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Forge Burner Question (Devil Forge)


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So, I opted to go the lazy route and buy a relatively inexpensive Devil Forge. It came with a prebuilt burner.
I modified the burner to change the hose barb size and to extend the rubber hose about 5 inches farther from the ball valve.

The burner works and seems to heat up this tiny forge VERY quickly.  The interior of the forge is about 5" diameter and 10" long and I have closed up the back with two insulating fire bricks. Ceramic wool has been coated with satanite and ITC100.

My question is, should the tip of the burner get hot enough to start glowing a dull red?

I have the regulator set at around 9psi. I would have tried a bit more, but I ran out of propane after about 10 minutes of fiddling with it.  I guess I should have gotten a new tank before starting.


Any insights would be very much appreciated.




Here are a few pictures that might help.

- Here you can see the dull glow of the burner tip.  The tip is almost even with the metal body of the forge.  It had been running for 8-10 minutes.



-The next pictures show the design of the burner, gas feed point and choke


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As far as the tip of the burner glowing red.... not a problem.  When the forge gets really hot it will be the at nearly the same temperature as the forge. Yellow/white.

while you have it handy you may want to get a couple of replacements for the tip.  Those things have a bad habit of melting or other wise deteriorating.

Don't obsess about the fuel pressure.  Running the pressure up and down and adjusting the air inlet are methods of regulating the temperature, atmosphere, and fuel consumption.    

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Thanks for the info.   I thought I remembered reading something about a glowing hot flare was an indicator of the flame burning inside the tube of the burner.  It does make sense that it will be near the same temperature as the inside of the forge, But I just wanted to make sure.  I have read so many threads on so many forums that I probably have a case of information overload.

I'm an electrical guy, highly flammable/explosive gasses are not my cup of tea and I would hate to do something and end up making the headlines on the evening news. 

As far as the pressure goes, I was just providing it as an information point.  I'm taking Frosty's advise from another thread and using the pressure as way to replicate conditions from one firing to another.


thanks again for the info and assistance.

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Here is a bit of additional info.

I removed the burner from the forge and fired it up for a few minutes to try and tune it a bit. While doing this I took a few pics and a short video

Video link https://goo.gl/photos/zCEZ242eSHNx7RYM9

Here is what it looked like after about 5 minutes.


It looks like the flame starts about 3/4" inside the tip of the flare.



Edited by RogueGeek
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Looks like I would expect. The flame is burning back to the section in which there is an increase in size.  Out of forge doesn't really matter.  Put it back in the forge with the flare not so deep in the forge as before and increase pressure of propane and more air.  Your forge looks ok. 

Your burner  is ok.  but more air could be added  when in the forge. 

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It sounds like you were originally running a fairly low pressure because of your near-empty cylinder and I'm guessing you had a relatively lean mixture (not much dragons breath) with the choke fairly wide open. This combination may actually get the burner tip hotter than most other settings: a hot flame with a fairly low mixture speed.


There are a number of different things going on at the same time and you'll get a feel for what they are and how they interact as you use the forge.

Basically, you have two variables that are under your control: the gas pressure and the choke adjustment.

Adjusting the pressure adjust the amount of flame you have. Adjusting the choke varies the air:fuel ratio and with it the flame temperature. Increasing air makes the mixture leaner (more Oxidizing), reducing air makes the mixture richer (more reducing). 

The highest flame temperature occurs when the mixture composition is such that all of the Oxygen in the air reacts with all of the fuel gas, leaving neither unburnt Oxygen nor unburnt gas. This is known as the stoichiometric ratio by combustion engineers and (supposedly) as a neutral flame by smiths. 

As far as I can tell, "we" tend not to want reducing atmospheres because they cause very rapid scaling. Scaling (oxidation) still occurs at the stiochiometric mixture and even some way rich of it, which I suspect makes a smiths idea of a neutral flame different to a combustion engineers idea of a stoichiometric flame. 

When I put together a forge burner, I aim to size the gas jet so that I get a mixture that is around stoichiometric with the choke fully open. This means that I can adjust the flame temperature by choking down the airflow.

Generally speaking, for a given choke setting, there is not a lot of change in the air:fuel ratio when the gas pressure changes in a Venturi burner: as the gas pressure increases, the gas speed through the jet increases, so the suction generated at the Venturi throat increases and the airflow therefore increases, keeping the air:fuel ratio constant.

In the burner tube, the fuel/air mixture needs to be travelling towards the forge faster than the flame-front moves through the mixture in the opposite direction.

The mixture speed depends on the gas pressure and the choke setting.

The flamefront speed is not a constant: it depends on the air:fuel ratio and the temperature. Flame speed is higher in hotter mixtures. It is also higher in mixtures closer to the stoichiometric ratio.

If the flamefront speed exceeds the mixture speed, at first the flame travels back down the burner tube until it runs out of mixture to burn. With nothing to burn, it goes out. The gas keeps flowing and it draws air in, so fresh mixture reaches the chamber after a short delay, ignites in the hot chamber and the flamefront again travels back down the burner tube. This cycle repeats, with each occurence heating up the burner tube slightly and increasing the flamefront speed of subsequent events, until the flamefront establishes at the point of mixing in the Venturi throat. The noise made during this is distinctive and you can usually just turn up the gas pressure and stop it if you catch it in time. If you leave it until there is an established flame in the throat, the burner tube gets properly hot and it's often not possible to just turn up the pressure and get the flame back where it should be.

Using a straight burner tube, the mixture speed is higher than the flamefront speed all the way to the end of the tube and all of the flame is in the forge chamber. Burners like this tend not to run outside a forge, which doesn't help the marketing guys. A flare or flame retention cup often gets added to allow the burner to run in the open.

The mixture speed is slower in the flare or cup, due to the increased cross-sectional area, and a stable flame can be established. The bit of the flare or cup downstream of the flamefront will get hot and should be considered a consumable part. In a running forge, it is not actually necessary, though it does make it a bit easier to get it started.

The flares/cups are usually made from stainless steel and tend to have a fairly good lifespan. By the time a novice smith has burnt the cup away, he/she will probably have sufficient skill/experience not to need it anyway.

Have a bit of a play with your burner out of the forge. Try setting the pressure at a value and then just open/close the choke to adjust the mixture. It looks like a pretty good choke design with that screwed adjustment and should be nice and progressive. Once you have a feel for the controls, put it in the forge and have another play.

How much time you need to spend tweaking will depend on the work you do. For many, it will be a case of finding the sweet-spot for the work they do, then leaving it alone. For others, particularly bladesmiths who Heat-Treat in their forge, it might be a case of marking graduations on the choke and fitting a pressure gauge so that its easy to return to any one of several settings.



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Good Morning,

There are lots of valid points above. Is it possible to move the burner, not quite so far into the fire-box chamber. Play with all adjustments when the forge is hot, it is not the same when warming up. Adjusting the burner when it is out of the forge does not work efficiently. By the time you have a problem with the forge tip, you will know everything about your forge. You will also know how to make your own with a little flare.


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  • 2 weeks later...


Maybe I can jump on this thread as well.  I just ordered a Devil Forge as well (2-burner) and Brian says "Ceramic wool has been coated with satanite and ITC100."  This was by Brian or by the Devil Forge people?     



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The Forge comes without any coating on the wool.  You will have to add them yourself.  It was really easy and only takes a few minutes to apply.
For each coat/application, I let my satanite/ITC100 dry overnight then slowly brought it up to an nice yellow/orange heat to fully harden.  I did this by doing several short (45 second) firings until I was sure all of the water was out of the satanite/ITC then I fired it for about 10 minutes.

I did two or three fairly heavy coatings of satanite, and one medium-light coating of ITC-100.


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  • 3 weeks later...

This is the first time I've seen one of these burners, but I can tell you a few good things about it. In the first place, seeing the red/orange hot flame nozzle out in open air  tells me that the fuel/air mixture is exposed to a generous ignition source (very good). Your combustion is mostly in the primary flame envelope; AKA combustion wave front (also very good). The orange streaks in the secondary flame are from a reaction between super-heated gases and that particular stainless steel alloy, which is undoubtedly #304, instead of the longer lasting #316 S.S. alloy; you needn't worry about them, but you will have to replace your flame nozzles much sooner than you would with #316.

Now we come to the color of your primary flame, which has a slight tinge of green in it, instead of being pure light blue. There was a time when I would have said VERY NOT GOOD, but so long as you use your forge outdoors, or are careful to provide your forge area with a powered exhaust system for it is  merely problematic; in other words both good and not so good. The good part is that it will provide a perfect heat source for welding, as the slightly reducing flame will protect your work from oxidation, while in the forge. The not so good part is that, if you ignore Frosty's recommendations about providing a powered exhaust system and CO alarm in your shop, you could end up with carbon monoxide poisoning, which is an outright bad thing.


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  • 5 years later...
On 10/17/2015 at 3:17 PM, RogueGeek said:

I modified the burner to change the hose barb size and to extend the rubber hose about 5 inches farther from the ball valve

Hi Brian, 

I recently had to replace my devil forge regulator and hose (separate issues/incidents). While im at it, I want to go ahead and make some mods. I have long wanted a ball valve, and to have the hose further away from the heat (MAJOR design flaw imho). 

It looks like you've done exactly what I'm trying to do, and I wo dear if you could point me in the right direction. What size fittings you used, and how you affixed them (welds brazing?). I'm not even sure what to search on YT. 

Any help or a push in the right direction  would be much appreciated .




P.s. I have been running a two burner devil forge for a year now, I tend to use the one burner option, and the tip of the burner has flared out, more than the other one, but that is all that has happened. Moving it farther back definitely helped

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This thread has been inactive for five years but I'm sure someone will be along to help you. I have a needle valve at the burner and a ball valve between the regulator and tank. I just used gas rated Teflon tape for the screw together fittings. I don't recall the exact sizes but they were standard propane tank fittings. 

To keep the hose farther away from the forge I used some 1/4in stock to hold the hose away. 


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