FSR increase, TTXM increase and CPD decrease

Hi Everyone,
currently I working with GT frame 6b and getting some problem in performance, cause DW output cannot increasing up to base load. stated base load is 30 MW.
in a week I made a trend among FSRN, TTXM and CPD. found that FSRN and TTXM getting higher but FSRT and CPD trend was decreasing. is that causing by small leakage at joint connection / piping from compressors to combustion section ?

did anyone here had similar experience ?
is the TTXM will increase up to trip point ?

Regards,
 
Hi Everyone,
currently I working with GT frame 6b and getting some problem in performance, cause DW output cannot increasing up to base load. stated base load is 30 MW.
in a week I made a trend among FSRN, TTXM and CPD. found that FSRN and TTXM getting higher but FSRT and CPD trend was decreasing. is that causing by small leakage at joint connection / piping from compressors to combustion section ?

did anyone here had similar experience ?
is the TTXM will increase up to trip point ?

Regards,
Firstly, I don't know which control system you are using, also you don't seem to understand much about turbine control systems. I'm assuming that you are using a GE Speedtronic MK? and I'm going to attach a Fundamentals document for
Speedtronic Controls MKVI, please read first and then comment again. Can you please attach a copy of your trend data and please also add Turbine air inlet temp. CTIF . Where are you located and what is your day & night average ambient temp over the year? Is your site frequency stable? How do you operate, Base Load, Preselected Load or what ?
Base Load capability changes every day as does CPD which is dependent on ambient temp. Compressor cleanliness etc. (When did you do an Offline Wash ?)TTXM will change when TTRX changes. FSR will change when CPD. All these systems are in the manual attached and also please read all your P&ID (System Flow Diagrams)
Good Luck and get to me any time once you have done some research
 

Attachments

I agree with glenmorangie; you need to do some studying. The exhaust temperature control ”curve” has a negative slope--and is the opposite of what happens to exhaust temperature as the machine is loaded up to Base Load (at Part Load, exhaust temperature increases as load increased). When the unit is operating at Bas Load, the exhaust temperature increases as ambient temperature increases and axial compressor pressure decreases--and load decreases as ambient temperature increases.

That's because at Base Load the IGVs are fully open and the axial compressor speed is (or should be) constant. So, if ambient temperature increases the density of the air entering the axial compressor decreases--meaning the axial compressor isn't moving as much air when the ambient temperature increases so the exhaust temperature goes up, CPD goes down and load also decreases. The opposite occurs when the ambient temperature decreases.
The change in exhaust temperature as ambient temperature changes is counterintuitive, and difficult for many to comprehend.
The gas turbine rating on the nameplate in the turbine compartment is based on the ambient conditions stated on the nameplate. If the ambient is above the nameplate rating the unit output will less than rated, and at a slightly higher exhaust temperature than nameplate. If ambient temperature is less than nameplate gas turbine output will be higher than nameplate, and at a cooler exhaust temperature than nameplate.
Study, Grasshopper. Not everything is as it seems it should be.
 
Firstly, I don't know which control system you are using, also you don't seem to understand much about turbine control systems. I'm assuming that you are using a GE Speedtronic MK? and I'm going to attach a Fundamentals document for
Speedtronic Controls MKVI, please read first and then comment again. Can you please attach a copy of your trend data and please also add Turbine air inlet temp. CTIF . Where are you located and what is your day & night average ambient temp over the year? Is your site frequency stable? How do you operate, Base Load, Preselected Load or what ?
Base Load capability changes every day as does CPD which is dependent on ambient temp. Compressor cleanliness etc. (When did you do an Offline Wash ?)TTXM will change when TTRX changes. FSR will change when CPD. All these systems are in the manual attached and also please read all your P&ID (System Flow Diagrams)
Good Luck and get to me any time once you have done some research
Hi Glenmorangie,

thanks for your respond to my question,
I use turboline control system,. as you mentioned above, I'm new for turbine control system, especially for gas turbine control system. I will read the document after I post this reply.

-> I also attach the PI trend for TTXM, FSRN, FSRT, CPD, and CTIM (I didn't found CTIF variable). is CTIF equal to CTD ?
-> my location is Indonesia, were average temperature in a day 33degC and at night 27degC.
-> since my GT operated in drop mode, grid frequency are following our national electricity power plant. I dont know how to define stable in term of frequency, but some time (once a years) has power dip here (in a split of sec.).
-> I use preselected load and maximize exhaust air flow for another process
-> last years I just replace turbine + compressors rotors, since replacement are never use offline washing.

previous condition, during FSRT are crossing FSRN, I got 30 MW,.
now I got max 26MW during FSRT are crossing FSRN.

regards,
Tresna Aglis Salawasna
 

Attachments

I agree with glenmorangie; you need to do some studying. The exhaust temperature control ”curve” has a negative slope--and is the opposite of what happens to exhaust temperature as the machine is loaded up to Base Load (at Part Load, exhaust temperature increases as load increased). When the unit is operating at Bas Load, the exhaust temperature increases as ambient temperature increases and axial compressor pressure decreases--and load decreases as ambient temperature increases.

That's because at Base Load the IGVs are fully open and the axial compressor speed is (or should be) constant. So, if ambient temperature increases the density of the air entering the axial compressor decreases--meaning the axial compressor isn't moving as much air when the ambient temperature increases so the exhaust temperature goes up, CPD goes down and load also decreases. The opposite occurs when the ambient temperature decreases.
The change in exhaust temperature as ambient temperature changes is counterintuitive, and difficult for many to comprehend.
The gas turbine rating on the nameplate in the turbine compartment is based on the ambient conditions stated on the nameplate. If the ambient is above the nameplate rating the unit output will less than rated, and at a slightly higher exhaust temperature than nameplate. If ambient temperature is less than nameplate gas turbine output will be higher than nameplate, and at a cooler exhaust temperature than nameplate.
Study, Grasshopper. Not everything is as it seems it should be.
Hi CSA,

I've been respond to Glenmorangie, and for the nameplate vs ambient temperature. at the nameplate stated that ambient temperature was 15 degC, actual condition is higher than that. I assume that was normal getting load lower than nameplate as well. because at nameplate stated base load will achieve 33 MW, actual performance test up to 30 MW at best.

please also respond to my above reply on Glenmorangie post.

regards,
Tresna Aglis Salawasna
 
Hi Glenmorangie,

thanks for your respond to my question,
I use turboline control system,. as you mentioned above, I'm new for turbine control system, especially for gas turbine control system. I will read the document after I post this reply.

-> I also attach the PI trend for TTXM, FSRN, FSRT, CPD, and CTIM (I didn't found CTIF variable). is CTIF equal to CTD ?
-> my location is Indonesia, were average temperature in a day 33degC and at night 27degC.
-> since my GT operated in drop mode, grid frequency are following our national electricity power plant. I dont know how to define stable in term of frequency, but some time (once a years) has power dip here (in a split of sec.).
-> I use preselected load and maximize exhaust air flow for another process
-> last years I just replace turbine + compressors rotors, since replacement are never use offline washing.

previous condition, during FSRT are crossing FSRN, I got 30 MW,.
now I got max 26MW during FSRT are crossing FSRN.

regards,
Tresna Aglis Salawasna
Firstly, I'm afraid the document I sent you is not going to be much good, it is for GE Speedtronic, I don't know what Turboline is, was that an upgrade installed by your company?
Your nameplate data is rated at ISO conditions, this is ambient temp=15Deg.C, Humidity = 60%, Altitude= Sea Level,Barometric Pressure=!.01 Bar. If you deviate from these conditions your output will change. The biggest contributor is Temperature, you will lose a lot. Somewhere in your company you should have turbine manuals (who manufactured your machines??), in those manuals there are conversion tables to let you calculate output at your conditions.
Give me some time to have a look at your data and I'll reply

(Anyone with Turboline experience please help if possible)
 
Firstly, I'm afraid the document I sent you is not going to be much good, it is for GE Speedtronic, I don't know what Turboline is, was that an upgrade installed by your company?
Your nameplate data is rated at ISO conditions, this is ambient temp=15Deg.C, Humidity = 60%, Altitude= Sea Level,Barometric Pressure=!.01 Bar. If you deviate from these conditions your output will change. The biggest contributor is Temperature, you will lose a lot. Somewhere in your company you should have turbine manuals (who manufactured your machines??), in those manuals there are conversion tables to let you calculate output at your conditions.
Give me some time to have a look at your data and I'll reply

(Anyone with Turboline experience please help if possible)
Turboline was installed as upgrade purpose, beside the one who manufacture my machine is GE. previously I use speedtronic up to six years ago then upgrade to turboline.

the machine located near to the beach, around 500 meters from beach.

let me find for conversion table then I will inform if I found something.

regards,
Tresna
 
Tresa Aglis Salawasna,

Even if you have a Turboline turbine control system on your GE-design Frame 6B heavy duty gas turbine it most likely was configured and programmed to control and protect the unit in accordance with standard GE practices. That's a guess, but a reasonable one.

Be that as it may, the fact that ambient temperature is one of the biggest influences on gas turbine power output. I have seen PLC-based turbine control systems that were badly configured and programmed that always operated the turbine at nameplate rating when Base Load was selected and enabled every day of the year, year after year. That's because the people who programmed and configured the PLC did not know how to program a proper turbine exhaust temperature control reference curve and have it switch bumplessly between Droop Speed Control and CPD-biased exhaust temperature control.

As glenmorangie said, the manuals supplied with the unit include performance correction curves which CLEARLY and graphically describe the relationship between power output and ambient temperature. No matter how the Turboline is or isn't configured and programmed. If the IGV LVDTs aren't properly calibrated, and/or the axial compressor isn't clean and/or the clearances aren't within specification, and/or if the turbine nozzles and buckets aren't within specification and/or the exhaust back-pressure isn't within specification the power output isn't going to be close to nameplate--even if the ambient conditions were exactly at nameplate rating.

It sounds as if there is some kind of performance guarantee or contractual obligations that aren't or haven't been met, and someone is trying to find out the cause(s). It may or may not be the programming and configuration of the turbine control system. But the ambient temperature sounds like a real reason (because it is a real reason).

Good luck with your situation and you really need to either come to grips with basic heavy duty gas turbine control philosophy because it's the same for all heavy duty gas turbines (that ambient temperature has a very large effect on gas turbine power output(performance)--just like I described). Or, you can continue to keep looking for reasons or answers without understanding how heavy duty gas turbines work and failing to come up with a solid justification for why the unit can't make rated power.

It is possible to say that if the Turboline is configured and programmed properly to control a GE-design heavy duty gas turbine that is very VERY LIKELY that it is working properly. That is based on what we have been told and our knowledge and experience with GE-design heavy duty gas turbines.
 
Tresa Aglis Salawasna,

Even if you have a Turboline turbine control system on your GE-design Frame 6B heavy duty gas turbine it most likely was configured and programmed to control and protect the unit in accordance with standard GE practices. That's a guess, but a reasonable one.

Be that as it may, the fact that ambient temperature is one of the biggest influences on gas turbine power output. I have seen PLC-based turbine control systems that were badly configured and programmed that always operated the turbine at nameplate rating when Base Load was selected and enabled every day of the year, year after year. That's because the people who programmed and configured the PLC did not know how to program a proper turbine exhaust temperature control reference curve and have it switch bumplessly between Droop Speed Control and CPD-biased exhaust temperature control.

As glenmorangie said, the manuals supplied with the unit include performance correction curves which CLEARLY and graphically describe the relationship between power output and ambient temperature. No matter how the Turboline is or isn't configured and programmed. If the IGV LVDTs aren't properly calibrated, and/or the axial compressor isn't clean and/or the clearances aren't within specification, and/or if the turbine nozzles and buckets aren't within specification and/or the exhaust back-pressure isn't within specification the power output isn't going to be close to nameplate--even if the ambient conditions were exactly at nameplate rating.

It sounds as if there is some kind of performance guarantee or contractual obligations that aren't or haven't been met, and someone is trying to find out the cause(s). It may or may not be the programming and configuration of the turbine control system. But the ambient temperature sounds like a real reason (because it is a real reason).

Good luck with your situation and you really need to either come to grips with basic heavy duty gas turbine control philosophy because it's the same for all heavy duty gas turbines (that ambient temperature has a very large effect on gas turbine power output(performance)--just like I described). Or, you can continue to keep looking for reasons or answers without understanding how heavy duty gas turbines work and failing to come up with a solid justification for why the unit can't make rated power.

It is possible to say that if the Turboline is configured and programmed properly to control a GE-design heavy duty gas turbine that is very VERY LIKELY that it is working properly. That is based on what we have been told and our knowledge and experience with GE-design heavy duty gas turbines.
HI CSA,

your guessing was right, I try to find out why separating only two month. at april the gas turbine were able to load up to 30 MW but at july just only 25 MW.

I have found the curve for inlet air temperature VS exhaust temperature, and inlet air temperature VS output percent design.

I try to figure out the ideal condition base on nameplate first, found that if operated at base load, 100% output design condition will generate 33 MW and 1005 degF or 540 degC if inlet air temperature 60 degF or 15 degC.

reflecting to current design inlet air temperature:
inlet air temp. average 33 degC or 91 degF, it was reflecting to condition TTXM = 551 degC or 1025 degF, and 87% output design condition which is equal to 28,7 MW.

but, actual value was,
TTXM = 557 degC or 1035 degF
output = 25 MW
inlet air temp. = 33 degC or 91 degF
I cant get more MW during this condition, FSFRT take control.

meanwhile, two month ago.
TTXM = 528 degC or 982 degF
output = 25 MW
inlet air temp. = 33 degC or 91 degF
in this condition, MW output are able to increase, up to 30 MW.

It sounds like I need to spare much time to grips with basic heavy duty gas turbine control philosophy to solve this performance issue.

Regards,
Tresna
 
You should also be checking and verifying things like IGV LVDT calibration (very important at Base Load), compressor bleed valve integrity, and IGV and axial compressor cleanliness. AND exhaust back pressure--if the HRSG and/or stack are limiting exhaust gas flow the turbine isn't going to be able to flow air very well.

Have you verified compressor discharge pressure transmitter calibration? Have you checked the exhaust thermocouple placement in the radiation shields? Have you verified the thermocouple extension wiring junctions along the complete length of the circuit--from the exhaust T/C to the Turboline T/C input terminals--to ensure there wires are not crossed anywhere and the junctions in each junction either both have or are both free of cold junctions? (I have seen improper exhaust T/C wire terminations and cold junctions cause as much as a 0.5% performance shortfall in a brand new and clean machine.)

Are the turbine axial compressor inlet air filters clean?

Does the Turboline have a backup exhaust temperature control scheme? If so, which exhaust temperature control scheme is in use when FSRT is less than FSRN--the primary exhaust temperature control scheme or the backup exhaust temperature control scheme?

WHAT ALARMS ARE ACTIVE WHEN THE UNIT IS OPERATING AT BASE LOAD??? LIST ALL ALARMS--EVEN ONES YOU THINK MAY BE IRRELEVANT!!!

What are the positions if the SRV and GCV when the unit is at Base Load? BOTH the LVDT positions on the HMI display AND the actual physical positions on the position indicators on the devices.

Has the fuel source changed since the rotor replacement?

You want help? We need actionable data.
 
You should also be checking and verifying things like IGV LVDT calibration (very important at Base Load), compressor bleed valve integrity, and IGV and axial compressor cleanliness. AND exhaust back pressure--if the HRSG and/or stack are limiting exhaust gas flow the turbine isn't going to be able to flow air very well.

Have you verified compressor discharge pressure transmitter calibration? Have you checked the exhaust thermocouple placement in the radiation shields? Have you verified the thermocouple extension wiring junctions along the complete length of the circuit--from the exhaust T/C to the Turboline T/C input terminals--to ensure there wires are not crossed anywhere and the junctions in each junction either both have or are both free of cold junctions? (I have seen improper exhaust T/C wire terminations and cold junctions cause as much as a 0.5% performance shortfall in a brand new and clean machine.)

Are the turbine axial compressor inlet air filters clean?

Does the Turboline have a backup exhaust temperature control scheme? If so, which exhaust temperature control scheme is in use when FSRT is less than FSRN--the primary exhaust temperature control scheme or the backup exhaust temperature control scheme?

WHAT ALARMS ARE ACTIVE WHEN THE UNIT IS OPERATING AT BASE LOAD??? LIST ALL ALARMS--EVEN ONES YOU THINK MAY BE IRRELEVANT!!!

What are the positions if the SRV and GCV when the unit is at Base Load? BOTH the LVDT positions on the HMI display AND the actual physical positions on the position indicators on the devices.

Has the fuel source changed since the rotor replacement?

You want help? We need actionable data.
Hi CSA,

some of item have been done during last investigation on july 2020, we decided to stop the machine and check several item, then some item are checked during on-grid. I try to write it as good as possible in attaced file.

letter I will check those item during next outage, hopefully there is no trip event, cause high indication in TTXM are make it possible to trip the machine.

is there any other point of view after you review my attachment ?

regards,
Tresna
 

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