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-   -   Scary Cracks in Ephrem Dome... (http://www.fornobravo.com/forum/f16/scary-cracks-ephrem-dome-16743.html)

cleverdick 09-21-2011 02:32 PM

Scary Cracks in Ephrem Dome...
 
Well, this is how it looks after getting up to cooking temperature. The two halves of the dome have separated at the base and the blanket is now visible from the inside through the gap. Even worse, the top of the dome has cracked so much that soot has gone through to the outside.

I don't know whether to (at least) fill in the gap at the back (but with what?), or leave well alone! Nothing's fallen off yet, but I just need some reassurance here...:eek:

Domecracks pictures by clever_dick - Photobucket

david s 09-21-2011 04:01 PM

Re: Scary Cracks in Ephrem Dome...
 
If you can see blanket through the casting joins, then presumably you did not cover the join with refractory cement. The assembly instructions from the manufacturer should have advised this. The fibres are a health risk and should be sealed away. You can fill the join from the inside. Regarding the other hairline cracks, they are normal and should not get any worse, but they shouldn't be any bigger than about 1mm. You should contact your supplier.

cleverdick 09-22-2011 02:16 AM

Re: Scary Cracks in Ephrem Dome...
 
Quote:

Originally Posted by david s (Post 120902)
If you can see blanket through the casting joins, then presumably you did not cover the join with refractory cement. The assembly instructions from the manufacturer should have advised this. The fibres are a health risk and should be sealed away. You can fill the join from the inside. Regarding the other hairline cracks, they are normal and should not get any worse, but they shouldn't be any bigger than about 1mm. You should contact your supplier.

Thanks David,

Interestingly, this manufacturer specifically says to NOT mortar the joints, although I did run a thin bead of mortar between the base of the dome and the cooking floor on both sides, just to fill a small gap. (They advised me to do this). I guess what I'm looking for is a flexible, fireproof sealant but as far as I know such a thing does not exist. OK, you can get heat-resistant silicone, but that is only good for 350c or so - and not permanently. I agree about the blanket fibres (hence my concern) - I was thinking of cutting a sliver of calsil board and wedging it in, but with adhesive on one side only, so as to still permit slight movement between the dome halves. Or even a small piece of stove rope. What do you think?

Rich

david s 09-22-2011 02:38 AM

Re: Scary Cracks in Ephrem Dome...
 
If the manufacturer had made the castings with interlocking joins there would be no gap to fill. As this has not been done, if it were mine I'd be using the 3;1;1;1 sand, cement, clay, lime mix and squish it into the gaps.I also find it odd that the Ephrem build instructions don't recommend insulation between the oven floor and supporting slab. You'll be grateful that you did insulate under your floor.

cleverdick 09-22-2011 03:19 AM

Re: Scary Cracks in Ephrem Dome...
 
Quote:

Originally Posted by david s (Post 120941)
If the manufacturer had made the castings with interlocking joins there would be no gap to fill. As this has not been done, if it were mine I'd be using the 3;1;1;1 sand, cement, clay, lime mix and squish it into the gaps.I also find it odd that the Ephrem build instructions don't recommend insulation between the oven floor and supporting slab. You'll be grateful that you did insulate under your floor.

David,

There are a few things with this manufacturer that I find surprising- for instance that they recommend putting normal rockwool over the top, covered by sand! And as you say, advising to mount on a layer of 'lean mortar' only.

Some of their more expensive ovens do indeed have interlocking sections, but this is the smallest and most basic.

I got a reply from them, translated with Google as follows:

" As we explained in the installation instructions are expansions required by the furnace and its operation that does not. We should not close the gap. You can put insulation over the sand or vermiculite to a concrete as indicated on the assembly instructions."

I have the ingredients to make the compound you suggest, but if it sticks too well and something needs to move, then won't this just cause a fracture elsewhere?

(And yes I did insulate under the floor with calcium silicate board.)

Thanks again


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