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Experiencing high exhaust temperature spread during load ramp up between 18 MW and 21 MW. High differential temperature for wheel space 1st stage aft 1 & 2.
We had been facing high exhaust temperature spread on our Hitachi H-25 gas turbine since August; therefore, HGPI was undertaken in October. However, high exhaust temperature spread observed again on machine start up.
A comprehensive presentation with pictorial observations and start up trends can be accessed from the dropbox link:
https://www.dropbox.com/sh/rpddpe8pv4wkjpa/AADk1hsag8aZD7RTLwuZyhpAa?dl=0
Summary is as follows.
Major observations during HGPI were:
- Deposition of molten cross-fire tube on 1st stage nozzle
- Splatter deposition on 1st stage bucket
- Extensive TBC / Parent loss on 2nd stage buckets (leading edge and trailing edge)
- No observations found on fuel gas lines, fuel nozzles, liners and transition pieces.
Actions Taken:
- Cross-fire tubes and retainers replaced
- Transition pieces cleaned
- 1st stage nozzles cleaned and cooling holes de-choked
- 9 segments of 2nd stage nozzles (from upper half) repaired
Observations on S/U:
- 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) appeared above 18.5 MW. Delta between right and left thermocouple is about 85 Celsius
Queries
1) What is the possible reason for high temperature spread between 18 & 21 MW? What can be done to rectify it?
2) Why is the first exhaust spread fluctuating at high loads?
3) What could be possible reasons for large difference in wheel space 1st stage aft # 1 & 2 and what are the consequential damages?
4) Does anyone has a swirl chart for H-25? If yes, please share.
5) Do you think this is related to combustion issue? For your information, All fuel nozzles installed during box up are clean with no choking. New cross-fire tubes and retainers installed. No damage on liners or transition pieces. Fuel gas composition is okay too.
6) How is the allowable temperature spread calculated for Hitachi Turbine (H-25) with Mark VI control system?
Looking forward to hearing from you guys soon.
We had been facing high exhaust temperature spread on our Hitachi H-25 gas turbine since August; therefore, HGPI was undertaken in October. However, high exhaust temperature spread observed again on machine start up.
A comprehensive presentation with pictorial observations and start up trends can be accessed from the dropbox link:
https://www.dropbox.com/sh/rpddpe8pv4wkjpa/AADk1hsag8aZD7RTLwuZyhpAa?dl=0
Summary is as follows.
Major observations during HGPI were:
- Deposition of molten cross-fire tube on 1st stage nozzle
- Splatter deposition on 1st stage bucket
- Extensive TBC / Parent loss on 2nd stage buckets (leading edge and trailing edge)
- No observations found on fuel gas lines, fuel nozzles, liners and transition pieces.
Actions Taken:
- Cross-fire tubes and retainers replaced
- Transition pieces cleaned
- 1st stage nozzles cleaned and cooling holes de-choked
- 9 segments of 2nd stage nozzles (from upper half) repaired
Observations on S/U:
- 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) appeared above 18.5 MW. Delta between right and left thermocouple is about 85 Celsius
Queries
1) What is the possible reason for high temperature spread between 18 & 21 MW? What can be done to rectify it?
2) Why is the first exhaust spread fluctuating at high loads?
3) What could be possible reasons for large difference in wheel space 1st stage aft # 1 & 2 and what are the consequential damages?
4) Does anyone has a swirl chart for H-25? If yes, please share.
5) Do you think this is related to combustion issue? For your information, All fuel nozzles installed during box up are clean with no choking. New cross-fire tubes and retainers installed. No damage on liners or transition pieces. Fuel gas composition is okay too.
6) How is the allowable temperature spread calculated for Hitachi Turbine (H-25) with Mark VI control system?
Looking forward to hearing from you guys soon.