Temperature Control at 19MW on our MS5001

Good day,

We are currently having issue with our MS5001 gas turbine. It gets to temperature control at 19MW. we have tried some few things in the cause of our troubleshooting, like changing the air intake filters and checking the compressor bleed valve actuator still no improvement.

We are currently experiencing this issue on 2 of our MS5001.

Please kindly assist with any info on what to do next.
Good day, yhorsef,

First of all, what kind of control system is being used on the two MS5001 gas turbines? And, is it SIMPLEX, DUAL Redundant, or TMR (Triple Modular Redundant)?

Second, what alarms are present when you are running at Base Load? AND, if the control system is a GE Mark* control system, what Diagnostic Alarms are present when operating at Base Load?

Third, how long has it been since the last maintenance outage (Combustion Inspection, Hot Gas Path Inspection, or Major Inspection)?

Fourth, what fuel(s) are being burned in this unit (during start-up, and also when running at Base Load)?

Fifth, what is the nameplate rating for your MS5001 (not the generator nameplate--the gas turbine nameplate)? (Usually, the gas turbine nameplate is located on the right side of the unit, in the Turbine Compartment, on the Inlet Plenum wall, just inside the door closest to the inlet.)

Sixth, what load have you been able to achieve in the past when operating at Base Load?

Seventh, describe the ambient conditions the unit is being operated in (maximum daytime temperature; minimum nighttime temperature; relative humidity; monsoon season; coastal conditions (salt air; fog); location (elevation; nearby process plant(s) (such as an oil refinery, or cement plant, etc.), nearby roads or highways from which exhaust and/or dust might be generated and ingested by the turbines).

Eighth, when was the last time an off-line water wash was performed?

Ninth, have you recently changed fuel suppliers and fuel(s)?

Tenth, when was the last time the IGVs (Inlet Guide Vanes) LVDTs (Linear Variable Differential Transmitters) were calibrated?

Eleventh, when was the last time the compressor discharge pressure transmitter(s) were calibrated? (usually device numbers 96CD; if there are redundant transmitters, sometimes it's 96CD-1A, -1B and -1C)

Twelfth, do the units exhaust directly to atmosphere, or into a HRSG (Heat Recovery Steam Generators--a "boiler")?

Thirteenth, what kind of combustors do the units have--conventional or DLN (Dry Low NOx) combustors?

Fourteenth, can you please tell us what the average exhaust temperature is when the unit is at Base Load (on temperature control)?

Fifteenth, can you please tell us what the Compressor Discharge Pressure is when the unit is at Base Load (on temperature control)?

Sixteenth, what are the exhaust temperature spreads of the units? (If the control system is a digital GE Mark* system, the values you will be looking for are TTXSP1, TTXSP2 and TTXSP3.) Or if unit has an older GE Mark* control system there should be a way to find the highest and lowest exhaust temperatures and report them back to us.

Please, Please, PLEASE provide the answers to all the questions--even if you think one or three of them are irrelevant. You really haven't given us much information, so we are completely blind about the units at your site, the conditions, etc. We don't know what kind of control system(s) is(are) in use on the turbines at your site--which would affect our suggestions for collecting data. And, without good data we can't do too much to be of immediate or specific help. Help us to help you by providing the requested information--again, even if you don't think some of the questions are relevant.

USUALLY, when something like this happens it's because the axial compressors and IGVs are dirty--very dirty. If there is lots of humidity where the turbines are located, and any kind of dust, that will usually build up on the IGVs and axial compressor blades (stationary and rotating) and decrease performance. The best way to clean the axial compressor is to perform an off-line water wash, using the correct amount of detergent, AND being sure to rinse the axial compressor thoroughly after the wash is complete (any detergent not fully rinsed out of the unit can cause build-up and decrease performance). If you perform on-line water washes you should already know that they are only good up to a point--and then on-line washes will not restore any performance, and at that time an off-line water wash is the only alternative to restore performance.

If it's been a long time since a maintenance outage, the hot gas path parts (and even the axial compressor blades) can be worn an inefficient. If you used parts from a supplier other than the OEM, they can degrade quickly (not all vendors produce such parts, but several do). And, that, combined with a dirty axial compressor and IGVs can cause a pretty big performance decrease.

Another common problem is compressor discharge pressure transmitter operation and calibration, as well as having the manual isolation valves of the transmitters in the proper position and the tubing runs free of leaks. The proper value of compressor discharge pressure is critical to calculating the maximum allowable exhaust temperature--which is then used by most any control system to determine how much fuel to put into the unit to achieve exhaust temperature control--Base Load.

If you have a GE Mark* control system, they usually have a back-up exhaust temperature "curve" which can at times become active and limit output. But, that is usually accompanied by an alarm (at least on more recent Mark* control systems) that the back-up control is active or something similar. The reasons for the back-up control becoming active can be numerous, but we need to know what kind of control system is in use at your plant to be able to tell you how to determine, if possible, if the primary or back-up exhaust temperature control is active.

Another somewhat common issue is incorrect calibration of the IGV LVDTs (the devices the provide the position feedback(s) to the turbine control system). If they are not calibrated correctly (if the feedback is not scaled correctly to match the actual, physical IGV angle) then the unit might not be getting the proper amount of air.

Sometimes, when fuel suppliers or sources are changed, the heating value of the new fuel is lower than the previous fuel, and that can cause issues.

Also, if the unit is exhausting into an HRSG, sometimes the back pressure of the HRSG can be too high, and that can cause issues for the turbine(s).

But, we need more information to be of more, better help!

Looking forward to hearing back from you with more information!
We checked and saw that the 20CB solenoid for the Compressor Bleed valve was faulty, and we had to change it, and everything was OK. Currently the units are generating 22mw before entering temperature control.

Thanks for your all encompassing diagnosis.
That is pretty unusual.... both units experiencing problems with the same solenoid. And in your first post you said the actuators were checked.

Anyway, thanks for the feedback! And glad you were able to solve the problems!