We have GE Frame9E gas turbine, and we MARKVI control system. For the Past 4 or 5 months 3 of our Igniter transformer got burnt. We could not find any reason whatsoever. Few months back we found the temperature at turbine compartment high than usual suspecting a leakage, so we surrounded the transformer with some insulation. but last night another one got burnt, now we have only one spare. Please can anybody give any suggestion.

 

hmmm....all our ignition transformers are mounted on the outside of the package. The two leads go thru a sealed off hole to the spark plugs inside the enclosure. Both our 9E and 6B transformers are mounted this way. Have you considered relocating. What does the data sheet say for max temp?

 

They should all be mounted outside of the turbine compartment--even the new high-energy ignitors used on DLN combustor-equipped machines (though I'm hearing that GE-Belfort, yet again, is changing things up and using the old retractable spark plugs in DLN combustor-equipped units).

This is very odd; the spark plugs (ignitors) should only be firing for 30-60 seconds (sometimes longer; sometimes shorter depending on fuel and the whim of the commissioning person on that day). So, the cause <i>should not be</i> overheating due to electrical current flow.

I wonder what the actual spark plug/ignitor tips look like. Are they blackened/burned, because that might indicate they were firing for much longer than they should be.

Could it be some kind of burned insulation on the wiring that is causing a short or ground? Some problem with the ignition circuit that's contributing to the excessively long energization of the spark plugs?

If the turbine compartment is so hot that it is the source of the heat that's causing the ignition/ignitor transformer to melt, then it would seem that it's possible that the explosion-proof junction box is mounted directly on the web of the I-beam of the turbine compartment base--and it should be on some kind of short stand-offs to allow for some air circulation behind it, between the back of the explosion-proof junction box the ignition/ignitor transformer is mounted in and the web of the I-beam.

If these are the high-energy ignitor exciters used with DLN combustors, they are probably NOT mounted in an explosion-proof junction box, just a weather-proof junction box. And, if that's mounted directly on the web of the I-beam, without some kind of stand-off to allow air circulation behind it (the air acts as a kind of "insulator"), then this could be the problem.

Good question, though, 309EGuy: Where are the ignition/ignitor transformers mounted? What kind of transformer(s) are they--the big heavy rectangular, black powder coated, ancient-looking transformers, or the new, sleek high-energy ignitor exciters?

Are they mounted on stand-offs on the web of the turbine compartment base I-beam?

Is there any air space behind the back of the enclosure they are mounted in (between the back of the enclosure and the web of the I-beam)?

If the ignition/ignitor transformers are "burning", has anyone meggared the wiring between the Speedtronic and the transformer enclosure to see that it hasn't melted, causing a short or ground of some sort?

And, lastly, <b>Why is the turbine compartment so hot?</b> What is being done to reduce the turbine compartment temperatures? Is it a leak at the four-corners joint? Is it a leak somewhere else? Is it a problem with the gravity-operated dampers not opening, or not being latched open properly? Are the fan(s) working properly? (Many of the fans used for this purpose are reverse tangential centrifugal fans--meaning they are supposed to rotate in the opposite direction that would would assume by looking at the angle of the fan blades. If they are operated in the wrong direction, they will (1) draw excessive current and usually result in tripping of the fan motor starter(s), and, (2) will not move nearly as much air as they will move when rotating in the proper direction.)

Please write back with the answers to all of the above questions so that we may help you better.

 

Looks like you have a pretty serious leak into the turbine compartment guys. That's what you need to fix or you are going to damage a lot of other equipment.

 

Hi CSA,

strangely, on the last 2 jobs I worked on, the Ignition Transformer boxes are now inside the Turbine Compt on the side wall of the walkway (GE Pignone Frame 7 and GE Alstom Frame 9E). The Turbine Compts. on both these units are cool enough to walk inside and make a brief inspection. If the compartment for this question is hot enough to cause damage to the transformers, there must be a pretty big air leak near that area. It should be reasonably easy to find and fix.

 

glenmorangie,

I'm presuming you're speaking about off-base enclosures (such as are used for DLN combustor-equipped units). Probably a cost-saving measure to prevent the need to make a penetration through the turbine compartment enclosure wall for the spark plug/ignitor leads--and also probably saves a few dollars because the leads can be a little shorter.

But, I agree--the problem (other than the location) is the leak of compressor discharge air or combustion hot gases that's blowing on the ignition/ignitor transformer or blowing in the direction of the transformer.

A low-tech trick to find leaks in a turbine compartment is to tie a half-meter white rag to the end of a long stick and wave that in the area of suspected (and even unsuspected) leaks. A high-pressure leak will cause the rag to move wildly. That is--if the Danger Rangers will allow personnel to enter the Turbine Compartment when the turbine is running.!