Good afternoon everyone
Who had problems with the cables (burned) of the fire detector inside the load tunnel (photo attached). what solutions have you tried? can you please share the results?

 

Mineral-insulated cables are about the only solution to the problem. They can be difficult to work with and require patience when disconnecting and reconnecting during maintenance outages. And, it's not inexpensive material.

But if it's getting as hot as it seems in the photos it certainly seems like either there's not air circulation in the Load Tunnel and/or there's an exhaust leak in some part(s) of the flex seal.

 

TTIB was around 110C

Mineral-insulated cables are about the only solution to the problem. They can be difficult to work with and require patience when disconnecting and reconnecting during maintenance outages. And, it's not inexpensive material.

But if it's getting as hot as it seems in the photos it certainly seems like either there's not air circulation in the Load Tunnel and/or there's an exhaust leak in some part(s) of the flex seal.

TTIB was around 110C

 

What was the highest temperature in the Load Tunnel--AND how close are the temperature sensors to the sub-junction boxes in the photos? (That's two (2) questions....)

Typically the wire and cable insulation used in most GE-design heavy duty gas turbines is rated for a minimum of 90 deg C. There have been a very few times when it seems that to get a unit finished and out the door to book the shipping for end-of-month or end-or-quarter numbers that wire/cable with lesser insulation was used, probably because they didn't have the proper rated cable in stock or not enough to complete the entire job. (I know that would NEVER happen in France, but somehow it does and has.)

Anyway, problems like these--unless the machine is under warranty or guarantee--require research and analysis, both of which you have asked for here (which is good). Take the information you were given and run with it. You might also consider building some heat shields (using aluminium or stainless steel) to try to protect the sub-junction boxes from direct impingement of hot gases.

If this is a recent problem which hasn't been happening since commissioning, or started after a recent maintenance outage or just before an upcoming maintenance outage it could definitely be caused by a leak of hot exhaust gases from the flex seals. Those seals see a great deal of flexing during starting, loading, unloading and shutdown. And, if the machine is started and stopped often, that means even more flexing. I have seen flex seal strips get blown out and the holding bracket bolts come loose causing them to slip and move (flex) more than usual during typical starting and operation and shutdown. The vent fans in the area can blow that hot gas around and into as well as out of the load tunnel.

The placement of TTIB T/Cs is also somewhat questionable. On most every Frame 9E machine I worked on there were three TTIB T/Cs, one at about the 6 o'clock position, one at the 10 o'clock position and one at the 2 o'clock position. The two upper T/Cs were almost ALWAYS indicating very high temperatures during shutdown and while on cooldown (turning gear)--simply because heat rises and gets trapped in the load tunnel where those two T/Cs are located. Some machines had load tunnel alarms which would go off during shutdown/cooldown.

And, lastly, if I'm not mistaken some of the exhaust frame cooling air is directed into the load tunnel--not a lot, but it's hot air none-the-less.

Mineral-insulated wire/cable is the simplest thing to try, BUT make sure the people installing it have had some to work on and play with before they climb in the load tunnel and start trying to make terminal connections--or there's going to be problems. Also, make sure when those T/Cs are removed and reinstalled during maintenance outages the personnel doing that task also have some experience with that type of cable--because it's not the easiest or most forgiving cable to work with, and damaging the mineral insulation makes it useless.

Even if mineral insulation cable/wire wasn't used in the original construction or called-for in the original construction (probably eliminated for cost-reduction reasons, the OEM is BIG on cost reduction...!!!) it's still the most resilient type of wire/cable for the application and was widely used (back when most ALL GE-design heavy duty gas turbines were built in the USA; GE Belfort has lots of "better ideas"--which aren't (better)).

That's all I got. Best of luck--please write back to let us know how you resolve the issue(s).