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Post by foxtatic on Oct 5, 2020 10:39:15 GMT -8
I'm all set to make a 7" DSR2. Even made a full size replica out of 1"pink foam insulation to make sure all my cuts would work on CFB.... and that's when I realized that a 7 inch system does not fit inside a 55 gallon drum! oops. Luckily I have a 300 gallon fuel tank to play with and the ISA math work out just about right.
So imagine a 300 gallon cylinder sitting on a flat end with a DSR2 core stuck in it (sitting on floor, 20 inches of clearance to the top of the cylinder.) I want to cut a hole in the cylinder top to fit an 8" black stove pipe that ends 8 inches from the floor. As usual, hot gas fills the bell, stratifies, and sinks, then gets drawn up and out of the black stove pipe/chimney.
Typical 24 gauge Black stove pipe is rated at 800 degrees F. I've read that the tops of steel drums can reach 1000 F, unverified. My question: is it too hot in the bell for black stove pipe to survive there?
I could do differently by putting an elbow low on the outside wall of the cylinder and chimney up from there, I'd just prefer not to (avoiding cutting into the rounded size, space considerations, etc.) I could use double wall, but that increases cost and I don't know if the higher temperature rating for double applies to the exterior or only the interior where the heat is suppose to be.
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Post by fasardi on Oct 7, 2020 5:14:05 GMT -8
I asked a question like this some time ago and Peterberg told me than if you put the chimney pipe inside the bell you have to isolate it. And I think the only material than can do it is ceramic fibre, so I think it will be a better and cheaper choice if you put an elbow low go up with the chimney out of the bell. And you'll have an easy way to clean the flue, if you put a "T" elbow with a lid. And to save a few bucks, if the flue is in the same room than the stove, it'll work fine even if you don't isolate it. I don't know the material and thickness of your fuel tank, but I guess you will have to start thinking a way to replace the top because eventually it will start deteriorating, unless you isolate it from the inside (and then you will have a smaller ISA)
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Post by belgiangulch on Oct 7, 2020 5:49:04 GMT -8
The black pipe would be fine inside the bell. Temps are well below 800 F away from the riser. I believe the reason to insulate that pipe inside the bell (rockwool would work) is to encourage flow up the exhaust stack.
With my 8" J. When I used a perlite cast core, reached temps of 1100 F. Anything over a 1000 you get a glowing red circle
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Post by foxtatic on Oct 7, 2020 6:24:55 GMT -8
The black pipe would be fine inside the bell. Temps are well below 800 F away from the riser. I believe the reason to insulate that pipe inside the bell (rockwool would work) is to encourage flow up the exhaust stack. With my 8" J. When I used a perlite cast core, reached temps of 1100 F. Anything over a 1000 you get a glowing red circle Thanks, I appreciate the reassurance here (and on Permies!) I kinda thought that NOT insulating the pipe would give me quicker draft since the pipe exposed to bell heat would warm right up and start air flowing up. But then again, maybe I need draft to begin with before the core will really start up. Seems like a chicken and egg question that I'll have to figure out in my particular situation. But I welcome your thoughts on that. Could always add a bypass if it smokes back. I'm not sure what you're implying about your 8" J. Was 1100 F was your metal drum temperature above the mega riser, so away from the riser (or DSR2 exhaust in my case) would be a lot less intense and should not be glowing hot?
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Post by foxtatic on Oct 7, 2020 7:02:38 GMT -8
I asked a question like this some time ago and Peterberg told me than if you put the chimney pipe inside the bell you have to isolate it. And I think the only material than can do it is ceramic fibre, so I think it will be a better and cheaper choice if you put an elbow low go up with the chimney out of the bell. And you'll have an easy way to clean the flue, if you put a "T" elbow with a lid. And to save a few bucks, if the flue is in the same room than the stove, it'll work fine even if you don't isolate it. I don't know the material and thickness of your fuel tank, but I guess you will have to start thinking a way to replace the top because eventually it will start deteriorating, unless you isolate it from the inside (and then you will have a smaller ISA) Good thoughts. If I do end up using the elbow method, I guess that would make it easy to plumb in a bypass toward the top of the bell. The tank is thicker metal than a drum, but I do have it in mind that metal doesn't last forever. The 20 inches of clearance between exhaust and tank top might help. I have a few ideas about how to use something sacrificial to take the brunt of the blast. I'll measure the temps on the tank top first to see if I should bother though.
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