Frame 9EA Combustion Nozzle Damaged

A

Thread Starter

ali

we have two GT that after two years working liners are deformed and nozzles head are melted very bad.

why our gt has damaged so bad?

five months before gt breakdown it could not go to premxed mode and it was working in lean lean mode with 100mw load and we could not be able to turn it off and fix the problem. because of the situation.
it was working until the last day that an alarm occurred: (uv flame detection alarm) and the operator does not pay attention he thinks it is because of chamber flame detectors. after some hours GT tripped with gas detectors alarm and we see that two flexibles are disconnected and melted. the transition manifold flange is melted too. and after we opened the chambers we saw all liners are vacuumed in and transition nozzles head part are melted.

another alarm there was low purge pressure, with 2 or 1.9 bar pressure. and it was working more than 1 month then we could turn off gt and fix the problem. in the last five months gt was working with more than 3 bar pressure.
 
ali,

I've actually been hoping some other contributor(s) would respond to this post....

This sounds like a textbook case of how <b>NOT</b> to operate a piece of equipment. Operators not paying attention to alarms (<b>especially</b> a fire alarm!!!) is not something anyone wants to read about. If the operator did not know and had not been trained about the fire detection system and its alarms, that's not good. I would have to imagine there were other alarms which were not being looked into and resolved (including "Extended Lean-Lean Mode - High Emissions", and most likely high exhaust temperature spreads, also).

Operating at 100 MW in Lean-Lean is actually "Extended Lean-Lean" mode--meaning that the unit is operating with diffusion flame in both the Primary- and Secondary Combustion Zones when it should be operating in Steady-State Premix Combustion Mode with no diffusion flame in the Primary Combustion Zone, and only a small diffusion flame in the Secondary Combustion Zone. The internal temperatures when operating with diffusion flame in both Combustion Zones at high loads are <b>MUCH</b> higher than the internal temperatures when operating in Premix Steady-State Combustion Mode.

In Lean-Lean Combustion Mode approximately 50% of the fuel is being burned in a diffusion flame in the Primary Combustion Zone, and only a portion of the remaining 50% is being burned in a diffusion flame in the Secondary Combustion Zone. And all this is being done at fuel flows that are less than approximately 80% (sometimes as low as 40-60%) of rated fuel flow.

In Premix Steady-State Combustion Mode, approximately 80% of the fuel flow is being "combusted" in the Primary Combustion Zone--but <b>>>>NOT<<<</b> in a diffusion flame!!! And only a portion of the remaining 20% of fuel flow is being burned in a diffusion flame in the Secondary Combustion Zone. And, again, this is done with fuel flows anywhere from 40-100% of rated (depending on whether or not the unit has Inlet Bleed Heat and ambient conditions).

So, if the unit was operating near rated power output in Extended Lean-Lean Combustion Mode(which at 100 MW it most likely was) for five (5) months, then the diffusion flame and hot gas temperatures in the BOTH the Primary- and Secondary Combustion Zones was more than likely well above what they would be if the unit was operating in Premix Steady-State Combustion mode--for five (5) months!!!!

DLN combustion is all about reducing the internal (flame) temperatures to reduce the formation of NOx, and CO. 'Extended' in Extended Lean-Lean <b>does NOT</b> mean a long period of time. 'Extended' in Extended Lean-Lean means that the unit is operating in Lean-Lean Combustion Mode at loads 'beyond' the point at which the unit should have tranferred to, and be operating in, Premix Steady-State Combustion Mode. (IN other words, 'Extended' is being used to mean 'beyond' in the naming of the Combustion Mode.) GE does not recommended "extended" operation in Extended Lean-Lean Mode, because the temperatures in the combustion liner in both the Primary- and Secondary Combustion Zones are higher than they should be--because the unit should be operating in Premix Steady-State (and temperatures are lower, especially in the Primary Combustion Zone).

Essentially, when the unit experiences a Primary Zone Re-ignition (or does not successfully transfer from Lean-Lean to Premix) and is operating in Extended Lean-Lean mode, the operator is <b>supposed</b> to lower load until the unit is back in Lean-Lean Combustion Mode, then re-load the unit until it transfers into Premix Steady State.

If the unit does not transfer successfully into Premix, or experiences primary zone re-ignitions while operating in Premix, the cause should be investigated and understood and resolved. The unit should <b>NOT</b> operated for long periods of time (more than a couple of hours in a emergency situation, and then not on a repeated basis) in Extended Lean-Lean mode. I believe there is written GE documentation to that effect in the manuals provided with equipment.

Purge air is essential; it's primary function is to purge gas fuel from the lines when the transfer is complete, and after than it serves to pressurize the lines to prevent hot combustion gases from flowing backwards into the nozzle passages, flexible fuel lines, and manifolds. If backflow of hot combustion gases does occur, there can be flows from one can into another through the flexible lines and the nozzles--and the nozzles and flexible lines can become so hot they literally glow red, and if left unattended the metal can eventually melt. Failure to respond to, investigate and resolve low purge air pressure alarms can cause serious damage.

If the above happened (backflow of hot combustion gases through multiple nozzles and the flexible fuel lines and manifold), I would expect there would have been high exhaust temperature spreads, perhaps even high enough to be alarmed ("Combustion Trouble" Process Alarm) and maybe even trip the unit. At least they would have been higher than normal, and an alert operator should have brought it to the attention of his supervisor and maintenance and/ore mechanical personnel.

The Speedtronic <b>DOES NOT</b> protect the unit from every potential problem that might occur. In many cases, rather than trip the turbine or initiate an automatic shutdown when a serious problem is encountered it annunciates an alarm and the operator (a thinking, reasoning--and hopefully trained--human being) is expected to take appropriate action. This might be reducing load while troubleshooting, and eventually shutting the unit down if the problem can't be resolved in an amount of time that does not result in damage to the turbine and/or auxiliaries. If the Speedtronic tripped the turbine or initiated an automatic shutdown for every alarm condition, owners and operators would both be SCREAMING about "unreliable" the Speedtronic was (more than already do!). There is not substitution for thinking, reasoning--and in the case of multimillion USD power plants, <b>TRAINED</b>--operators.

Again, this is just textbook 'how NOT to operate' a power plant. If management made a decision to continue to operate the turbine in the face of all the evidence of serious problem<b>S</b>, they actually made a decision to sacrifice the unit. And to raise the danger level of all personnel working in the area of the turbine(s).
 
Just an addition to CSA's comments. GE's policy on DLN machines running in Extended Lean-Lean is 1 hour in Ext. L-L = 10 hours normal firing. This is how damaging they reckon running in Ext. L-L is. So, 5 months is 3,600 Hrs. = 36,000 Fired Hrs. It is just unbelievable how badly some people can run their equipment. If it is help you are looking for, the biggest help would be to learn how to operate your equipment properly.
 
Hi,

A Few Tips:

- in this unit (100 MW and extended lean lean for 5 months) Purge Air pressure was low (0.3 bar) at the start time and after FSNL was normal (~ 3.5 bar), but transfer Fuel nozzles and flexible lines are damaged. Why?

- In another unit the load was 45 mw For a long time in primary mode but the Liners have been deformed. why?

- ttxsp1 was 12 °C without high Exhaust temp spread.
 
we have two frame9, mark V & DLN1 type unit, that one of them is damaged now.
Addition to ali's question I want to inform you more about our damaged unit conditions.

1. we hadn't done CI maintenance & HGP maintenance.

2. The unit was worked for 24000 hrs.

3. three nozzles of Transfer was melted.
when we opened the combustion chamber, three nozzles included (11, 1, 12)

4. Two of flexible lines of Transfer was melted. which is relevant two nozzles, NO. 13, 14

5. The liners NO. 12, 13, 14 was fragmented.

6. Transfer's Manifold was Ruptured.

7. We are not sure about the low purge pressure

8. Some of Cross Fire was melted.

alarm with 2 or 1.9 bar pressure.

We have another same unit that its condition is:

1. It has been worked for 23000 hrs.

2. We haven't done CI maintenance & HGP maintenance.

3. It was in Extended Lean-Lean Mode for 46 hrs & 2180 hrs in premixed Mode in other hours it was in primary & Lean-Lean Mode.

4. We have opened the Nozzles no. 13,1, 5 of this unit & we have seen that the liners was deformed & there was fracture in one of the flexible transfer's lines without leakage.

5. The color of three of primary gas lines was changed to Dark black which seem it was caused by internal Heating.related to nozzles NO. 1, 13, 5

By this conditions can we start the second unit?

In both units,we don't use liquid fuel yet,but there is cock in primary's liquid fuel nozzles. Why? our Gas's Methane was between 85-91% in the last 8 months.

finally there isn't any alarm in the spreads,Why?

That would be my pleasure to receive your answer.
 
Why operate a £100m gas turbine and not carry out Combustion Inspections and Hot Gas Path Inspections?

These things need maintenance. Are you deliberately trying to wreck your investment?
 
david,

The maintenance "interval" you described seems a little long. Were the units equipped with the "long-life" combustion hardware (sorry; I can't recall the GE product name)?

As for the Transfer Nozzle hardware damage, it certainly sounds like there was a problem between two or more combustors that resulted in a crossflow of combustion gases between combustors. If the Transfer Nozzle purge pressure was sufficient, this should not have happened.

I have seen people leave the gas fuel piping commissioning strainers ("witches hat strainers") installed for too long after commissioning, and they can become plugged with rust and other contaminants which can come from the gas fuel supply piping, especially if filters and separators are bypassed (which I find they frequently are... usually because there was no provision made for duplex filters/strainers for on-line changing/cleaning and supervision will not shut the unit down for cleaning/changing).

As for why there was no exhaust temperature spread alarm, that's really questionable. It's very difficult to imagine a scenario where, if the control system was properly configured and the T/Cs were all working properly, and the Control Constants for detecting magnitudes were correct that at least a very high, but less than the allowable limit, was not being experienced at some point for the damage described. Just because the Speedtronic doesn't alarm or trip due to high exhaust temperature spread doesn't mean the spreads aren't too high and are not indicative of a serious problem or problems. We also don't know what Diagnostic Alarms were present during operation, etc.

The damage you described is not typical, and the information you provided is not sufficient. It would take an on-site investigation and analysis to be of more help. We don't know if the combustion hardware was provided by GE with the turbines, or as part of a combustion system change, or if the hardware was purchased from a vendor other than GE.

Finally, GE-design heavy duty gas turbines with DLN combustors are <b>NOT</b> like other GE-design heavy duty gas turbines with conventional (diffusion flame) combustors. DLN combustion systems, considered a "mature" technology by GE, do not tolerate the kinds of wear and combustion issues that conventional combustor-equipped units do. Even when operating in diffusion flame mode (Lean-Lean; Extended Lean-Lean), the internal temperatures and flows are NOT normal for DLN combustion systems. Lean-Lean is intended to be a transitional mode for reaching Premix Steady-State mode, which is what the DLN combustion systems were designed for: LOW EMISSIONS operation. Extended Lean-Lean Mode is intended to be a mode that allows limited trouble-shooting of problems getting into or maintaining Premix mode. Neither Lean-Lean nor Extended Lean-Lean modes were ever intended to be long-term operation combustion modes.

A lot of nations and regions are demanding low emissions turbines for new installations, and while these turbines produce electricity just like conventional combustor-equipped turbines, they cannot be operated just like combustor-equipped turbines. They are also not well suited for grids where the frequency is unstable and varies--at least if they are intended to be continuously operated in the combustion mode that produces lowest emissions. Operators--and their supervisors--of DLN combustor-equipped turbines need to have proper training and familiarization of DLN combustion systems in order to achieve the best reliability and availability--and the lowest emissions.
 
> I corrected:

> 100 MW at lean lean mode for 4 months and extended lean lean for twenty days.

The answer is the same: It should NOT have been operated in either mode for so long a period.

DLN-I Primary and Lean-Lean combustion modes are intended to be "transition" modes, to get to low emissions mode (Premix Steady-State mode). That's the whole intent of DLN combustion systems--to reduce emissions. DLN-I combustor-equipped turbines are NOT intended to be operated at loads which result in combustion modes other than Premix Steady-State.

Extended Lean-Lean mode is intended to be a temporary mode, for short-term (an hour or two, say) to troubleshoot and resolve an inability to transfer into or maintain Premix Steady-State mode. If the turbine tripped (emergency shutdown) every time it wouldn't transfer into Premix Steady-State mode or experienced a primary zone re-ignition while it was in Premix Steady-State mode, operators and owners would deem the unit unreliable and difficult to operate.

So, Extended Lean-Lean mode is only intended as a short-term combustion mode to allow troubleshooting of the inability to transfer into or maintain Premix Steady-State combustion mode without tripping the turbine and having to go through a coast-down and re-start to try to get back into Premix Steady-State mode. If the unit can't transfer into or remain in Premix Steady-State combustion mode, then it needs to be shut down and the problem investigated and resolved and re-started.

Again, DLN-I combustor-equipped turbines are intended to be operated in Premix Steady-State mode in order to reduce emissions without the use of water or steam. Pure and simple. They are not intended to be "part load" machines (without Inlet Bleed Heat, anyway, which only gets Premix Mode down to about 40% of rated).

If the operations staff (operators and supervisors) and Plant Management didn't know that then, they should learn it now--and communicate it to whatever entity they are "coordinating" the power production of the plant with. If they are being directed by some entity or regulator to limit output to some load which means the turbine is NOT operating in Premix Steady-State mode, the entity or the regulator needs to be so informed so they can work with the plant to operate the turbine(s) properly.

If the unit was operated for four months (or even one month) in Lean-Lean Mode, it's no wonder why it wouldn't transfer to, or remain in, Premix Steady-State mode, and "had" to be operated in Extended Lean-Lean mode. The liners were probably damaged from the long-term operation in Lean-Lean mode because of the "intense" diffusion flame and probably impingement on the combustion liner walls/venturis.

<b>This is >>>NOT<<< a design or hardware or quality problem.

It >>>IS<<< an operations problem.</b>

Just because a turbine will "run" in Lean-Lean or Extended Lean-Lean mode for long periods of time does not mean it was intended to be or should be operated in Lean-Lean or Extended Lean-Lean (or even Primary) mode for long periods of time.

Just because a turbine will run with [this] Process Alarm or [that] Process Alarm <b>DOES NOT</b> mean it should be operated for long periods of time with [this] or [that] Process Alarm, or that the unit will not sustain damage if operated for long periods of time with [this] or [that] Process Alarm. (I'm referring to purge air pressure low alarms, and the like.)

I repeat: This is not a design or hardware or quality problem. It is an operations problem--pure and simple. The unit was not being operated properly.

DLN-I combustor-equipped turbines CANNOT be operated the same as conventional (diffusion flame) combustor-equipped turbines. They are intended to be operated in low emissions mode--that's what they were designed for. Which means the "part load" operation is significantly limited--to whatever load the unit can be unloaded to while still remaining in Premix Steady-State combustion mode.

That's what they were intended for.

That's how they should be operated. Everyone who is involved with the operation of these DLN-I combustor-equipped units needs to know and understand these facts. Regardless of what anyone understood, or didn't understand, or thought, or didn't think, or reasoned, or didn't reason.

Full stop.

Period.

I'm sorry if this is a rude awakening for some, but <b>these are the facts.</b>

No matter what the salesperson said.

No matter what anyone wants to believe.

No matter what anyone wants the facts to be.
 
These are my final words on this thread: GER-3620.

If you don't have a copy, get one--from GE; from the World Wide Web; from anywhere you can. (No; I can't supply one via email to anyone.) It's a difficult read, and it talks about several different turbine/combustor configurations, but find the applicable sections to your Frame 9E (or Frame 5, or Frame 6B or Frame 7E/7EA)with DLN-I combustors, and read it.

Then re-read it.

Then re-re-read it.

Summarize it.

Train everyone associated with operating and maintaining the turbines about how GE-design heavy duty gas turbine with DLN-I combustors are to be operated--and what their limitations of operation are. This list of people to be trained includes, but is not limited to: operators; maintenance personnel; instrumentation and control technicians; operations supervision; plant management; associated regulatory and grid agency/entity personnel.

The most difficult part of all this for everyone is that invariably someone will want to operate at, say, 100 MW, and that happens to be right on the Lean-Lean-to-Premix transfer temperature for that day, and the unit loads into Premix Steady-State and ends up at 107 MW.

So Pre-Selected Load Control unloads the unit to 100 MW, which drops the unit out of Premix Steady-State--which is where the unit should be operated. It's maddening, but operators and operations supervisors and plant management and grid/regulatory agencies need to understand that DLN-I combustor-equipped GE-design heavy duty gas turbines CANNOT be operated like a GE-design heavy duty gas turbine with conventional combustors.

The operators need to be able to tell operations supervisors and plant management and grid regulatory agency/entity personnel what the minimum load for that day's conditions for that turbine to remain operating in Premix Steady-State combustion mode--and they need to understand and be able to say, "Thanks! That's what I needed to know. I'll plan accordingly. Keep the unit in Premix Steady-State, or we'll have to shut down until the load on the plant/grid will allow us to operate while remaining in Premix Steady-State Combustion mode."

Good day, all!
 
HI,Martin

Because we hadn't the spare material to change it if these was destroyed.

I have question, when this machine can't do CI & HGP maintenance what happen for combustion chamber's equipment?

Thank you very much.
 
Hi

We start the unit that's 23000 hrs widout CI & HGP. After 3 hours the unit trip at loss of flame. We check the alarm & event list.

1.The first the SRV Valve position goes to reduce.

2. FSR = 0 , SRV = 1.4% , flame detector available,
MW = _ 15 .

Loss of flame trip.

After trip start GTG and unit work.

I mentioned we didn't do any thing to resolve the problem.
Why the unit start again? I think just one reason to cause loss of flame. It is the cross fire & combustor damage.
 
> Because we hadn't the spare material to change it if these was destroyed.

You need to buy your spares well ahead of the inspection........... then you either use them if needed or keep them for next time. This is planning.
 
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