power generation project experiences

8/3/2019 Power Generation Project Experiences

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POWER GENERATION PROJECT

EXPERIENCEST H I S P A P E R I S B A S I C A L L Y U S E D E N G I N E E R A S G U I D A N C E F O R

G E N E R A T O R I T ' S C O M P I L E D B Y S I S W A N T O B A S E D O N M A N Y S I T E W O R K S

P R O J E C T S E X P E R I E N C E S F O R S E R V I C E S A N D I N S P E C T I O N S O F T U R B I N E

G E N E R A T O R S . T H I S I S A N E F F O R T T O P R O V I D E A S M U C H I N F O R M A T I O N

T O O U R C U S T O M E R S A S P O S S I B L E I N O R D E R T O S E L E C T T H E B E S T

S E R V I C E S F O R T H E O P T I M A L P E R F O R M A N C E O F T H E G E N E R A T O R .

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


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ROTOR REMOVAL AND DETAILINSPECTIONS

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

2. Dismantling

Generator StorageGenerator 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


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Rotor removalGenerator 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 area arrangement

4. Generator leveling

5. Rotor removal special tools arrangement

6. Roofing erection

7. Scaffolding erection

Cover removal


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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.


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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


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Copper and steel wedges melt

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

air gap was done by using hammering to made pieces size.

Metal melt was collecting in approximately 100 kgs, see photos


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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


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wooden block

.

Generator leveling prior mechanical parts dismantling

Rotor rail and special tools assemblyRotor 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 to replace the steel structure method.

see illustration below.


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

installed between rail legs as a jacking landing facility.


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3. INSPECTIONROTOR VISUAL INSPECTIONSRotor 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


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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 photos below.


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Typical damaged on Retaining rings Exciter end and Turbine end


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Slot wedges taken form Turbine End Side

Slot wedges taken from Exciter End Side

Typical damaged of Retaining ring Turbine end and Exciter End)


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Slot divetail Turbine end

Slot dovetail Exciter end


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Body flex slot Turbine end

Body flex slot at middle rotor


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Body flex slot Exciter end

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

PREPARATION ROTOR TO WORKSHOP FORINSPECTIONS

Transportation to Workshop


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Receive rotor at workshop for machanical inspection

.


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Preparation for mechanical inspectio


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ROUND OUT INSPECTION

Electrical Round Out


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Electrical Round out data


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Max deviation round out exciter end

= 0.721Volts= 721 mVolts

= 3.605 mils

= 0.0915 mm

Max deviation round out turbine end

= 0.301 Volts

= 301 mVolts

=1.505 mils

= 0.0382 mm


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NDT INSPECTIONS


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-

4. SUMMAY

Rotor to be inspected when rotor was successfully removed from the stator bore,

1. 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


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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.

2. Rotor winding, Rotor winding is not possible to be measured by electrical measurements,

due to the winding was totally damaged.

3. 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

5. CONCLUSION

1. Rotor forging, total damaged

2. Both 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.


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