Arnold Howard on thu 3 feb 05
The firebricks expand and the kiln grows a little taller at high
temperature. This is why the lid must "float." The hinge holes must be
slotted so that as the kiln grows taller, the lid does not bind at the
hinge. If the lid has a gap in front, the lid may be binding at the hinge
due to brick expansion. To tell if your lid can float, lift the back of the
lid when the kiln is cold. You should feel play in the hinge.
Also, the inner lid surface expands more than the outer lid surface during
firing. The expansion of the inner lid surface causes the lid to bow inward
toward the firing chamber. The lid no longer rests flat on the kiln walls at
high temperature. So a slight gap between the lid and kiln body is normal.
There should be little heat loss unless the lid is binding at the hinge.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
arnoldhoward@att.net / www.paragonweb.com
----- Original Message -----
From: "primalmommy"
> For some reason, ever since I moved my big evenheat kiln off its
> previous cinder block platform, (I know, I know) and onto the kiln vent
> stand, the lid seems to bow in the hottest part of the firing so that
> there's a big, heat-losing, cold-sucking gap in the front. I just
> figured I would tighten and readjust it once it cooled, but when it's
> not in mid-red heat, it behaves itself.
william schran on fri 4 feb 05
Arnold wrote: >Also, the inner lid surface expands more than the
outer lid surface during
firing. The expansion of the inner lid surface causes the lid to bow inward
toward the firing chamber. The lid no longer rests flat on the kiln walls at
high temperature. So a slight gap between the lid and kiln body is normal.
There should be little heat loss unless the lid is binding at the hinge.<
As this is known by kiln manufacturers, would it not be appropriate
to attend to this issue?
Perhaps the surface of the bricks at the top of the wall, that the
lid rests on could have a slight angle cut into them that would match
the change in the lid deflection?
Or something similar to what is done in Amaco square kilns, a strip
of fiber rope sits in a groove on the top of the wall, helping to
seal the top?
Or, perhaps this simply is not that big of an issue, and kiln
manufacturers should include this information in their manuals
stating this is normal?
I've added thin strips of fiber between the sections of all of our
sectional kilns, but have not done this on the wall/lid area as the
fiber would get knocked around, causing more problems than it's
worth. But I am considering routing out a groove in the top of the
wall to insert a fiber rope.
Bill
Arnold Howard on mon 7 feb 05
Actually, kiln manufacturers are happy to make whatever people are willing
to buy. Paragon offers the rope lid seal, but not many people order that
feature.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
arnoldhoward@att.net / www.paragonweb.com
----- Original Message -----
From: "william schran"
To:
Sent: Friday, February 04, 2005 9:40 AM
Subject: Re: [CLAYART] Keeping a stiff upper lid (lid leaks heat)
> Arnold wrote: >Also, the inner lid surface expands more than the
> outer lid surface during
> firing. The expansion of the inner lid surface causes the lid to bow
> inward
> toward the firing chamber. The lid no longer rests flat on the kiln walls
> at
> high temperature. So a slight gap between the lid and kiln body is normal.
> There should be little heat loss unless the lid is binding at the hinge.<
>
> As this is known by kiln manufacturers, would it not be appropriate
> to attend to this issue?
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