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exhust temprature
- Thread starter abdooo99
- Start date
Hi @abdooo99
We will need some datas like frame unit OEM
Also if some trends are available , you can share here
How do you operate these units Base load /Peak load???
We will need some datas like frame unit OEM
Also if some trends are available , you can share here
How do you operate these units Base load /Peak load???
Ok
We would need also some trends about datas related to the unit like exhaust spread temp.. Load FSR ..speed..and other controls constants
We would need also some trends about datas related to the unit like exhaust spread temp.. Load FSR ..speed..and other controls constants
WHY is no one asking the original poster WHEN does the exhaust temperature appear to be excessive? During start-up/acceleration? At FSNL (Full Speed-No Load)? During loading? During shutdown?
Because during start-up and acceleration it's NOT unsusal for the exhaust temperature to be high and then to decrease after the axial compressor approaches rated speed and the IGVs open (IF the unit even has modulated IGVs). 371 deg F is NOT excessive for part load conditions; a typical Base Load exhaust temperature would be in the range of approximately 565 deg C (depending on the machine, the fuel being burned, the ambient temperature, etc.)--so 371 deg C is a temperature which would be seen during loading and unloading.
Is the turbine control system annunciating alarm(s) about excessive exhaust temperature? If so, when--at what speed (during start-up or shutdown) or what load(s)?
What else is going on at the time of this excessive exhaust temperature? If the unit is multi-fuel (gas/distillate, for example) is the unit transferring fuels? If the unit has DLN combustors, is the unit transitioning combustion modes (and which modes)?
Again, 371 deg C is not an unusually high exhaust temperature for most operating conditions--but it could be for some conditions. WHAT ARE THE CONDITIONS when the original poster (and/or the turbine control system) appear to be excessive?
WHAT ALARMS are being annunciated and/or active when the exhaust temperature appears to be excessively high?
Is the load (MW) stable or unstable?
Is the frequency stable or unstable?
Is the fuel flow stable or unstable?
How long does this high exhaust temperature condition persist? Is it just for a second, or three seconds, or 30 seconds or more?
It would also be helpful to know what turbine control system the unit has, what fuel(s) are being burned, and if the turbine drives a centrifugal compressor or a generator.
I hear this complaint often during commissioning of new gas turbines in combined cycle applications. Because often the HRSG manufacturers only design the heat recovery system to experience the 100% speed temperature during start-up, when, in fact, the exhaust temperature can approach more than 500 deg C during acceleration to FSNL (100% speed). And they scream the first couple of times the turbine is started, "WHY IS THE EXHAUST TEMPERATURE SO HIGH??!!?!?!! MAKE IT LOWER!!!" They don't have the necessary metal for these high temperatures at low air flows and/or the boiler feedwater system isn't set up to prevent swell or keep the steam drum(s) full without experiencing carry-over at the transient high exhaust temperature conditions. (This usually only happens for a couple of minutes or so during starting/acceleration, but it can stress the HRSG if not considered in the design/operation.)
BUT, we need to know WHEN the exhaust temperature is higher than expected or appears to be higher than expected. Without this information no one can say if the exhaust temperature IS too high or not.
Correct?
Because during start-up and acceleration it's NOT unsusal for the exhaust temperature to be high and then to decrease after the axial compressor approaches rated speed and the IGVs open (IF the unit even has modulated IGVs). 371 deg F is NOT excessive for part load conditions; a typical Base Load exhaust temperature would be in the range of approximately 565 deg C (depending on the machine, the fuel being burned, the ambient temperature, etc.)--so 371 deg C is a temperature which would be seen during loading and unloading.
Is the turbine control system annunciating alarm(s) about excessive exhaust temperature? If so, when--at what speed (during start-up or shutdown) or what load(s)?
What else is going on at the time of this excessive exhaust temperature? If the unit is multi-fuel (gas/distillate, for example) is the unit transferring fuels? If the unit has DLN combustors, is the unit transitioning combustion modes (and which modes)?
Again, 371 deg C is not an unusually high exhaust temperature for most operating conditions--but it could be for some conditions. WHAT ARE THE CONDITIONS when the original poster (and/or the turbine control system) appear to be excessive?
WHAT ALARMS are being annunciated and/or active when the exhaust temperature appears to be excessively high?
Is the load (MW) stable or unstable?
Is the frequency stable or unstable?
Is the fuel flow stable or unstable?
How long does this high exhaust temperature condition persist? Is it just for a second, or three seconds, or 30 seconds or more?
It would also be helpful to know what turbine control system the unit has, what fuel(s) are being burned, and if the turbine drives a centrifugal compressor or a generator.
I hear this complaint often during commissioning of new gas turbines in combined cycle applications. Because often the HRSG manufacturers only design the heat recovery system to experience the 100% speed temperature during start-up, when, in fact, the exhaust temperature can approach more than 500 deg C during acceleration to FSNL (100% speed). And they scream the first couple of times the turbine is started, "WHY IS THE EXHAUST TEMPERATURE SO HIGH??!!?!?!! MAKE IT LOWER!!!" They don't have the necessary metal for these high temperatures at low air flows and/or the boiler feedwater system isn't set up to prevent swell or keep the steam drum(s) full without experiencing carry-over at the transient high exhaust temperature conditions. (This usually only happens for a couple of minutes or so during starting/acceleration, but it can stress the HRSG if not considered in the design/operation.)
BUT, we need to know WHEN the exhaust temperature is higher than expected or appears to be higher than expected. Without this information no one can say if the exhaust temperature IS too high or not.
Correct?
More information
#The type of fuel is gas
#Turbine in IGV temp. Control
#Compressor discharge 5.8 Bar, 259 c
#Exhaust temp 370 c
#IGV 59.85 DGA
#LOAD 7 MW, the full load can be reached to 26MW
#FSR is in SPEED CONTROL
# frequency and flow rate are stable
# No abnormal alarm appeared
# the exhaust temp for one turbine is 371 c but for another one is 321c
#MSG_FLD3 IGV FULL OPEN
#The type of fuel is gas
#Turbine in IGV temp. Control
#Compressor discharge 5.8 Bar, 259 c
#Exhaust temp 370 c
#IGV 59.85 DGA
#LOAD 7 MW, the full load can be reached to 26MW
#FSR is in SPEED CONTROL
# frequency and flow rate are stable
# No abnormal alarm appeared
# the exhaust temp for one turbine is 371 c but for another one is 321c
#MSG_FLD3 IGV FULL OPEN
Okay; we got something to work with here.
By the way I neglected to ask a really important question: When did this problem start? After a maintenance outage or a forced outage or some other work (please detail the work and the reason for it)?
BUT, you can have two machines built one right after the other on the same assembly line and they will almost NEVER have identical operating characteristics. Why? Because they are almost never operated similarly at all times. Maintenance outages are almost never done at the same time. One might have 40 more trips than the other, and one might have 50 more starts than the other. One may have 5,000 hours of operation more than the other--or more. One may have recently been water-washed (off-line), and the other might not have been off-line water-washed for 9 months. One might have dirtier air filters than the other. We don't know if they were installed and commissioned at the same time, or if one is 4 years older than the other.
If they are both being operated in combined cycle mode with no bypass stack, it's entirely possible that one boiler/stack has a higher back-pressure than the other. (I've seen insulation dislodged from behind internal wall plates in the boiler build up on the superheater tubes and cause a high back-pressure (which translates into a lower output and poor boiler steam output)--on two machines which were installed and commissioned at the same time.
You failed to mention what kind of turbine control system is in use. If you have a Mark* V or -VI or VIe you have the capability to capture data which you can share (as ControlsGuy25 mentioned before). If you have two MS5001 machines and you can share data for the two machines at similar operating conditions that would be helpful. Things like IGV angle, CPD, fuel flow-rate, TNR, TNH, load, axial compressor inlet temperatures, exhaust temperature spreads (all exhaust temperatures would be very helpful--for both machines).
But, 371 deg C is NOT high, even if it's more elevated than another similar machine operating at similar conditions. IGV temp control (on a machine without DLN-I combustors) is used to elevate exhaust temperature in order to make more steam at low loads/exhaust temperatures. Are the IGV angles identical for the same load, and the only difference is the exhaust temperature? Again, being able to look at the individual exhaust T/C values as well as the exhaust temperature spreads would be very helpful.
There's just a lot of things we don't know about the machines and the boilers and how they've been operated and maintained over the years. Yes--they (might) have digital control systems, but they are not even as sophisticated as on some 4-cylinder super-economy automobiles with fuel injection (which monitor air/fuel by monitoring oxygen levels)--the Mark* systems don't do that. (In reality, the turbine control systems are really pretty simple, though they can seem to be very complicated.) Sorry, but without a lot more information there's not a lot more we can offer to try to explain the difference. High exhaust duct back-pressure will cause elevated exhaust temperatures (in addition to poor performance)--the exhaust doesn't flow as easily when the back-pressure is high and this causes the machine to have a higher exhaust temperature because it's burning more fuel to make the same power.
Anyway, again--we would need to have a lot more information and real data. You would need to tell us when the last maintenance outages were done, and what was done during each outage on each machine.
I wish the news was better, but this isn't a simple problem and people complain about this on multi-unit sites all the time because it seems like all of the units should run pretty much the same--but the reality is: they don't. Sometimes the differences are minor; other times the differences are larger.
And, the causes of the problem you are describing aren't always the turbine OR the control system. Often it's hot gas path hardware problems (cracked liners; plugger fuel nozzle orifice(s); broken exhaust diffusers; blown-out insulation in the boiler transition duct; even axial compressor inlet filter problems (maybe rain soaked some filters in one unit and not in the other). Or one unit's inlet air intake is closer to a dusty road or a road used by a lot of diesel-engined lorries. And, yes--the number of fired starts and the number of emergency trips--especially from load--can make a awful ot of difference in how two machines operate. Thermal stresses during starting/acceleration and trips from load (when the fuel is abruptly shut off) have a profound effect on hot gas part parts and parts life.
If you can give us more data, we can provide more information. But, you're going to have to provide a LOT more data and information.
By the way I neglected to ask a really important question: When did this problem start? After a maintenance outage or a forced outage or some other work (please detail the work and the reason for it)?
BUT, you can have two machines built one right after the other on the same assembly line and they will almost NEVER have identical operating characteristics. Why? Because they are almost never operated similarly at all times. Maintenance outages are almost never done at the same time. One might have 40 more trips than the other, and one might have 50 more starts than the other. One may have 5,000 hours of operation more than the other--or more. One may have recently been water-washed (off-line), and the other might not have been off-line water-washed for 9 months. One might have dirtier air filters than the other. We don't know if they were installed and commissioned at the same time, or if one is 4 years older than the other.
If they are both being operated in combined cycle mode with no bypass stack, it's entirely possible that one boiler/stack has a higher back-pressure than the other. (I've seen insulation dislodged from behind internal wall plates in the boiler build up on the superheater tubes and cause a high back-pressure (which translates into a lower output and poor boiler steam output)--on two machines which were installed and commissioned at the same time.
You failed to mention what kind of turbine control system is in use. If you have a Mark* V or -VI or VIe you have the capability to capture data which you can share (as ControlsGuy25 mentioned before). If you have two MS5001 machines and you can share data for the two machines at similar operating conditions that would be helpful. Things like IGV angle, CPD, fuel flow-rate, TNR, TNH, load, axial compressor inlet temperatures, exhaust temperature spreads (all exhaust temperatures would be very helpful--for both machines).
But, 371 deg C is NOT high, even if it's more elevated than another similar machine operating at similar conditions. IGV temp control (on a machine without DLN-I combustors) is used to elevate exhaust temperature in order to make more steam at low loads/exhaust temperatures. Are the IGV angles identical for the same load, and the only difference is the exhaust temperature? Again, being able to look at the individual exhaust T/C values as well as the exhaust temperature spreads would be very helpful.
There's just a lot of things we don't know about the machines and the boilers and how they've been operated and maintained over the years. Yes--they (might) have digital control systems, but they are not even as sophisticated as on some 4-cylinder super-economy automobiles with fuel injection (which monitor air/fuel by monitoring oxygen levels)--the Mark* systems don't do that. (In reality, the turbine control systems are really pretty simple, though they can seem to be very complicated.) Sorry, but without a lot more information there's not a lot more we can offer to try to explain the difference. High exhaust duct back-pressure will cause elevated exhaust temperatures (in addition to poor performance)--the exhaust doesn't flow as easily when the back-pressure is high and this causes the machine to have a higher exhaust temperature because it's burning more fuel to make the same power.
Anyway, again--we would need to have a lot more information and real data. You would need to tell us when the last maintenance outages were done, and what was done during each outage on each machine.
I wish the news was better, but this isn't a simple problem and people complain about this on multi-unit sites all the time because it seems like all of the units should run pretty much the same--but the reality is: they don't. Sometimes the differences are minor; other times the differences are larger.
And, the causes of the problem you are describing aren't always the turbine OR the control system. Often it's hot gas path hardware problems (cracked liners; plugger fuel nozzle orifice(s); broken exhaust diffusers; blown-out insulation in the boiler transition duct; even axial compressor inlet filter problems (maybe rain soaked some filters in one unit and not in the other). Or one unit's inlet air intake is closer to a dusty road or a road used by a lot of diesel-engined lorries. And, yes--the number of fired starts and the number of emergency trips--especially from load--can make a awful ot of difference in how two machines operate. Thermal stresses during starting/acceleration and trips from load (when the fuel is abruptly shut off) have a profound effect on hot gas part parts and parts life.
If you can give us more data, we can provide more information. But, you're going to have to provide a LOT more data and information.
If the machine you say is experiencing high exhaust temperature is operating with IGV Temperature Control ON and the IGVs are at 59.85 DGA, and the other machine is operating with IGV Temperature Control OFF and the IGVs are FULL OPEN this fully explains the situation.
As was written, IGV Temperature Control (which, by the way, is technically called IGV EXHAUST Temperature Control) is a way of INCREASING exhaust temperature when operating at Part Load in order to increase steam production and steam temperature in the HRSG (boiler). IGV Temperature Control works by closing the IGVs more than they would normally be closed in order to reduce the airflow through the turbine which causes the exhaust temperature to increase, thereby increasing steam production and steam temperature at Part Load operating conditions. Gas turbine exhaust temperature is at maximum when the unit is at Base Load and the IGVs are fully open--and that’s when steam production and steam temperature is at maximum. So, by increasing exhaust temperature at loads less than Base Load (when exhaust temperature is less than at Base Load) steam production and-temperature can be increased above what would otherwise be possible when operating below Base Load.
Many sites use IGV Temperature Control to improve steam production and steam temperature when the unit is operating below Base Load (Part Load operation). Some sites don’t.
So, if one machine is operating with IGV Temperature Control ON and the other with IGV Temperature Control OFF and the loads of the two machines are about the same, then the exhaust temperatures of the two machines will be different—especially if the loads are low (around 7 MW in this case). This would be expected, so it would be normal. And the IGV angles of the two machines would be different (if the loads of the two machines were about the same).
Problem solved. One machine is operating with IGV Temperature Control ON and the other machine is operating with IGV Temperature Control OFF, and if both machines are operating at about the same load the IGV angles and the exhaust temperatures will be different. And that is normal and to be expected. The differences in exhaust temperature and IGV angle will be larger at lower loads (again presuming the two machines are operating at approximately the same loads).
Does this help explain the differences in exhaust temperatures?
As was written, IGV Temperature Control (which, by the way, is technically called IGV EXHAUST Temperature Control) is a way of INCREASING exhaust temperature when operating at Part Load in order to increase steam production and steam temperature in the HRSG (boiler). IGV Temperature Control works by closing the IGVs more than they would normally be closed in order to reduce the airflow through the turbine which causes the exhaust temperature to increase, thereby increasing steam production and steam temperature at Part Load operating conditions. Gas turbine exhaust temperature is at maximum when the unit is at Base Load and the IGVs are fully open--and that’s when steam production and steam temperature is at maximum. So, by increasing exhaust temperature at loads less than Base Load (when exhaust temperature is less than at Base Load) steam production and-temperature can be increased above what would otherwise be possible when operating below Base Load.
Many sites use IGV Temperature Control to improve steam production and steam temperature when the unit is operating below Base Load (Part Load operation). Some sites don’t.
So, if one machine is operating with IGV Temperature Control ON and the other with IGV Temperature Control OFF and the loads of the two machines are about the same, then the exhaust temperatures of the two machines will be different—especially if the loads are low (around 7 MW in this case). This would be expected, so it would be normal. And the IGV angles of the two machines would be different (if the loads of the two machines were about the same).
Problem solved. One machine is operating with IGV Temperature Control ON and the other machine is operating with IGV Temperature Control OFF, and if both machines are operating at about the same load the IGV angles and the exhaust temperatures will be different. And that is normal and to be expected. The differences in exhaust temperature and IGV angle will be larger at lower loads (again presuming the two machines are operating at approximately the same loads).
Does this help explain the differences in exhaust temperatures?
You are:
1) Not providing the details of the loads of the two units
2) Probably over-thinking this and making it more difficult than it is (and it's not difficult).
You haven't said if one or both units have IGV (Exhaust) Temperature Control ON. Or which unit has IGV (Exhaust) Temperature Control ON and which unit has IGV Exhaust Temperature Control OFF (presuming it's ON for one unit and OFF for the other unit). THIS IS IMPORTANT INFORMATION. Identify the units (for example, Unit 11 has IGV Temp Control ON and Unit 12 has IGV Temp Control OFF, or both units 11 & 12 have IGV Temp Control ON).
The topic of how IGV (Exhaust) Temperature Control works has been covered several times on Control.com. At the top of every Control.com page there is a magnifying glass icon--the Search function. Click on it and start searching for IGV Temperature Control or IGV Temp Control. Granted, you're going to have to go through a LOT of search results to find what you're looking for, but in the process you will learn a lot about IGV (Exhaust) Temperature Control. If the units at your site don't have DLN-I combustors (that is, they have conventional combustors) the discussion will not be applicable. If the units at your site have DLN-I combustors--that's definitely something you should have told us in the beginning. It changes a LOT of things.
I am presuming the units have conventional combustors (that is, they do not have DLN-I combustors). I am presuming the units have selectable IGV (Exhaust) Temperature Control (that is, it can be selected ON or OFF, usually on the IGV Display on the operator interface (<I> or HMI). But, you have to identify the units, tell us if IGV (Exhaust) Temp Control is ON or OFF on each unit and tell us what the loads are on each unit for these conditions you are describing. In Post #9 you said the the MSG FIELD 3 indicated the IGVs were full open on one unit--but you didn't say WHICH unit.
And all of the things I wrote above can also impact exhaust temperature even when the IGV angles on two similar machines are within a couple of degrees of each other. But, you need to clarify some information and perhaps we can help you. You need to find relevant information about IGV Temp Control on conventional combustor-equipped machines.
1) Not providing the details of the loads of the two units
2) Probably over-thinking this and making it more difficult than it is (and it's not difficult).
You haven't said if one or both units have IGV (Exhaust) Temperature Control ON. Or which unit has IGV (Exhaust) Temperature Control ON and which unit has IGV Exhaust Temperature Control OFF (presuming it's ON for one unit and OFF for the other unit). THIS IS IMPORTANT INFORMATION. Identify the units (for example, Unit 11 has IGV Temp Control ON and Unit 12 has IGV Temp Control OFF, or both units 11 & 12 have IGV Temp Control ON).
The topic of how IGV (Exhaust) Temperature Control works has been covered several times on Control.com. At the top of every Control.com page there is a magnifying glass icon--the Search function. Click on it and start searching for IGV Temperature Control or IGV Temp Control. Granted, you're going to have to go through a LOT of search results to find what you're looking for, but in the process you will learn a lot about IGV (Exhaust) Temperature Control. If the units at your site don't have DLN-I combustors (that is, they have conventional combustors) the discussion will not be applicable. If the units at your site have DLN-I combustors--that's definitely something you should have told us in the beginning. It changes a LOT of things.
I am presuming the units have conventional combustors (that is, they do not have DLN-I combustors). I am presuming the units have selectable IGV (Exhaust) Temperature Control (that is, it can be selected ON or OFF, usually on the IGV Display on the operator interface (<I> or HMI). But, you have to identify the units, tell us if IGV (Exhaust) Temp Control is ON or OFF on each unit and tell us what the loads are on each unit for these conditions you are describing. In Post #9 you said the the MSG FIELD 3 indicated the IGVs were full open on one unit--but you didn't say WHICH unit.
And all of the things I wrote above can also impact exhaust temperature even when the IGV angles on two similar machines are within a couple of degrees of each other. But, you need to clarify some information and perhaps we can help you. You need to find relevant information about IGV Temp Control on conventional combustor-equipped machines.
We still need consistent and gathering datas like it has been asked on previous posts..
I know you understand that we can support from here with reliable service ...
I know you understand that we can support from here with reliable service ...
What do you call the way of gathering data?
The process of gathering and analyzing accurate data from various sources to find answers to research problems, trends and probabilities, etc., to evaluate possible outcomes is Known as Data Collection.
The process of gathering and analyzing accurate data from various sources to find answers to research problems, trends and probabilities, etc., to evaluate possible outcomes is Known as Data Collection.
The Mark* V has MANY data collection tools (software tools) depending on what kind of operator interface is being used with the machines. BUT, I don't think the original poster knows how to use them and we can't teach someone on this forum at this time. (There have been several posts over the last couple of decades about how to use them and they can all be found using the Control.com Search feature.)
He could take CLEAR photos of the same display for each of the two machines showing IGV angle, IGV Temp Control status, exhaust temperature, load, and whatever else is on the display. Photos can be posted to threads on Control.com and the original poster could post the CLEAR photos (ones that can be read and zoomed in to get more details). That's all it might take for us to help with clarifying his situation.
We'll see how it goes....
He could take CLEAR photos of the same display for each of the two machines showing IGV angle, IGV Temp Control status, exhaust temperature, load, and whatever else is on the display. Photos can be posted to threads on Control.com and the original poster could post the CLEAR photos (ones that can be read and zoomed in to get more details). That's all it might take for us to help with clarifying his situation.
We'll see how it goes....
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