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I am going to go see about building a forced air burner, Using the design off of this burner I have here.
I would like to know if anyone has done one like this before and the problems they ran into?

jfxcar.jpg

If i build it exactly as shown will is work well and safely? Also for the flared end i was going to take the 1 1/4 and forge it into the flared fitting described here with a 1 1/2 opening.

Thanks and merry smithing,
Matthew

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Introduce the propane before the bend, where it's shown won't allow enough time in the airstream to mix well. Propane and air don't mix well without turbulence and time and if it isn't mixed well you'll end up with a flame that not only produces excessive dragon's breath but is oxidizing in the forge. Having the propane go around the bend does two things, it enhances mixing and explosions do not like going around a bend, especially into the wind. Better and safer is a good thing.

My personal preference is to introduce the propane into the blower impeller but that needs some careful eyeballing, thought and preparation or BAD things can happen.

Asking advice is a good idea, some of us have messed with these things for decades and others you see online are trying to figure it out without any experience. When playing with fire or flammable gas be careful.

Frosty the Lucky.

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Since my blower is very powerful (recycled from an inflatable slide) i wanted to make it so i could regulate the airflow like shown there with a ball valve and then introduce the propane a little after the valve. However, would it simply be easier to do a Venturi burner instead? I do not want somethign overly complicated.

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As for the taper, a 1:12 taper seems to be the optimum ratio for burner flares. Also, a graduated pipe flame holder woks pretty good in a forced air system. The business end doesn't seem to be as picky about shape on forced air opposed to venturi (naturally aspirated) burners

Here is an example of a forge design using the graduated pipe flame holder.

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I used a variation of it using 1.25" pipe instead of 2" and a Tee and drilled pipe plug instead of the elbow in a 6" x 15" forge chamber and it get so hot I can melt steel at less that 5 psi (on my regulator) where a 1" Tee style ala Frosty ;) NA burner in my freon tank forge that has about a 5.5" x 9" chamber has to be turned quite a bit higher to get hot enough to weld.

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Now with the flame holder, does that hold more efficient that a flared end? I ask because I myself can not weld, however I know a place that will do it for me for $. So I am trying to keep welding to a minimum. the design seems to be simpler over all though.

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I have decided on the design where the propane is introduce at the bend, and I am getting the supplies necessarily, black iron pipe fittings, plugs, etc. i can do most of the assembly myself, but I will have external help from a welder for the injectors. I plan to hopefully make two, and thus build two forges out of soft fire brick. I will would them horizontally firing into the sides of each forge, and they will feed from separate tanks. my blower is more than powerful enough to supply both forges running at once, even if I add a coke forge into the system it will still have excess power. So to regulate the flow of air I thought about using a valve so I may adjust to the perfect amount of air, and have the valves mounted on a post or on the wall so I have access quickly. The same goes for the propane, I will have the regulator close by, should it need to be cut off in a hurry.

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The same goes for the propane, I will have the regulator close by, should it need to be cut off in a hurry.


The regulator should NOT be used as an emergency shut off. It takes several turns to shut down. By then you could be a crispy critter. A ball valve is the fastest, and probably cheapest shut off. When things go bad with propane, they go bad very quickly and there would not be time to shut down a regulator. Beside, a ball valve is nice to have at the forge to shut off gas between heats. The best shut off, albeit expensive, is a solenoid that, at the flip of a strategically placed switch, the gas can be immediately be killed. In production and industry, these are called E-stops (for Emergency Stop). They are normally closed and electrically open so even if you lose electrical power, the gas shuts off.
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I second the crispy critter comment, having been one because of inexperience + over enthusiasm + propane. Ruined a good leather jacket and burned my neck and half my face bright red. Having to explain to an irate DG why the house stinks of burned hair, half your beard is gone and you're redder than a stop light is not fun (connected garage). Shut off valves that require anymore than a quarter turn are sweet F.A. use in my opinion if you want to contain any sort of bad day out with gas. In my case an incorectly (read barely) tightened rubber hose blew off under pressure and turned into a fire breathing snake that would not lie still and die.
Several years later and several gas builds later I'm much less likely to fry myself or anyone else by using propane but the best advice I was given was this: until you understand it you'll never be its master.

play careful :)

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I second the crispy critter comment, having been one because of inexperience + over enthusiasm + propane.


Exactly what I don't want is half a hairdo. No offense, I'm sure you made it look good, but I don't think I could get away with that. My Original idea was to have to ball valves, one for gas and for air. Since I am building my shop from the ground up, Grin, I am setting everything up my way, not the garage way or the shed way.

With the gas shut off, the idea is to have a regulator AS WELL AS a ball valve, so I can cut the psi to .000253454 or something, to save in between heats. I have gotten the land staked out and the spot for all my tools and such laid out. I will be heading down to get the rest of my burners parts when i'm off from work and such to get a proto. built. That will hopefully be this weekend.
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  • 6 years later...

I amb shoure that on combination with a forced air burner, a ribbon burner would make the gas forge gain a much greater  efficiency. As It It will mix the air and the propane (or any other gas fuel) inside of the precombustion chamber, therefore, virtualy all fuel molècules (C3H8 for propane) would react with all  O2 molecules present n the mixture.

Where as with a normal tip blower, the mixing is not as efficent and productes a greater noise and poorer flames.

And also, I agree with the emmergency thing. I have a huge gas forge 6500inch cubed, and i have four ball balbes all the way through the hose to the gas tanck. This way I can quickly acces any valve even if I amb at my worck bench! It might be a litle oberkill but...

Despite this, the more joins on the hose the more risck due to leacks there is, so I check for leacks with soapy watter on a regular bases.

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