Oven crack

[ginoamato]

I have built a pompeii style oven with and now have a crack. I have a steel frame with two cast iron doors on the front. The dome is enclosed with 1 1/2 inches of insulation followed by 2 inches of vermiculite & cement. This covered with cement and stucco. I have dried and fired as per the directions. The crack started when I reached over 400F and starts at the frame of the door through the arch up to the chimney and along the outside of the dome. The dome is intact and the crack seems to be on the outside only as the dome on the outside does not heat up and I can not find any cracks on the inside. I tried to repair it once with high heat mortar, bricks and vermiculite but the crack reappeared in the same place. I though the steel frame may have caused the crack as it may expand when heated up causing the bricks around it to spread. I have since cut the frame in the top center, near the start of the crack. This did not solve the problem. Does anyone have any ideas what is causing the crack and how do I repair it.

Gino

[nissanneill]

Re: Oven crack

Hi Gino,
like you, I built a 40" Pompeii with a heavy angle iron and arch bar lintel with 2 cast doors but I allowed for a different expansion coeficient between the steel and the firebricks.
My oven has been in use now for a year with no problems or cracks as the steel frame can move independently from the bricks.
Check out the.pdf attachment for the finer details.
More discussion is at:

http://www.fornobravo.com/forum/f6/t...cern-1859.html

As far as the repairs are concerned, I need a picture or some to see the damage, but I would be tempted to cut the crack out with a grinder to say 5-8mm wide and pack the groove with stands of fibreglass plugged with either refractory cement or mortar.

Neill

[dmun]

Re: Oven crack

Steel does have a higher coefficient of expansion from masonry: it expands more in heat, and it also heats up much faster than the surrounding brick, which would tend to accentuate the problem. You may want to find some way for the steel frame to float in the masonry surround, perhaps packed with the kind of fiber rope that's used in woodstove door seals.