Bhel Rsc Varanasi

8/12/2019 Bhel Rsc Varanasi

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HIGH CRONIC VIBRATION AT ANPARA

U# 1

Anpara Unit # 1 210 MW reported sever Axial andHigh Vertical vibration in Brg # 6 and Brg # 5 alsoshowed High Vertical Vibration

High Vibrations were also noted in Stator Endshield and water header.

The axial vibration and vertical vibration suddenlyincreased to the tune of above 50 microns ad

machine had o be debarred

Spectrum showed sever 2x components andother higher frequency components


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USPV test

Ultrasonic Pulse Velocity Test

54KHZ , 24KHZ

Velocity=Distance/time

Homogeneity

Presence of Cracks/voids, imperfections

Change in structure which occurs with time

PUNDIT :- Portable Ultrasonic Non-destructive Digital Indicative tester

>4.5 Km/sec :- Excellent

>4 km/sec :- Very good to Excellent

3.5 to 4 Km/sec :-Good to very good

3.0 to 4.0 km/sec :- Satisfactory but integrity suspected


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PEAK TO PEAK

NUMBER VIBRATION() NUMBER VIBRATION() pk-pk

1 32.20 10 53.10

2 30.00 11 45.80

3 31.00 12 41.60

4 34.70 13 32.40

5 42.80 14 55.00

6 41.80 15 32.10

7 46.10 16 46.10

8 47.10 17 65.4

9 54.70 18 63.4

15

2

1

3

456 7

89

10 11

121314 16

A CRACK IS BEING NOTICED(PIC S ATACCHED)17 18

METAL BASE PLATE

CIVIL FOUNDATION AREA

BEARING NO .06 PADESTAL MAPPING(v)

*READING OF THE COLUMN

OF THE PEDESTAL WASTAKEN AT 6M AND 0M

FRONT (BRG # 6)6 METER

60.1

0 METER 43.1

REAR COLUMN BRG # 5 6

METER 34.3


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OBSERVATIONS

THERE IS SEVERE VIBRATION IN THE STATOR WATER INLET ANDOUTLET LINE. DUMMY WOODEN SUPPORT AT BENDS WEREPROVIDED AND SOME REDUCTION IN VIBRATION WAS OBSERVEDBUT STILL NOTICABLE VIBRATION IS OBSERVED WHICH REDUCESGOING AWAY FROM THE GENERATOR

THE ENDSHIELD OF TURBINE SIDE SHOWS NOTICABLE VIBRATION

THERE IS VIBRATION IN FOUNDATION AREA OF BRG # 6 .

THERE HAS BEEN DAMAGE OF COPPER TUBE OF THE BUSHING OF YPHASE IN APRIL 2013. THE TUBE WAS FOUND IN 2 PIECES (BROKEN)WE HAD INSISTED CUSTOMER FOR NFT BUT NFT HAD NOT BEENDONE

SEAL OIL FLOW WAS AROUND 30L/MIN AT TE AND 35L/MIN IN EEWHICH HAS NOW INCREASED TO 45L/MIN IN TURBINE SIDE AND50L/MIN IN EXCITER END AFTER INCREASE IN VIBRATION IN BRG # 6


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ACTION TAKEN1. INTEGRITY OF SECONDARY FOUNDATION GROUTING WAS SUSPCTED

AND CHECKED BY NCCBM.

2. INSPECTION OF FOUNDATION WAS ALSO DONE BY BHEL ENGINEERS3. UPV REVEALED HONEYCOMBING IN COLUMNS 11 & 12 AND ALSO

CRACKS WAS FOUND IN SECONDARY GROUTING OF BRG # 6 PEDESTAL

4. AS SUGGESTED BY NCCBM AND BHEL ENGINEERING ,THE HONEYCOMB

IN THE FOUNDATION WAS REPAIRED BY PRESSURE EPOXY GROUTING

AND SECONDARY GROUTNG WAS REDONE BY REMOVING BRG # 6 BASEPEDESTAL AND REGROUTING USING CONBETRAX GP2 .

5. DESTRETCHING & STRETCHING OF FOUNDATION BOLTS WAS ALSO

DONE.

6. BRG. 4 WAS REPLACED

7. GENERATOR ROTOR WAS REPLACED TO REMOVE GENERATOR INDUCED

VIBRATION COMPONENTS.

RESULTS : MACHINE SUCESSFULLY SYNCHRONISED WITH VIBRATIONS OF

SHAFT BELOW 60 MICRONS PK-PK AND PEDESTAL BELOW 30 PK-PK IN

ALL BRGS


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MOULDS PREPARED FOR TEXT BEFORE SECONDARY GROUTING


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MOULDS TEXTED FOR STRENGTH


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Primary


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BRG # 6 SPECTRUM AFTER RESTORATION WORK


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NIT # 4 PANKI 105 MW HEAVY SPARKING AT EXCITER

Heavy Sparking in exciter commutator of Unit # 4 Panki TPS was reported andsoon the problem rose to alarming level and machine had to be debarred onJune 21 2013.

Vibrational analyses and electrical test were carried out by UPRVNL and basedon that following were suggested.

1)Undercutting of mica on the commutator

2)Carrying out the drop test on the commutator segments and on polepitchapart. This check will give you data about any dry soldering joints.

3)Checking the commutator for any non uniform wear out

4)Checking all the brush holders for their correct spring pressure andthe usage of correct grade of carbon brush.

5)Check for the parallality of collecting mechanism arms.

6)Check for the magnetic neutral axis of the collecting mechanism forany shifting during running of the Machine.

7) Groove chamfering has to be carried out, using form tool

Results : The sparking though reduced but still was totally resolved


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ACTION TAKEN BY RSC VARANASI

RSC ENGINEER VISITEDTHE SITE AND FOUNDTHAT THE UNDERCUTTING AND GOOVECHAMFERING WERE IMPROPER AND STILLDEMANDED MORE BUT THE COMMUTATORBEING OLD AND RESUED CONTINOUSLY RAISEDSUSPICIONS OVER POSSIBILITY OF FURTHERUNDERCUTTING

THE EXCITER ARMATURE WAS SUGGESTED FORREPLACEMENT AND UNIT WAS BROUGHT BACKTO BAR WITHIN 7 DAYS.


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Chronic axial Vibration Problem at Unit # 3 Unchahar TPS

Unchahar Unit # 3 NTPC during overhauling inApril 2012 discussed with BHEL RSC Engineersregarding high axial vibration of LPT Rear

Bearing Unit # 3. The axial vibrations were reportedly high to

the tune of above 50 microns zero-pk andvelocity above 20 mm/sec

The spectrum was analysed which revealedunloading of Brg # 4


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U-3 LPT rear brg vibration

0

10

20

30

40

50

60

70

11/20/00

11/20/01

11/20/02

11/20/03

11/20/04

11/20/05

11/20/06

11/20/07

11/20/08

11/20/09

Measurement Samples

Velocity-mm/

Axial

Vertical


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ACTION TAKEN

1. CATENARY CORRECTION AND DECK CORRECTION

2. PROPER BLUE MATCHING OF BRG WITH TORUS AS WELL AS TORUSWITH PEDESTAL

3. DESTRETCHING & STRETCHING OF FOUNDATION BOLTS WERE

CARRIED BUT THE REAR BRG WAS STRETCHED TO 2.43 AND THE

FRONT BOLTS WERE STRETCHED TO 2.30 DEVIATING FROM THRNORMAL APPROACH OF STRETCHING THE FRONT TO A HIGHER

VALUE AS COMPARED TO THE REAR .

4. ALIGNMENT CORRECTION .

RESULTS

The axial vibration were brought to below 25 microns and

velocity to less than 8 mm/sec.


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U#3 PEDESTAL 4 BOLT STRETCHING


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STRETCHING DETAILS U # 3 BRG NO

4,O/H 12

BOLT NO. DESIGN

VALUE

STRETCHI

NG VALUE

FRONT-L 1.83 2.30

FRONT-R 1.83 2.30

REAR-L 1.80 2.43

REAR-R 1.80 2.43


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SEVERE EARTH FAULT AT DEVIGHAT NEPAL(MACHINE BROUGHT TO GRID WITHIN 20 DAYS)

NEA had reported about the earth fault of stator Unit # 2,Devighat. BHEL RSC engineer reported at site on 3/01/12for attending the earth fault. The fault after analyses wasfound to be severe in nature and had resulted in melting

of overhang portion of two coils of B phase and burningdown of insulation of the nearby three other coils.

Constraints : Space constraint on removal of poles & Timeon removal of rotor.

Solution: Stator Removal Causing Both Time, Cost andWork easier

Machine Relevelled aligned and Brought Back to Grid on23/1/12 with better running parameters compared to

other running Units

Aft l t f th i di id l il HV f th


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IR AND PI AFTER PLACEMENT OF STATOR AND

FINALISATION OF LEVELLING AND ALIGNMENTDATE 15/1/2012

15 secs 60 secs 600 secs PIR-E 1000 3500 9000 2.57

Y-E 1000 3500 9500 2.71B-E 1000 3250 8500 2.62RYB- E 200 1500R-Y 2500 8500B-Y 2500 8000

Y-B 2500 8000

After replacement of the individual coils HV of the new

coils were carried out at 14.2 KV for 1 minute.

After finalization of the stator the HV of all coils/phases

was carried out at 9Kv in two parts.The stator was then re-position and final IR & PI was

recorded.


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U# 2 with better

vibration

parameters as

compared to U #

3

Bhel Rsc Varanasi

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