Overtemperature trip in exhaust, MS6001B with MKV

Hi everyone!... I hope this beginning of the year is being good for all of you.

I return to the forum to comment on another failure occurring on the GT MS6001B with MK V.

The thing is that due to a problem with the gas supply in the plant, it was decided to startthe turbine with diesel oil (distillate), the machine had not run with this fuel in about 2 years.
When we started with the first attempt, there was a trip due to loss of flame. On the second attempt, it ignited, but there was an exhaust overtemperature trip.

We assumed that maybe was the MOOG servo valve with a problem (2 years without moving), so we changed it, did another test, but the same thing happened. We check filters, both diesel and hydraulic oil, all good. We decided to check the flow divider.
We open its inspection covers, and with a flat screwdriver we try to turn the shaft (it should move without much problem), but we find it heavy, impossible to move, that is already a problem, we must replace or repair the flow divider.

The thing is that after solving the problems with the gas supply to the turbine, we decided to do a gas start, and to our surprise, the same thing happened, overtemperature trip in the exhaust.
The strange thing is that only a couple of temperatures are those that rise with great speed, immediately when the chambers are fired (3 actually, numbers 14, 15 and 16) corresponding to the combustion chambers numbers 8, 9 and 10, the others rise also, but not so fast. At the time of ignition, a strange noise is heard, apparently coming from the combustion chambers, like a loud air blowing or air restriction... Also, the pressure gauge for gas after the GCV stays in 0 bar (even though both valves move, and the combustion chambers are ignited).
Both valves move well giving them command in manual mode.

We tought that maybe some fuel nozzles were blocked, thus the gas pressure was entering chambers 8,9 and 10 with more pressure than normal.
We removed the nozzles for chambers N°2 and N°3, but they were clean... then we removed all check valves for liquid fuel (air and fuel) thinking that maybe some were stuck in open position, perhaps creating a problem with pressures inside the nozzles or with the atomizing air.
Effectively, some were stuck in the open position, specially the air ones, full of fuel, and you could blow one way or the other, so we clean them until they were normalized.

We did another gas start, thinking this discovery was the problem, but the problem continued.

We also simulate temperatures with a calibrator, directly to the TBQB card in core <R> (at the points of the temperatures that rise faster) and the inputs are perfectly fine. In turn, just to rule out, we measure one of those thermocouples with the same calibrator, at the moment of turning on, and it behaves in the same way as seen on the screen, it rises steeply, in ranges of 100 ° C per second.
It would seem that these temperatures, instead of being in contact with combustion gas, were in contact with a live flame.

We are thinking of doing a boroscopy, to see for any irregularity inside the chamber, the transition piece, or the exhaust.

Do you have an idea, or have you ever had a similar problem?


Thanks in advance!






.
 
Hi everyone!... I hope this beginning of the year is being good for all of you.

I return to the forum to comment on another failure occurring on the GT MS6001B with MK V.

The thing is that due to a problem with the gas supply in the plant, it was decided to startthe turbine with diesel oil (distillate), the machine had not run with this fuel in about 2 years.
When we started with the first attempt, there was a trip due to loss of flame. On the second attempt, it ignited, but there was an exhaust overtemperature trip.

We assumed that maybe was the MOOG servo valve with a problem (2 years without moving), so we changed it, did another test, but the same thing happened. We check filters, both diesel and hydraulic oil, all good. We decided to check the flow divider.
We open its inspection covers, and with a flat screwdriver we try to turn the shaft (it should move without much problem), but we find it heavy, impossible to move, that is already a problem, we must replace or repair the flow divider.

The thing is that after solving the problems with the gas supply to the turbine, we decided to do a gas start, and to our surprise, the same thing happened, overtemperature trip in the exhaust.
The strange thing is that only a couple of temperatures are those that rise with great speed, immediately when the chambers are fired (3 actually, numbers 14, 15 and 16) corresponding to the combustion chambers numbers 8, 9 and 10, the others rise also, but not so fast. At the time of ignition, a strange noise is heard, apparently coming from the combustion chambers, like a loud air blowing or air restriction... Also, the pressure gauge for gas after the GCV stays in 0 bar (even though both valves move, and the combustion chambers are ignited).
Both valves move well giving them command in manual mode.

We tought that maybe some fuel nozzles were blocked, thus the gas pressure was entering chambers 8,9 and 10 with more pressure than normal.
We removed the nozzles for chambers N°2 and N°3, but they were clean... then we removed all check valves for liquid fuel (air and fuel) thinking that maybe some were stuck in open position, perhaps creating a problem with pressures inside the nozzles or with the atomizing air.
Effectively, some were stuck in the open position, specially the air ones, full of fuel, and you could blow one way or the other, so we clean them until they were normalized.

We did another gas start, thinking this discovery was the problem, but the problem continued.

We also simulate temperatures with a calibrator, directly to the TBQB card in core <R> (at the points of the temperatures that rise faster) and the inputs are perfectly fine. In turn, just to rule out, we measure one of those thermocouples with the same calibrator, at the moment of turning on, and it behaves in the same way as seen on the screen, it rises steeply, in ranges of 100 ° C per second.
It would seem that these temperatures, instead of being in contact with combustion gas, were in contact with a live flame.

We are thinking of doing a boroscopy, to see for any irregularity inside the chamber, the transition piece, or the exhaust.

Do you have an idea, or have you ever had a similar problem?


Thanks in advance!






.
Hello ,


Did you have a look on similar case/threads here....

Sounds like now you got problem with both/dual fuel machine operations...


Did you try to monitoring various signal/trendS RELATED/During to this "failed satrt up"?


James
 
Mauricio Marquez,

As much as I HATE to agree with ControlsGuy25 (and I do!), this topic (of dual fuel (gas/distillate, or gas/liquid) operation, especially when distillate/liquid fuel has not been used for a long time) has been covered MANY times before on Control.com. MANY times. All past threads and responses on Control.com are searchable; will you find exactly what you're looking for on your first or second, or even fourth, search attempt--probably not. Will you learn something each and every search attempt? You probably will. You will also find different search words and terms you can use in subsequent searches to help improve your searching and results.

Dual fuel GE-design heavy duty gas turbines simply CANNOT switch to distillate/liquid after long periods of not running on distillate/liquid and be expected to start and run without any issues. It's a completely unreasonable and illogical expectation. There are just SO many things that can go wrong--and lot of things and parameters that ARE NOT controlled by the Mark* but which must be correct. Let me list a few potential problems:

--Air in the distillate/liquid fuel supply piping and fuel filter vessels, including the liquid fuel forwarding pressure regulator (if one is used, and they are often used when GE supplies the forwarding system)
--Bacteria growth in the distillate/liquid fuel components (filter vessels; forwarding pump suction strainers; storage tanks; piping; liquid fuel flow divider; liquid fuel tubing runs)
--Failed purge air check valves
--Servo-valve problems due to lack of flow of hydraulic oil through the servo for long periods of times leading to build-up of varnish and sludge (yes; there's always a very small flow of hydraulic oil through the servo when it's not being used, but it's such a small flow it's almost inconsequential)
--Failed liquid fuel check valves
--Carbonized liquid fuel in the liquid fuel assemblies of the fuel nozzles
--Inoperative check valves in the Atomizing Air system
--Booster Atomizing Air Compressor issue
--Atomizing Air Pre-cooler bypass valve operational issues

That's a fairly comprehensive list of issues.

GE strongly recommends (in several publications) that if distillate/liquid fuel operation is important to unit reliability that the unit be operated on distillate/liquid fuel at least once per week to exercise the system and components and to keep air out of the lines. They also sell some very complex and expensive systems to purge air from the supply piping and recirculate distillate/liquid fuel through the system and back to the storage tank.

As for the problems with gas fuel operation. you have not provided ANY actionable data. None. Zero. Niente, Nunca. Zilch. Zippo. Nada. You need to monitor--and use recording methods (VIEW "tools"; Historian; whatever the system is capable of using to gather data for analysis) and then analyze the data, or attach it to a thread response so others can analyze it. Anecdotal data is not very useful; not very useful at all. We/You need recorded data values and times to be able to say with any degree of certainty what is or might be happening when the problem is occurring.

And, again--use the 'Search' feature of Control.com to look for past threads about transfers to or switching to distillate/liquid fuel from gas fuel. And, get your P&IDs for the Liquid Fuel System, the Atomizing Air System, and the Fuel Purge system out and use them to walk systems down, identify components, and begin to try to restore distillate/liquid fuel system operation and reliability.

AND, make it a point to regularly run on distillate/liquid fuel to check for problems and to exercise the system components and try to keep air out of the lines and components and to prevent the growth of bacteria in the system piping and components. Proper distillate/liquid fuel supply pressure--the correct pressure, and stable pressure--is VERY critical to start-up and stable operation on distillate/liquid fuel. And the Mark* DOES NOT (normally) control liquid fuel supply pressure.

Hope this helps! Provide meaningful, actionable data recorded during these attempts and we can provide more concise and meaningful suggestions and analysis.
 
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