[TheForge] On the table monday.

[Kathy]

Frosty,
I had not even considered an air curtain. I am planning on combining an internal
shoulder (ring of refractory to compress the flame path's spiral) with a two
(upper and lower) part external baffle. The lower half is affixed to the forge
and uses a half ring to prevent exhaust from escaping any way but upward, .while
still allowing the baffle to be placed at a 1 1/2" distance beyond the forge
opening. The upper half is movable and has a small opening at its base for stock
to be slid through it; to insert or remove scroll ends, the upper baffle slides
up and down.  Escaping IR is bounced back into the forge, and exhaust gases are
forced upward and away from the operator. The back end of the forge has a small
hinged door, allowing stock to protrude from both of the forge's ends, but
remaining closed most of the time. Running the forge with a single opening most
of the time allows the burner or burners to be aimed at a backwards facing
tangent, increasing hang time for the spiraling gases.
Mikey

-----Original Message-----
From: theforge-bounces at mailman.qth.net [mailto:theforge-bounces at mailman.qth.net]
On Behalf Of Jerry Frost
Sent: Thursday, April 26, 2007 1:55 PM
To: Sponsored by ABANA
Subject: Re: [TheForge] On the table monday.


-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.

http://www.artmetalradio.com/

From: "Kathy" <keporter at comcast.net>


> Jerry,
> Theoretically "X BTUs in X volume (out)" is correct. 
> However, the applications
> between gun burners and some tube burners differ 
> drastically. Not to nag, but
> complete primary flame combustion allows sealing of 
> the burner portal, thus zero
> secondary air contributes to dragon's breath at 
> exhaust exit; instead, a good
> deal more heat is expended within the firing chamber 
> and less into the
> operator's face...
>

You don't close the open space around your burner 
tubes? Unless It's going to be a real short burn I 
always wrap a little Kaowool around the nozzle to close 
off the port. Properly tuned and secondary air will 
lower flame temperature regardless of air:fuel burner 
type.

How well the burner works is more dependant of having 
sufficient exhaust portage to prevent backpressure. 
Guns are less sensitive but still susceptible.


> However, you will quickly deduce that I'm nit picking 
> :-) Your point is well
> taken; if the gun burner is fine tuned and the forge 
> is designed properly for
> it, dragon's breath should not be a problem. That is 
> a BIG if though. It is
> likely that most of the designs simply suffer from a 
> "let's just throw this
> thing together fast and get to work" mentality. I 
> think the glass blowers have
> worked their way around dragon's breath pretty well 
> in many of their glory hole
> designs.
>

This depends entirely on what you're using your furnace 
for. In a forge you want a reducing atmosphere and will 
get dragon's breath. You will get exhaust regardless 
but a properly mixed neutral air:fuel fire will have 
little or no exterior flame.


> You wrote:
> "If you're serious about reducing or eliminating
> dragon's breath, switch over to an oxy propane torch
> for high BTUs at low volume.
>
> <grin>"
>
> Actually, that is a very good direction to go, but I 
> would use Chem-O-Lene to
> soup up the propane, and ten percent oxygen 
> enrichment in order to get the
> Chem-O-Lene to burn properly. I would choose this 
> method because I is cheap and
> always has been :-) If I lived in a state (or foreign 
> country) where butane is
> available at low prices, than butane and oxygen 
> enrichment would be my first
> choice (as gun burners can handle butane's ugly side 
> nicely, where tube burners
> cannot).
> Mikey
>
>

If I were to go the oxy:fuel route for a regular 
furnace, I'd buy an oxy generator and burn whatever I 
liked for fuel. They're a bit spendy up front but you 
never have to refill a bottle for the shop again; 
portable torches still require a bottle unless you want 
to haul a trailer of course.

It's only minorly nit picky though and it's good to get 
it out of the way early.

The easiest way to eliminate the unpleasant 
characteristics of dragon's breath is with an air 
curtain at the forge mouth. Simply duct a portion of 
the blower's output to a door wide slit below the forge 
door aimed up. The air from the curtain port will 
simply blow the dragon's breath away from you. An air 
curtain will not only keep the flames off you, it'll 
keep your tongs, etc. cooler. You have to use care 
aiming the curtain port so it doesn't blow into the 
forge door but that's a minor adjustment.

The next little trick is to have the air curtain aimed 
at an exhaust hood above the forge door so all the CO 
and other combustion byproducts are removed directly 
from your shop. If a person wishes it's then pretty 
easy to make a heat exchanger in the "hood" to preheat 
the intake air and fuel.

Believe me, gun burners have their advantages well 
worth considering.

Frosty 

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