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Slewing Ring Bearing Use Conditions
- Nov 01, 2018 -

Slewing bearing is the rolling element bearing commonly used in large industrial machineries such as turntables, steel mill cranes, offshore cranes, rotatable trolleys

, excavators, reclaimers, stackers, swing shovels and ladle cars. They typically support high axial and radial loads. Slewing bearings are often critical production

parts. An unplanned downtime when one of these bearings breaks down can be very costly due to the interruption of production. Moreover, as replacement of large slewing bearings takes long lead time to arrive due to long manufacturing and

delivery time, plants often carry spare bearings to guard against these unforeseen circumstances, adding extra cost. In order to prevent extended unplanned downtimes, an accurate condition monitoring method is needed.

While maintenance is critical to lengthening the life of large slewing ring bearings, the severity of use of heavy equipment means that eventually, any large slewing ring bearing will become worn. Detection of bearing wear makes repair a less costly alternative to replacement. If you practice proper maintenance and watch for common warning signs, a worn bearing is likely to be deemed repairable.

application of slewing ring bearing

In lifting equipment, the large diameter bearing serves as a joint between the upper structure and the undercarriage, providing a means of 360-degree rotation. Lifting devices typically have a complex load spectrum: the slewing ring bearing can simultaneously handle all combinations of thrust, radial, and tilting moment loading. The use of a slewing ring bearing provides yet another benefit: its shaftless design eliminates the need for a spindle or kingpost. The center of the bearing remains open to allow passage of various hydraulic and control components.



The accuracy of the condition monitoring method depends on the selection of the monitored features. The change in rolling element bearing condition is usually reflected by changes in the vibration signal features. However, it is difficult to select the proper features for the slow speed slewing bearing case (≈1 rpm). Statistical time-domain features which are commonly used in high speed rolling element bearings show low sensitivities when applied to low rotational speed slewing bearings due to the low impact energy emission as the rotating elements contact with defect spots (Tan, et al 2008). The low energy impact generates a very weak vibration signal which is deeply masked by the background noise. Because the features are taken from the vibration signal where the noise is dominant, they are insensitive to any alteration in the bearing condition. When eventually the vibration amplitude exceeds the background noise, the features values do increase significantly but at this point serious bearing damages have already occurred:

often by this stage the bearing condition is already close to unsustainable fault.