RY,

Is there any new information?

 

Hi guys,

Sorry for the delay. We had two days outage recently in September. We managed to replace the atomizing air booster compressor. After replacing the AA booster compressor, we tested the start up on diesel. It was successful without any hiccup on first try. The GT was at FSNL for 5 minutes while we observed the parameters in the accessory compartment. The followings are the parameters observed:

1. Fuel forwarding pump discharge - 8 bars
2. Fuel discharge pressure at accessory cmpt - 4.5 bars
3. Hydraulic - 100bars
4. Lube oil pressure - 8 bars
5. AA pressure at FSNL 6 bars.
6. Flow divider - 10 kg/cm2.
7. Selector #15 - 5 kg/cm2.

The only thing left to do is to measure the discharge pressure of the AA booster pump by blanking off the check vlv and install a 3 bars pressure gauge and also check the amp drawn by the motor. Looks like the clear culprit from the beginning is the atomizing air booster pump. But i still have a tingling feeling that the fuel is "too much". I am also gonna run the test once more to extract data from VIEW1 like i have posted in the previous post from start up until FSNL on diesel for reference purpose.

This problem has allowed me to garner so much more knowledge. I would like to thank each and every1 of the contributors especially u CSA for the relentless guidance and help. Looking forward to learning alot more from you. thanks.

 

RY,

Thanks for the feedback!

What leads you to believe there is too much fuel?

 

CSA,

Just a tingling feeling after we tried tapping in instrument pressure at 1 bar, 3 bars and 8 bars. Although we didn't actually blank off the check vlv at the discharge of the AA booster and tap it instrument pressure at the inlet and increase to the rated capacity of the AA booster pump, i realise that the FSR differs from the original setting which is lower. Original setting of FSR during firing is 18.8%. Now, it is 23.67% during firing.

I will post up the amps of the motor soon. Thanks again.

 

we have GE 6B GT. During start up it's tripping on "FAILURE TO IGNITE". only one flame scanner is showing flame, other 3 have no flame. ignitors, flame scanners, check valves are checked and found ok. in flow divider we are getting >6 bar pr. yes there is white smoke at stack. we doubt the atomising air. we are getting atomising air pr of 0.4 bar at AA Booster compressor discharge, but almost zero pr in atomising air header, i. e. after check valve. can any body pls tell what should be the atomising air pr at booster compressor discharge and in header? also what other causes of this tripping?

 

Booster AA pressure is very difficult to measure, especially with gauges that are sized for normal operation (200 psig; 16 barg).

If you're not measuring any pressure (with a gauge of appropriate range) at the AA manifold downstream of the check valve, it would seem there is likely a problem with the check valve. (Connect a gauge with a suitable range (for example, 2-5 barg) to a spare threaded tap in the piping using an isolation valve that can be closed after troubleshooting to protect the gauge.)

If this problem just started, and hasn't been going on for some time, one has to consider any recent changes/modifications, or the condition of components (we don't know how long the unit has been in service or what the quality of maintenance has been).

A big problem with AA system components is moisture/water. Some of the check valves have been known to rust and stick (fail to move).

Hope this helps. Please write back to let us know what you find!

 

Dear CSA,

Good information and useful, thanks to ALL

As asked by 4-20ma, why booster air by-pass valve kept open (VA22) till compressor bleed valves close (At 95% TN) / Gen. br. close, when booster motor is running only until L14HC(60% TNH)? Why can't close VA22 at 60% speed?

there is a good in every event,
G. Rajesh

 

grajesh,

That would be an excellent question for GE Belfort.... And the answer would be very interesting. Personally, I see no problem with the sequencing not changing the position of the bypass valve until 14HS. And, from what the original poster wrote it doesn't seem to adversely affect the firing or start-up/acceleration of the unit on distillate fuel.

But, again--that's a question for GE Belfort. It may be something they overlooked, or they might have a reason for that bit of logic, or it may just be one of those things that GE Belfort believes needed to be changed from GE's standard, because it was GE's standard and GE Belfort always has a better idea. (That's why I would be very interested to hear their answer/response. The good thing I have heard about GE Belfort is they seem to be a little more responsive to questions like this than GE Greenville (which wouldn't take much, because GE Greenville pretty much doesn't respond to questions like this at all--if it ain't broke don't fix it is their predominant feeling and that's what no answer from them means.))

Best regards.