GT-B High Exhaust Temperature Spread_Start Up_rev1.ppt

Gtg

1. GT-B High Exhaust Temperature
Spread & Wheel Space
Temperature Issue

2. Gas Turbine Specifications

3. OEM Recommended Inspection Frequency
Type Interval Downtime
Combustion
Inspection
16,000 hrs
(1.8 yrs)
7 days
Hot Gas Path
Inspection
32,000hrs
(3.65 yrs)
16 days
Major Inspection
64,000hrs
(7.30 yrs)
25 days
History
•Commissioning date:2009
•Running hours: 61,889
•Total starts: 84
•Fired Starts: 78
•Emergency trips: 43
•Inspections:
–Combustion inspection -2012
–Hot Gas Path Inspection -2014
–Combustion Inspection -May 2016
–HGPI taken in October 2016 to
address high exhaust temperature
spread issue
PartsReplacement History
Component LastReplaced
Fuel Gas Nozzles May ’16
Cross-Fire Tubes May’ 16
1
st
Stage Nozzles Oct ’14
1
st
Stage Buckets Oct’ 14
2
nd
Stage Nozzles 2009
2
nd
Stage Buckets 2009

4. HGPI Findings & Action Taken
Part Observation during HGPI Action
Fuel Nozzle Slight carbondeposition on tip Cleaned
Combustion LinersFound okay. Linerstoppers found eroded.
Cross-fire seal plates found eroded
Linerstoppers repaired. Cross-fire seal plates
installed as is as spare unavailable
Cross fire tubes +
retainers
Retainers had lost tension Replaced both cross-fire tube and retainers
Flow Sleeves 04 sleeves had worn stoppers No action
Transition PiecesOkay Cleaned
1
st
Stage nozzlesExtensive depositionof molten cross-fire
tube from a previous failure of cross fire
tube
Nozzles cleaned and cooling holes de-choked
1
st
Stage bucketsSplatterof molten cross fire tube No action
1
st
stage shroudCrackedand deformed No action.Spare unavailable
2
nd
Stage nozzlesExtensive TBCdamage + parent metal
loss
Top halfnozzles repaired. Bottom half
inaccessible
2
nd
stage bucketsOkay No action
3
rd
stage nozzlesOkay No action
3
rd
stage bucketsOkay No action

5. Additional Checks
•Air blowing of fuel gas lines to ensure de-choking -found clean
•Inspection of cooling air lines and associated orifices –found clean
•IGV functional test –found okay
•GCV / IGV filters inspection –found okay
•Fuel gas strainer inspection –found okay

6. Observations After Start Up
•Combustion Alarm (High exhaust temperature spread) observed from 18.5
MW to 20 MW. After 21.5 MW, first exhaust spread is generally lower than
allowable spread; however sometimes exceeds the allowable spread.
•Wheel space temperature alarm (High 1st Stage AFT wheel Space
temperature) above 18.5 MW. Delta between right and left thermocouple
is about 85 Celsius

7. Variation in allowable spread and actual spread with change in Load
DATA TRENDS AFTER S/U
Note: Further spread trends after start up in attached excel file.

8. DATA TRENDS AFTER S/U

9. DATA TRENDS AFTER S/U

10. PICTORIAL OBSERVATIONS FROM
OCTOBER HGPI (as found)

11. 1
st
Stage Nozzle Segment # 03
Back

12. 1
st
Stage Nozzle Segment # 04
Back

13. 1
st
Stage Nozzle Segment # 05
Back

14. 1
st
Stage Bucket Shroud # 06
Back

15. 1
st
Stage Bucket Shroud # 07
Back

16. 1
st
Stage Bucket Shroud # 09
Back

17. 1
st
Stage Bucket Shroud # 10
Back

18. 2
nd
Stage Nozzle Segment # 03
Back

19. 2
nd
Stage Nozzle Segment # 06
Back

20. 2
nd
Stage Nozzle Segment # 09
Back

21. 2
nd
Stage Nozzle Segment # 10
Back

22. 2
nd
Stage Nozzle Segment # 11
Back

23. 2
nd
Stage Nozzle Segment # 12
Back

24. 2
nd
Stage Nozzle Segment # 13
Back

25. 2
nd
Stage Nozzle Segment # 15
Back

26. 2
nd
Stage Nozzle Segment # 22
Back

27. 2
nd
Stage Nozzle Segment # 24
Back

28. Fuel Nozzle / Combustion Liner # 1
Back

29. Fuel Nozzle / Combustion Liner # 2
Back

30. Fuel Nozzle / Combustion Liner # 3
Back

31. Fuel Nozzle / Combustion Liner (#7)
Back

32. 2
nd
Stage Buckets
Back

33. 3
rd
Stage Nozzles (upper half)
Back

34. 3
rd
Stage Buckets
Back