China's first slewing ring was developed in 1964, and slewing bearings have been widely used in the past 40 years. It is a new type of machine component. Firstly used in military machinery and later used in civil machinery such as excavators and cranes.

What is a slewing ring?

The slewing ring, also known as slewing bearing, slew bearing, turntable bearing, mainly refers to heavy duty bearing capable of withstanding combined load. Its diameter ranges from 0.4m to 10m, and it can withstand large axial, radial loads and overturning moment.

Slewing ring consists of the following parts: inner ring, outer ring, rolling element, spacer or cage, and sealing. According to the external structure, the slewing bearing has three types: non-gear type, external gear type and internal gear type. According to the internal structure, slewing bearing can be divided to four series with following features:
* Four point contact ball bearings: provide high static load capacity and smooth rotation.
* Double row angular contact ball bearings: easy to assemble, can withstand large axial forces and overturning moments, suitable for medium and heavy duty loading and unloading machinery, such as tower cranes, truck cranes, etc.
* Crossed roller slewing bearing: has high dynamic load capacity, and can achieve high support stiffness & rotation accuracy through preload.
* Three-row cylindrical roller combination bearing: with extremely high loading capacity, and the bearing diameter can be greatly reduced under the same force condition, which makes the mechanism structure more compact.

What is the difference between a slewing ring and a normal rolling bearing?

1. A set of slewing bearing can withstand combined loads from multiple directions.
2. The running speed of the bearing is generally not high.
3. In most cases, slewing bearing do not make continuous rotation, and only rotate back and forth within a certain angle.
4. The installation is fastened to the upper and lower supports by screws or bolts.
5. Compact structure and low overall height.
6. Without a central pivot, other components can be installed in the hollow shaft.
7. Easy installation and maintenance, long service life.

Material

Most slewing ring use 42CrMo, 50Mn as raw material, GCr15 bearing steel is usually for small size, and BRS can produce with customized material such as stainless steel. More info. please check slewing bearing material.

Installation of slewing bearing

Check the matching surface before installing the slewing bearing. The components supporting the slewing bearing should have sufficient rigidity. The matching surface should be machined to achieve the flatness and inclination of the relevant standards. Each set of slewing bearings will be marked with a "S" on the soft spot, which should be placed in a non-loaded area during mounting. When installing, first position the bearing radially, then cross-tighten the mounting bolts and check the rotation of the slewing bearing.In order to ensure smooth rotation, the condition of gear meshing should be inspected before the bolt is not fully tightened. The pre-stress of the tightening bolt should be 70% of the yield limit of the bolt material.
The slewing bearing of BRS has been well lubricated before leaving the factory. Normally, after installing the bearing and putting it into operation for 100h, it should be inspected and re-lubricated once (how to add grease), and then re-lubricated every 500h after continuous operation. For the slewing bearing in high temperature environment, the cycle of replenishing the grease should be shortened appropriately. When storing the bearing for a long time, or when the machine stops running for a long time, it should also be re-greased.

Major slewing ring manufacturer

The main worldwide manufacturers of slewing bearings are RothErde, Schaeffler, Rollix, SKF, NSK, each company has its own type and size series. BRS can produce most bearing models of above companies.

Slewing ring application

Slewing bearings are widely used in heavy duty rotary devices such as lifting machinery, mining machinery, construction machinery, port machinery, marine machinery, high-precision radar antenna mounts, missile launchers and wind turbines. Besides, we can design, develop and produce various special structure slewing bearings according to the specific requirements of users.