Crane And Excavator Slewing Ring Bearing

Large diameter slewing ring bearings are critical components in many applications. Military applications include tank turrets, missile launchers, communication antennae, precision radar antennas, and gun mounts. Common commercial applications include aerial lifts, hydraulic excavators, boom cranes, and tunnel boring machinery. Large bearings for these applications are not only expensive to buy, but typically require lead times ranging from two months to a year or longer.

Since the bearing is so critical, careful maintenance is necessary. More than 96% of slewing ring bearing failures are due to surface-originated lubrication problems, contamination, overloading, and improper installation and mounting fits. These surface failures occur much earlier than classical fatigue failures and are less predictable.

Slewing ring bearing life is calculated assuming infinitely rigid and flat mounting structures. A structure that distorts significantly under load, and/or one that is out-of-flat, applies loads to localized areas rather than evenly distributing them. This causes permanent deformation in the local area, leading to early failure.