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Burner huffing

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I have tried two different burners in my forge with the same end result. The first burner was one I built following a friends design, pipe with #70 hole in it mounted across the mouth of a 1.5" to 3/4" reducer. I aligned the jet by hooking it up to a hose and used a 1" to 3/4" reduccer on the forge end for a flare after machining the threads out. It seemed to work fine on about 7 psi initally, got things good and hot but after a half hour started huffing with the flame burning back down the burner tube. I tried cranking the pressure up, and that would work for a little while and then the same results. I decided to step up and get a T-rex burner after reading good things about it, set things up per the instructions and it gets good and hot for a while, then starts huffing and sputtering as well. I am running the large 100# tank so am reasonably sure its not freezing up, have a Victor regulator so think my fuel delivery system is pretty squared away. I'm not exactly sure how much pressure these venturi type burners should run on, I havent cranked them much about 15 psi to try and stop the sputter, wasnt sure what the upper limit was.





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Good Morning,


Connect two bottles in parallel and try it. I think you have a bottle freezing up. Propane gas is from the surface of liquid propane, if you double the surface area, you cut in two the draw from each bottle. If you were using a smaller bottle, I would suggest to put the 20 or 30 lbs. bottle in a container of water. The water acts as a heat sink and doesn't allow it to freeze as fast.


If you buy and read the propane forge/ gas handbook, you will understand.


If you lie the 100lbs. bottle on it's side, you will get liquid propane and burn your house/shop down!!!  Propane tanks for a residence are on their side, this provides the greatest surface area to draw from. They are made to work when on their side, the gas port is above the 80% mark.


Ciao fur now,


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I have this problem with my atmospheric or self aspirating burners. After the forge gets up to heat it can start, as you say, "huffing".


I have a much bigger problem with this in smaller forges. I can usually regulate by adjusting my oxygen supply and/or cracking or opening up 

one end of the forge. I have open ended forges for running long stock through for texturing. Letting a smaller fire box "breathe" a little usually does the trick. 



Also, I happened on a forge a couple of years ago that was a good fit for a medium size that I could definitely use. It had an atmospheric burner

that other than having a "bell" at the intake instead of a cone, was basically identical to my other burners. I couldn't hardly make it work. As you described earlier, it ran well until it got up to heat and then started huffing. I figured out real quick why the guy wanted to get rid of his forge. I grabbed

one of my burners off of one of my other forges with the cone end and while it didn't run great (no huffing through the whole range of the oxygen supply) it worked well enough to melt steel. The firebox for this forge is just a tad too small for the larger burner sizes used and runs very well with my smallest forge burner though it's none too fast heating up. 


I would guess you suffer from one or all of these problems.


1) Too small of a fire box relative to burner size

2) Crappy burner


Try swaging a piece of round or square thin wall tubing into a cone shape on your anvil horn for your burner. They can also be formed in a hydraulic press. If you have to weld the cone onto a tube then make sure your inside seam is as smooth as possible to allow for the intake air to come in straight and uninterrupted as possible. 

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I would say crappy burner in one case, since I built the first one. The second is one of Rex Price's T-Rex burners with the correct flare as he supplies them. These are reckend by some folks to be the cadillac of aspirated burners so I purchased it to use as a baseline of what I could expect. It is set up using his recommendations as far as tip and flare placement in the burner. I need to calulated the volume of my forge still, I have read on here that around 350 cu in is max for a 3/4 inch burner.

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Two things come to mind: The #1 cause for huffing is typically exhaust gasses getting in the combustion air flow. OR breezes across the intake.


Your home made burner will work a lot better if you use a thread protector rather than a bell reducer for a flare. Bell reducers enlarge the cross section far too abruptly to work well, they induce bad turbulence which inhibits induction. The 1:12 taper is the MAX diameter change without inducing turbulence. Don't scrap your old burner, it only needs a little tweeking.


If a Rex is huffing it's probably exhaust in the intake air, I often have to put up a shield when using mine outdoors to break breezes and block the exhaust gasses.


Frosty The Lucky.

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I have not had that problem with a 2" to 3/4" reducer. I have seen forges not work as well with the 1 1/2" to 3/4". They are harder to find so some guys just try the 1 1/2". Whom ever wrote the pamphlet I have did not sign it for liability reasons. I found if you build the burners exactly to his design, they work fine. Typically forging at 10 to 15 pounds, welding at 20.

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