#11  
Old 04-27-2010, 02:46 AM
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Location: saugerties, ny
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Default Re: spalling hearth

ok, I'm hitting the post reply button faster than I'm thinking. It's still early and I haven't had the first taste of tea yet...

At this point I think I'd like to know about the difficulty of replacing the bricks. I still have several left over and of course I could likely just flip these bricks, provided they are indeed refractory. I could just go buy new brick and triple check that that's what they are. But how hard is it to replace? What are the risks? Is there a tried and true method? (And I mean tried and true, not guessed and suspected). Naturally, they are not cemented so in theory they should more or less pop out once the first one is out, which I suspect would have to be the sacrificial brick in order to allow the others to come out. (I can't wait to crawl inside and lie down in a dark, used, cramped wood-fired oven. How much fun can one guy have?)
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  #12  
Old 04-27-2010, 05:35 AM
egalecki's Avatar
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Location: Virginia
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Default Re: spalling hearth

I think the easiest way to get one out is as Neil suggested- drill a hole with a masonry bit and put a tapcon screw in (masonry screw, blue in color) and pull it out using the screw as a handle. You can buy them at the local hardware store and they sell the bits right with the screws.
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  #13  
Old 04-27-2010, 09:46 AM
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Location: Washington State USA
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Default Re: spalling hearth

Kim,
Sorry to learn of your problem with the bricks. My personal opinion is that Neil's suggestion regarding expansion bolts to lift a sacrificial brick is probably the best. I would also suggest that after drilling and installing the expansion bolts that you spend a few minutes with a shop vac vacuuming out as much of the ash etc from the seams between all the bricks in the floor.

Having a few spare bricks from the batch used in construction of the floor is great. Just like tile for floors or shingles for a composition roof, having identical spares for replacement makes the job easier and the result less noticeable. While in this case there are no cosmetic concerns, any variance in the dimensions of bricks over time (our WFOs are designed for lots of years/decades of use) would certainly be problematic in making repairs. Your idea to simply invert and use the otherside of the bricks will be money saving. However, if I am reading the archives correctly, your WFO came online in October of last year; if it was somehow a problem with the bricks the other side will probably have the same issue. This would mean you might be faced with the same problem again in another six months :-(

Bests,
Wiley
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  #14  
Old 04-27-2010, 02:40 PM
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Default Re: spalling hearth

Test a brick.

Set one edge on a support and start giving it a few wacks with a sledge. It should not spall, powder or delaminate in any way. When it fails it should be by a clean break all the way through. If the batch you have is the wrong brick then there is no point in replacing the failed bricks with the same.
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  #15  
Old 04-27-2010, 04:00 PM
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Default Re: spalling hearth

Neil,
I just did a quick test by simply hitting one of the left over bricks with a regular hammer and in one easy hit it split in two quite cleanly. Does that tell us anything?

Wiley,
I agree that if the bricks are not refractory then the problem will repeat. But if they are refractory then flipping would be ok, wouldn't it?

And if I haven't said so already, thanks.
Kim
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Old 04-27-2010, 05:41 PM
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Default Re: spalling hearth

"one easy hit it split in two quite cleanly"

One measure. A standard brick should weigh about 9 pounds.
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  #17  
Old 04-27-2010, 06:50 PM
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Default Re: spalling hearth

I just weighed one which came in at about 6.5#. It's an 8.5" x 2.5" x 4.25" (more or less) brick.
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  #18  
Old 04-27-2010, 07:20 PM
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Default Re: spalling hearth

That looks like heat spalling to me. Note that spalling is more a function of heat differential than it is too much heat. Too much heat will cause it to crumble, while a heat differential will almost always cause concave spalls like yours.

My guess is you had a good amount of heat in the bricks then cooled the surface rapidly enough to cause spalling.

It could also be caused by an extremely cold oven being heated up too quick, although I would say that is more likely on the dome than the floor.
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Old 04-27-2010, 09:15 PM
Il Pizzaiolo
 
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Location: Tampa, FL
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Default Re: spalling hearth

Kim,
From a size and weight perspective, your bricks sound the same as my. Size is the same, the weight of mine are around 6 lbs 2-3 ozs. I used light duty "fireplace" firebrick. (yes, a data sheet was provided when I purchased them, so I am pretty certain of what they are)
For the record, I just came from my garage where I measured and weighed a leftover as well as a "fired" brick paver I will soon be using to update the fascia on my oven. Both bricks probably have zero moisture in them (the firebrick has been sitting high and dry for 3 yrs, the paver - 4 months)

I would say weight only matters when trying to determine what type of firebrick you have, not IF it may be a firebrick. The clay pavers that I have look identicle on the outside as my firebrick, only difference in appearance is the color. The paver is the same width and thickness, but 1" shorter (7 1/2"), and weighs 5 lbs 9 ozs., Damn near the same as the firebrick.
I'm certain the weight rule matters when comparing types - insulating firebrick usually run 2.5 - 3 lbs., light duty= 6 -7 lbs., medium = 8 - 8.5, and heavy duty = 9+ lbs.

Just thought I would throw this info out there...food for thought

RT
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  #20  
Old 04-28-2010, 05:49 AM
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Default Re: spalling hearth

I think what I'll do is go ahead and flip the ones I have in place right now and just be more cautious about firing when the hearth might be wet, and to be cautious about the mopping when baking bread. Even if the brick are not refractory, which I don't believe is the case, and they spall even with the precautions, then I'll just re-do the removal and assure I have the right brick. I'll keep you posted on the progress. All in all, it's really an inconvenience at this point. I mean to bake some bread tomorrow anyway and will slate a time for repairs when I don't plan on any baking.
Thanks all. Ain't this great?
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