water-free diesel or kerosene is typically used as the cleaning agent, and it should be frequently filtered to maintain cleanliness. After cleaning, rust-preventive oil or grease should be applied to the bearing surface immediately to prevent oxidation and corrosion.
Inspection and Judgment
To determine whether a removed imported bearing can be reused, its dimensional accuracy, rotational accuracy, internal clearance, and aspects such as mating surfaces, raceway surfaces, cage, and seals need to be carefully inspected. The inspection results can be evaluated by personnel familiar with or proficient in bearings. Judgment criteria may vary depending on mechanical properties, importance, and inspection frequency.
If the following damage occurs, the rolling bearing must be replaced and cannot be reused:
Broken or defective imported bearing parts.
Peeling between the raceway surface and the rolling surface.
In summary, when determining whether an imported bearing can continue to be used, it is necessary to conduct a thorough inspection and evaluation, and make a judgment according to relevant standards. If the above damage occurs, the bearing must be replaced immediately to ensure the safe operation of the machine.
