#1  
Old 01-25-2013, 03:40 AM
Serf
 
Join Date: Jan 2013
Location: Devon
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Default steel liner question

Hello everyone! We've been badly let down by our 'builder', so the cement is crumbling between the bricks on our dome and the builder left very big gaps between the bricks too (despite them being shaped for the purpose). Ours is a shallow dome, for breads & pizzas hopefully. Space is too small to crawl in and fix the problem, so we want to line it with stainless steel - hopefully avoiding the concrete crumb pizza topping. Does anyone know how thick the steel should be, how much it will warp or buckle over time and at temperatures of 450 C? We are thinking of welding steel ribs to minimise buckle, but not sure what gap to leave between the steel liner and the bricks. Please help - we're getting very down about this Thanks in advance!
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  #2  
Old 01-25-2013, 11:30 AM
david s's Avatar
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Default Re: steel liner question

Quote:
Originally Posted by La Boulangere View Post
Hello everyone! We've been badly let down by our 'builder', so the cement is crumbling between the bricks on our dome and the builder left very big gaps between the bricks too (despite them being shaped for the purpose). Ours is a shallow dome, for breads & pizzas hopefully. Space is too small to crawl in and fix the problem, so we want to line it with stainless steel - hopefully avoiding the concrete crumb pizza topping. Does anyone know how thick the steel should be, how much it will warp or buckle over time and at temperatures of 450 C? We are thinking of welding steel ribs to minimise buckle, but not sure what gap to leave between the steel liner and the bricks. Please help - we're getting very down about this Thanks in advance!
I think you're in unchartered territory. Stainless is notorious for warping and the thinner it is the greater the tendency. I assume your oven is a barrel vault because a dome would be extremelly difficult to line given the compound curve.
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Old 01-25-2013, 03:56 PM
Laurentius's Avatar
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Default Re: steel liner question

Add photos, please.
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  #4  
Old 01-26-2013, 09:12 AM
Master Builder
 
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Location: Washington State USA
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Default Re: steel liner question

As an owner/builder with a steel lined WFO I concur with everything stated in the replies so far. IMHO A steel lined WFO is a very viable way to go and I would suggest it to someone building an oven. However, as a repair technique for a failing WFO I would not advise taking that route. There needs to be intimate contact between the liner and the refractory heat sink/heat reservoir for efficient heat transfer between them. This is not difficult to achieve when building, but as a retrofit or repair I can see it as very hard to assure.

Like Wotavidone, I would also advise carefully deconstructing your WFO and rebuilding.

Bests,
Wiley
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Old 01-27-2013, 02:38 AM
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Thumbs up Re: steel liner question

La Boulangere
Thee is only one way to overcome this problem.
Knock it down carefully, without damaging the bricks, and rebuilding it.
Should you want a steel lined oven, and as Davis assumes that you have a vault oven, get a sheet metal worker to bend you up a 3mm steel liner and even you can then easily lay the bricks to sit on this liner which doubles as your formwork. Just put a thin mortar coat to bed the bricks up against the liner so that no air gaps will be present as the air acts as an insulator.
Could you have don as bad a job as your "builder"? I built my 40" pompeii in 2 days so it will not prove to be a too difficult a job to rebuild, and you will end up with a much better job.

Neill
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  #6  
Old 05-29-2013, 09:52 AM
Peasant
 
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Location: Upstate New York
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Default Re: steel liner question

Hello Wiley,
I have both, a stainless 55 gallon barrel and a 15 gallon keg I was considering using one of them to line (build over) my wfo. My thought is to cut the barrel length direction (top to bottom) and lay it flat to create a barrel dome. Then cover with perlite/concrete insulation and possibly some fire blanket - then brick the top for the finish as I have 200 red bricks laying around. The floor would have fire brick with insulated perlite/concrete form poured under that.
Does this sound workable?
I was hoping to use the 15 gallon keg option for a small oven. 14" wide by 23" long by 15" high (inside dimensions). I like the smaller keg because the front and back "walls" if you will, are curved to create a smooth transition to the ceiling. The larger 55 gallon drum has 90 degree wall angles.
With a very small oven like this - I'm not sure that the curved aspect would matter much...but this is all speculation in my part.
Any thoughts and suggestions?
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Old 06-04-2013, 11:49 AM
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Default Re: steel liner question

lovibond69,
Sounds workable but you will need to have some sort of refractory heat sink/reservoir outside the stainless keg half. You should be able to easily figure the space available between the outside of the half keg and the inside of the half 55 gallon drum before doing any cutting. As the WFO will be small you probably won't be looking at 4 inches of refractory but I would think 2 to 3 inches would heat up fairly fast, yet be sufficient to bake pizzas. Whether the remaining space (outside the refractory but inside the drum) is sufficient for insulation is another matter. Perhaps using a kaowool type ceramic insulation around the widest part of the keg might be worth considering to keep the outside of the WFO from getting too hot.

Hope this helps,
Wiley
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  #8  
Old 06-04-2013, 05:39 PM
Peasant
 
Join Date: May 2013
Location: Upstate New York
Posts: 29
Default Re: steel liner question

Hi Wiley,
Thanks for the reply! You pose an interesting view which I had not considered. Your idea (tell me if I read this wrong) is to cut both kegs and place the smaller one inside the other. The space in-between would be filled with a heat sink refractory and above that would lay the insulation layer and above that, the larger barrel...is that correct? Sounds like a very good idea.

My thought (and main question) was to use either of these kegs - one or the other....and if going this way, which one should I use to get the best efficiency based on internal size? I would only be cooking a couple of pizza's once or twice a week and would like it to be able to reach the 700 - 900 degree mark that is typical of the brick domes.
Do you think it would perform as well?

I assume by your response that when using either liner alone, I could still cover the barrel dome shape with a dense refractory - 3:1:1:1 sand:fire clayortland:lime mix?
Then cover that layer with ceramic cloth and place a "finish" coat of percrete - 5:1 perliteortland insulation layer on the outer-most section?

Thanks again!
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  #9  
Old 06-04-2013, 05:48 PM
Peasant
 
Join Date: May 2013
Location: Upstate New York
Posts: 29
Default Re: steel liner question

Here is what I have so far.
4" layer deck of perlcrete on top of rebar/contrete form. I cantilevered the large double angle iron to support the granite shelf to the left side.

I have plenty of full fire bricks to form the base (floor) of the oven. Now to choose what type of oven to build!
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  #10  
Old 06-04-2013, 07:08 PM
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Default Re: steel liner question

Lovibond,

Yes, that was my assumption: cutting both and placing one inside the other with refractory and insulation between the two. My bad if I got that wrong. It has been done successfully, (see: http://www.dentedbuoy.com/ and Ľ History of the Buoy oven). Having enough space between the two shells to have both the refractory and the insulation is the issue. Dented Bouy's WFO has an interior done of 48 inches diameter and a 60 inch diameter exterior dome. Plenty of space for refractory and for insulation. The two shells you have may not be so accommodating.

Regardless, using either with a refractory and insulation and exterior shell of whatever (stucco, framed small building, etc) will most likely work well. There has been one WFO made by a member of this forum with formed stainless steel sections welded together to form the interior dome. Very cool and I am envious of that owner/builder's skill.

Which of the two shells you decide to use (that is if the measurements preclude using one within the other) something to keep in mind is the height of door to interior ceiling proportion of 63%. Vary much from that and most likely the WFO will not draw well or have good interior gas flow. That 63% ratio controls the final height of the door. My WFO can accommodate a fairly large turkey in a roaster (although I had to modify the handle on the top of the lid to fit the height). To me the larger of the two would be desirable as it would permit a higher door height thus larger pots, roasters etc.

There was a WFO built here that used a half whiskey barrel for a form and which was burned out with the initial firing so having a shape cornered aft wall joining the rounded ceiling seems to work...or at least did in his case. There has been a lot of WFOs built with a barrel roof and a flat aft wall as well. Check archives: http://www.fornobravo.com/forum/f3/i...ioni-4420.html (I embark upon the jouney and the journey is the destinationi).

As for the actual mix of the refractory, IMHO lots of stuff can work, I have seen where some use crushed firebrick and portland cement and lime mix. Personally I like the calcium aluminate (Fundu) as it is high temp and goes off quite fast...I don't suggest adding lime as it really speeds it up.

Hope this helps,
Wiley
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