Raccoon Mountain Generator Thrust Bearing Cooling Project

摘要

The Tennessee Valley Authority’s Raccoon Mountain Facility has four pump turbinegenerators rated at 425 MVA each. The Raccoon Mountain generators have had ahistory of thrust bearing over heating and high vibration levels throughout the power trainfrom the time of initial unit commissioning. The over heating has shortened the life of thebearings and other components which has resulted in a high forced outage rate. TVA isuprating the Raccoon Mountain units by 12% to 476 MVA. To successfully accomplishthe uprate, the thrust bearing temperature had to be reduced. The over heating wasinvestigated and modifications were made to the cooling system. The modificationsimplemented lowered the thrust bearing temperature to acceptable levels. Lowering thethrust bearing temperature provided some unexpected benefits. Lower bearingtemperatures allowed for tighter clearances on the lower generator guide bearing, whichreduced vibration levels throughout the power train. The economic advantage of lowervibration and temperature levels was improved reliability of the thrust bearing shoes,runner seals, shaft mechanical seals and the rotor rotating water manifold seals. Thispaper discusses the source of the bearing over heating, the modifications to correct theoverheating, and the benefits of lowering the vibration levels.