Rotor Services

Be it a forced or planned outage, Keystone responds to customer needs for rotor services in a swift, effective manner. Inspections, Electrical testing, Rewinds, Mechanical repairs and Retaining ring replacements are but of few of the tasks Keystone’s experienced staff provides customers for generator rotors.

Visual inspections


  • Inspection of tooth tops and wedges for stress cracking
  • Inspection for loose wedges and/or balance weights
  • Inspection of retaining ring fit for arcing or burning
  • Inspection of collector rings for discoloration or wear
  • Journal inspections
  • Inspection of cooling passages for blockage
  • Radial lead inspection
  • Visual inspection of blower assemblies

Mechanical Testing


  • Rotor bore pressure test to check radial lead seals
  • Boroscopic inspections
  • Journal dimensions and run outs


  • UT & PT retaining rings/zone rings
  • UT & PT blower hubs/couplings/shaft ends
  • Boresonic inspections
  • Tooth top inspections

Electrical testing


  • RSO testing of rotor winding
  • Short and/or ground locations
  • Step impedance/pole balance
  • DC resistance measurement
  • Insulation Resistance


  • Complete rotor rewinds with class F insulation including high or low speed balance
  • Retaining ring replacement
  • Journal machining on or off site
  • Collector ring changeout
  • Radial/axial lead refurbishment/replacement
  • Repair top turn migration and/or cracking (GE)
  • J-strap and/or coil crossover replacement (GE)
  • Pole crossover replacement (WH)
  • Repairs of turn-to-turn shorts and/or grounds