our 100 MW gas turbine we observed the gas turbine load restricted to 90 MW load with persisting of temperature control if we tried to raised load further. turbine air inlet filters and fuel oil nozzles has been change but the problem still persisting there. CPD reading is 9.7 bar and all the spread normal. bleed valves has been checked but it was normal. could any body please help us to find the solutions.

thanks

 

Dirty compressor? Off line Compressor Wash may be the answer!
- M M Ahsan

 

Some questions:

1. What is your ambient temperature, temperature at inlet of compressor?

2. Does the gas turbine operate on open cycle or is a boiler fitted on its exhaust? If the latter, what is the back pressure on the gas turbine?

Compare the above parameters with respect to design conditions.

 

Shift Charge Engineer... what is MVAr (if any) corresponding to 90 MW Load?

Phil Corso

 

All good questions and comments.

But the most important question is: <b>When did this problem start?</b>

When was the last major inspection?

When was the last hot gas path inspection?

When was the last combustion inspection?

When was the last time the compressor discharge pressure transmitter(s) were calibrated? How many CPD transmitters are there: One or three?

When was the last time the IGV angle versus LVDT feedback was physically measured and compared?

Are there any Diagnostic Alarms which are active when the load is "limited"?

What is the frequency range of the grid the unit is synchronized to? What is the frequency during this period when the load is "limited"?

There has been a <b>LOT</b> written on control.com about the factors that affect combustion turbine performance. The cleverly-hidden 'Search' feature (on the right side of the band at the top of every page) can be used to search for related topics (using the Search help is strongly recommended, as is using several different search terms and combinations to find the largest number of related threads).

We also don't know what kind of control system is in use on the turbine, whether it's SIMPLEX or TMR.

 

Some items to check:

Check that your bleed-heat values are not leaking (assuming you have some)

Verify your compressor efficiency is OK - a borescope may also help locate a problem if FOD is to blame.

Good luck!

 

Dear,
Like all people I too waiting for your reply for the raised questions.

Regards
G.Rajesh.

 

More questions we'll likely never get the answers to, but they should be asked.

Is the unit operating on Primary Exhaust Temperature Control or Back-up Exhaust Temperature control? If the control system is a Mark IV, Mark V, Mark VI, or Mark VIe, the usual signal names for Primary- and Back-up (Secondary) Exhaust Temperature Control are TTRXP and TTRXS, respectively. They feed into a MINimum SELect function, and the lower of the two values becomes TTRX, which is the reference which will be used to control exhaust temperature, and therefore load when Base Load is selected.

It would also be helpful to know if there are any external biases on the Exhaust Temperature Reference, usually applied via signal TTRXB, on the unit which may be affecting or casing exhaust temperature control to become active before it's expected to.

As has been said previously, compressor cleanliness, inlet (bellmouth) cleanliness, and compressor condition (worn blades or casing; FOD (Foreign Object Damage, which usually results in higher-than-normal vibrations; and axial compressor exit guide vane condition) can all have an impact on compressor discharge pressure and efficiency.

It would also have been helpful to know if the exhaust temperature being experienced when the unit is at Base Load and "limited" is higher or lower than when the unit was at a higher load.

Unfortunately, I think we've heard the last from this originator, at least on this question.

 

> Shift Charge Engineer... what is MVAr if any) corresponding to 90 MW Load?

normally , not more than 65 mvar

 

> 1. What is your ambient temperature, temperature at inlet of compressor?

> 2. Does the gas turbine operate on open cycle or is a boiler fitted on its exhaust? If the latter, what is the back pressure on the gas turbine?

> Compare the above parameters with respect to design conditions. <

the ambinet temperature is only 32 c and we started the machine as opened cycle

 

> But the most important question is: ><b>When did this problem start?</b>

> When was the last major inspection?

> When was the last hot gas path inspection?

> When was the last combustion inspection?

> When was the last time the compressor

basically this happen after cyclon by which filters got dirty and have been cleaned but the problem still persisting. then , fuel oil nozzles have been changes without any affected occurred. some cards in speedtronic have been replaced but still problem persisting

 

In one of the posts further up, it is indicated that the derating occurred following the passing of a cyclone. Filters have been cleaned afterward.

Some further questions:

1. When you said filters were cleaned, do you mean cleaned by an in-built puffing system, or taken out, inspected one by one, cleaned and put back in place?

2. What was the GT suction pressure before the passing of the cyclone and after the filter cleaning process?

3. Were all the filters found intact after the cyclone passed, or did one/some fail resulting in the GT injecting some filter material?

4. Is your GT equipped with implosion doors that protect against excessive suction pressure in case of filter fouling, and if yes did these open while the cyclone was passing (assuming the GT was kept in operation while the cyclone was passing)?

5. Did you inspect your IGV blades?