[TheForge] Question for Tom, Strengthening castable refractory

Fri Aug 22 15:50:02 2003

Tom,

In building furnaces using castable refractory -- how have you done a "dry
out" before going on to use under high fire?  What has worked for you?  How
long have you let it air cure etc.?

In industrial practice for large aluminum melting furnaces we developed
rather complex dry out schedules -- then went to work with an aluminum
producer in China and found they just built a wood fire in the furnace and
let it burn itself out.  They would limit the draft at the start, so as not
to overheat but then would open up the draft more as the "burn" progressed.

Dave Smucker

----- Original Message ----- 
From: "Thomas A. Troszak" <[email protected]>
To: <[email protected]>
Sent: Friday, August 22, 2003 3:27 PM
Subject: [TheForge] Strengthening castable refractory

> > Date: Fri, 22 Aug 2003 12:07:26 -0500
> > From: [email protected]
> > Subject: Re: Subject: [TheForge] Strengthening castable refractory
>
> > Another thought. Someone else mentioned using bricks. I've already got
the
> > castable, but now I'm thinking of putting in expansion joints. When
casting, I
> > could insert some thin cardboard dividers running the entire length of
the
> > shell. The cardboard would just burn out during the curing.
> > Would that even be necessary with the needles?
>
> Dear Marc,
>
> I hesitated to mention this because, well, I seem to stick my foot in my
> mouth (or keyboard) every time I attempt to reply to someone on this list.
>
> My personal recommendation is that separation between the roof and walls
(to
> allow expansion) is a good thing, regardless of the size of the furnace.
The
> cardboard should work fine.
>
> I would suggest using the needles either way. Refractory blocks that are
> properly mixed, reinforced, cast, and fired will be tough enough to
survive
> even a medium blow with a sledge hammer. Even after a LARGE blow, the
blocks
> with the needles stay together even when cracked, which is the whole
point.
>
> I have built more than 100 industrial furnaces since 1985, including the
> ones I mentioned with the slab roofs, bunches of pottery kilns, etc. and
my
> recommendations come from that experience. I know what has worked (or not
> worked) for me, what works well for others may be different.
>
> Most of my furnace designs are based on the concept that refractory
linings
> should be allowed freedom to move when heating and cooling, and this comes
> from my experience repairing and maintaining the settings for large steam
> boilers, etc, where the expansion from cold to hot can be measured in
> inches.
>
> I now expect we will hear from ALL of the guys who made their (1) forge by
> casting a refractory liner in a five gallon bucket with no needles, or
> expansion joints, or anchors, and how they never even measured the water
> when they mixed the cement and how their forge has been working for 15
plus
> years with no cracks... and I'm sure that they are telling the truth.
>
> I am just attempting to share from my experience, I hope it is helpful.
>
> Let me know if you can't find the needles, I can get them for you.
>
> Tom Troszak
>
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