Maintenance of Imported Bearings: Addressing Damage Causes and Conditions

1. Raceway Sound and Control Measures

Raceway sound is a smooth, continuous noise generated by the rolling elements moving along the raceway when a bearing operates. This is a fundamental characteristic sound common to all rolling bearings. The typical sound of an imported bearing is the raceway sound combined with other noises.

The noise of a ball bearing's raceway is irregular, with a frequency above 1000 Hz. Its dominant frequency does not change with rotational speed, but the overall sound pressure level increases with speed. For bearings with loud raceway noise, the sound pressure level decreases as the lubricant's viscosity increases. However, for bearings with initially low raceway noise, when the viscosity exceeds 20 mm²/s, the sound pressure level may begin to increase after an initial decrease. Higher housing stiffness generally results in a lower overall sound pressure level.

When the radial clearance is too small, both the sound pressure level and the dominant frequency of the raceway sound increase significantly as the clearance decreases. The method to control raceway sound is to use low-noise imported bearings (e.g., bearings with small surface waviness) and carefully select the application conditions. Since raceway sound often dominates the overall noise of machinery, reducing it can effectively lower the total machine noise.

2. Rolling Element Impact Sound and Control Measures

In large-size ball bearings or cylindrical roller bearings operating under pure radial load at low speeds, the centrifugal force on the rolling elements is small. This can cause rolling elements in the non-load zone to impact the cage or raceway, generating noise. This noise typically disappears as the speed increases.

Control measures for rolling element impact sound include:

● Appropriately reducing the radial clearance.

● Using bearings with optimized cage designs and materials (e.g., bearings with smooth synthetic cages).