Subject: Insulation for boiler firebox

From: [email-masked] (Bart Smaalders)
Date: 3 May 1996 17:49:58 GMT

As part of my new boiler for the Otter (our 19' steam launch), I need
to build a circular firebox.  The burner uses oil and the air/oil mist
is introduced tangentially into the 14" diameter firebox.  There's a
hole approx 11" in the top of the firebox; the resulting lip serves to
keep the flame front in the firebox under all but the most outrageous
firing rates :-).  The heat from a 3 gallon/hour fire is pretty amazing.

I made a prototype of the firebox using heavy firebrick which apparently
worked well, but I'm looking for something a lot less heavy.  FiberFrax
or Kaowool have been suggested, but these flexible blankets seem rather
subject to mechanical damage from the rather vigorous circular flame
front, loading paper/kindling for starting the fire,  and the occasional
introduction of a steam lance for tube cleaning.

Can anyone recommend a relatively thin stiff refractory board from
which I could construct such a firebox?  I'll use FiberFrax to provide
insulation around the material, so it doesn't need to be a good insulator.
In other words, the board would serve as a facing layer to protect the
FiberFrax from injury.  What is the modern equivelent of asbestos 
millboard?

Any advice to suitable material is appreciated, as are experiences indicating
I don't need to do this :-).  

Thanks -

- Bart

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Bart Smaalders			Solaris Clustering	SunSoft
[email-masked]		(415) 786-5335		MS UMPK17-301
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From: [email-masked] (J. Kimberlin)
Date: 3 May 1996 16:02:36 -0700

In article <[email-masked]>,
Bart Smaalders <[email-masked]> wrote:

snip

>worked well, but I'm looking for something a lot less heavy.

>Can anyone recommend a relatively thin stiff refractory board from >which
I could construct such a firebox?  I'll use FiberFrax to provide
>insulation around the material, so it doesn't need to be a good
insulator. >In other words, the board would serve as a facing layer to
protect the >FiberFrax from injury.  What is the modern equivelent of
asbestos >millboard?

 >- Bart > 

How about castable refractory?  This stuff comes in various heat 
resistances and some is quite finely divided.  There are some pastes that 
come in 25 lb cans that are loosely called furnace cement also.  The 
blanket stuff is good on the outside, but inside the firebox the castable 
is about the best way to go.  We use it in refinery furnaces alongside 
firebrick and it seems to hold up OK.

JerryK

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From: tonylos <[email-masked]>
Date: 4 May 1996 01:54:54 GMT

>Any advice to suitable material is appreciated, as are experiences 

Why don't you go to an oil burner/boiler/plumbing supply house
and get some refractory material. A popular brand is "TARGETWALL".
It is also possible you can get a pre-cast chamber that might fit.
They make generic chambers and are cheap.
Good luck.

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From: [email-masked] (Norbert Senf)
Date: Sat, 04 May 1996 11:26:09 GMT

>FiberFrax from injury.  What is the modern equivelent of asbestos 
A.P. Green Refractories has a number of products:
Insblok 19  - a fairly rigid mineral fiber millboard 
Zirconium Rigidizer - a liquid that you paint onto ceramic fiber to
rigidize the surface - this is how glass melting furnaces are done.
Insulating firebrick - various grades. Basically they are foamed clay
- very light, rigid abrasion resistant surface.
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