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Power plant: generator starter and valve failures prompted multi-day repairs; parts replacements underway
Summary
Staff described a starter failure on generator 4 and a major failure on generator 5 that damaged pistons and intake components. Repairs included replacing starters, cleaning intakes, replacing a turbo nozzle ring and scheduling valve rebuilds; staff said replacements and design changes are expected to reduce repeat failures.
Power department staff reported two recent generation problems: a starter failure on generator 4 that took it offline, and a larger mechanical failure on generator 5 that damaged pistons and intake passages and required significant teardown and repairs.
Staff said a starter for generator 4 was ordered and installed quickly and the unit returned to service the next day. Generator 5 suffered a catastrophic internal failure: valves and piston material disintegrated and contaminated the intake, which required removing and cleaning intake and exhaust components, replacement of a turbo nozzle ring and other repairs.
"It beat it down and clear it into the ... cooling passage," the presenter said, showing a damaged piston and describing debris that passed through intake screens and required extensive cleaning. Staff said the damaged components were replaced and the unit ran for about 45 minutes after repairs.
Staff stated the valves on the older engines had been welded (head to stem) and were nearing the equipment's service life (about 10,000 hours mentioned). They are working through a program of rebuilding or replacing valves and noted newer designs are forged-through and shaped differently to better withstand higher horsepower applications.
Staff also reported substation and transformer procurement activity was out for bid and that they expected bid results in weeks. No board action was requested.
Ending: Staff said repairs returned generation capacity to service and a program to rebuild or replace aging valves is underway; board members thanked staff and asked no additional action be taken at this time.
