Turbine Tripping on "Combustion Trouble" & "High Exhaust Temp Spread Trip"

We have GE 6FA Gas turbine and Mark-VIe system with TMR configuration. During shutdown of machine load command was changed from 65 MW to 15 MW, and m/c unloaded normally up to 15 MW, but unloading did not stopped at 15 MW. Load further decreased down to 1.89 MW. At same time fuel mode change-over M6BQ to M6Q, as a resultant GCV4 closed. Load started hunting up/down and GCV-1, 2, & 3 also started hunting.

Exhaust thermocouples TTXD1_1, TTXD1_19, TTXD1_20, TTXD1_21 values decreased. It has occurred two times. Please suggest probable reasons.

Is it advisable to check the combustion internals?
 
vinodkpandey,

It really sounds like there is something wrong with the fuel control system that is causing the problem, and that flame is being lost because of low fuel flow-rate through the nozzles in one or more combustors resulting in the Combustion Trouble and High(-High) Exaust Temperature Spread Trips. If the unit exhaust temperature spreads are normal during normal loaded operation, but this problem only occurs during unloading, then it's mostly likely some kind of problem with the fuel control valves or the sensors monitoring fuel pressures or the hydraulic actuators or possibly the servo-valves (which would be the result of DIRTY oil--not usually a servo-valve problem).

However, it's pretty likely that there are Diagnostic Alarms being annunciated which would help troubleshoot the issue. Can you please provide the Alarm History from one or both events? (Many people post electronic files to web-sharing/hosting sites and then post the link to the files in a reply to the post so we can access the file(s) and examine them).

Wish we could be more help--but we just don't have enough information to say more than the above. Alarms--Process <b><i>AND</i></b> Diagnostic--are always very important when trying to troubleshoot operational issues.

Hope this helps! Please write back to let us know what you find, or to provide more information.
 
@uche,

You haven't provided any useful information to troubleshoot a particular tripping problem. (Maybe you are just asking a general question, but even that would be useful information!)

SO, the first place to look is ALWAYS the alarm display/list. A properly configured and programmed gas turbine control system will annunciate an alarm for EVERY condition that results in a turbine trip. One manufacturer uses a kind of "catch-all" alarm when something occurs that results in a loss of flame when no trip condition was detected BEFORE the loss of flame occurred--such as when the fuel supply to the gas turbine is insufficient to maintain flame in the combustion section. That alarm is "LOSS OF FLAME TRIP". A LOSS OF FLAME TRIP might also occur if the fuel shut-off valve to the turbine suddenly closed, possibly because a wire in the circuit is loose or the fuel stop valve solenoid is failing or has failed. But the point is--this manufacturer does everything possible to alert an operator to the possible problem, even if a condition that would result in a turbine trip (high-high vibration, low-low Lube Oil pressure, etc.) was not detected before flame was lost in the majority of combustors with flame detectors.

WHAT HAS BEEN DONE TO TRY TO TROUBLESHOOT THE PROBLEM AT YOUR SITE--AND MORE IMPORTANTLY WHAT WERE THE RESULTS OF THE TROUBLESHOOTING?

Some gas turbine control systems have a special function that captures operating data (not for every parameter, but for the most common parameters) for some time before a trip occurs, along with the alarms that were occurring at the time of the trip. This "Trip Display" or "Trip History" function is EXTREMELY USEFUL for capturing data for review and analysis--almost all of the time.

If the tripping problem is occurring often some gas turbine control systems have a method for capturing operator-selected data prior to the trip even which can be reviewed and analyzed; this is very useful when the parameters in the "Trip Display" or "Trip History" function don't have enough useful information.

If you could tell us the manufacturer of the turbine, the control system being used, what's happening prior to the trip(s) (Is the load fluctuating? Is the grid frequency stable or unstable prior to the trip(s)? (I'm presuming the gas turbine drives a synchronous generator--but you haven't told us what it powers.) Is fuel supply pressure and flow up to the turbine stable or unstable prior to the trip?) we could probably offer some help.

AND, if you can provide CLEAR photos of the machine control system display (photos and files can be attached to posts here on Control.com) immediately before or after the trip that would be helpful, also.

For future questions, if you click on FORUMS at the top of most any Control.com webpage:

1700907000960.png

and then click on LATEST you will go to the question & answer area of Control.com. At the top of that page you will see a selection to open (post) a new thread on the right:

1700907107386.png

By clicking on that you can open a new thread if you have what you believe is a unique problem, enter in as much information as you can (Control.com does not have avatars where people can post information about themselves and their work site and equipment they work on that could be very helpful in trying to answer questions...) along with a relevant subject line you will usually find you will get more, faster and concise answers to your question(s). But, just to say, "If a gas turbine trips, where should i check first?" doesn't provide any useful information. Unless you are new to gas turbine operation and are just asking a general question (which you could also tell us--which would be helpful!). We answer a LOT of GE-design heavy duty gas turbine operation and controls-related questions here and have for more than 20 years; all of those past questions are searchable using the magnifying glass Search function at the top of just about every Control.com webpage.

Help us to help you--by providing as much information as possible, even if you're just asking a general question and not having a particular problem. You posted in a thread titled "Turbine Tripping on "Combustion Trouble" & "High Exhaust Temp Spread Trip", which sort of implies those alarms might be what you are specifically asking about--but we don't know.

I hope the information provided above is helpful--if for no other purpose than how to open a new thread in the future. AGAIN, remember we aren't standing or sitting next to you, so we can't see what you see or have seen. We don't know what you know, what your experience is (and we have welcomed a lot of "newbies" or "freshers" to Control.com and watched them learn and grow to provide the benefit of their knowledge and experience over the years), and what was done to try to troubleshoot and resolve the problem they are experiencing. DO REMEMBER, if you are working an any gas turbine from any manufacturer if that gas turbine has been produced for decades the auxiliaries (the fuel control system; the turbine control system; the inlet filter system; the exhaust system; etc.) have changed many times over those years. Some manufacturers license the packaging of their turbines to other companies, and those other companies often use different auxiliaries than the turbine manufacturer might use. Combustion systems have also changed over the decades in order to reduce air pollutants. Just because you might be working on a Frame 6 gas turbine doesn't mean it's exactly like every other Frame 6 gas turbine (the turbines all draw air into the axial compressor, compress the air, add fuel to the compressed air and burn the mixture, and pass the hot gases through the turbine section) but the auxiliaries to support that can be VERY different and important to understanding what's happening).

Just as with this answer to your very vague and broad question, we often try to provide multiple things to check--in the way of questions. Getting the answers to those questions can be very useful; however, sometimes troubleshooting is a process of elimination--meaning that sometimes conditions can be caused by more than one stimulus or problem so it's necessary to check several conditions and eliminate the ones that AREN'T causing the problem until you find the one that IS causing the problem. Gas turbines are complicated machines--not so much the turbine and axial compressor or even the generator, but the auxiliaries and even the operation and condition of the machine and its auxiliaries can be causes of problems. So, again, please try to post as much information as possible--and we can probably provide a quick and concise answer.

Welcome to Control.com!
 
@uche,

You haven't provided any useful information to troubleshoot a particular tripping problem. (Maybe you are just asking a general question, but even that would be useful information!)

SO, the first place to look is ALWAYS the alarm display/list. A properly configured and programmed gas turbine control system will annunciate an alarm for EVERY condition that results in a turbine trip. One manufacturer uses a kind of "catch-all" alarm when something occurs that results in a loss of flame when no trip condition was detected BEFORE the loss of flame occurred--such as when the fuel supply to the gas turbine is insufficient to maintain flame in the combustion section. That alarm is "LOSS OF FLAME TRIP". A LOSS OF FLAME TRIP might also occur if the fuel shut-off valve to the turbine suddenly closed, possibly because a wire in the circuit is loose or the fuel stop valve solenoid is failing or has failed. But the point is--this manufacturer does everything possible to alert an operator to the possible problem, even if a condition that would result in a turbine trip (high-high vibration, low-low Lube Oil pressure, etc.) was not detected before flame was lost in the majority of combustors with flame detectors.

WHAT HAS BEEN DONE TO TRY TO TROUBLESHOOT THE PROBLEM AT YOUR SITE--AND MORE IMPORTANTLY WHAT WERE THE RESULTS OF THE TROUBLESHOOTING?

Some gas turbine control systems have a special function that captures operating data (not for every parameter, but for the most common parameters) for some time before a trip occurs, along with the alarms that were occurring at the time of the trip. This "Trip Display" or "Trip History" function is EXTREMELY USEFUL for capturing data for review and analysis--almost all of the time.

If the tripping problem is occurring often some gas turbine control systems have a method for capturing operator-selected data prior to the trip even which can be reviewed and analyzed; this is very useful when the parameters in the "Trip Display" or "Trip History" function don't have enough useful information.

If you could tell us the manufacturer of the turbine, the control system being used, what's happening prior to the trip(s) (Is the load fluctuating? Is the grid frequency stable or unstable prior to the trip(s)? (I'm presuming the gas turbine drives a synchronous generator--but you haven't told us what it powers.) Is fuel supply pressure and flow up to the turbine stable or unstable prior to the trip?) we could probably offer some help.

AND, if you can provide CLEAR photos of the machine control system display (photos and files can be attached to posts here on Control.com) immediately before or after the trip that would be helpful, also.

For future questions, if you click on FORUMS at the top of most any Control.com webpage:

View attachment 3634

and then click on LATEST you will go to the question & answer area of Control.com. At the top of that page you will see a selection to open (post) a new thread on the right:

View attachment 3635

By clicking on that you can open a new thread if you have what you believe is a unique problem, enter in as much information as you can (Control.com does not have avatars where people can post information about themselves and their work site and equipment they work on that could be very helpful in trying to answer questions...) along with a relevant subject line you will usually find you will get more, faster and concise answers to your question(s). But, just to say, "If a gas turbine trips, where should i check first?" doesn't provide any useful information. Unless you are new to gas turbine operation and are just asking a general question (which you could also tell us--which would be helpful!). We answer a LOT of GE-design heavy duty gas turbine operation and controls-related questions here and have for more than 20 years; all of those past questions are searchable using the magnifying glass Search function at the top of just about every Control.com webpage.

Help us to help you--by providing as much information as possible, even if you're just asking a general question and not having a particular problem. You posted in a thread titled "Turbine Tripping on "Combustion Trouble" & "High Exhaust Temp Spread Trip", which sort of implies those alarms might be what you are specifically asking about--but we don't know.

I hope the information provided above is helpful--if for no other purpose than how to open a new thread in the future. AGAIN, remember we aren't standing or sitting next to you, so we can't see what you see or have seen. We don't know what you know, what your experience is (and we have welcomed a lot of "newbies" or "freshers" to Control.com and watched them learn and grow to provide the benefit of their knowledge and experience over the years), and what was done to try to troubleshoot and resolve the problem they are experiencing. DO REMEMBER, if you are working an any gas turbine from any manufacturer if that gas turbine has been produced for decades the auxiliaries (the fuel control system; the turbine control system; the inlet filter system; the exhaust system; etc.) have changed many times over those years. Some manufacturers license the packaging of their turbines to other companies, and those other companies often use different auxiliaries than the turbine manufacturer might use. Combustion systems have also changed over the decades in order to reduce air pollutants. Just because you might be working on a Frame 6 gas turbine doesn't mean it's exactly like every other Frame 6 gas turbine (the turbines all draw air into the axial compressor, compress the air, add fuel to the compressed air and burn the mixture, and pass the hot gases through the turbine section) but the auxiliaries to support that can be VERY different and important to understanding what's happening).

Just as with this answer to your very vague and broad question, we often try to provide multiple things to check--in the way of questions. Getting the answers to those questions can be very useful; however, sometimes troubleshooting is a process of elimination--meaning that sometimes conditions can be caused by more than one stimulus or problem so it's necessary to check several conditions and eliminate the ones that AREN'T causing the problem until you find the one that IS causing the problem. Gas turbines are complicated machines--not so much the turbine and axial compressor or even the generator, but the auxiliaries and even the operation and condition of the machine and its auxiliaries can be causes of problems. So, again, please try to post as much information as possible--and we can probably provide a quick and concise answer.

Welcome to Control.com!
 
@WTF
Thanks so much, I just asked a general question, am new to turbines and am preparing for an interview in a well known oil and gas company in my country, and I think that question can be thrown at me, thanks for your detailed analysis .
 
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