Slewing bearing in tunnel boring machines
Large and heavy triple-row roller slewing bearings are commonly used as the primary bearing in the drill head. The rollers must be capable of coping with tremendous axial forces and are therefore equipped with cages.
The positioning of tubbing segments during tunnel construction can be achieved with the assistance of crossed-roller slewing bearings. Additionally, bearings may be outfitted with steel sheets or a steel labyrinth to protect the sealings from dirt and debris.