Heat Sink Compound Application

[Matter]

Hey all,

In trying to dial in my cooling system during some COVID downtime, I discovered that the thermometers on my fermenters (E&H TMR31) are not actually designed to be used in thermowells (which in this case are welded straight through into the fermenter), but rather threaded in-line for direct contact with product. In what way this has affected their readings is unclear besides the air around them being a good insulator, although there isn't too much space around them - maybe 1/8". Nevertheless, any time I see something being used in a place it was specifically not designed for, a little warning light goes off.

Rather than replacing all 9 of the probes we have, I was thinking of applying some heat sink compound to close the gap between the probe and the well, but I've never done it before and was wondering if there are any best practices I should consider. Seems sort of trivial, but I figure there are still better and worse ways to do the job.

Does the well need to be packed full or just have a few contact points with the probe? Better to fill the well with a syringe or apply to the probe then insert? Stuff like that. Thanks!

[dick murton]

I know we used to use some form of compound but unfortunately have no idea what. Why not talk to someone like Endress & Hauser, Emerson or whoever supplied your probes. They may say that being in such close proximity to the housing, and a slow response system such as an FV, you don't really gain much. You might want to, or benefit from using a compound in something like a heat exchanger where you want a faster response though.

[TGTimm]

We bed all our RTD probes--which are designed for use in a thermowell--with thermal compound. If nothing else, it prevents any intrusion of ambient air into the tip of the thermowell.

I use some thermal paste that comes in a big hypodermic syringe. I put a piece of hose small enough to fit into the thermowell on the syringe so I can be sure I'm getting the paste all the way to the end of the well. You'll also need to do something to keep the probes in contact with the end of the well. Ours have a spring for this.

I can't see why your probes wouldn't work, it's just a matter of fitting them carefully.

Best of luck--

[Starcat]

The compound is known as Silicone Heat Sink compound.
What Dick is saying is valid, and you can use permagum at the outlet end say if you have a 1/2 male conduit connector and junction box.
While not ideal, the digital probes we are running on Fermentation work fine being loose in an oversized well with the back sealed.
The FV OEM runs a design like Timm is speaking about where the probe is meant to spring load to the end of the well and is slow response.
I have also modified some way oversized thermowells on other devices by getting a piece of round stock to fit the well, and then having the center drilled exactly to accept the probe diameter, and using paste on both members.