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Old 07-22-2013, 03:10 PM
Peasant
 
Join Date: May 2013
Location: Lethbridge
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Default CRACKS!!!!Stress rising

After a long week to dry out, I have started my cure. 2 days in , CRACKS. It looks like the dome pieces are separated by about 1/8" ,back wall looks about a 1" deep all around and like there are patch areas on the side walls.

I hope others have had this and say " don't worry, have a cold one and relax"
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  #2  
Old 07-22-2013, 03:19 PM
boerwarrior's Avatar
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Location: Santa Rosa, CA
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Default Re: CRACKS!!!!Stress rising

I think cracks are part of the experience! I have a Pompeii oven so someone else with a Toscana can comment on your situation. I believe the thing to look for is if smoke is coming out of the cracks. If yes then you need to fill them in (I filled mine from the outside before the insulation was put on.) If not then consider them to be useful, natural expansion joints! So I say relax!
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Old 07-22-2013, 03:29 PM
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Location: Townsville, Nth Queensland,Australia
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Default Re: CRACKS!!!!Stress rising

Quote:
Originally Posted by austinmc View Post
After a long week to dry out, I have started my cure. 2 days in , CRACKS. It looks like the dome pieces are separated by about 1/8" ,back wall looks about a 1" deep all around and like there are patch areas on the side walls.

I hope others have had this and say " don't worry, have a cold one and relax"
Did you cure it with the blanket on or off? It looks like a cast oven, is it in sections or a one piece dome?
Don't worry too much, because it is a dome it is self supporting and can't collapse. You must have gone too fast with the fire. You can't go too slow, but you can go too fast.If you bought it from a manufacturer ask them to look at it.
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Old 07-22-2013, 05:35 PM
Peasant
 
Join Date: May 2013
Location: Lethbridge
Posts: 29
Default Re: CRACKS!!!!Stress rising

no blanket....it is a 3 piece dome. Had a few sticks in there, but was not to bad, sent the pictures to Forno bravo, they told me, and I quote..... "I had my production crew Look at your photos, and this type of crack is something that can happen on occasion with brick ovens due to the expansion and contraction that results from thermal cycling. But it will not cause you any problems, either with how well your oven cooks or on its long-term durability. You can continue using your oven and not worry about this. As far as the gap he said that is not abnormal and will not cause any problem what so ever. You can continue your curing it is not going to separate or damage the dome.", .........so I guess I keep going......So maybe I relax, have a cold one
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Old 07-22-2013, 06:10 PM
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Join Date: Feb 2013
Location: Bundaberg. Australia
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Default Re: CRACKS!!!!Stress rising

I figure that if more ovens have cracks than not then it is probably abnormal not to have them. Provided of course that they stay within the realm of being cracks. Once smoke emanates from them then they become fissures and probably need some remedial action.

Probably a bit like wrinkles, part of the character of what they appear on.

I think the relaxed cold one sounds like the right strategy.
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Old 07-22-2013, 07:43 PM
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Default Re: CRACKS!!!!Stress rising

A monolithic cast dome shape is going to crack, period. Drink beer, fire it up and if bits start dropping off, hold Forno's feet to the fire.
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Old 07-22-2013, 10:02 PM
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Default Re: CRACKS!!!!Stress rising

I don't mean to be the worry wart here but that doesn't look like a stress crack. I looks to me like it has the potential to "pop" off. If no one breaks a tooth when it happens no worries. Even if is does drop, your oven will perform as hoped for many years. Have a cold one...
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Old 07-23-2013, 11:42 AM
Peasant
 
Join Date: May 2013
Location: Lethbridge
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Default Re: CRACKS!!!!Stress rising

hey....thanks for the feed back. feeling a LITTLE better about it all. Kind of scary when you take a boo inside the oven and see that. still going at the cure(up to 3 sticks today)if I can get me to the 800f mark, with no more worries, I think I will be good. Going to have that "cold one" and relax. Also when I looked in it, it looked like a small piece was going to "pop off" as you mentioned Les, you still think all is good?? Man, that cold one is sounding better all the time!!!!cheers all
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Old 07-31-2013, 11:14 PM
Laborer
 
Join Date: Jul 2013
Location: tomball texas
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Default Re: CRACKS!!!!Stress rising

I build pizza ovens and outdoor kitchen for a living but I'm by no means a refractory engineer but I got a hunch that heat stress can crack an oven either by heating it to high at too fast a rate or cooling it at too fast of a rate especially considering there's still moisture in the casting.I think cooling an oven from 500* to room tempature in one hour may be as stressful as going room to 500 in one hour.A high wind or cold weather could make make this worse.Ill start a fire in them without the blanket to help release more water from the casting but I always throw a blanket on it before putting out the fire.But thats just redneck engineering and it seems to work for me.Years a go I use to weld huge gear hubs together on a sub arc machine on a huge positioner and if you don't preheat them pretty hot before welding the welds would crack from heat stress from heating to fast but by the same token If you didn't put ceramic insulation blankets over the gears as soon the welds were being made the weld would crack from cooling to fast.I belive Tscarbourgh use to or still does rep these materials(Refractory and masonary)maybe he can comment because I could be wrong as it pertains to refractory.
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  #10  
Old 08-01-2013, 03:51 AM
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Default Re: CRACKS!!!!Stress rising

I agree Txt, that's why I asked if it was cured with the blanket on or off. I believe it's not only the rapid rise and fall of the temp of the refractory that's important, but also the temperature differential between the inside surface and the outside surface which also leads to uneven expansion, stress and hence possible cracking. If the oven is heated and it's uninsulated, the ambient temperature fairly low, maybe some wind and the outside surface wet, this will be enough to hold down the temp of the outside surface lots. To be safe to the refractory the temperature riseor fall should not exceed 100C/ hr, but nobody firing a WFO does it this slowly.The highest quality refractory materials may still fail if heated or cooled too fast.

Last edited by david s; 08-01-2013 at 03:54 AM.
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