Ontario Power Generation’s Sir Adam Beck – Pump Generating Station (PGS) experienced recurrent bearing failures into the early 1990’s, at which time there was an exhaustive review of the bearing and its split runner plate design (deemed to be the root cause for several failures). This review resulted in a number of changes to the existing design of the bearing, the assembly tolerances, and the high pressure oil lift system. As well, the adjustable flaps on the stay vanes leading into the runner were welded into one location which choked off some of the water entering the turbine limiting some of the hydraulic thrust.
The thrust bearings at PGS then ran reliably until 2002 when the PGS G4 bearing failed. Investigation into the cause of this failure identified quality issues with the post overhaul refurbished bearing and a glitch in the shutdown system that could, under some circumstances, allow the unit to rotate without oil lift.
A thrust bearing upgrade could be simply accomplished with the installation of new Polytetraflouroethylene (PTFE) bearing pads to replace the existing Babbitt pads. Permissible thrust bearing loads would then be greatly increased and bearing losses would be minimized. In addition, a newly designed split runner plate with a reliable keyed clamping system, using new high quality hardware, would alleviate the risk of the runner plate becoming loose during operation. Stabilization of the runner plate would contribute to the prevention of catastrophic bearing failures.