Old thermocouple wire... still any good?

[JaBob]

Howdy all.

Has anyone here had any experience with using older TC wire , i.e. stuff that's been sitting around in storage for some unknown time? I need to instrument a test bed for some fire testing (using a JP-8 pan fire), and have been trying to keep costs to a minimum due to recent budget issues. I found a couple of rather large spools of K-type fiber insulated TC wire sitting out in a shed at the test site, so they were out of the rain but not temperature or humidity controlled.

I've found some good information from Sandia, NASA, NIST, ORNL, etc. about TC time-dependent degradation and accuracy at elevated temperatures, but can't readily find anything about stuff stored at normal temperatures. There was no obvious signs that the spools themselves had water sitting on them or anything like that, but I cannot be certain that they never got wet.

Am I better off assembling the whole thing (and maybe using a TC calibrator for verification), or should I just scrap it all and buy new?

 

[danw2]

It's metal alloy surrounded by insulation. Type J has an iron wire, if it was wet storage you might be dealing with rust in insulation. K is nickel alloys, T, copper alloys either of which should be as good today as the day they were made.

The insulation might be iffy, but visual inspection will tell you if that's the case. It's a no-no to let the thermocouple wires touch anywhere except at the hot junction, it's known as a false junction.

The surface is likely to have some corrosion, but clean the corrosion off the ends that connect to terminals (junction blocks) and you're good.

If you're making your hot end junctions, it's considered good practice to weld the junction, but I've known furnace surveyers to twist the wire ends round-and-round 5 or 6 twists. That has to be clean alloy too.

 

[Skogsgurra]

And a tight twist, too. Use pliers.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[KiwiMace]

TC wire is easy to test. Why not cut out a few sample sections?