Overhaul inspection

When does the need for an overhaul inspection arise? Routine inspection results, along with the generator operating hours, may demonstrate a need for an overhaul inspection. If the routine inspection results are good, then the need for an overhaul can be determined on the basis of the equivalent hours.

teq = tpo + 20Ns (h)

teq = equivalent operating time
tpo = effective operating time
Ns = number of starts

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Experience has shown that the first overhaul is performed after approx. 20 000 equivalent hours, and following after approx. 60 000 equivalent hours. Determining the status of components is partly based on a visual control, control of the dimensions, verticality and cable armor, electrical and mechanical tests. Basic overhaul inspection operations are determining of:

  • Stator housing status
  • Stator packet status
  • Stator winding status
  • Status of the stator windings water chambers¬†
  • Winding supports status
  • Rotor caps status
  • Rotor pins status
  • Rotor current supply status
  • Status of the shaft, flange and sleeves¬†
  • Hydrogen seals status
  • Other seals status
  • Bearings status
  • Ventilator status
  • Cooling device status
  • Slip rings status

Based on these data and the routine inspections data, the generator status and the required interventions may be appraised. The overhaul implies the generator dismantling with decoupling of the rotor and its pulling out.