Hello Control Community

We had a problem with our frame 6 ms6001 GT controlled with GE Mark 5 TMR
The problem has begin last week the GT wasn't able to fire up. no work has being done on the GT
FQL1 at 3% at 20FL openning pressure is at 5 bars
The 3 77FD's looks identical
We check the 2 spark plugs they works fine
we check the nozzles of the chambres 1 & 10 they work fine
Check valves of the 10 nozzles works fine
we suspect the booster and we changed; same result ignition failed
we put an external source of air we had ignition once we tried again same way we had same problem
any suggetion please

 

@Zaam10,

You seem to have done all the usual things during troubleshooting--and thank you for providing details of the results of the troubleshooting!--and identified a potential issue: The Booster Atomizing Air flow/system. If this is a dual fuel machine (distillate/natural gas) there are usually one or two check valves in the Atomizing Air system to prevent blackflow during starting and possibly during off-line water washing; have you checked the Atomizing Air P&ID to see if the Atomizing Air system has any check valves which may be not functioning correctly?

Usually, problems with starting on liquid fuel are: 1) insufficient or unstable liquid fuel supply pressure to the machine; 2) air trapped in the liquid fuel supply piping and/or liquid fuel filter vessel(s) (indicated by wildly fluctuating Liquid Fuel Flow Divider speed pickups--which you seem to have eliminated); 3) failing liquid fuel check valves (which you appear to have eliminated); 4) failed or failing liquid fuel purge system check valves (these are typically only present on a dual fuel machine).

Are you certain the liquid fuel suction strainer between the liquid fuel storage tank(s) and any liquid fuel forwarding pump is clean? Have you physically checked the liquid fuel filters to be sure they aren't clogged/dirty? Does the liquid fuel flow-rate (FQL1) match the liquid fuel flow-rate reference (usually signal name FQR) during firing?

Does the machine have an induction electric motor starting means, or a diesel engine starting means? Does the machine speed appear to be normal during the firing attempts (indicating a properly functioning torque converter for an induction electric motor starting means, and a properly functionling diesel governor for a diesel starting means)?

Was there a trip before the machine needed to be re-started, or was the prior shutdown a normal, operator-initiated shutdown? If the machine was tripped, what was the cause of the trip?

What were the exhaust temperature spreads prior to the trip/shutdown when the machine was at rated speed and some load--normal or excessive?

I'm presuming the Booster Atomizing Air Compressor is induction electric motor driven; but older machines had different means of driving the Booster Atomizing Air Compressor. If it's electric motor driven is it directly coupled to the Atomizing Air Compressor or are there rubber belts and pullies coupling the electric motor to the Atomizing Air Booster compressor--and are they properly tightened?

Most Atomizing Air Booster Compressors are high flow/low pressure positive displacement compressors, which, unfortunately makes checking the pressure difficult to impossible by just looking at the Atomizing Air Pressure gauge (because the discharge pressure of the Atomizing Air Booster Compressor is very low compared to the normal Atomizing Air Compressor discharge pressure so it barely registers on the main gauge). Also, it's unusual for GE to provide a minimum Atomizing Air Pressure required for firing.... You say you've replaced the Atomizing Air Booster compressor; with a new or refurbished or used compressor?

There are some types of liquid fuel nozzle assemblies that have been known to have internals that loosen during operation (due to vibration and thermal cycling during starting/stopping).

That's about all I can suggest. It would appear you have identified low Atomizing Air Booster Compressor flow/pressure as the source of the problem, so what remains is to identify the cause for the low flow/pressure. I have seen some atomizing air tips on fuel nozzles that were worn/eroded that cause problems during starting--but also often resulted in higher than normal exhaust temperature spreads during operation.

Finally, if the machine tripped while running at load prior to the failed start attempts it could be that there are hardened liquid fuel "bits" blocking the tips of the liquid fuel nozzles, or dribbling into the atomizing air tips of the nozzle assemblies, because they weren't properly purged from the fuel nozzles and/or atomizing air tips of the nozzle assembly. And, while the problem could be low atomizing air pressure/flow during starting there might also be some liquid fuel flow restrictions either in the supply system or the liquid fuel filters/vessels.

I hope this helps. Please let us know what you find and how you resolve the issue!

 

@WTF? Thanks for your reply
First i want to mention that the mean drive moteur is a diesel engine on the ignition phase the diesel is at 1950 rpm (normally the right speed to have the right atomizing air to the nozzles) and the booster is coupled to the diesel engine with rubber belt and pullies
2- The nozzles are dual fuel (distillate/heavy fuel)
3- No trips before that problem
4- Filters combustible checked OK
5- the booster is a new one ( we tried with an externel source of air why it's take some times and some times no)
6- FSR at firing order is at 14% and FQL1 at 3% but when we had ignition and GT goes to warm up state the FQL1 goes to 14%
7- Spread exhaust temprature was 20°C at max load (good i think)
we will check the instability pressure of the liquid fuel from the frowarding pump
On the new booster we found that the max pressure he can give is 0,8 bars 300 CFM at 4000 rpm like you say high flow/low pressure

 

@Zaam10,

Has the liquid fuel flow divider ever been serviced/refurbished? Heavy fuel oil can be very "rough" on flow dividers and liquid fuel bypass valves, as well as check valves and fuel nozzle internal passages. It could be that the liquid fuel bypass valve and/or its servo-valve isn't working correctly. Has the liquid fuel bypass valve servo-valve been replaced recently? Or the liquid fuel bypass valve?

Are there any Diagnostic Alarms related to excessive differences between the liquid fuel flow-rate reference and actual flow-rate during firing?

It does seem the FQL1 value is a little low during firing; usually during initial firing fuel flow-rate is increased slightly to help establish flame and then cut back slightly during warm-up.

During the failed firing attempts is there any smoke exiting the exhaust--usually large puffs of white smoke indicate flame has not been established in only a small number of combustors, and exhaust temperature indicates only small areas of temperature rise. Flame has to propagate through the cross-fire tubes to combustors where flame detectors are present (so from the combustors where the ignitors ("spark plugs") are located to the combustors where the flame detectors are located. And, yes, it's very important to have atomizing air flow during firing and initial fired operation until the Main Atomizing Air Compressor gets closer to rated speed.

Have the ignitors ("spark plugs") been checked to see if the tips are excessively wet or worn? Also, if they are the spring-loaded, retractable ignitors they will have ceramic "tubes" inside which can become cracked and cause shorts which don't let the current get to the ignitor tips, or be weak at the ignitor tips. Ignitor tips can also wear down over time and need to be replaced or readjusted. I have also seen sites where the flexible leads of the retractable ignitors were improperly secured and they either were damaged by heat because they were laying on the combustion wrapper for long periods of time OR they weren't letting the plugs fully extend into the combustion liners to ignite the fuel. (The latter usually happens after a maintenance outage when untrained personnel don't know how the ignitors work.)

That's all I have to offer. Please let us know what you find and how you resolve the problem.