Slewing bearings – in the service of wind energy
We encounter large-diameter bearings in many applications, such as wind turbines, cranes, streetcars, articulated buses and even in medical technology. Without slewing bearings, the world would literally stand still. At thyssenkrupp rothe erde, slewing bearings are manufactured that have to withstand enormous forces.
A look inside: Components of slewing bearings
To understand how large-diameter slewing bearings work, it helps to look at their structure and main components: the outer ring, the inner ring, the rolling elements, and the cage.
Inside a rolling bearing, the rolling elements are evenly distributed and guided by a cage. The outer and inner rings run around them. The outer ring is usually connected to the rotor. The inner ring is connected to the drive shaft. One ring is always stationary, whereas the other ring rotates. Thus, if the rotor is connected to the outer ring by means of a flange, the generator is also flanged directly or via a shaft/gearbox on the other side. In this case, the inner ring is stationary and connected to the outer housing structure of the plant. Thanks to this transmission mechanism, large-diameter slewing bearings in wind turbines, for example, can transmit the kinetic energy of the wind power to the drive shaft and finally to the generator, where it is converted into electric current
Function of slewing bearings: mobility and transmission
Rolling bearings and large-diameter slewing bearings are used wherever there is an interaction between motion and drive. At heights of over a hundred meters, for example, they perform an important function: Large-diameter slewing bearings transmit the forces of the wind to the entire wind turbine. The rotor blades of wind turbines are subjected to axial and radial forces. These are forces acting along the axes or perpendicular to the axis of rotating bodies. In the case of wind turbines and their rotor blades, which are often over 60 meters long and weigh around 20 tons, these are considerable forces. Large-diameter slewing bearings absorb and transmit these forces.
3,500 households and 70 passenger cars – test of strength in the rotor bearing
To illustrate the forces acting on slewing bearings in wind turbines, let’s take a look at the rotor bearings at the base of the rotor blades.
An onshore turbine with three rotor blades, each 63 meters long and weighing 20 tons, generates an energy output of 6.1 megawatts per hour at a wind speed of 14 meters per second. That’s quite a lot, because 6.1 megawatts can theoretically supply around 3,500 households with electricity for an entire year! Under these conditions, axial and radial forces of 1 mega Newton act on the center of a single rotor blade alone. A force equivalent to about 70 passenger cars tugging on a single rotor blade.
To withstand forces of this caliber and ensure smooth movement of the entire turbine, slewing bearings for wind turbines have to meet very specific requirements. That’s why the experts at thyssenkrupp rothe erde have been carrying out intensive research and development work on wind energy for several decades. thyssenkrupp rothe erde offers customers slewing bearings that are optimally adapted to the requirements and locations of the turbines.
In addition to wind energy, slewing bearings are important key components for many other industries. thyssenkrupp supplies customers from all over the world. With diameters of up to 25 meters, transporting the huge components is just as spectacular as their function and performance. rothe erde logistics expert Dirk Saager explains in an interview how the mammoth logistical task and the transport to air, water and asphalt works.
Our experts at thyssenkrupp rothe erde will be pleased to answer any inquiries for information and details about our slewing bearings.