High Volume Propane Torch

The intended purpose for this torch is to heat an aluminum melting furnace (coming soon to an instructable near you!).  Since I'm using it strictly as an area heating device, I'm not too concerned with the flame quality.  I haven't tried it out in a furnace since that piece is yet to be built.  

This burner is Lionel's "Oliver-Upwind" Burner design over at http://www.backyardmetalcasting.com/

Specific Link:  http://www.backyardmetalcasting.com/oliverburner1.html

This is by far the simplest burner design I have found, and he does a pretty decent job of explaining the process.  I improved the design slightly and have some suggestions for construction.

SAFETY Statement :  Fire is hot, propane is potentially explosive, power tools and welders can hurt you in many spectacular fashions.  Please take proper precautions to avoid losing eyebrows and digits.

Step 1 Materials

 - High Pressure / High Volume Propane Regulator
 - 6 Foot  Braided Steel Propane Hose
 - 1/8" ID Black Pipe and Connectors
 - #57 Drill Bit
 - 3/4" ID Steel pipe
 - Old rusty propane tank

The propane regulator I found is variable from 3-35 PSI, and was the most costly part of this build at ~$40.  Hopefully I'll get a lot of life out of it.  The 3/4" ID pipe was one that I had laying around, and is not the same size as 3/4" black pipe.

Note that you can mix brass and black pipe fittings to get whatever configuration you need.  Brass connectors are more expensive, so use whatever black pipe pieces you can find.

Notice that "Higher Pressure" in propane terms doesn't mean the same thing as regular compressed air.  Most BBQ grills run at 3 - 5 psi, and the big turkey fryers run at 15 psi.  

I probably have my regulator set at ~18 psi.  I could have saved $30 by getting a fixed 15 psi regulator, but this one looks a lot cooler (definitely makes it worth the extra $25...).

Comments

[NutandBolt]

Good Ible, If you are planning to use a steel crucible be careful with that Oxidising flame, before you know it you will have a hole in your crucible. It is very annoying when a good crucible is ruined and all the molten aluminum ends at the bottm of your foundry. I experimented a lot and learned from my mistakes at this stage I know exactly the adjustment for my propane burner its just a bit of trial and error.
In the video I made you can see my crucible that I used for over 30 aluminum pours.
You can have a look at my foundry blog for more info:
http://www.flamingfurnace.blogspot.com/

[snowluck2345]

I'm thinking our running a reducing flame, so the flame still wants to give up more electrons to the oxgen, so all the oxygen is reacted, preventing the crucible from being oxidized.

[joshgoes]

Thanks for the comment, looks like you have a lot of great information on your site. I have my foundry built and I've been looking for some good crucible designs. I'll definitely check out your videos when I have some time this weekend.

[rrrmanion]

how would you adapt this design to have an awesome(looking), enormous, yellow flame? would you skip the air intake holes?

[joshgoes]

A yellow flame would be less hot than blue, so I think starving it of oxygen might work. If you watch the videos you see it start off with a relatively yellow flame. You could also try experimenting with different port sizes, nozzle shapes. My best guess would be a higher volume, lower pressure flow of propane would achieve the results, but you might have problems with the sustainability of the flame at that point due to inadequate oxygen for ignition.

Liquid fuels would most likely produce a more yellow flame since the more complex molecule burns in more stages than a gaseous fuel. Think about a Coleman camp stove - it starts off with a yellow flame when you first pressurize the container then turns blue and self-sustaining when the flame is hot enough to vaporize the incoming fuel. A propane stove generally starts off with a blue flame with no pre-heating.

Of course, pressurized liquid shooting out of a nozzle in a stream with an ignition source is called a flame thrower, so dont do that.

[muffin1]

Would you need a check valve to stop the flame from going into tank and blowing up at low pressures or is that impossible?

[joshgoes]

Good question. I don't think the flame going into the tank is a problem for a number of reasons. The main reason is that the propane doesnt burn very well (or at all) without oxygen. You can turn the flow down to barely a trickle, and it still stays nicely in the torch. The regulator also provides a bit of separation, and maintains a high pressure / low pressure system, such that the flame is never "sucked" back up the line into the tank. Even if that were the case, it would require a significant amount of energy to rupture the tank and cause an explosion. Mythbusters did a pretty good demonstration of this - I don't remember what they where testing, but they essentially tossed a propane tank into a bonfire. Keep in mind that this is a much higher flow system than even an ordinary propane BBQ, which generally uses a less sophisticated regulator. Thanks for the comment, let me know if you have any additional questions.

[muffin1]

Thanks. I do have another question, Could I use soldered copper pipe instead of welded steel pipe? I have no idea how to weld nor do I have a welder so copper pipes would be ideal. The only problems I see are the solder on the joints melting or maybe the copper pipes not being able to take the pressure.

[joshgoes]

The pressure shouldn't be a problem in copper but I think most solders melt between 400F and 500F, which would probably not be able to withstand the operating temperatures. You could also look into a purely mechanical stabilizer, such as a set screw going through the main portion of the torch to hold the gas tube. Something like JB Weld might work, but I imagine you would also run into operating temperature issues.

[caitlinsdad]

But wouldn't you want to be concerned about the flame quality to get the most efficient use of the amount of fuel in the tank and heat up as quickly as possible?  A true white or blue flame is the hottest?  I guess the welding prevents the adjustment for the air mixture.

[joshgoes]

You are correct that a higher quality flame would be desirable, but since this will be used exclusively in the foundry, I am thinking the back pressure of inserting it into an enclosed area might have an effect on the flame.  I'm not concerned about getting the hottest heat at a single point, but the most amount of heat distributed throughout the entire volume.  Aluminum melts around ~1200-1500 F depending on the alloy, which this should reach fairly easily.  I also dont want  the heat source too concentrated on a single point, because my refractory cement is only rated to ~2500 F (so I dont want to heat a single point above that or it will start to melt).

As long as all of the propane is burned before it exits the foundry, all of the potential energy of the fuel should be expended in heating it up (right, thermodynamic physics?  It's been a while).  You're right that welding it reduced my my ability to adjust the flame, but didnt completely eliminate it - the flame quality also depends on the length of the burner tube, the end point aerodynamics (affected by a flange, which I dont use), and internal aerodynamics and routing (I have none to speak of). 

Anyway, this response is a little longer than I intended it to be, but you asked for it!  :-)   The foundry is complete, but I have yet to fire it up since I'm letting the refractory cure.  That's the next Instructable, coming soon!  Thanks for the comment, and let me know if you have any more questions.

[caitlinsdad]

That is interesting.  I have seen multi-pipe/jet  configurations that glassblowers have used and thought all you needed was a good blast of heat.