Burner construction question

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bjalongi

Joined
Oct 23, 2006
Messages
640
Well, I'm building the forge that I've been dreaming about for a few years now. My current forge works well, but isn't quite hot enough to forge weld and isn't big enough for hawks.

It's overly elaborate as usual. I got it all welded up and the fire brick shaped over the weekend. I'll paint it and coat the inside with satanite tonight. I'm just waiting on a new squirrel cage fan from Grainger to come in and I'll have the burner done.

I built the burner out of some pipe and fittings I had laying around. The last burner I built was out of 3/4" pipe and it worked very well without a fan. This time I used 1" pipe, because the forge is pretty big and I had 2 1/2" reducer that will match up to the fan perfectly. However, without a fan, or back pressure, the flame doesn't get a hot light blue core. It gets a lot hotter when I shoot compressed air into the reducer. I'm hoping it will be more efficient with forced air and some back pressure from the forge. Has anyone built a burner out of 1" pipe, or do I need to use something smaller? It looks wicked, that's for sure.

Also, I'm concerned about the rubber gas hose getting hot. It attaches to a brass pipe, like normal homemade forge burners, and is about 2.5 inches from the burner. Is that too close? It about the same distance as other burner designs I've seen online. However, now that I've built it, I worry about it heating up. I think the fan will keep the back end of the burner cooled off, but I'm not sure. I really don't want to have an explosion if the hose melts. My regulator/hose assembly is off of a turkey frier, so it should be rated for the heat.

Anyway, Thanks in advance. I'll try to get some pics up when I get home today.

Brook
 
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The flame temperature and forge atmosphere are a product of the amount of air and the amount of fuel. You should have a way to regulate both. Most folks either use a gate valve in the 2.5" pipe from the blower, or use a fan controller to change the fan speed. The gas is controlled by a needle valve.
1" pipe is the norm for blown burners.
Stacy
 
The turkey fryer regulator easily controls the gas flow from 0-10 psi. Should I think about a secondary control valve?

I plan to control the fan flow with a standard rheostat for controlling home lights. I also planned on having a mechanism for controlling the air flow as well. Probably a piece of sheet metal over the intake to the fan that is adjustable.
 
As for keeping burner heat off of the hose assembly, I usually have plugged the burner tube with something after shutting down, be it a pipe plug on a side arm burner or a ball of wadded up paper on a Ron Reil style venturi. (yes, it works!) Turkey fryer heat is less than residual forge heat bleeding up your bell reducer. If you run a thumb screw for your burner tip depth setting, you can easily pull the tip completely out after every forging run to escape residual heat. As for 0-10 p.s.i., what size orifice are you running? I know that blown forge guys usually run a larger orifice than venturi guys, but it's important to figure whether 10 p.s.i. will supply all the fuel necessary for your forge welding needs. If your burner does not produce a nice hot neutral flame running atmospheric, does it have a burner flare? I ask this because it seems you expect it to, which implies to me that you designed it as an atmospheric burner first. Does it have a burner flare or any degree of internal taper? This refinement tends to hold a flame and define it better. If you plan to run blown, I can't say if this makes a difference.

Venturi! Venturi!
 
A regulator from a turkey fryer has too small of an orifice to deliver enough gas to a blown burner. You need a regulator like the ones Darren Ellis sells (along with anything else you will need to build a forge). Gas volume being consumed (usually stated in BTUs) is more important that the pressure. That is partly why a blown forge can run at 1-4 PSI and a venturi forge runs on 5-15 PSI. The BTUs produced are the same for any given forge temperature.
http://forgegallery.elliscustomknifeworks.com/

The burner should not get hot enough to cause a problem with the gas hose. I use Darren's quick connect fittings on the gas hose, and just un-snap it when done. Really makes for a simple shut down and put away at the end of the day.
 
I currently have a number 57 hole in the brass propane delivery tube. The last burner I built was venturi and had a #57 hole, so I figured it would also work. It put out a ton of BTUs. It had a bright blue neutral flame at atmospheric conditions. Should I consider a larger hole?

I currently have no flare on my burner. I've almost hit my max budget on this project, because it is nickel and diming me to death. I need to reconsider how I want to construct the burner.
 
Most people don't use any orifice at all with a blown burner. Just a 1/8" or 1/4" pipe input . Look at some burner designs and you will see why there is no need to inject the gas in a blown burner. Just meter in ( using the needle valve) the amount of gas that is needed for the amount of air being blown in.
Here is all you will need to know about forge building and operation. From Kevin Cashen's site.
http://www.cashenblades.com/Info/Gas forges.html
Stacy
 
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