Material / Diameter for Thermocouple?

beyaz_kopek

I have a 4 year old Dash 1 (actually 4 plates, t's, sight glasses, dephlegmator and condenser from SD modified to work with parts I already had) which I am dusting off as I build a mobile stand for it which I will keep adjustable for working as a pot still support as well. To the point...

What is a good choice as far as size / wall thickness / weld or bulkhead - for thermocouples?

I've built a few for other people using a corny keg dip tube. Basically pinch the end off then pass a TIG torch over it to seal it. From there I would usually buy a Swagelok bore through 5/16 tube x 1/4" NPT fitting and make a bulkhead out of it. They fit the Ranco temperature controllers used at the time (10 years ago).

My high quality thermocouple has an OD of 5mm, I make it work with a compression fitting and a lot of Teflon tape. The corny keg dip tubes had a 1/4" ID (6.35mm). The fittings sold by SD state they hold most 4mm probes.

Should I decide to use a cheaper temperature measuring devices available currently, what size tubing works?

Thin enough to measure temperature changes quickly? I'm not so skilled at welding as to weld a copper tube to stainless. As far as locations for probes in a Dash 1, I had mine mounted about 12" / 300mm above the dephlegmator. I can also see a reason to have one at the top plate or to be geeky, at each plate.

Thanks!

GD50

I would silver solder in a 1/8 or 1/4 female socket then buy a 1/4 or 1/8 male threaded double compression fitting and use either your 4 or 5 mm thermocouple directly into where you want it. There should be no need for thread tape except for maybe the connection into the socket as the thermocouple should seal perfectly on the compression fittings. That way there is direct contact with the product and quick response. The only time i use a thermowell is say in a fermenter where temp change is slow and not so important.

You can get double compression fittings on ebay for next to nothing and available in any size you want.

CothermanDistilling

I buy 1/4" thermowell tubes from brewer's hardware, I get longer ones, and cut them to the length I need, then I take the leftovers and make short ones, I put 2 v-notches in at 90 degree angles and fold to a cone, then hit with the tig welder..