Symmetry methods applied to the condition-monitoring of slow speed slew bearings

All data has symmetry and anti-symmetry embedded in it. This paper discusses various aspects of symmetrical transformations that can be applied to data to give machine condition information. These transformations lead to novel views of the information. Combining these symmetrical transformations with the more traditional methods of Eigenvalue/vector and Fast Fourier Transform analyses provides views of the source and extent of the problem. To illustrate the various views of the vibration information, results from a large (4.2m diameter) Coal Reclaimer slow speed (4rpm) slew bearing are presented. Many of the transformations are also currently being evaluated on an experimental test-rig specifically designed for the monitoring of horizontal slow speed (1 to 4 rpm) slew bearings.