Heat Riser Steel vs. Brick...

[matthewwalker]

I can only speak from my own experience, and I don't have the technical details(grade, temperatures, etc.)but I tried a riser from stainless class A insulated chimney just as a temporary riser on a core experiment. It was rendered useless after only the first hour of burn. Warped badly, with visible spalling or similar deterioration, such that it impeded the CSA significantly.

[Donkey]

Yep.. me too. The double and triple wall stuff simply can't deal with the heat.
On the other hand, I used a piece of single walled stainless (don't remember the gauge, but kinda heavy) in a sauna rocket.. a few years later and it's still rockin.

[thomas]

Sure wish I knew what "kinda heavy" was. lol

Thanks for your replies.

[Donkey]

Right..
See, I expect ALL metal inside the heat riser to burn away in fairly short order. So IF I'm going to use (say) a piece of pipe, I treat it as a sacrificial form. I don't BUY new pipe for this purpose but pull it out of the dump instead. I don't (generally) pay attention to the gauge, quality or type, I just use the stuff and (carefully) pull out the shattered wreckage when the time is right.

I use a pearlite/clay mix that does just fine (so far) all on it's own. Recently, I've used those cardboard tubes intended to pour concrete piers with. I just pack my mixture between two (appropriately sized) tubes and simply burn them out.

[ukdan]

I think I have some steel that will work well up to about 1150ºc and am planning to use it for the inner (and probably outer) skin of a prototype riser on a prototype horizontal batch burner. Can anyone tell me the absolute best insulative material to use between these two skins for this riser?

It seems a shame to waste a castable refractory in there so should I try 100% expanded vermiculite? Maybe I should mix a bit of fireclay with it so it won't fall out loose if my inner riser skin does not hold up as promised. This is all new to me so I am all ears

[Donkey]

The good thing about using pearlite/clay is that if the metal fails, the mix will stay together.

I can't say what the "absolute best" would be..
Pearlite without the clay will be much more insulative but if the metal fails, it will end up blowing loose all over the inside of your stove/bench/bell/what have you..

[JJ]

Jan 4, 2012 21:47:45 GMT -8 Donkey said:

I like doing it with metal, 1/8 inch or better steel is nice, thinner stainless works.
Metal can be insulated REALLY well while brick tends to have higher thermal mass. Higher mass heat risers take a little longer to get fully hot, a little longer to really kick into action.

I use black, single wall chimney pipe and insulate around it with pearlite/clay. I'll go a little extra heavy on the clay slip, single wall stovepipe WILL burn out and I want the pearlite/clay mix to hold together well. I try to hold off on plasters right away and just live with the thing for a while. When the stovepipe does burn out, I'll take off the barrel, open up the stove, give it a good cleaning, pull out the metal shards and do any last minuet fix/adjustment. After all that and things are still working fine, THEN I go ahead and plaster it and make it pretty.

Soooooo...you use the black stove pipe. Check. I only have 8 inch black stove pipe here. What do you do...pull it apart and use two pieces around the thing and connect them?

[Donkey]

I don't do it for the outside, just the inner part of the riser. I find something else for the outer jacket.
I've actually stopped using the stove-pipe so much for this.
I did it more when I could get old junk out of our local trash/transfer station (what we used to call the dump).
Now that I gotta pay for new stuff, I'm NOT so quick to go sacrificial.

I've been going with the sonotube, concrete formers and either burning them out or peeling them out.
Burning them out presents it's own challenges, the cardboard as it burns will swell and temporarily plug the works. Gotta use a piece of rebar or something to poke it through. This has me doing it with the barrel off, hot ash flying around, burning crap all over the floor...
Might not want to go there in your nice new house.. Might want to peel it out.

[JJ]

Oct 23, 2014 6:40:15 GMT -8 Donkey said:

I don't do it for the outside, just the inner part of the riser. I find something else for the outer jacket.
I've actually stopped using the stove-pipe so much for this.
I did it more when I could get old junk out of our local trash/transfer station (what we used to call the dump).
Now that I gotta pay for new stuff, I'm NOT so quick to go sacrificial.

I've been going with the sonotube, concrete formers and either burning them out or peeling them out.
Burning them out presents it's own challenges, the cardboard as it burns will swell and temporarily plug the works. Gotta use a piece of rebar or something to poke it through. This has me doing it with the barrel off, hot ash flying around, burning crap all over the floor...
Might not want to go there in your nice new house.. Might want to peel it out.

Oh it's not a new house lol. It was built in 1871 - and it's completely gutted at the moment - studs...joists...etc. All the lathe and plaster is off and I want to incorporate cob into the walls. I'm in the process of reinforcing the floor in order to do this. Unfortunately, in Michigan as I told you recently, has outlawed strawbale construction but they've told me as long as I keep the cob on the "inside" of the house and not the outside...it's legal and no permit is needed (so long as I don't alter the structural integrity of my house unless I have a permit). I'll have to post pics soon somewhere. I'm having an excavator come out next week to dig a huge hole (where my natural pond will eventually be next summer) before it gets too cold and frost forms in the ground so I can work through the winter.

These concrete forms...do you have any pics of the swelling so I can get a better visual?

[hpmer]

I build mine square with a sheet of floor underlayment. It'll burn out too, but not with the flaming bits of fly ash all over the place. I find the square shape easier to patch. I've heard it's not quite as good as round but seems to work pretty well for me.

[Donkey]

I don't have any pictures of that process.. My hands are usually too busy at that point to want to pick up a camera.
It's just doing what cardboard does when you burn it, the layers come apart and so it swells, then sheets fall off but don't immediately shatter to crumbs. These sheets clog up the works so you gotta clear the riser with a piece of rebar or some such..
It's a messy job, though kind of fun if you like that sort of thing.

[luddite]

Hello. Anyone have a guess as to how long a 6"inch diameter .25" thick piece of well casing will survive in a heat riser? i know its a waste but its in my scrap pile rusting away.