Subject: Fuel-air ratio gas fired brass melt furnace

From: David Anderson <[email-masked]>
Date: Mon, 23 Jan 95 10:42:41 -0500

Can anyone help me optimize fuel-air ratio for small natural gas fired
brass melting furnace?  Furnace about 8 inch dia x 12 inches deep blower
is old Electrolux domestic vacuum cost one buck at flea market.  I seek
slightly reducing furnace atmosphere to minimize oxidation of melt.
WW Grainger and others offer O-2 and CO analyzeers but I hope for lost
cost solution.  One advisor says to maximize noise leve.  Furnace works
grteat but maybe I need to control atmosphere to upgrade casting qualtiy.
Thanks for any comments.   Dave

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From: [email-masked] (BrnzCaster)
Date: 23 Jan 1995 11:48:16 -0500

Dave
For a furnance your size, about a 2 inch visible flame feather out of the
exhaust port will be about right. Let the furnace temperature come to a
stable state (about 10 minutes after initial fire-up) before attempting
final adjustment.
For small melts of yellow brass, don't expect too much in the way of high
quality.
Winston

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From: [email-masked] (J. Kimberlin)
Date: 23 Jan 1995 17:40:16 -0800

>Thanks for any comments.   Dave

Oxidizing flames are all blue, reducing flames have various amount of 
yellow.  It seems to me that you might want to adjust the gas useing a 
valve so that the flame has the proper amount of yellow.  On the other 
hand, natural gas is methane, which is hard to oxidize in the first place 
so your flame may contain yellow from the get-go.  I don't think I'd 
worry about the furnace atmosphere.  Maybe there is something you could 
float on the melt to protect it if the yellow flame doesn't work.

JerryK

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From: [email-masked] (David Hoopes)
Date: Thu, 26 Jan 1995 16:17:31 GMT

>Thanks for any comments.   Dave

If the blue part of the flame extends outside the furnace, that is a
pretty good indication that all of the O2 is being consumed.  Adjust the
gas/air mixture until you have just a small wisp of blue flame outside the
furnace.  

At least this is what I do for my propane forge.  Adjusted this way I get
very little scale.

-- 
David Hoopes                              Exabyte Corp.
[email-masked]                       11100 W 82nd St.          
Voice: (913) 492-6002 x3323               Lenexa, Ks  66214

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From: [email-masked] (Barry Workman)
Date: Fri, 27 Jan 1995 04:06:06 GMT

>Thanks for any comments.   Dave

Dave Gingery recommends regulation for reducing atmosphere by blocking
the vent in the furnace.  Watch the flame as an indicator.  You can
get a fair idea and with a little playing around find a good working
arrangement.  I use a firebrick on the top blocking about 1/3 of the
exhaust opening.
-- 
    - Barry Workman