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Conner Michaux

Little propane forge build

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My ‘mount’ is simply a close fitting hole through the body of the tank with a slightly wider hole in the blanket. This inner hole is then coated with the refractory which brings it to the same size as the outer hole. The burner just rests in the hole.

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Very helpful indeed! Thanks.

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I drilled out the hole in the forge for the burner. I should be getting this thing running tonight. Thanks for the help everyone :)

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Oh I forgot to ask, the regulator I have is a 1-30 psi I think, what amount of gas do I want to be using? Less gas equals for more oxidation right?

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I'd recommend starting at about 5 psi, then play with it.  Every forge is going to be a little (or a lot) different.  Watch the flame color at the burner and quantity of dragon's breath.  Experimentation time!  

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Thanks, after dinner I’ll go light it up for the first time and play with it a bit.

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Posted (edited)

So I had it running for about 15 minutes, it works very well and it heats steel very quickly. But it started making a little fluttering sound and little bursts of fire would come out of the forge, and it looked like the fire was fluttering inside the burner. Is that normal?

other than that, this forge is going to be a game changer! 

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Edited by Conner Michaux

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Somethings up. What's your tank size, last time you filled it, ambient temp there, psi? 

 

And, congrats!

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Also, the wind (even if only a bit of a breeze) can do that. Congrats.

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Posted (edited)

I had it refilled yesterday evening, and I was running about 5ish psi 

Weather was low 50s. But there was a breeze, and it would make an odd sound when ever there was even a tiny little bit. That’s what I’m guessing is the issue.

Edited by Conner Michaux
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Yup that would be the problem. The wind is disrupting the venturi effect. This happens to me when I have the garage door open. you can make a wind block but as long as your outside a breeze will do that. You will find  a sweet spot where it will run good. Glad to see you have it running!!!

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Alright thanks, is it in any way dangerous when the wind does that? 

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Only if the flame stays in the burner long enough to burn the paint off, but even then it's not a big danger.  More of an annoyance.  

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If you get the same with no wind, one thing you might try is increasing the gas pressure. Burnback is usually because the flamefront travels through the mixture faster than the mixture is moving through the burner tube in the opposite direction. Flame speed depends on several things: air:fuel ratio, pressure, temperature. Pressure in the burner tube is about atmospheric and you don't want to be messing with the air:fuel ratio if it's right. Initially, things are cold and the flame speed is slow. As the forge heats up, the flame speed increases. If the flame speed gets fast enough, it will travel back until it runs out of mixture and will go out. Fresh mixture will flow and will ignite when it reaches the hot forge. When the flame travels back along the tube, it heats the tube a little. Often there will be a burnback, followed a few seconds later by another, followed by more at reducing intervals as the tube heats, until the burn is just a rapid succession of burnback cycles (or sometimes the flame stabilizes within the burner tube). Increasing the gas pressure at the first sign of burnback might get the mixture speed up enough to prevent the problem. I would aim to double the pressure if tying this. Gas flow through a jet varies as the Square Root of the pressure difference across it, so doubling the pressure will give about a 41% increase in gas flow and therefore mixture flow.  

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Posted (edited)

Alright thanks, I lit the forge again tonight but within about 20 minutes turned it off again. I guess I’m just paranoid but watching blue flames pop out the air holes in the burner is giving me one heck of a scare. There was no breeze at all tonight, and when the sputtering flames happened again I increased the pressure a little but and it started happening more. Just to make sure (because I’m paranoid) this is in no way dangerous right? As in the fire won’t push back into the hose and blow up the propane tank. :wacko: Sorry to bother, I’m just a little bit less than comfortable around burning gas.

Edited by Conner Michaux

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Ok. Try this: 

Unscrew the burner until you have access to that copper piece (nozzle). Unscrew the nozzle, and clean out the hole with probably .030 welding wire, or whatever else you can fit in there, and while you have the nozzle off, open up the propane line to blow it out. Screw it all back together and tighten it good, check for leaks with soapy water. 

 

Sometimes some of that teflon tape, or that loctite paste junk they use can gum it up from the  get go. 

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When you “increased the pressure a little bit”, what was the proportion?  It will need a big change in pressure to make a significant change in flow/mixture speed.

 

If you poke out the gas jet, be very careful. The diameter, shape and surface finish of the jet are all important. If you change anything by poking it through with something inappropriate, you will alter the air:fuel ratio of the burner. I usually end up using Copper wire to poke out gas jets because it is soft enough not to scratch the bore but stiff enough to work. 

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I didn’t increase it a lot, maybe 5 Psi to 7 or 8. but I’ll try again today and if the sputtering starts again I’ll double the pressure and see what happens, I’ll also unscrew the burner and make sure nothing is clogging it up.

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Just an observation. When running my venturi burner I have the pressure quite high....like 20 psi or so. I have a feeling if you increase the pressure it will have a better venturi effect and will run better. At 5 psi it's not enough pressure to push the propane and air into the forge and its igniting in the burner tube which is why I recommended the 30 psi regulator. Try cranking up the pressure to around 15-20 psi. 

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Posted (edited)

Experimented with higher psi, 15-20 psi seems to do the trick, I was able to knock in the edge on a kiridashi I’m forging before the wind started picking up and the rain started. Thanks for all the help folks, I’ll be back when I have more questions. :D;)

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Edited by Conner Michaux
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Posted (edited)

I run 2 of those burners on my forge.  I find that if I run much below 10 PSI I will get the fluttering, so I would expect your burner to run reasonably well down near 5 PSI.

 

If it runs well for 15 or 20 minutes every time, and then starts acting up, you may be freezing up your propane.  This is easy to do with a 20lb tank. (Gas grill size)  To test for this, the next time it flutters, go over and shake your propane tank back and fort a bit.  If it stops fluttering for a bit you are freezing up your propane.

 

I use a 40lb tank on my forge but when it gets down to about 1/3 full I will freeze it up any time I am at welding temps.

Edited by Brian Dougherty

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