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Old 03-18-2004, 12:38 PM
Kurt Walrath's Avatar
Kurt Walrath Kurt Walrath is offline
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Join Date: Apr 2002
Location: Corning
Posts: 155
Kurt Walrath is on a distinguished road
I built mine based on the elements that Brice was using
which I have been buying from jen ken kilns for the past
3 years. They are 20 bucks a piece.

12.7 ohm 15 gauge 63" long elements run 2 each in series.

The way it used to be set up is descibed in detail on my site.
http://www.kurtwalrath.com/largeglassstudio/furnace.htm

I now run 4 sets of 2 on 240V single phase in my new shop.

Brice, I'm curious if you switched to a different element
because you mentioned 11 gauge in your post above.

My grooved brick has me locked in to this small element
but if I had it to do over I'd use a beefier gauge. the 11
gauge is almost twice as thick.

I think the best life I had was 7 months or so on the 1st set
of elements. Its been degrading though and I don't keep
close track of it anymore. Where the element fries it leaves a
mark on the brick and I think that they tend to give out in the
same place. my groove is just big enough to shove the elements
in it and I would make them bigger for a loose fit if I was
doing it again.

I use SPB and charge like brice at my working temp of 2100
filling up the pot to the rim each time and adding more as soon
as it is flat till full. I step to 2070 now and hold for 5 hours
then step to 1900 to squeeze. with my level of insulation
it takes 3 hours or so to get to 1900. then it sits there
until an hour or so before I 'm ready to blow and I send
it up to 2100.

I fire with a SSR set to 80% maximum heat, I use the EC
16" round bottom 100# crucible, s type thermocouple,
Eurotherm controller.

Richard, you don't say what size pot you have but I suspect
you can use a drastically shorter melt cycle. I started melting
much hotter and longer but I keep cutting it back and it keeps
working just as well.

I doubt if it matters if you shut down or leave it on in terms
of element life. There have been many times in the past
3 years that I'd turn mine off every 2 weeks to go to a show.

if my pot is empty I can just pull the plug. no ramping down,
the insulation takes care of that. also if I go out of town I can
program my controller to have it ready to charge whenI pull
in after a show. I ramp up at 150 degrees an hour after
stepping to 250 when I bring it up. I don't do anything fancy
around 1000 for inversion and I've had good life out of my pots.

The absolute worst mistake I made in my design was a soft brick
floor! You know I was going to be carefull and never have a
pot break which has not happened to me but.....
over time it has gotten eaten up by overflow from my careless batching and the fact that 100#s is just not enough
glass for me so I always try to get it as full as possible ( read
too full). The last time I changed elements I chipped out the
remains of the grungy soft brick and replaced it with about 3"
of sand. I opened it up after trucking it 6 hours to my new
studio to discover that the pot seems to be fused in place in
the sand bed. I suspect that when I need to pull it to replace
elements I'll have to bust the pot apart and rebuild the floor
with some castable.

I think I have come up with a new design for a wire melter that
will utilize hot swapable heavy gauge elements that will make
maintaining a wire furnace a simple thing and allow you to get
as many Kilowatts in there as you need to melt quickly.

Basically it would be an wound element that slips over a hollow
quartz or mullite tube, one of the leads would pass down the
middle of the tube and you would pass these tubes through
holes in your furnace where they would rest in a notch that
would support it in the back. You could briefly fire the element
on the supporting tube to preheat the tube so it doesn't thermal
shock when you slip it in the hot furnace.

I think this type of setup would be a big improvement over
grooved brick because the elements would run cooler as the
heat could radiate away from them easier than when they
are in the brick grooves.

I probably will go with waste oil when I build my
next furnace though. I like the sound of cheap energy.

Kurt
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