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  #59  
Old 01-22-2010, 08:52 PM
Cecil McKenzie
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Marcel.... While I have not built a moly furnace I have thought that the elements could be put in indentations in the wall.

When I built my gas furnace I tried to address the minimizing volume issue by making a throat on one side of my lid which is two part castable. The opening is vertical so there is less chance of debris falling into the glass. The back half of the lid is only about 4 inches above the edge of the crucible. The door is like the old Denver doors that lift straight up. I know that many don't like the Denver style door because it can't be opened half way. It does have advantages.. one is the area to the sides of the door can be better insulated and it can be made to have a pretty tight fit. When I change the crucible which means removing all the insulation and cast pieces [ much harder as I get older] I make a gasket of zircon impregnated fiber gasket to seal the door .

The idea of basically making a cup or tub to hold the glass if the crucible fails seems like a good idea. Of course if the clean out could be attached with seamless integrety to the tub itself and the tub was large enough to hold a total blowout then you wouldn't have to worry about glass seeping through joints. You would have keep the bottoms of your moly elements from hanging low enough to be wetted by the rising glass level from a blow out.
I'm not sure if I have been that clear about how my lid is constructed but could get a photo sometime if any one is interested.
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