Hi everyone

I was just wondering whether anyone here knows good materials that can be used to protect the 'naked' welded tip of a thermocouple? I know that OMEGA produces epoxy that can be used up to 105*C but I'm worried that's going to be very close to the actual temperature on the machine. I was thinking maybe some sort of silicone? I've also read on HB that someone used superglue to cover the tip.

I'm going to use type T thermocouple, which should not corrode, but still I would like to protect the tip somehow.

I'd be grateful for any suggestions:)

Cheers,
dsc.

dsc wrote:Hi everyone

I was just wondering whether anyone here knows good materials that can be used to protect the 'naked' welded tip of a thermocouple? I know that OMEGA produces epoxy that can be used up to 105*C but I'm worried that's going to be very close to the actual temperature on the machine. I was thinking maybe some sort of silicone? I've also read on HB that someone used superglue to cover the tip.

I'm going to use type T thermocouple, which should not corrode, but still I would like to protect the tip somehow.

I'd be grateful for any suggestions:)

Cheers,
dsc.

Where are you placing the thermocouple. Is it gonna get immersed in liquid?

-Greg

Hi Greg,

sorry for that I didn't give you enough detail. So the TC is going to go through a drilled M6 nut which is going to be placed where the original nut on the e61 group is. I'm going to use silicone to fix the thermocouple to the nut and seal the whole thing. I was thinking of using a teflon coated thermocouple, but now I'm thinking of using a standard TC and something to protect the tip.

So to sum it up it's going through the original nut on the e61 and yes it's going to get immersed. Temperatures of around 85*C - 95*C and 9 bars of pressure.

Cheers,
dsc.

First question is why not use a grounded tip and Eric's thermocouple adapter? It's well worth the cost. It's 100% foolproof.

If you want an exposed tip, why not get an ungrounded probe? I believe it is sealed. However, a grounded tip gives a response more than adequate for dialing in an espresso machine..

If you use a teflon sheathed thermocouple, and there is any unsealed portion, liquid will be forced down the wire inside the sheath. Depending on the connector, you may end up with espresso in your meter.

Neither super glue nor RTV silicone will form a permanent seal. They will eventually leak.

HTH

Hi,

the answer is pretty simple, because I can't afford it:) well I can, but put it like this, I'd like to spend less.

The teflon coated one is entirely covered in teflon:

http://www.omega.co.uk/ppt/pptsc....ef=HSTC&nav=tema02

so no leaks or similar things will happen.

I will eventually stick part of the cable in silicone, that's why I was asking whether I can cover only the tip in something to protect it, as I don't really need teflon on the rest of the cables. That will further allow to cut costs, as a standard TC costs 6GBP and a teflon coated one is 17GBP. Still cheaper than a sheathed probe for 25GBP or so.

I'm pretty sure I will buy the teflon covered TC, I was just curious what you might suggest as there are some pretty 'wisdomous' people on HB:).

Cheers,
dsc.

dsc wrote:Hi,

the answer is pretty simple, because I can't afford it:) well I can, but put it like this, I'd like to spend less.

The teflon coated one is entirely covered in teflon:

http://www.omega.co.uk/ppt/pptsc....ef=HSTC&nav=tema02

so no leaks or similar things will happen.

I will eventually stick part of the cable in silicone, that's why I was asking whether I can cover only the tip in something to protect it, as I don't really need teflon on the rest of the cables. That will further allow to cut costs, as a standard TC costs 6GBP and a teflon coated one is 17GBP. Still cheaper than a sheathed probe for 25GBP or so.

I'm pretty sure I will buy the teflon covered TC, I was just curious what you might suggest as there are some pretty 'wisdomous' people on HB:).

Cheers,
dsc.

Well I'd submit that Eric's price is probably less than the cost of your education in this matter. Nothing will adhere adequately to the teflon. High pressure water will also force its way down insulation. I would also be careful of what materials you choose to soak in the hot water, because you may end up drinking it unwittingly, either as chemicals that leached into the brewing water, or solid material when things fail.

"I didn't have the money to do it right, but I had the money to do it twice", is the saying that applies here. Rather than assist you in duplicating Eric S's contribution to espresso, I suggest that you contact Eric S directly, either purchasing his proven device, or obtaining his assistance directly.

-Greg

Hi Greg,

thanks for your opinion. I was afraid that teflon might not be the best material to stick to. I already talked to Eric and he did help me out a lot. I guess I will just have to think about it some more.

Cheers,
dsc.

Hi

finally I decided to go with a hollow tube TC which I'm going to use with a custom manufactured fitting (pretty much a screw with a screw-on cap and two holes to fit seals). I did some calculations the other day and the force acting on the sheath of the thermocouple is very small. I used some basic physics equations:

p = F/S (using SI units: Pa = N/m^2)

The surface of the TC sheath is really small, for example using a 2mm dia sheath means that S = pi*(0.001m)^2. Pressure equals 9bars, which is 900000Pa or 0.9MPa. Multiply p and S and you've got yourself the force which is roughly around 5N or so. That basically means that I can take a rubber cord, 5mm dia, cut two pieces around 5mm long and than use a pin to make holes in them. Afterwards simply stick the sheath through those holes, stick it all in that manufactured screw and friction should do the rest. A friend of mine uses a similar config (although only one rubber seal) and it works like a treat.

I will have to test it out with a blank basket and cold water, but I'm pretty sure it will hold without any problems.

Cheers,
dsc.