Installing a thermocouple inside a forge

[Jonas Liebel]

Heya,  

I'm about to finally finish my propane tank gas forge, and I want to install a thermocouple for temperature control. Now my question is, how, ahm, do i stick it in? 

My Forge will consist of a layer of ceramic wool and a layer of furnace cement. The termocouple's diameter is 3mm. 

Now my rough plan is to drill a 6mm hole and weld a 6mm tube into it, sticking the tube as far inside as the cement layer will later go. Then I should obviously stick the thermocouple into the tube and I'm done.

Does this make sense? And most importantly, how deep should i put the thermocouple into the forge?

 

Thanks guys 

 

[Vern Wimmer]

Makes sense to me. My SWAG on it would be that you want to consider 3 factors, keeping it out of the way of the work pieces, keeping it at the a position similar to the work pieces( that is so it reflects the temp the work is actually exposed to as opposed to the temp of the insulation) and keeping it away from the hot spot of the flame point. A long winded way of saying: As long as the tip is above the insulation out of the direct flame and out of the way of the work it should be ok.

Edited January 5, 2018 by Vern Wimmer

[Kreg Whitehead]

I put mine inside my muffle. When I tried it without it was all over the place. It may have steadied out after the forge was up to temp but I didnt wait that long.

[Jonas Liebel]

Thanks for your advice guys!

[Gary Mulkey]

Jonas,

First let us know if you have a vertical  or horizontal forge.  This will effect the location of the thermocouple. 

 

Typically the thermocouple should  extend approximately an inch past the insulating layer of the forge.

[Jonas Liebel]

Hey Gary, my burner sits in a 45° angle. Thanks!

[Zeb Camper]

8 minutes ago, Jonas Liebel said:

Hey Gary, my burner sits in a 45° angle. Thanks!

Nah, he's asking if your forge body is standing vertical like a soup can, or horizontal like a portable air tank. 

[Jonas Liebel]

Whoops, I see. Its something like this: 

[Gary Mulkey]

Jonas,

With this style of forge I would avoid placing the thermocouple  directly across from the intake manifold as you will likely have a cold spot there.  Were it me, I would  place it on the same side of the forge as your  intake and about halfway from the intake  and the end of the  forge.  This should give you a fairly accurate reading.

[Jonas Liebel]

I understand, thanks a lot for your help Gary! 

[Joël Mercier]

Like Kreg, I did put my thermocouple inside a baffle pipe, since I use it only for heat treatment. Of course if you want to forge weld it's a different story.

[konstantinos]

hello there, i really appreciate all the info you shared here, i wanted to ask your advice on the solution i used, so after a bit of research i put the thermocouple in side a 15mm pipe, it actually does not tach the walls of the pipe, then the pipe goes on the floor of the forge. the forge is a relatively small one  thus there isn't really a way of keeping the pipe or the knife out of the flame, what i try to do is have a carbonised flame on a very low pressure. pls let me know if this is very wrong

best Konstantinos

[Brian Dougherty]

21 hours ago, konstantinos said:

hello there, i really appreciate all the info you shared here, i wanted to ask your advice on the solution i used, so after a bit of research i put the thermocouple in side a 15mm pipe, it actually does not tach the walls of the pipe, then the pipe goes on the floor of the forge. the forge is a relatively small one  thus there isn't really a way of keeping the pipe or the knife out of the flame, what i try to do is have a carbonised flame on a very low pressure. pls let me know if this is very wrong

best Konstantinos

That will work fine.  Your temperature reading will be a bit slower to respond to changes, and probably always be a bit lower than the temp outside the pipe, but it will save you from having to replace your thermocouple as often.  I leave mine in the forge while welding, and have to replace them after a few hours at that kind of heat.

[Vern Wimmer]

23 hours ago, konstantinos said:

hello there, i really appreciate all the info you shared here, i wanted to ask your advice on the solution i used, so after a bit of research i put the thermocouple in side a 15mm pipe, it actually does not tach the walls of the pipe, then the pipe goes on the floor of the forge. the forge is a relatively small one  thus there isn't really a way of keeping the pipe or the knife out of the flame, what i try to do is have a carbonised flame on a very low pressure. pls let me know if this is very wrong

best Konstantinos

Pity you don't have room in the forge for a baffle pipe for the blade. That would solve two problems at once.