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Old 03-28-2011, 10:08 PM
Brian Wong Shui Brian Wong Shui is online now
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Join Date: Oct 2002
Location: Atlanta, GA
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Lawrence, since I'm the one who looks after the technical aspects of this shop and you are posted a photo of our equipment, I guess I should contribute to this thread.

Everything that you've read on this thread about venting, gathering ports, crowns, insulation, wiring, etc. is true. Listen and try and take care of the problems now while it is apart.

The seal between the door and the gathering port is worth about 10% in energy consumption. We reface the gathering port and change the door once a year without fail to keep a good seal and a gap on the bottom edge of the door helps with the dribbles and allows most of the gases to vent without too much heat loss (found out after much experimentation). The picture that you posted is one of the experiments.

We had hole once and found the drain port in this version of the furnace to be lacking. It ate the bricks and got into the insulation. It was a pain to clean out. Your drain port seems to be a little better designed but it should stick out beyond the metal of the cylinder.

We charge batch weekly and pull our crucibles religiously at 72 charges and always have a spare on hand.

Like Pete, I've always thought that the bottom and the front face of the furnace is a little underinsulated. If you scan it with an IR thermometer it will be a higher temperature than the rest of the cylinder.

Since your furnace is under a hood, ensure that there is enough space work and to pull and install the elements. You'll be doing this hot one day. Using a piece of Angle Iron around the corners of the passage bricks makes a good extraction tool and can aid installation to allow the brick to slip in without getting hung up on the insulation.

Get a high temp IR Thermometer. It will help you find hidden trouble spots and hot connections. Grid the skin and take measurements when new. It will help to identify when tunnels are being formed in the insulation. Get a 1000A True RMS Clamp Ammeter and take readings (primary and secondary) when new. It will provide a baseline for your monthly measurements and identify when something is changing in your furnace. Try and take the readings under the same operating conditions.

Put a dialer on the Watlow. Elements break in the night with a full pot of glass. You'll need to know.

Put a time delay relay on a warning light for the door. People will leave your door ajar and you'll wonder why your furnace temperature is dropping.

Allow the stainless panel on the front to move. This panel buckles under the heat. Expansion allowances may help. (Not tested)

Build a maintenance checklist and follow it. Perform Root Cause Analysis on every failure. No one ever said that this was a maintenance free furnace but it makes great glass.
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