Ontario Power Generation

Background

Reversible pump-storage turbines can create aggressive environments for thrust bearings due to their typically large loads, intermittent operation, and, most challenging of all, their need to reverse direction. These effects tend to compound other problems experienced by the bearing during its service life and result in costly down time. Such was the case with the bearings at Ontario Power Generation’s Pump Generating Station (PGS), where assembly problems resulted in multiple failures and a de-rating of the turbine output.

Bearing Design

The original split runner plate was prone to becoming loose during operation, creating steps at the splits. Hydro Tech Inc.’s redesign combined tight-fitting keys and an easy, reliable torquing method to prevent separation of the two halves.

Polytetrafluoroethylene (PTFE) was chosen as a replacement of the original Babbitted pads. In addition to a higher specific load and greater resilience during transient operation, PTFE pads typically operate with a centre of effort much closer to the middle of the pad; ideal for the reversing nature of pump-storage operation.

The resulting design has allowed the units to operate much more reliably in all regimes, and has allowed the units to once again generate at full load.