slewing bearing

A slewing bearing or slewing ring is a rotational rolling-element bearing that typically supports a heavy but slow-turning or slow-oscillating load, often a horizontal platform such as a conventional crane, a swing yarder, or the wind-facing platform of a horizontal-axis windmill. (To "slew" means to turn without change of place.)

Compared to other rolling-element bearings, slewing bearings are thin in section and are often made in diameters of a metre or more; the slewing bearings on the Falkirk Wheel are 4 metres diameter and fit over a 3.5 metre axle.

Slewing bearings often use two rows of rolling elements. They often use three race elements, such as an inner ring and two outer ring "halves" that clamp together axially.

Slewing bearings are often made with gear teeth integral with the inner or outer race, used to drive the platform relative to the base.

As for other bearings that reciprocate, rather than rotating continuously, lubrication can be difficult. The oil wedge built up in a continuously rotating bearing is disrupted by the stop start motion of slewing. Instead, a hydrostatic bearing with pumped oil flow may be used.

Slewing bearings comprise an inner ring and an outer ring, one of which usually incorporates a gear. Together with attachment holes in both rings, they enable an optimized power transmission with a simple and quick connection between adjacent machine components. The bearing raceways, in conjunction with the rolling elements and cages or spacers, are designed to accommodate loads acting singly or in combination, and in any direction.

Application engineering service

Selecting the appropriate slewing bearing can be a challenge, particularly if there are stringent technical, reliability or economic demands. In these cases, for example, application engineering service can provide advanced calculations and simulations utilizing state-of-the-art analyse methods to optimize and validate the best design to meet the customer requirements.

Remanufacturing service

We also offers worldwide a wide range of added value services for slewing bearings, including remanufacturing. A slewing bearing with only 30% left of its calculated service life can be well worth remanufacturing.  standardized remanufacturing processes can extend significantly the service life of critical equipment.

All of these combine to improve rotating equipment performance and reduce total cost of ownership. 

Bearing features

Depending on their design, slewing bearings have the following features: 

High load carrying capacity

High stiffness for rigid bearing application

Low friction 

Long service life

Surface protection and corrosion resistance

Integration of additional features, including:

driving mechanism

control devices

lubrication systems

monitoring systems

sealing cassettes 

Designs

We manufacture standard and customized slewing bearings in various designs with outside diameters from 0,1 to 18 m to meet the demands of particular applications. The most common designs are: 

Four-point contact ball bearings

Optimal economy and capacity for given dimensions or when replacing existing multi-bearing arrangements

Four-point contact ball bearings 

80% increase in capacity compared to a same-sized single-row four-point contact ball bearings

Crossed cylindrical roller bearings 

High stiffness and constant resistance to rotation

Triple row roller bearings 

Provide highest capacity for a given diameter

Wire race bearings

60% lighter compared to same-sized all-steel bearings

We extensive experience in designing and manufacturing customized or special slewing bearings. Examples are:

Combined roller/ball bearings

Segmented bearings

Inserted raceways bearings

Applications

We offers high-performance slewing bearings for a wide range of applications, including: 

Wind turbines 

Tunnel boring machines 

Excavators

Forestry vehicles 

Rail vehicles 

Dockside and deck cranes

Mobile cranes

Water treatment equipment

Bottle filling systems

Metals

Material handling

Marine pods

Offshore buoys

Stacker reclaimers

Surveillance systems (e.g. radars, cameras)

Medical equipment 

Tidal turbines