we operate GE 7EA machine in COGEN mode with MARK VI/DLN-1,fuel Natural gas. when we shutdown the machine or reduce load to 30MW the machine trips in "failure to reignite primary zone" (dln trouble trip). we inspected the igniters/cable and restarted it fired very fine then we forced a command to fire at 50MW and at base load to check, but it failed to ignite even though the command initiated and we checked the flame intensity but negative. then we also tried changing the timers yet no affect. we also ensured the orientation of spark plugs as per the manual. still it fires when startup but fails to fire at shutdown-can any body guide us on this?

 

There should be two ignitors, for redundancy, and while it's not impossible it certainly is unlikely that both of them are not working well enough to re-ignite the primary zone during operation. I have seen it happen, but it's usually on older units which are operated in cyclic duty (that is, not Base Load machines). The two times I've seen this problem have been on machines on which the ignitor insertion depth of one of the ignitors was way too shallow and the other ignitor was marginal, and the electrodes of both ignitors on the two units were fairly deteriorated. They both started just fine, but would not re-ignite on shutdown. On both sites, the Customer only had one spare ignitor, and when that one was inserted to the proper depth the re-ignition problem went away. (And on both sites, they never replaced the second ignitor and reset it's insertion depth on replacement.)

The position of the ignitor tip in relation to the combustion liner is very important. There is a lot of "gas" (fuel/air mixture) rushing past the ignitor tip when it's in Premix Steady State combustion mode. Sometimes the sheer volume of gas rushing past the tip can be enough to prevent much of a spark from being developed.

The ignitor tips also wear out; the center electrodes get shorter with time, requiring replacement of the ignitor. This increases the gap between the electrode and the grounded outer sheath tips which can weaken the spark, especially when there is a high volume of gas rushing past the tip.

So, while the tip may "look" okay, I believe the manufacturer has specifications on the limits of the gap (just like the spark plug in a car). Another way to "check" the gap is to compare it to a new one in your stores if you don't have the manufacturer's spec's. On the two sites I saw this problem, the tips looked okay until we put them alongside the new ignitor, and then the difference was visually obvious.

But positioning the tip at the proper point in the combustor is really the key to proper operation as well as longevity. I can't remember the ML number of the drawing, but there is a drawing that shows how far the tip is to protrude into the liner. Too far and there will be too much air rushing past it during re-ignition attempts. Combine that with a worn or deteriorated electrode-tip clearance, and this will cause exactly the problem you are experiencing.

Conversely if the tip is not inserted far enough into the liner, then it can't do it's job, either.

If your unit starts and stops fairly regularly, and you've never done any maintenance to the ignitors, then it's likely the gap has deteriorated and/or the electrode is worn. I've even heard of cracked porcelain in the upper portion of the ignitor allowing leakage current and decreased spark intensity.

And, when replacing the ignitor, do so with careful attention to the insertion depth of the tip into the liner. It's best *NOT* to set the locating ferrule fully on the body of the ignitor until you're confident that it is inserted at the proper depth. (Another tip here is to not cinch down really tightly when setting the ferrule, as this can damage the internals of the ignitor. I believe that many sites do this, over tighten the ferrule, when re-installing the ignitors after maintenance outages without even realizing it.)

One of the best ways to do this is to use a piece of brazing rod with a short 90-degree bend on the end to determine the exact distance from the ignitor mounting flange to the inside edge surface of the combustion liner (by hooking the bend on the inside of the liner through the ignitor penetration hole and then making a mark on the rod at the flange surface). Now, make another mark on the rod further away from the bend and the first mark equal to the distance that the ignitor tip is to be inserted into the liner. The distance from the hook to the furthest mark back is the amount of ignitor body that must be extending into the combustor past the mounting flange.

The only other method I know of for checking the insertion depth is to remove the end cap to look inside the liner, and that's also not very easily done!

 

Dear ASPX,

we operate 2 7EA's gas only in load following mode. We are at approximately 42K fired hours, not sure how that compares to yours. We inspect plugs and cables at each CI, hot gas etc. I have seen wear on the spark plugs where they pass through the liner, due to looseness in the spark plug ball joint that can compromise the ability of the plug to spark at the tip. I have also seen lots of problems with the cables themselves, mainly damage to the woven shield at the plug or at the ignitor box, that allows a short circuit to ground rather than through the plug.

As CSA says the air/fuel ratio and dynamics are very different at the time that re-ignition must occur on a normal shutdown VS ignition at 20% speed on a start. Re-ignition is even more difficult at loads higher than the normal 32-38mW premix to lean lean mode transition on a shutdown. A note for checking spark plug insertion depth, as CSA says the best way is to with the main fuel nozzle off. That's exactly what we try to do at the CI events!

I would test your ignition system in whatever safe way possible, that "stresses" it to produce its maximum available spark, like what happens on a re-ignition from shutdown. I have been near our units on a shutdown to observe the spark plug cables, when I found arcing occurring near the ignitor box that pointed to a failing cable.

I have heard some users having this trouble that are part of a 7EA users group, but have not heard of a single smoking gun for this issue.

On the plus side, I have heard of lots of other users that have problems with "primary zone re-ignition" events that they can't explain, that would much rather have your issue!!!

 

thanks a lot CSA we are planning a shutdown. definitely we'll look in to this spark plug orientation. mean while GE collecting Split Checks data while GT is on based load. They will be collecting data by increasing FXKSPMMX constant gradually up to 84% and then decrease FXKSPMMN gradually as well up to 78%. hope they could come up with a solution.

 

I neglected to ask the single most important question in troubleshooting:

When did this problem start?

If the unit has been working fine for some time and the problem just recently started, then it's likely one of the things which have been mentioned previously.

If this has been an on-going problem since commissioning (and we don't know how long since commissioning), it could be improper ignitor insertion depth since day one, or problems with the ignitors (they can be damaged during any installation or re-installation, or even removal), or cable problems, or ignitor exciter problems.

For my part, I don't see how split checks would help with this problem, regardless of when it started. I don't understand how changing fuel splits would affect re-ignition ability, without affecting emissions. More fuel to the primary (which is what would seem would the intent of checking the splits would be to try to improve re-ignition) would seem to cause lower NOx (and excessively low NOx usually results in very high combustor dynamics, higher than desired and not good for the unit), as well as high CO (since increasing the primary fuel split would reduce the fuel to the secondary, which would decrease the secondary diffusion flame temperature which would also help to decrease NOx but would cause the CO emissions to increase).

So, I would be extremely interested to learn if simply (only) changing the fuel split would improve the re-ignition problem, and what the as-found emissions levels (NOx and CO) were and what the as-left NOx and CO emissions levels were after the split was changed to reduce or eliminate the re-ignition problem (re-igniting during normal unloading or shutdown, not primary zone re-ignition caused by other problems).

 

We have six 7EA DLN1 gas only Simple Cycle machines with MARK V's commissioned in 2001. We are a peaking facility (peaking as in we only run during peak demand) so when our machines are started we only run a few hours. One of our units had this same problem, but only when the ambient temperature was above 80 deg F. During a shutdown the unit would transfer from Pre-Mix to Lean-Lean, back to Pre-Mix, and then try to go back to Lean-Lean because of sudden drops and rises of the firing temperature (TTRF1). We could always tell when the unit was going to trip because we would see the primary zone light and then go out. The following is part of a write up made after going through months worth of PI data and many VIEW2's.

While the unit is coming down in normal fired shutdown mode, there is a sudden drop of MW’s from about 57 MW's down to about 43 MW's in less than 2 seconds. This occurs at a firing temperature (TTRF1) of about 1980 deg F. After about 5 or 6 seconds, the MW’s suddenly increase from 43 MW's back up to 57 MW’s. The sudden drop in MW’s seems to be the first thing that happens. We have discovered this happening on three units so far but only unit 5 has tripped as a result. On unit 5, when the sudden drop occurs the firing temperature is about 1980 deg F as compared to 1960 to 1970 deg F on the other units. During shutdown, unit 5 goes into Lean-Lean mode when TTRF1 reaches 1975 deg F and the other units at 1970 deg F.

Now for the details of a trip scenario on unit 5. Within 3 seconds of the sudden drop in load, the firing temperature drops from 1985 deg F down to 1895 deg F. For a brief period, the unit goes into “Secondary Load Recover Mode” which lights the primary zone and puts the unit in Lean-Lean. This mode only lasts about 2 ½ seconds. Then, because the firing temperature falls below 1900 and rises back above 1900 deg F (there is a directional latch at 1900 deg F TTRF1 which tells the control system whether the unit is loading or unloading) in response to the sudden drop and rise of TTRF1, the unit then goes into “Lean-Lean Positive Mode” which is a permissive to load the unit. The unit stays in this mode for about 8 seconds. Then, because TTRF1 rises above 1950 deg F(this is the temperature setpoint at which the unit transfers from Lean-Lean to Pre-Mix on a normal startup), the mode switches to “ Secondary Transfer”, extinguishes the primary zone, and puts the unit in “Premix Transient Mode”. The unit stays in “Premix Transient Mode” for about another 8 seconds while the load and firing temperature continue to decrease. The unit then switches back to “Secondary Load Recover Mode” at about 1910 TTRF1 and tries to relight the primary zone once again. If the primary zone does not light within 60 seconds, the unit will trip. It seems that because the primary zone was extinguished only 8 seconds earlier, the primary zone cannot relight which results in a trip ("Failure To Reignite Primary Zone" trip).

Temporarily, to keep the unit from tripping, we would MANUALLY place the unit in Extended Lean-Lean when the firing temperature reached about 2000 deg F during the shutdown. As long as the unit went into Lean-Lean Mode before about 1980 Deg F firing temperature, the shutdown was normal. So as a more permanent solution, WITH VERIFICATION FROM GE, we changed some constants (FXKTL2, FXKTL2DB, & FXKTL3) to make the unit transfer from Pre-Mix Mode to Lean-Lean Mode at 1985 deg F TTRF1. We also changed the time delay for lighting the primary zone during shutdown (constant K26FXL2Z)from 3 seconds to 1 second.

Our problem was there during commissioning in the summer but when the weather turned cooler, the problem disappeared. The following summer when the temperatures reached above 80 deg F, it started happening again. GE never gave us an answer as to why this was happening but at least we found a solution.

 

RichT88,

Fuel is "moved around" between combustion zones in a DLN-1 combustor and as you have noted, it's all about TTRF1. TTRF1 is a "calculated" firing temperature, and it's just used as a "switch" for DLN-1 combustion modes. The fact that load is suddenly changing is an indication that combustion is changing, and the inputs to TTRF1 will also change. And, the gas fuel control valves (including the transfer and/or splitter valve(s)) don't jump from one setting to another, they are ramped at programmed rates for most mode switches, especially during transfers from Primary to Lean-Lean, and Lean-Lean to Premix Steady State.

In a DLN-1 combustor, most of the air enters the combustor through the "head end", which is where the fuel nozzles protrude through the "base" or bottom of the liner. This is as opposed to a conventional combustor in which only a portion of the air enters around the fuel nozzle for combustion, and the remainder of the air entering the combustor does so through slots and holes in the body of the combustion liner as "cooling and dilution" air to cool and dilute the temperature of the diffusion flame gases before it enters the first stage turbine nozzles.

Because in a DLN-1 combustion liner almost all of the air enters through the head end of the combustor, in an effort to produce a lean air/fuel mixture to reduce the combustion gas temperature without cooling and dilution air, the air flows into the combustor are directly proportional to ambient air temperature. Cooler air means more the air is more dense and the mass flow through the compressor and turbine is therefore higher. Warmer air means the air is less dense and the mass flow through the compressor and turbine is less dense and therefore lower. (Inlet Bleed Heat is a terrible name for the function it provides, and is not a means for controlling air flow rates by adjusting air temperature.)

Combine this with the fact that fuel is switched between combustion zones in the combustor based on calculated firing temperature (TTRF1), and the actual air/fuel ratio is never monitored or controlled, and you have a recipe for potential problems such as what you are describing. And, the fact that it only happens on one unit may also be related mechanical factors such as ignitor insertion depth variations (even the factory didn't get it exactly right every time) and IGV LVDT feedback calibration, and even IBH control valve configuration.

There are just a lot of variables that are all presumed to be working correctly, assembled correctly, configured correctly, and calibrated correctly on a DLN combustion system. It's really quite amazing that they work as well as they do when one stops and thinks about all the variables that are not even monitored or controlled.

(Adding the necessary instrumentation for monitoring and controlling all of these parameters would increase the cost of the units greatly, and GE is continually told by their Customers that their equipment is too expensive, rightly or wrongly. Think about automobiles before the advent of on-board computers and fuel injection; there was no monitoring of O2 content which is an indication of air/fuel ratios. The mechanic usually just adjusted the carburetor by intuition. Heavy duty gas turbines are very similar, but just as with automobiles, are getting more sophisticated with every passing day.)

Air flow and fuel flows in a DLN-1 combustion system are not monitored or controlled; they just are what they are. Sure, fuel splits are used to change emissions levels, but every machine is not the same and the fuel splits of machines installed at the same time sitting side-by-side are not always identical. I wonder what the fuel splits are on Unit 5 versus the other units.

Lots of DLN machines have to be re-tuned in spring and fall when the ambient weather changes because of air flow changes which affect emissions (NOx and CO).

But the fact that you have five machines that work well, and one that doesn't, seems to indicate that there's something physically different about that one machine, or that it's configured/calibrated differently.

Anyway, good to hear that you've come up with a solution to your problem. GE don't have a lot of experience operating turbines, though they're gaining that with the Contractual Services organization and through the massive data they collect via the OSMs (On-Site Monitors) installed at many plants around the world. They have so much data they don't have the resources sometimes to sift through it all, and the operational experience isn't always present in the engineering organization to help with problems like this, even the Product Service organization.

 

CSA,

You're right that even though we have six identical units, the fuel splits are not all the same. See below.
<pre>
UNIT 1
FXKSPM_*..FXKTPM_*
77..............1950
81..............2000
81..............2060
83..............2080

FXKSPMMN...........76
FXKTPMMX...........82

UNIT 2
FXKSPM_*..FXKTPM_*
77.............1950
81.............2000
81.............2060
83.............2080

FXKSPMMN........76
FXKTPMMX........81

UNIT 3
FXKSPM_*..FXKTPM_*
77.............1950
83.............2000
83.............2060
83.............2080

FXKSPMMN.......77
FXKTPMMX.......83

UNIT 4
FXKSPM_*..FXKTPM_*
77.............1950
79.5...........2000
79.5...........2060
83.............2080

FXKSPMMN........77
FXKTPMMX........79.5

UNIT 5
FXKSPM_*..FXKTPM_*
77.............1950
82.25..........2000
82.25..........2060
83.............2080

FXKSPMMN........76
FXKTPMMX........82.25

UNIT 6
FXKSPM_*..FXKTPM_*
77.............1950
83.............2000
83.............2060
83.............2080

FXKSPMMN.......77
FXKTPMMX.......83
</pre>
Just as you stated about a lot of machines needing re-tuned every spring and fall, GE's first answer was to change the split on unit 5 by 2% every spring and fall. We can't do that because we don't have CEM's so changing anything that affects emissions is a big no-no at our site.

 

RichT88,

It's good that we got the whole story; thanks!

I still suspect that there's something not quite right with the ignitor tips or insertion depth on Unit 5. I've seen many machines where one of the two ignitors has not worked properly for some period of time, and it wasn't discovered until the other ignitor developed a problem. The ignitors (or spark plugs) are redundant just for this reason, but if one isn't working it's very difficult, if not impossible, to determine until the second plug develops problems.

I've also seen brand new units from the factory (7EAs and 9Es, both) with the insertion depth not properly set from the factory. I used to have this checked when starting-up new units with DLN combustors because it happened more than once that we had difficult establishing flame during initial firing (usually on liquid fuel) and the ignitor insertion depth was found to be the cause. In one case the tips were too far into the liner and they would get so wet they wouldn't fire.

Anyway, thanks for the information!

 

Hello Folks,

Back to the same old subject of GE Frame 7 DLN-1 Failure to reignite primary zone.

We have been struggling with this problem for two month, in one of our two units.

Unit completed HGPI when we installed brand new full set of extender 24K six months ago and was running fine, problem suddenly started last month. The only thing that changed since HGPI is ambient temp which is getting pretty hot here in the Middle East up to 115F
Unit keeps tripping during unloading at 50 MW, 60 seconds from spark signal to reignite primary zone.

GE removed, inspected and tested spark plugs 3 times, this week GE removed the primary and secondary nozzles to set the depth from inside, yesterday they did a full BI to confirm that everything is good inside, We ran the unit last night and again it tripped at 50 MW during unloading because of Failure to reignite primary zone.
It looks like flame is lost from one can during transfer as 3 adjacent Exhaust TC and MW keeps fluctuating during the 60 second spark signal is on

Last week unit tipped two times at base load because of Failure to reignite primary zone. It looks like it suddenly lost flame from one can (at base load ), 3 adjacent thermocouples suddenly dropped (18, 1& 2), MW dropped by 5MW, TTRF1 changed and tried to ignite primary zone (at base load) and unit tripped in 60 seconds, the two trips are identical

Any help is appreciated as GE has been struggling clueless for more than a month with no fix - trial and error

Ashraf

 

Dear Ashraf,

So it sounds like this issue is a new one for you, but an old topic you were able to find. This particular issue has been discussed in the past, but I do not think it is a real common issue for the DLN1 combustion system. No doubt you have read all you can find about it. My suggestions are these. It sounds to me like you have two different things going on that may or may not be related.

You mention you have had two trips at base load due to a failure to reignite the primary zone. Can you clarify and list what other alarms you are getting?

Typically for a scenario like you describe of a lean blow out you will get a "combustion trouble alarm" due to a high exhaust spread. The cause of the high exhaust spread is usually due to a can flaming out due to a lean condition. The recovery mode for this is to attempt to reignite the primary zone, if the unit is unable to establish flame in the primary zone and the exhaust spread remains high then the unit will be tripped. The typical cause of a lean blowout at base load can be either a hardware problem, or tuning.

Your second issue that you are fighting is being unable to establish flame in the primary zone during what sounds like a normal unit shutdown. It sounds to me like you cycle these units on a somewhat regular basis? It also sounds like GE has established that the spark plugs are installed at the proper insertion depth inside the liner.

Have you replaced any components of the ignition system? I typically test plugs, cables and ignitors at each CI interval to verify proper operation since we have seen problems with all 3 components. But as CSA mentioned in a previous post, testing the components with the system at rest is much different than what is required especially with the unit at load. The airflow going by the spark plug tip at part load and full load is much different than when the unit is at 20% speed firing from a start.

Since this all sounds like it began after installation of new hardware I would be suspect of the new hardware, and any components of the ignition system. I am not a fan of throwing parts at the unit, but a systematic replacement of an ignitor box, new cable, new spark plug would be steps to try one at a time to see if you can repair the issue. Please write back and let us know how you proceed. I will be curious to hear what is found to be causing or contributing to the issue.

 

Dear Ashraf and MIKEVI,

Based on the information provided, the problems started approximately six months after an HGPI during which 24K extender hardware was installed AND when the ambient temperature started reaching approximately 115 deg F. It is hoped that spark intensity was observed when the end-covers were removed to check insertion depth, and that insertion depth was measured correctly. One-eighth of an inch can be the difference between working and non-working ignitors during a Premix-to-Lean-Lean transfer, and as MIKEVI has said there is a LOT of air flowing through the primary combustion zones of DLN-I combustors when the unit is at rated speed and the IGVs are open. A weak spark can be easily blown out. Ashraf didn't say if the ignitors had been replaced during this troubleshooting.

Also, knowing what Process Alarms--and what Diagnostic Alarms--are present and annunciated during the events is critical to understanding the sequence of events, as well as what inputs to the Combustion Reference Temperature calculation may not be working properly.

A lean blow-out occurs when there is too much air for the amount of fuel, and when the ambient temperature is high air is less dense so, unless the unit has an evaporative cooler or some kind of inlet air chiller/fogger the amount of air flowing through the compressor is going to be lower than when the ambient is colder. And, we don't know if the unit has any kind of inlet air temperature-reducing method.

We also don't know when the most recent off-line water wash was performed, which will increase the air flowing through the axial compressor.

We also don't know how accurate the IGV LVDT calibration is, nor how accurate the GSV (Gas Splitter Valve) LVDT calibration is--nor when was the last time either was "calibrated" nor what the as-found and as-left calibration constants were. And, we don't know if the calibration was physically verified (using a measuring device). Also, we don't know what the null bias value is or has been changed to (I have run across a couple of sites where the "auto" null-bias calculation scheme wasn't working correctly, also, impacting the position of the GSV).

If the TTRF/TTRF1 calculation is inaccurate or is being affected by bad inputs this could cause a real problem. Quite often people don't realize how non-working or inaccurate inputs can affect DLN operation, thinking that those nuisance Diagnasty Alarms don't really mean anything--until they start having problems like this.

As a previous poster to this thread said problems with a fluctuating TTRF/TTRF1 calculation can also cause real serious problems if the unit is trying to transition into and immediately out of Premix and Lean-Lean and back.

We also don't know what the exhaust temperature spreads were during Premix operation and during the failed transfers. This could indicate problems with fuel nozzles, or liners, or hula skirts, or side seals.

There's just a lot we don't know--and this means the possible list of causes is quite long. If I recall correctly when transferring from Premix to Lean-Lean the ignitors are energized and only when flame in the primary combustion zone is detected does the GSV move from approximately 80% stroke to approximately 50% stroke. And, only after primary flame has not been detected for some time (usually 60 seconds, I believe) during a Premix-to-Lean-Lean transfer is the unit tripped--because fuel is continually being reduced as the unit is unloaded and if primary flame isn't established it probably isn't going to be, so the unit can't go to Lean-Lean and it's therefore tripped. This means the fuel is being reduced which could lead to a lean blow-out prior to the expiration of the time delay waiting for primary flame to be establish. But without knowing the Process Alarms we aren't able to say for sure what is/isn't happening.

So, again--the list is long because of the lack of information provided. This is not a really common problem for many machines, but the most likely causes are weak spark/improper ignitor insertion depth, hardware problems (usually resulting in elevated exhaust temperature spreads), inaccurate LVDT calibrations, inaccurate or problems with Combustion Reference Temperature calculation inputs, problems with GSV position, unknown time of most recent off-line compressor water wash, other problems not known because of lack of alarm (Process and Diagnostic) information.

More help requires more detailed information.

 

Dear MIKEVI

This unit is driving a generator and has HRSG to generate steam for plant process. It runs at base load all the times. Right now it running on a simple cycle for a month because it trips if we unloaded to to startup the HRGS and admit steam

Regarding the first issue loss of flame at base load
Unit tripped two times in the same day last week at base load (66MW) and here is what happened

1. Exhaust TC 18,1 & 2 suddenly dropped by around 130F

2. MW fluctuated (66 to 57 to 71 and back to 66)

3. "combustion trouble alarm"

4. Control added more fuel to recover . all Exhaust TC went slightly up

5. Control attempted to reignite primary zone

6. All TC and MW recovered back to normal in 10 seconds

7. reignite primary zone frail to reignite in 60 seconds

8. unit trip because of failure to reignite primary zone

As mentioned we installed new Extender 24k during HGPI last December
I believe this is the first time we see flame out at base load (two times in one day).

Full BI of combustion parts revealed no abnormality

Primary and secondary fuel nozzles in can 1 & 10 removed to check and adjust spark plug depth.

One interesting thing I found was that ONE secondary fuel nozzle (Can # 1) has the 3 pilot fuel holes at the tip of the nozzle drilled in the opposite direction of the swirl. These 3 holes should be drilled at an angle to inject pilot fuel in the direction of the swirl
My understanding is that the main function of the Pilot holes in secondary fuel nozzles is to create a pilot diffusion flame by burning around 2% of fuel. This function of this diffusion flame anchor and stabilize the secondary flame.

So we replaced this one fuel nozzle with the wrong swirl hole even though GE engineering agrees that it is the wrong direction but they THINK it is ok.

So far unit is being running for two day at base load. I'm not sure if the wrong pilot holes in one fuel nozzle is the cause or contributor, or just a non-conformity that I wanted to get rid of for the big $$ we paid for this new extender set. May be this one is hard to validate because it happened suddenly out of the blues after 10 years for installation and 6 six months from last HGPI.

We did ONLY Exhaust DLN tuning after last HGPI (as usual for us). NO Dynamic Tuning.

Will come back with more info about the 2nd problem (failure to reignite primary zone during transfer from premix to LL).

Ashraf

 

Dear MIKEVI

Now the Second problem (failure to reignite primary zone during transfer from premix to LL). This is being going on & GE has being trouble shooting for more than a month including

1. Spark plugs, exciter and cables inspected. one cable replaced.

2. Spark plugs tested and showed good and strong sparks

3. Spark plug insertion depth adjusted from inside the can by removing the nozzles

4. Full combustion hardware BI inspection for (CL, TP, TP seals , Xfire tunbes)

5. One secondary fuel nozzle with opposite swirl direction pilot holes replaced

6. Exhaust TC checked and verified

7. Control constants changes <pre>
a.FXKTS1 from 1950 to 1987
b.FXKTL2 from 1975 to 2012
c.FXKTL3 from 1985 to 2022

d.FXKSPM_0[0] from 76 to 75
e.FXKSPM_0[1] from 83 to 76.5
f.FXKSPM_0[2] from 83 to 78
g.FXKSPM_0[3] from 83 to 78

h.FXKSPMMN from 79 to 76
i.FXKSPMMX from 81 to 81</pre>
Started and loaded successfully, however

1. Unit reached baseload successfully, spreads were good during transfer to Premix and at baseload.

2. During unloading, all was go spark plug turned commanded ON

3. Spark plug remained ON but all four primary flame detectors did not see any flame.

4. The very moment spark turned on and during the 60 seconds, Secondary flame lost from one CAN and recovered 4 times, 3 TCs fluctuated by around 75F and, MW flu fluctuated by +/-3

5. During the 60 seconds spark and fluctuation , 3 spreads fluctuated between 50 -130F, allowable 225F

6. The spark plug remained ON, after 60 seconds unit is commanded to trip due to no flame detection in primary zone with spark plug ON.

We did ONLY Exhaust DLN tuning after last HGPI. We have high inlet delta P of 7, too much dust and sand storms here. Every time (10 times so far) flame is lost during transfer or at base load, TC 18, 1& 2 fluctuates, even after we replaced Can# 1 secondary fuel nozzle.

Snap shots of above trends are available in a pdf.
[email protected]

Ashraf

 

Dear CSA

Spark plugs were installed during HGPI last December. Spark plugs intensity checked 3 times with spark plugs removed After the plug depth adjusted and locked. the ball assembly removed with the plug and tested outside the unit. Spark intensity was good

Unit is gas fuel only. No compressor washes at all despite the harsh environment.

Air inlet filters PI = 7 & PT = 9.3 input to control ..base load MW = 66 and .TTRF1 = 2012

No inlet air temperature-reducing method. SRV, GCV1, GCV2 & GCV3 calibration checked, feedback following command perfectly. TTRF1 fluctuating bad during transfer 60 second reignite because of loss & recover of flame from one can. Spread was good during premix (40 - 60 F)

ashraf