GT trip due to spread hi. following are condition:

(i)if TTXSP1 > TTXSPL
(ii)if TTXSP2 > .8*TTXSPL
(iii) if two adjacent TCs are lowest.

then after 9 sec GT trip.

what is meaning of adjacent TC? Here it mean is adjacent by Temperature or by number like TCs 10 and 11 are adjacent. and TCs 15 & 16 are adjacent etc. or it is meaning any lowest TCs adjacent by temperature?

 

It means adjacent by physical location on the turbine. So you can go by number, remembering that 1 is adjacent to 2 and to the highest number (not all machines have the same number).

 

Here adjacent means, two of the lowest T/C are physically next to each other in array. For example lowest is 945 and second lowest is 951. Then if two T/C next to each other are reading 945 and 951, your condition becomes true.

 

If the two lowest TCs are numerically adjacent (10-11). What you are looking for is a true combustion low point which should normally cause a low point over more than one TC

 

Dear team
The 9frame E unit DLN with natural gas operations after major began get trips during shutdown from premix to lean lean by the reason “ fail to reignite primary zone “ .

splitter change position up for more gas to primary zone did not get completed result , some times unit trips and some times not .

How to find problem?

also happens that during spread reignite on base load the primary zone not ignite and unit trips by “ fail to reignite primary zone “ .
In this situation splitter is stays in the premix position.

If it is possible to help , I will be very appreciated
Leon

 

leonid_r,

Your question is not related to the original post at all.

This very subject has been covered before several times--it's NOT a spread trip, it's a failure to reignite the primary zone. You can use the 'Search' feature (the magnifying glass at the top of every Control.com webpage) to search for keywords and terms (composed of several words).

Usually, when the condition you are describing occurs after a maintenance outage, it's because the high energy ignitors (the "spark plugs") were NOT inserted to the proper depth. The proper depth is shown on an unexpected drawing in the Parts List volume of the Operations & Maintenance Manuals--I think it's the drawing that shows the outer combustion "can" enclosure and the various devices which are attached to the various combustion cans (combustors).

So, find the proper insertion depth on the drawing, and then check the insertion depths of BOTH high energy ignitors to see if they are at the proper depth. (Too deep can cause the tips to be burned/melted. So, a quick inspection of one or both ignitor tips (easy to pull the ignitors to check) will tell if they are inserted too deep. If they are not inserted to the proper depth then the air flows at high loads (such as when transferring from Premix Steady State to Lean-Lean) will blow out the spark and it won't ignite the fuel--no matter how much fuel is flowing into the primary combustion zone.... Richening the primary combustion zone is a risky thing to do without factory consult--and if the factory told me to do it without first checking the insertion depth, I'd be suspicious. VERY suspicious.)

And, please write back to update us on what you found and how you resolved the problem. The topic of checking insertion depths and a suggested method for doing so (using a welding rod or brazing rod) has been covered before on Control.com, so search for something like "welding rod" (without the double quotation marks) and you may be pleasantly surprised.

Hope this helps!

 

CSA,

As expected, you are correct. The location of the drawing for ignitors depth is something that most people search for and never find. Bravo Zulu for helping others.

The part about easily removing ignitors is where I have a bit of trouble. Enough said!

 

Curous_One,

I wish I could remember the ML number of the drawing, but it's been too long--and I don't have access to any electronic copies of Parts List at this writing. I think it's in the 500 series of ML numbers, but I can't remember exactly. It's an odd drawing to find it on, that's for sure. Again, it's a cutaway drawing of a single combustor, and it shows all the various types of devices which can be mounted on the combustor exterior--like ignitors, and flame sensors, etc. It clearly shows the ignitor protruding in through the combustion liner, and shows the distance between the ignitor tip and the INSIDE wall of the liner.

Most of the high-energy ignitors I worked with were simple tube-like devices, and in fact, a compression tubing fitting (such as a Swagelok or Parker compression fitting) is used to clamp and hold the tube in the pipe it passes through. The pipe it is inserted in is actually on a ball swivel, and the assembly is bolted to the outside of the combustor (the combustion "can") with four bolts (12-point hex head bolts, if I recall correctly). The bolt pattern is JUST LIKE the old high-voltage, retractable spark plugs--four bolts attached the assembly to the combustion can.

Nothing difficult; I just bent a small 90-degree section of brazing rod (about 250 mm) and inserted the rod through the pipe and into the combustion liner. I turned the rod and "hooked" the bent section on the inside of the combustion liner (it's easier to do with the can cover removed) and then put a permanent marker mark on the wire at the top of the pipe. I removed the brazing rod and transferred the mark to the ignitor by hooking the bent section on the sparking end of the ignitor and laying the rod alongside the ignitor. I then slip the compression nut and swage rings on the ignitor body and insert it into the pipe until the mark is at the top of the pipe. I hold the ignitor firmly while I slip the swage rings and compression nut into place and start wrenching on the compression nut. I usually pull a very short (100 mm) bit of the ignitor out of the mounting pipe (because it's going to slide down as the compression nut and swage rings are compressed. Never had an issue. (I actually think this is what they do at the GE factory(s) also--except I'd be willing to be GE Belfort has some kind of complicated, electronic device which takes half a day to install and a rocket scientist to operate to do the same thing, only half as good.)

Anyway, what does Bravo Zulu (BZ) mean? (If it's not too vulgar, that is.)

 

The scheme of ignition probes attached.
We will check .
it is very strange that trip during shutdown happens sometimes.
BR
Leon

 

leonid_r,

It’s not strange at all if the insertion depth is incorrect.

It also happens to units when the igniter tips get old and worn. They do not have an indefinite life, contrary to (false) popular opinion.

What IS UNUSUAL is that there are two (2) igniters—redundant—and that both aren’t working at the same time. There could also be some problem with the igniter power supply and/or the cables. If the cables are allowed to lay on the combustion can(s) or the combustion wrapper, or they are mistreated (most mechanical personnel have little or no respect for electrical cables or equipment—it’s a fact!) they can be damaged.

If the compression nuts used to secure the igniters in place are over-tightened, that can damage the igniters as well, though if that happens the unit will usually have trouble firing during startup.

Finally, it’s highly unlikely but it could be that the cross-fire tubes were not installed properly. That would usually manifest itself in higher-than-usual exhaust temperature spreads after the outage.

Please write back to let us know how you resolve the problem. Pictures of the tips of the igniters would be helpful, also

 

CSA,

“Bravo Zulu” is a Naval signal, conveyed by flag-hoist or voice radio, meaning “well done;” it has also passed into the spoken and written vocabulary. There are some myths and legends attached to this signal.

Regarding the ignitors, I have found them very difficult to remove after turbine operation. We have created a slide hammer with old ignitor cable parts and swagelock fittings that helps.

Your comment " (easy to pull the ignitors to check) " is not something that I have found to be true. I my opinion unless you have created a tool like I have described above, you will find them very difficult to remove.

 

Curious_One,

My experience with Naval signals was only in Naval drill familiarization classes (how to form up for this or that type of movement of Merchant Marine vessels being escorted by Naval vessels through dangerous waters). And, that was 40 years ago now....

My comment was related to removing the four bolts which hold the igniter assembly to the combustion can--not so much removing the igniter from the tube--which, as you rightly say, can be difficult without the right tool. A hammer used to "persuade" the igniter to move by pounding on the sparky end is NOT the right tool (I've seen mechanics do this AS WELL AS I&C technicians...).