Electrical pitting of tilting-pad thrust bearings: Modelling and experimental evidence

Electrical discharges in bearings may occur in shaft lines equipped with electrical machines. This effect, known as electrical pitting, consists of the removal of material from the pad surface; this can lead to bearing pad failure mainly because of overheating and reduced load capacity. The case history of a fault caused by electrical discharges that occurred in the thrust bearing of a turbine is described in the first part of the paper. This phenomenon is then simulated by means of a thermal elastohydrodynamic model of the bearing, considering the effect of electrical pitting on the surface of the pad. Finally, the results of the simulations allow the irreversible failure of the bearing caused by the electrical pitting to be shown.