A slewing ring (slewing bearing) is a specialized bearing capable of carrying axial, radial, and overturning moment loads simultaneously, while its internal or external gears allow direct drive. Single-row ball profile bearings with four-point contact stand out in mobile cranes and conveyor systems for their compact design. Cross-roller configurations are employed in defense turrets requiring ±0.03° positioning accuracy, while three-row roller heavy-duty versions operate in wind turbines with a lifespan target of over 20 years.
The design process begins with calculating the combined load of axial force, radial force, and overturning moment. This value should not exceed 80% of the permissible capacity stated in the catalog. Internal gears, by protecting teeth from external influences, provide advantages in concrete pumps operating in open fields; external gears, on the other hand, simplify maintenance access.
For ring materials, heat-treated 42CrMo4 steel is most commonly selected; in saline environments, 17-4 PH or nitrided 18CrNiMo7-6 extends service life. Bolt installation using a three-stage star tightening sequence minimizes vibration, while pre-tightening keeps axial clearance close to zero, ensuring quiet operation. When properly selected and regularly maintained, a slewing ring can deliver more than 25,000 operating hours.