Facebook
Google
GitHub
Linkedin
A GE 6FA gas turbine equipped with 4 flame detectors. Recently it was observed that after turbine shutdown, one flame detector still showing flame intensity about 50% and came to zero after 40-50 minutes during which the GT shows "NOT READY TO START" status. Detail inspection was carried out of cables and sensor, tested also and found with normal feedback. After installation the issue was observed. So what could be the possible reason
Gas Turbine Flame Detector
- Thread starter Axix7
- Start date
Can you please first state your exact name, location, company name before we answer?
I think it's not necessary here
@Axix7,
GE and its packagers have used different types of flame detectors/sensors over the years, including the product life of the 6FA model series. Many of the detectors/sensors were Geiger-Mueller devices which required very high DC voltages to work correctly (supplied by the turbine control system). Newer versions were SiC types that only require 4-20 mA source (usually at approximately 28 VDC) to operate correctly. It would help if you told the forum what flame detectors/sensors are in use on the machine and what turbine control system is in use (if the turbine control system is a Mark* IV please be specific--it's either a Mark* VI OR a Mark* VIe).
It might also be helpful if you can tell us if the machine has conventional combustors (including MNQC fuel nozzles (Multi-Nozzle Quiet Combustor fuel nozzles)) or if the machine uses one of the variants of the DLN (Dry Low NOx) combustion systems.
It would also be helpful if you told us if any repair or maintenance activity in the turbine compartment requiring removal/re-installation of the flame detectors/sensors was done prior to the beginning of the problem.
From the information you have provided, it appears you have eliminated the wiring and terminations between the turbine control system and the detector/sensor as well as the sensor itself. Did the wiring check include meggaring the interconnecting wiring between the turbine control system and the detector/sensor? (When meggaring the wiring, usually with a 500 VDC meggar, the wiring should be disconnected from the turbine control system AND the detector/sensor.) CAUTION: If the flame detectors are the Geiger-Mueller style (usually manufactured by Honeywell company) the 300+ VDC power is applied to the sensor AT ALL TIMES. Exercise appropriate caution when determinating/terminating the wiring for checks/verification, usually by isolating the power supply voltage from the turbine control system.
Have you tried switching the detector/sensor with one of the other three to see if the problem follows the detector/sensor or if it remains on the same turbine control system input channel?
If the turbine control system is a Mark* what Diagnostic Alarms related to the input channel and associated printed circuit cards (terminal board(s); input/output cards; processor rack; etc.) and what has been done to resolve those Diagnostic Alarms?
If the turbine control system is a Mark* it is common for the control system to monitor the inputs from the flame detector sensors when them machine is not running and if one or more of the flame detectors/sensors indicates flame when there shouldn't be flame that is considered an unsafe condition for STARTing the machine and hence the NOT READY TO START indication is annunciated.
Often, troubleshooting and resolution is a process of elimination--analyzing the situation to determine what might be causing the problem) and then prioritizing the list in terms of most likely to least likely and start by checking the most likely possible cause--thoroughly--and if that's not determined to be the problem moving to the next most likely cause, eliminating possible causes (after thorough testing and analysis) until the cause or causes is or are found and then resolving the issue(s).
These questions are designed to help you understand the larger picture of the flame detection/monitoring system and components. You seem to have eliminated the wiring and the detector/sensor, but possibly not thoroughly, and it doesn't seem you've considered or investigated to turbine control system terminal boards and input/output cards. (Again, if the turbine control system is a Mark* there are usually Diagnostic Alarms which can be helpful in pinpointing the problem--not just Voter Mismatch alarms but alarms regarding the input/output channels and associated printed circuit cards and/or power supplies.)
Best of luck--if you need more help, please provide the information requested above. If you resolve the problem, please write back to let us know what was discovered and how the problem was solved.
GE and its packagers have used different types of flame detectors/sensors over the years, including the product life of the 6FA model series. Many of the detectors/sensors were Geiger-Mueller devices which required very high DC voltages to work correctly (supplied by the turbine control system). Newer versions were SiC types that only require 4-20 mA source (usually at approximately 28 VDC) to operate correctly. It would help if you told the forum what flame detectors/sensors are in use on the machine and what turbine control system is in use (if the turbine control system is a Mark* IV please be specific--it's either a Mark* VI OR a Mark* VIe).
It might also be helpful if you can tell us if the machine has conventional combustors (including MNQC fuel nozzles (Multi-Nozzle Quiet Combustor fuel nozzles)) or if the machine uses one of the variants of the DLN (Dry Low NOx) combustion systems.
It would also be helpful if you told us if any repair or maintenance activity in the turbine compartment requiring removal/re-installation of the flame detectors/sensors was done prior to the beginning of the problem.
From the information you have provided, it appears you have eliminated the wiring and terminations between the turbine control system and the detector/sensor as well as the sensor itself. Did the wiring check include meggaring the interconnecting wiring between the turbine control system and the detector/sensor? (When meggaring the wiring, usually with a 500 VDC meggar, the wiring should be disconnected from the turbine control system AND the detector/sensor.) CAUTION: If the flame detectors are the Geiger-Mueller style (usually manufactured by Honeywell company) the 300+ VDC power is applied to the sensor AT ALL TIMES. Exercise appropriate caution when determinating/terminating the wiring for checks/verification, usually by isolating the power supply voltage from the turbine control system.
Have you tried switching the detector/sensor with one of the other three to see if the problem follows the detector/sensor or if it remains on the same turbine control system input channel?
If the turbine control system is a Mark* what Diagnostic Alarms related to the input channel and associated printed circuit cards (terminal board(s); input/output cards; processor rack; etc.) and what has been done to resolve those Diagnostic Alarms?
If the turbine control system is a Mark* it is common for the control system to monitor the inputs from the flame detector sensors when them machine is not running and if one or more of the flame detectors/sensors indicates flame when there shouldn't be flame that is considered an unsafe condition for STARTing the machine and hence the NOT READY TO START indication is annunciated.
Often, troubleshooting and resolution is a process of elimination--analyzing the situation to determine what might be causing the problem) and then prioritizing the list in terms of most likely to least likely and start by checking the most likely possible cause--thoroughly--and if that's not determined to be the problem moving to the next most likely cause, eliminating possible causes (after thorough testing and analysis) until the cause or causes is or are found and then resolving the issue(s).
These questions are designed to help you understand the larger picture of the flame detection/monitoring system and components. You seem to have eliminated the wiring and the detector/sensor, but possibly not thoroughly, and it doesn't seem you've considered or investigated to turbine control system terminal boards and input/output cards. (Again, if the turbine control system is a Mark* there are usually Diagnostic Alarms which can be helpful in pinpointing the problem--not just Voter Mismatch alarms but alarms regarding the input/output channels and associated printed circuit cards and/or power supplies.)
Best of luck--if you need more help, please provide the information requested above. If you resolve the problem, please write back to let us know what was discovered and how the problem was solved.
