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Old 12-04-2011, 12:51 PM
Rollin Karg Rollin Karg is offline
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Join Date: Apr 2002
Location: Kechi, KS
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We recently tore down an Old Moly and got a surprise. It had been getting a little sluggish, so we expected a Jellyroll. There was about a two inch thick Jellyroll but above that there was cavity of about eight or nine inches high and maybe four to six inches wide. There was still some Frax left against the metal and it was still making glass, but it was way under performing. At first it was a puzzle. After some I believe the moisture in the batch was causing enough pressure to force air and batch out through any opening, including the crack at the bottom. This mixture ate up the Frax.

Our furnace wall is 3.5ď thick and the bottom 17Ē is Mizzou. The rest is Kast-O-lite 30.The Mizzou is stout but after enough cycles it will crack. This furnace is over six years old and melted twice a week for a lot of that time. If you donít keep the bottom clean and/or you break a pot the crack is going to allow the glass back where it doesnít belong. The cavity thatís something new.

Before we saw this, the plan was to make a change in construction. I think it will solve two related problems. Our plan is to add four layers of soft brick(10Ē) on the outside of the Mizzou part of the furnace liner. Iím hoping this will stop the jellyroll and give some protection against the batch gases.

We have a vent hole in the door to let out some of the gases. Weíre going to add another step and start doing as Pete says and leave the door open for 45 seconds after throwing in the batch.
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