Test and Maintenance of Turbogenerators and Hydrogenerators (L1, L2, L3, L4 level maintenances)

Static (Offline) Tests

• Visual Inspections (dirties, cracks, rusts etc. )
• Insulation measurement, DAR and PI calculations
• Winding resistance measurement
• High voltage withstand test
• Partial discharge test
• Slip ring ovality measurement, surface roughness measurement, brush and brush holder inspection, spring tension measurement
• Tandelta/power factor capacitance, impedance measurements, tip-up test
• Air gap check
• Coupling run-out check and line alignment
• Sleeve bearing check, lubrication clearance and white metal control,
• Bearing / pedestal insulation measurement
• Videoscope control of invisible areas
• RSO test of turbogenerator rotor, impedance measurements of rotor at different voltages

Dynamic (Online) Tests

• Current , voltage, harmonic and cosQ measurements
• Vibration measurements, analyse of results and definition of below problems
• Bearings and bearing seats problems (inner and outer rings, ball and roll problems)
• Unbalance
• Looseness at bearing seats
• Looseness, weakness of chassis
• Mis-alignment
• Some electrical problems (air gap etc.)
• Heating map by thermal camera
• Analyse and comments of results, reporting

Maintenance of Turbo Generators and Horizontal Hydro Generators, Geothermal, Wind and Biogenerators

• Coupling run-out check
• Disconnect coupling by taking the measurements of shell-shaft positions
• Dismantling bearing covers and pedestals and shells
• Withdrawing the rotor out
• Stator core test (ring flux test or ELCID test)
• Core tightness and bolt looseness check
• Wedge tightness test (by Wedge Tightness Tester or Hammer Method), replacement of wedges or tightening
• Check of end windings’ bandages and blocks looseness, tightening and fixing, bump test
• NDT tests (to fan blades, retaining rings, White metals, bearing seats…)
• Eddy Current Test to pipes of coolers (hydrogen coolers etc.)
• Manufacturing end (retaining) rings and replacement with new under ring insulations
• High speed balancing of rotors (at nominal speed) and overspeed tests
• Cleaning (by dry ice or cleaning chemicals) and drying rotor and stator
• Impregnation and polimerization
• Static tests (including RSO to rotor) to stator and rotor, evaluation the results and comments
• Insertion the rotor into stator and assembling,
• Assembling bearings and pedestals by providing lubrication clearances
• Measurement of bearing insulations
• Line alignment
• Commissioning, vibration measurement and analyse

Horizontal Hydrogenerators Maintenances

• Disconnection of rotor from turbine according to turbine type
• Dismantling pedestal, bearings and endshields, extracting the rotor from stator
• Stator core test (ring flux test or ELCID method)
• Stator wedge tightness tests ( By wedge tightness tester or by hammer method)
• Looseness check of endwindings’ bandages and blocks, remedy if there is any problem
• Corona control at slot ends
• Winding resistance and insulation measurements, PI/DAR Calculations, Power factor, Tip-up capacitance, impedance measurements, step down voltage measurements for salient type rotor poles if possible, pole impedance measurement, inspections of dampening windings and connections
• Measurements and checks of bearing shells, bearing seats, bearing journals, pedestals
• Dynamic balances of rotors
• Cleaning, maintenance and drying of rotors and stators
• Electrical tests to stator and rotor
• Varnishing and drying
• Assembling of generator, line alignment
• Commissioning and vibration measurement and analyse

Coil Manufacturing and Rewinding

• Removing old windings
• Manufacturing the coils as original
• Manufacturing the missing parts by reverse engineering (wedge etc..)
• Rewinding the stator as original
• All electrical tests and mechanical checks
• Drying and completion varnishing process

Rotor rewinding (renewing the insulation)

• Dismantling fan blades, retaining rings and slip ring sif exist
• Removing the wedges
• NDT tests to retaining rings , blades and shaft
• Removing the existing copper coils
• Cleaning the coppers and correcting the forms
• Cleaning the slots
• Rewinding the rotor with new insulation materials
• Re-installation of retaining rings with new under ring insulations
• Assembling the fan blades (and slip rings if exist)
• High speed balance (at nominal speed ) and overspeed test
• Electrical measurements (RSO, winding resistance, insulation resistance, impedance)

Retaining ring manufacturing and replacement

• Recording dimensions of existing rings
• Choosing suitable grade according to santrifugial forces
• Manufacturing the retaining rings from 18Cr18Mn forged material with suitable grade and rough dimensions including sample parts for destructive and non-destructive tests
• Destructive tests to samples taken from mnufactured rings
• Final machining the rings with suitable shrinking tightness
• NDT tests to new rings
• High speed balance at nominal speed
• Impedance and insulation measurements at different speeds (for Slip ring type rotors)
• Flux measurments at different and nominal speeds, turn to turn short circuit tests
• Over speed test
• Dimensional check after overspeed test