During the rotation of rolling bearings, the free vibration of the cage and its impact with rolling elements or rings can generate noise.

This noise may occur in various bearings, but it exhibits a low sound pressure level and is characterised by low frequency. Its features include:

a. This noise can be produced by both stamped and plastic cages.

b. It occurs regardless of whether the bearing is lubricated with oil or grease.

c. It is most likely to occur when the outer ring is subjected to bending moments.

d. It is more likely to occur when the radial clearance is large.

As clearance between cage pockets and between the cage and rings is unavoidable in finished bearings, completely eliminating cage noise is very difficult. However, it can be mitigated by reducing assembly errors, optimising clearance, and minimising cage movement.

Another distinct cage noise originates from self-excited vibrations induced by friction between the cage and other bearing component guide surfaces, producing a rattling sound. Stamped cages in rolling bearings are thin-walled with low bending stiffness in both radial and axial planes, resulting in poor overall stability. At high rotational speeds, bending deformation causes self-excited vibrations, generating a ‘buzzing’ sound.

When bearings operate under radial loads with substandard grease performance, an initial ‘clack-clack’ noise may be heard during running-in. This primarily results from rolling elements suddenly accelerating upon leaving the load zone and colliding with the cage. Such impact noise is unavoidable but typically diminishes with extended operating time.

Methods to resolve bearing noise caused by unsuitable lubricants include: selecting the correct lubricant; applying lubricant at the specified quantity; and regularly replacing lubricant to prevent ageing and hardening.

Should bearing noise arise from improper lubrication, there is no need for undue concern as this issue can be effectively resolved. Similarly, damage to bearing surfaces or ingress of dust warrants no alarm, as appropriate solutions exist.

Cleaning

First, the bearing must be disassembled for inspection, with its external condition documented. Concurrently, determine the quantity of residual lubricant within the bearing, take a sample, and then proceed with cleaning.

Cleaning comprises coarse and fine washing stages, typically employing neutral, water-free diesel or kerosene as the solvent, which should be frequently filtered to maintain purity. Immediately after cleaning, apply rust-preventative oil or grease to the bearing surfaces to prevent oxidation and corrosion.

Inspection and Assessment

To determine whether a disassembled rolling bearing is reusable, specific checks must be conducted on its dimensional accuracy, rotational precision, internal play, as well as mating surfaces, raceways, cages, and seals. Inspection results should be evaluated by personnel familiar with bearings or possessing expert knowledge. Assessment criteria may vary based on mechanical performance, criticality, and inspection intervals.

Fractures and defects in rolling bearing components.

Rolling bearings must be replaced and cannot be reused if exhibiting the following damage:

- Flaking on raceway surfaces and rolling surfaces.

In summary, determining whether a rolling bearing remains serviceable requires comprehensive inspection and evaluation against relevant standards. Should any of the aforementioned damage occur, the bearing must be replaced immediately to ensure the safe operation of machinery and equipment.