Power Generation Project Experiences

c
      c     c       V




  

  V
V 
 
V 
V  V
 
 
 V
V 
 VV

VV
 
V
 V  V
 
 V  VV V 
V V
  V V

ROTOR DETAIL INSPECTION WITH ROTOR REMOVAL ON GE GENERATOR 125 MW, DUE TO HIGH REVERSE POWER ATTACK

ROTOR REMOVAL AND DETAIL INSPECTIONS Detailed inspection was carried to identify what the generator condition is, and to identify whether the unit is still repairable or not. Inspections

was

planned

with

the

following

test:

1.

Electrical

measurement

for

rotor

winding

2.

Electrical

measurement

for

stator

winding

3. Mechanical inspection incl, electrical round-out, NDT for journals and retainingrings 4. Visual inspection for the stator, incl. ELCID on the stator core

© Dismantling Generator

Storage

Yenerator unit (excl exciter) was moved from unit location to field free area, +/- 150 m from the unit foundation generator was storage at open air without shield or roof, For round 7 months, till date of inspection.

Generator storage

Rotor

removal

Yenerator was placed at open area and close to overhead transmission line 150 kV, in app

40

M

with

generator

location.

No dismantling facility are available at site, such as heavy crane, support, etc Following are site activities mobilization and preparation for rotor removal. 1.

Direction

kits

site

office

and

electricity

facility

2. Lifting facility incl. Raughterr crane 20T, Forklift 5T, Wire sling 40 T, Hyjack 60 T, etc 3.

Site

4. 5.

area

arrangement

Yenerator Rotor

removal

special

leveling tools

arrangement

6.

Roofing

erection

7.

Scaffolding

erection

Cover removal

Top covers including top bearings TE & EE are the main priority to be removed prior other activities will be done, all of parts removed to be marked based on its position and storage at safe area.

Air gap Copper melted was found entire air gap, to remove the copper melting need more free space in the air gap, rotor was hanged on the frame by using wire sling 40T, its purpose to get max air gap at bottom rotor areas, see illustration as below: Top Air Gap Viewed from Exciter End

|

Copper and steel wedges melt Metal melting including copper and steel wedge was found entire air gap, removing from air

Metal

gap

melt

was

was

done

by

collecting

using

in

hammering

approximately

to

100

made

kgs,

pieces

see

size.

photo¶s

Rotor removal special tools and rotor bed support Rotor removal special tools was arranged based on the generator storage area conditions, prior removal and any mechanical dismantling generator parts, leveling on the generator is required and was done using jacking systems and supported by

wooden

block

.

Yenerator leveling prior mechanical parts dismantling

Rotor rail and special tools assembly Rotor rail and special tools was prepared and arranged based on the site conditions, time schedule and safety precaution are basically concern for removing this rotor, wooden blocks and jacking method were used to support of the railway and rotor, due to the generator area is very close to the overhead line 150 kV, and the space area has not possible for moving heavy mobile crane, high electrical shock and direct contact to OH 150 kV can occurring when using heavy crane, therefore, wooden block and jacking systems

are

chosen

see illustration below.

to

replace

the

steel

structure

method.

Rotor removal process Rotor was removed by combination using jacking and chain block, a jacking rail installed

between

rail

legs

as

a

jacking

landing

facility.

ÿ INSPECTION ROTOR

VISUAL

INSPECTIONS

Rotor shaft was planned to be inspected by using ERO (Electrical Run-Out), to identify rotor shaft deflections, this planning has defined when the generator still in complete assembly to purpose repair criteria with assuming when rotor forging is not damaged. After rotor was completely remove, visual inspection can assessing to whole of rotor conditions, totally damaged was found on the retaining rings (both exciter end and

turbine end), damaged also found on the rotor forging and steel wedge at exciter end and turbine end close to the retaining rings area, see photo¶s below.

Typical damaged on Retaining rings Exciter end and Turbine end

Slot wedges taken form Turbine End Side

Slot wedges taken from Exciter End Side Typical damaged of Retaining ring Turbine end and Exciter End)

Slot divetail Turbine end  

 Slot dovetail Exciter end 

  Ôody flex slot Turbine end 

 Ôody flex slot at middle rotor



Ôody flex slot Exciter end 

 Steel wedge (typical damaged for Turbine side and Exciter side)  

PREPARATION INSPECTIONS

ROTOR

TO

WORKSHOP

 Transportation to Workshop

   

FOR

               Receive rotor at workshop for machanical inspection

.         



         creparation for mechanical inspectio



              



ROUND OUT INSPECTION 

               Electrical Round Out 

   

Electrical

Round

out

          

data 

               



    

  Max deviation round out exciter end       Max

deviation

0.721Volts  mVolts mils  mm

721 3.605 0.0915

round

out

turbine

end

 

0.301 301

Volts mVolts

  0.0382 mm

1.505

mils



 

NDT INSPECTIONS 

 

 

 

 

              

D SUMMAY  Rotor to be inspected when rotor was successfully removed from the stator bore,  ’ Rotor Forging, retaining rings, found totally damaged on the rotor forging including body flex slot, slot dovetail, both retaining rings, retaining rings locking ,steel wedge at end portions close to retaining rings, see previous pages 

NDT and round-out also has been inspected, found minor scratching due to electrical discharge and minor deflection on the journal at exciter end side but still in tolerance.  © Rotor winding, Rotor winding is not possible to be measured by electrical measurements, due to the winding was totally damaged.  ÿ Rotor Shaft dimensional , Rotor shaft has been inspected using mechanical run-out and ERO, rotor shaft dimensional have a minor deflection Exciter side journal shaft. Diameter  355.55 ± 355.57 mm, max TIR  0.05 mm Turbine end journal shaft Diameter  355.56 ± 355.58 mm. max TIR  0.02 mm 

À CONCLUSION  1. Rotor forging, total damaged 2. Ôoth retaining rings, heavy crack 3. Steel wedges, some of them was melted and almost of them was overheated 4. Copper bars winding rotor, melting 5. Journal shaft, minor scratch 6. Shaft, minor deflection  Total damaged on the rotor forging and retaining rings, repair is not possible, new unit must be planned to replace it    

          

  

 |