[TheForge] Problems with propane burner

Sat Sep 6 17:01:02 2003

Grant, I can forge weld very nicely in my current forge. It's also a
square shape, using stacked insulating firebricks, with an opening of 4"
X 6" X 12" deep. But I have a sliding back wall to make the insides
smaller. 

I've only got 1 burner, a 3/4" Reil-type. It's mounted on the forge to
the left of center, looking from the front, maybe 3" from the front, and
it's angled slightly so the flame shoots towards the back. This suits my
purposes nicely. I get a hot-spot that quickly heats up a small area, if
need be, and that's mostly how I use it. I'm not into blades, so I don't
heat a large area that often. And angling it towards the back keeps the
heat inside and reduces the dragon's breath. I've used a couple
commercial forges and their breath is really hard to deal with.

Some thoughts - What kind of walls do you have? I'm using insulating
firebrick, coated with ITC-100. Can you close any doors to keep the heat
in? Is there any way to limit the air intake? Maybe you're getting too
much air and excessive scaling. What pressure do you use and what size
orifice for the gas jet?

That's about all I can think of.

-Marc

On Sat, 2003-09-06 at 15:16, gblacksmith wrote:
> Frosty:  Good info on burner performance!  I use a Forgemaster Blacksmith
> unit with two atmospheric, vs. forced-draft burners.  Mine also has a 90
> degree downward bend on the burner tubes, with a 2.5 " dia.  intake end on a
> 1.5" main/flame end.  This unit works well for general work and
> heat-treating, but I have not been able to weld with it.  I am guessing that
> this problem is a combination of venturi construction, 2 burners, vs. 3 and
> the fact that it is rectangular in shape, vs. circular.  I have heard that
> efficient welding requires a "vortex" for even heating of  the interior. I
> have been sticking to coke or charcoal fires for welding, to date.
> 
> What are your thoughts on this issue.
> 
> I would welcome comments from all hands as well.
> 
> I plan on building a sword-length propane forge that will get hot enough to
> weld in.  I am interested in the thoughts of others on these issues.
> 
> 
> Grant
> ----- Original Message ----- 
> From: "Jerry Frost" <[email protected]>
> To: <[email protected]>
> Sent: Saturday, September 06, 2003 10:33 AM
> Subject: Re: [TheForge] Problems with propane burner
> 
> 
> > Morning Marc:
> >
> > There are a number of factors determining what your minimum operating psi.
> > will be for a naturally aspirated burner. You can't just look at the
> > pressure gage; you have to adjust your expectations to the entire device's
> > characteristics.
> >
> > Thanks to your reasonably complete description I can hazard a couple
> > opinions with some hope of accuracy. <grin>
> >
> > First, you have a 90* bend in the burner tube, this will cause back
> > pressure, requiring more psi to drive around.
> >
> > Second, you're running a "sidearm" configuration jet ejector with only a 1
> > 1/4" intake on a 1" tube. This is not a free breathing configuration and
> > requires higher psi to draw sufficient air.
> >
> > Thirdly you're using a 0.035" orifice which requires more psi to deliver
> > sufficient propane. How well aligned is your jet in relation to the burner
> > tube? This is really critical.
> >
> > You have several  options open:
> >
> > First accept higher operating psi as normal for your burner, you're
> getting
> > plenty of heat even though it doesn't idle like you want. Still, running a
> > "smaller" orifice delivers less gas at a given psi so you may have the
> > economy you're looking for already. In short it could already be singing
> the
> > tune you want, just in a higher key. <grin>
> >
> > Second look at changing the 90* to a longer sweep or even two 45*s . This
> > will increase the radius of the direction change and reduce the back
> > pressure a bit though probably not enough for a stable idle. You should
> also
> > place any bends as far as practical from the throat (narrowest point
> between
> > the intake and burner tube) of the burner. The longer the jet of propane
> can
> > travel down the exact (as possible) center of the tube, the more
> efficiently
> > it'll draw.
> >
> > Thirdly you could try a "T" configuration jet ejector, I have a pic of
> mine
> > on photoaccess under forges and hoods. Mine is a 1 1/2" x 1 1/2" x 1 1/2"
> > "T" reduced to 1" with a simple bushing. I had to drill through the back
> of
> > the "T" to install the gas supply. (#7 drill, tapped 1/8" pipe) It has two
> 1
> > 1/2" intake ports and runs with a 0.045" orifice (Miller mig tip). Mine
> > burns stably at any psi my gage registers, 30psi. to below 1 psi. but the
> > low end is inadequate to keep my forge in range so I just run it around 5
> > psi. My old forge only has 1" of Kaowool insulation around 3/4" rammable
> > refractory so if I idle it very low it cools down and I burn more fuel
> > reheating it than just keeping a steady burn. I do bump the psi up to 7-8
> > psi. to weld but for general forging 5 psi. is just right.
> >
> > Fourth, filing the port in your forge liner to form a taper might be well
> > worthwhile. On my next forge I plan on building my burner nozzles into the
> > refractory liner myself, mostly to save on tube burnout but also to
> improve
> > performance.
> >
> > Lastly, how completely are you closing your forge up? If you're not
> allowing
> > enough opening for exhaust gasses to escape you're really building back
> > pressure and inhibiting your burner performance.
> >
> > Frosty
> > ------------------------
> > If it ain't forged
> > it ain't real.
> > Wrought iron is.
> > The FrostWorks
> >
> > Meadow Lakes, AK.
> >
> >
> > ----- Original Message -----
> > From: "Marc Godbout" <[email protected]>
> > To: "TheForge" <[email protected]>
> > Sent: Saturday, September 06, 2003 7:13 AM
> > Subject: [TheForge] Problems with propane burner
> >
> >
> > > First of all, my castable project went really well. The forge has been
> > > through its first firing with only a few small stress cracks. Now time
> > > will tell.
> > >
> > > But my new burner has some problems and I'm hoping to get some ideas
> > > from you guys. I'm trying some slightly different design to better match
> > > my application. First, the mixing tube is a 90 degree sweep of 1" rigid
> > > conduit. I wanted to lower the profile.
> > >
> > > The other difference is that I cast the nozzle into the refractory wall,
> > > but I didn't flare it. Also, this is a side-arm, using a 1 1/4" cross
> > > fitting with a reducer to the 1" tube. I've got a .035 mig tip for the
> > > orifice.
> > >
> > > The problem is that I have a tough time keeping it running at low
> > > pressures. I don't have a gauge on it, but from the sound it's probably
> > > well over 5 psi, maybe even 10, before it starts sputtering (with a
> > > nifty "whoop" sound), and then the flame travels all the way to the mig
> > > tip. I was able to get much lower when I had it out of the forge, using
> > > just a straight pipe for the nozzle.
> > >
> > > High end is no problem. Things get bright yellow hot in there in no time
> > > at all. And that's with just one burner in an 18" long half-tube,
> > > half-stacked-brick, with 25 psi (the max that my delivery system will
> > > do).
> > >
> > > I'd like to get really low for idling between heats to save propane, so
> > > any thoughts would be welcome. Should I try flaring the nozzle? This
> > > castable is easy enough to carve with a round rasp.
> > >
> > > Thanks.
> > >
> > > -Marc
> > >
> > > --
> > > Marc Godbout
> > > http://www.ironringforge.com
> > >
> > > New England Blacksmiths Membership Director
> > > http://www.newenglandblacksmiths.org
> > >
> > >
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> > >
> > >
> >
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> >
> >
> 
> 
> _______________________________________________
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> theforge mail list group photo site is
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> Login:  [email protected]
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> 
-- 
Marc Godbout
http://www.ironringforge.com

New England Blacksmiths Membership Director
http://www.newenglandblacksmiths.org