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Heater Core Insulation Cracked  RSS feed

 
Posts: 55
Location: Shenandoah Valley
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Hello All,

I did a test run the other day on my J tube Rocket Stove, and I got blow back after about an hour. I took off the steel drum, and checked for leaks in the insulative layer, and I have a lot of cracks. I'd like to get advice as to whether I should completely scrap or break apart the cracked insulation, or whether it would be worth my while to try to patch the cracks. If I patch the cracks, do I need refractory cement? Or, could I just use regular cement with sand?

Any thoughts appreciated!
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Posts: 26
Location: Western central Illinois
10
hunting trees wood heat
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It's hard to tell from the picture, but it looks to me like you have a thermal expansion slip plane. How is your heat riser built? Can you give a breakdown of the construction of your RMH? Clearances between the riser and drum/bell, both on top and the sides?

From what I can see I'm guessing it's a stacked brick with a cob type layer of insulation around it. If that's the case, I would recommend removing all the cobish material and using either a ceramic blanket insulation or a perlite and clay slip or perlite and Rapid Set mortar mix as the insulation. I would wrap  1/4" hardware cloth/ steel mesh around that to keep it from falling apart should you get another split like you have in the picture. On the outside of your riser the hardware cloth will hold up for a long time as the temperature doesn't get too high, relatively speaking.
 
Adam Jonathan
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Location: Shenandoah Valley
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Hi Caleb,

Yes, it's firebrick with clay/perlite/lime insulation around the sides for insulation.  The top was simply lime and sand.

I filled in cracks with 1 part Type 1 Portland, 4 parts all purpose sand, and 1 part hydrated lime.

Would you suggest adding chicken wire or steel blanket outside of that?

Thanks!
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Caleb Mayfield
Posts: 26
Location: Western central Illinois
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hunting trees wood heat
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Yes, I would add some type of reinforcement to the outside so if it cracks again it will not fall outward and gap open blocking off your air flow. I think that was what caused the smoke back on the first go.
 
Adam Jonathan
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Location: Shenandoah Valley
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Caleb Mayfield wrote:Yes, I would add some type of reinforcement to the outside so if it cracks again it will not fall outward and gap open blocking off your air flow. I think that was what caused the smoke back on the first go.



Would you suggest anything in particular? I have chicken wire, wire mesh from Windows, and could obtain a number of other things. Please let me know your thoughts. Thanks!
 
Caleb Mayfield
Posts: 26
Location: Western central Illinois
10
hunting trees wood heat
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Adam, I would think chicken wire would be sufficient. It may be a little thin, but if it were me and I had it on hand I would give it a shot. I would also make a few wraps of tie/bailing wire on top of the chicken wire to help hold it in place. Either single wraps spaced every 6 inches up the riser, or spiral it up and back down and twist the ends together.
 
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