Stator Services


At a moment’s notice, Keystone’s staff of experienced generator specialists and technicians can mobilize to a site with state of the art equipment to affect a broad array of stator services. Whether the need is to test, inspect, evaluate the stator, re-stack iron, completely rewind and upgrade the stator coil support structure, Keystone provides customers with cost effective solutions to any stator problem that might be encountered.

Visual Inspections

  • Core
  • End-winding and support system
  • Main and neutral leads
  • Bushings
  • Main and neutral lead box and enclosures

Mechanical testing

  • Frequency response testing
  • Digital wedge tightness evaluation
  • Frame foot loading
  • Pressure decay test
  • Vacuum decay testing
  • Helium leakage testing

Electrical testing

  • Insulation Resistance/Polarization Index
  • DC winding resistance
  • RTD resistance measurements
  • DC high potential testing
  • Transportation testing
  • Tube to tube resistance
  • Vent tube/parallel ring flow testing
  • Tube to copper resistance
  • Electromagnetic Core Imperfection Detector Test (EL CID)
  • Thermovision scan (loop test)
  • Capacitance mapping

Repair services

  • Rewind with new coils and class F insulation
  • Rewinds with refurbished coils/ coil repair on site
  • Core tightening
  • Core lamination repairs
  • Core lamination replacement
  • End winding tightening
  • Strand repairs
  • Bushing repair and replacement
  • Re-wedge
  • Water box leak repair
  • Epoxy
  • Permanent mechanical repair


  • End winding support system decoupling
  • Through bolt nut upgrade
  • Stator coil design upgrade
  • Flux probe installation
  • PDA coupler installation
  • Tagging compound installation