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Easy fire bowl repair and despair


philpom
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Over a year ago I was cooking pizza and suffered a single crack in my fire bowl.  It grew over time and 1 turned in to 2.  Next thing you know the fire bowl was in 2 pieces kinda just sitting down in there.  I just kept cooking and could have left it that way for a very long time but I needed to do a good cleaning so the time was right.

Before I go any further I want to let you know that I didn't need to do this, I have a new fire bowl in my garage right now.  I am a curious person though and I want to see how long I can go from one fire bowl.

 

This method should work on any ceramic kamado.

Material:

  • T304 lock wire
  • small 1/4"-3/16' mason bit
  • cutters
  • pliers

Pull the fire bowl out and clean it up.  Put it together, use a strap etc to hold it in place.

Drill a pair of holes down the crack - 3, maybe 4 depending.  Push the wire through and twist it tight with the pliers while carefully setting the crack in place as you go.  BAM!  That's it.

 

IMG_20160919_134024550_zpsj92k4oio.jpg

IMG_20160919_161749879_HDR_zpsixitg3co.j

IMG_20160919_161759451_zpsxikabfff.jpg

IMG_20160919_162215408_zpsaofricre.jpg

IMG_20160919_163519958_HDR_zpsrkdyxkci.j

All better.

And now despair.  I discovered another hairline crack while doing this repair, this tells me that over time the fire bowl will slowly crumble.  We'll see how long it takes.  You can just see it in this photo, it leads off of crack #2 and is about a foot long at this point and it is all the way through.

IMG_20160919_161818581_zpsnoudjs4f.jpg

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Nice info. At one point early on in my ceramic research it was pointed out that this was not a good approach because the metal will expand more than the ceramic. After years with my kamados, I am not sure I buy that argument.  

I am curious how the 304 SS holds up. At FB temps, I expect the stainless properties to be less than acceptable. 

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You and I apparently think a lot alike.   :)   I used the same repair technique (as a test) a while ago on my Big Joe fire bowl using copper wire. Looks like the stainless wire lets you get a tighter pull down in the twisting than copper which will break at the twist if done to much.

I noted the same issues of additional cracking just as you did.  It is like once the ceramic cracks in a major way from the stresses, that only relieves the stress where it  finally fractured and the stress is still there in other areas just waiting for the right trigger event.  Which could be heat or clinking it with the ash tool or setting a fire ring or ash grate down on or in the bowl slightly too hard, or ???

Mine eventually succumbed and was set aside as the race between wire repairs on new fractures or impending fractures was a losing cause.    I even "stress relieved" the cracking but not broken fracture lines with holes drilled at each end of the crack to stop further propagation but that was marginal at best. It seemed that a crack would branch off in other directions from the main line.  On this particular fire bowl the ceramic seems much more crumbly in texture overall which became evident when drilling the holes.

I had wondered if skim coating with a good bond of furnace cement after the repair would help ???

The solution you outlined works and can buy time - even for a good long while but eventually it had diminishing returns - at least in my case.

On my KJ grill family, I have noticed a differing density in the material among the ceramic fire bowls between models and over time in the model lines (perhaps as suppliers have changed)  - some harder/denser  some softer/more porous.  However,  I don't have enough data to theorize which material characteristic approach is better/worse.   My limited evidence leans toward the hard/denser being more robust.  I have wondered if the less dense might absorb more moisture in highly humid climate and somehow water vapor out gassing during heating could be a cracking factor... But what do I know??  

Any ceramic scientists, engineers, or pottery experts around to weigh in?  Just out of curiosity driven by an engineers mind rambling out loud.

Ceramic warranties in Kamado land are wonderful and sometimes necessary thing.

 

 

:|

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On 9/19/2016 at 7:14 PM, Mewantkj said:

Nice info. At one point early on in my ceramic research it was pointed out that this was not a good approach because the metal will expand more than the ceramic. After years with my kamados, I am not sure I buy that argument.  

I am curious how the 304 SS holds up. At FB temps, I expect the stainless properties to be less than acceptable. 

I found this info, was curious myself.

 

Temperature Tolerances for Grade 304 Stainless Steel

When steel is red-hot, it usually means that the tensile strength of the steel has been compromised.One of the key properties of any stainless steel alloy is its resistance to oxidation. High temperatures can compromise the the oxidation resistance of steel alloys, leading them to become rusted and weakening their structural integrity.

As stated by AZO Materials, grade 304 stainless steel possesses “good oxidation resistance in intermittent service to 870 °C and in continuous service to 925 °C.” However, they warn that “continuous use of 304 in the 425-860 °C range is not recommended if subsequent aqueous corrosion resistance is important.”

In other words, you can expose grade 304 alloy steel to temperatures of up to 1,598 °F for short periods of time without ill effect, and for extended periods of time in temperatures of up to 1,697 °F. However, this can compromise the corrosion resistance of the metal, making it more susceptible to corrosion damage from exposure to moisture.

As noted in an AK Steel data sheet on 304 stainless steel, the alloy reaches its melting point at the 2,550 °F – 2,650 °F (1399 °C – 1454 °C) range. Naturally, the closer the steel is to its melting point, the more tensile strength it loses.

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On 9/20/2016 at 9:51 AM, Smokehowze said:

 

On my KJ grill family, I have noticed a differing density in the material among the ceramic fire bowls between models and over time in the model lines (perhaps as suppliers have changed)  - some harder/denser  some softer/more porous.  However,  I don't have enough data to theorize which material characteristic approach is better/worse.   My limited evidence leans toward the hard/denser being more robust.  I have wondered if the less dense might absorb more moisture in highly humid climate and somehow water vapor out gassing during heating could be a cracking factor... But what do I know??  

Any ceramic scientists, engineers, or pottery experts around to weigh in?  Just out of curiosity driven by an engineers mind rambling out loud.

Ceramic warranties in Kamado land are wonderful and sometimes necessary thing.

 

 

:|

The fire bowl on my Primo was much harder than I expected it would be.  I bought a new set of BOSCH masonry bits and went through 4 of them to get 12 holes drilled.  They were rated at 2000rpm and I used a slow speed and moderate pressure.  After a hole or 3 they would no longer do more than create a dimple on the surface.  I did notice that the larger the bit the longer they lasted.

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I did do a test cook, some leg quarters at about 400 and then ramped it up to about 650 dome temp for 30 minutes.  No crack separation was observed and post cool down the repair looked the same as before the first cook.  Time will tell how long this will last.

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2 hours ago, philpom said:

I found this info, was curious myself.

 

Temperature Tolerances for Grade 304 Stainless Steel

When steel is red-hot, it usually means that the tensile strength of the steel has been compromised.One of the key properties of any stainless steel alloy is its resistance to oxidation. High temperatures can compromise the the oxidation resistance of steel alloys, leading them to become rusted and weakening their structural integrity.

As stated by AZO Materials, grade 304 stainless steel possesses “good oxidation resistance in intermittent service to 870 °C and in continuous service to 925 °C.” However, they warn that “continuous use of 304 in the 425-860 °C range is not recommended if subsequent aqueous corrosion resistance is important.”

In other words, you can expose grade 304 alloy steel to temperatures of up to 1,598 °F for short periods of time without ill effect, and for extended periods of time in temperatures of up to 1,697 °F. However, this can compromise the corrosion resistance of the metal, making it more susceptible to corrosion damage from exposure to moisture.

As noted in an AK Steel data sheet on 304 stainless steel, the alloy reaches its melting point at the 2,550 °F – 2,650 °F (1399 °C – 1454 °C) range. Naturally, the closer the steel is to its melting point, the more tensile strength it loses.

I have seen this. Basically in SS you have iron, carbon and chromium. At high temps the carbon and chromium react leaving the iron unprotected. Taking my dork hat off now. 

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