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Exhaust Thermocouple
Exhaust Thermocouple give and miss the reading

hello everyone,

I have problem with exhaust thermocouple. it's not stable, sometimes give good reading, sometimes miss the reading. When I remove and reinstall the wires give normal reading.

Is the problem with thermocouple? And I should install new one or I have another problem?


for more information and photo contact me
seherymeska@gmail.com

thanks to all

1 out of 1 members thought this post was helpful...

We have seen faulty thermocouple, cables, cable connector ends/crimps, and terminations in the J box and in the Turbine Control Panel cause the same errors. Sometimes it is hard to identify the exact cause and we have had to replace parts and solve by process of elimination. But, the thermocouple head is rather sensitive to over-tightening, see GE information regarding proper installation and torque. If not properly torqued can cause the same failure you describe. If not properly installed, I would suspect the thermocouple.

Good Luck!

Thank you for your reply. All terminals and connections are ok, cleaned and tightened. Also test for ground, it seems good no ground.

1 out of 1 members thought this post was helpful...

Hi,

To try and analyze your problem we really need a lot more information.
Machine Model, age & type, Control System, Fuel, Alarms showing? When did this problem start? installation location?

1 out of 1 members thought this post was helpful...

It sounds like the wire is coming lose from the lug that connects to the thermocouple. When you move the wires around it makes connection and then works lose during operation. Try replacing the end connector or the whole cable/connector assembly.

Our exhaust thermocouples have typically lasted 3-5 years.

elmeskawi,

>It sounds like the wire is coming lose from the lug that
>connects to the thermocouple.

Not everyone has the "Frankenstein" style of thermocouples; there are still a LOT of machines that haven't upgraded. And, I think the original poster hasn't posted enough information for us to be able to presume if the site has the newer or older style of thermocouples.

If the turbine control system is a GE Mark*, they are designed to work with either grounded or ungrounded thermocouples, so if the thermocouples are grounded by the manufacturer or if the ground is unintentional the Mark* will still work with them.

As others have said--we need more information, usually, to be of help. But, if you've cleaned, checked and tightened ALL connections all along the ENTIRE circuit from the thermocouple to the thermocouple input terminal board, it is most likely a problem with the thermocouple itself, and they don't last indefinitely (as has also been said).

If it's a Mark* turbine control system, and it's a problem with the thermocouple card, input channel or I/O pack there would most likely be a Diagnostic Alarm to indicate the problem. If there's no Diagnostic Alarm, then it's probably the thermocouple, or the interconnecting wiring. (But nobody pays any attention to Diagnostic Alarms; they don't trip the turbine, right?!?!)

One quick check you can make is to temporarily exchange the thermocouple with another measuring the same temperature and see if the problem "follows" the thermocouple or remains with the terminal board and input channel. That's a little risky, though, with exhaust thermocouples because of exhaust temperature spreads. If the unit is having high exhaust temperature spreads it will take a little care and planning to select one that won't cause a spread alarm/trip when swapping. And, then there's the issue of if a spread problem should develop while the two thermocouples are swapped (exchanged). If you do this the swap (exchange) it should only be temporary and for as short a run as possible.

It's probably just simplest at this point to replace the thermocouple with a new one.

Please write back to let us know how you fare in resolving the problem!

Thanks a lot for all people trying help me. I have solved the problem. I found loose terminal connection cutting the end of TERMO>> wire and install >>> Everything is ok now. Thank you.

elmeskawi,

Thank you for the feedback!