[TheForge] Gas Forge "Chuffs"

[Steve Bloom]

At 11:42 PM 1/28/2003 -0500, Scott wrote:
>         I participated in a gas forge construction workshop this weekend, 
> in which we build 14 new double burner atmospheric gas forges.  They are 
> made out of 10" thin wall pipe, with two non-blown burners coming in 
> horizontally near the top of the forge.
>         Got mine home and fired it up.  Runs great at 20lbs gas, but when 
> I reduce the psi down to 5 or 7psi the combustion "chuffs" (surges) and 
> does not burn completely.  There is a massive amount of blue flame coming 
> out the front, no matter how far I open or close the air gates 
> (adjustable disks on the end of the burner pipes).
>         I have seen a number of these exact forges run well, so I don't 
> think it's the design.  However, with any mass construction effort there 
> is bound to be minor differences.  For instance, most of the forges built 
> had the burner pipes running slightly "down hill" into the forge, where 
> mine run slightly "up hill".
>         Any suggestions on the combustion problem?

The typical atmospheric burner has a gas delivery tube running at right 
angles to the 'bell' of the burner. The tube has an orifice.  The orifice 
must be correctly aimed down the burner and centered. This is usually done 
by locating the orifice (which in my burners is a tiny hole) and marking 
the delivery tube on the opposite side.  You then eyeball the mark to be 
over the center of the burner (the reason for the mark is you do not want 
the gas jet to come out 180 degrees from where you expect it!). Do this for 
both burners. Light the forge.  Slowly rotate the tube and draw it back and 
forth across the bell - listen for the maximum roar. When you've got it 
sounding off at the max level, lock the tube down.  Repeat on the second 
burner.  If you can, cut gas flow to the burner which is not being adjusted 
to minimize confusion.  My usual burner is a 2"..1.75" black pipe ~ 4" long 
swaged down to 1" (=the bell) welded to a length of 1: OD black pipe (~8" 
long w or w/o a 45 degree bend a couple of inches below the bell). The gas 
delivery tube is a 6" long 1/4" pipe nipple (~1/2" OD) with a #60 hole  3" 
from an end. There is a 9/16" hole drilled through the bell about 1" from 
the open end (thru which the gas delivery tube is inserted). Around one of 
the holes is a 1/2" hex nut - drilled out to 9/16" and taped for a 1/4x20 
cap screw = the lock screw. The nut is welded to the bell.  A unit like 
this idles on 1..2 psi of LP pressure (at sealevel).

Steve
Steve Bloom, IronFlower Forge. Archer, FL
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