[TheForge] Problems with propane burner

Sat Sep 6 16:21:01 2003

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
> >
> >
> > _______________________________________________
> > http://mailman.qth.net/mailman/listinfo/theforge
> > theforge mail list group photo site is
> > http://www.photoaccess.com
> > Login:  [email protected]
> > password:  anvil
> > ___________
> >
> >
> >
>
> _______________________________________________
> http://mailman.qth.net/mailman/listinfo/theforge
> theforge mail list group photo site is
> http://www.photoaccess.com
> Login:  [email protected]
> password:  anvil
> ___________
>
>