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

• The fault caused by electrical discharges in a thrust bearing is described.
• The mechanism of the electrical discharge has been analysed.
• The cause of the bearing fault has been identified.
• The phenomenon is simulated by means of a TEHD model of the bearing.
• The simulation results are in good accordance with the experimental evidences.
• The simulations highlight a decrease of the runner distance from the pivot.
• The simulations highlight an increase of the bearing temperature.

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.