First forge build; I'm gonna need help.

RangerMadeKnives

RangerMadeKnives

KNIFE MAKER
Not too long ago I asked about buying an Atlas Mini Forge. One thing lead to another and here I am about to build a blown forge as my first forge. I received several components from Bruce Bump and I've begun purchasing/scrounging everything else. I ordered and have received a 60cfm blower and my ITC100 came in today. I already had plenty of Satanite on hand. I still need to find some material for the body which will likely be 12" pipe but, I am considering a 20lb propane tank as well.

Get ready, I'm going to ask a lot of questions. I'm just not a fan of being blown up. I've done a lot of research and have found an abundance of information on naturally aspirated venturi type burners but, very little on forced air setups. From what I can tell, there is no jet on the blown burners but rather, an inlet tube. How does the placement of the gas inlet affect the combustion of the mixture? How far does the gas inlet need to be away from the end of the burner tube? Why is the end of the tube flared? I understand that the metal portions of the burner tube will melt if they extend into the forge but, how far recessed should they be? Where will my flame sit in relation to the end of the burner tube? I'm probably going to need someone to get very basic with me on this.

Bob
 
IMG_0053.jpg

This is the blown burner that I have on my large forge. About the only change that has been made since this picture was taken was to replace the burner tube because it had burned rather short. The replacement sits within the 3" Ins-wool lining that has been coated with Mizzou refractory. What holds the burner in place is that I made the hole in the Ins-wool a little larger than the outside diameter of the pipe and packed Mizzou around it. The Mizzou is also over the rim of the burner tube to protect it from the flame. The black hose is a flexible drainage pipe that attaches to my bounce house blower and is attached just below a gate valve to adjust the air flow. The propane tank is conned to the burner via a POL connection, regulator, and a gas hose. The gas hose is attached to a ball valve to quickly cut off the gas flow. The ball valve is connected to a needle valve for fine adjustment of the gas flow. Get one designed for gas regulation. Most of the hardware stores carry ones to regulate water flow. You could check a welding supply store for the correct one or someplace like High Temperature Tools and Refractory carry the gas valve.

The needle valve is attached to a ball valve for rapid shut off and then to a brass nipple that I have inserted through a plastic plug in a T fitting. You can use a cast iron fitting but you will have to find the correct tap to match the threads on the brass nipple. The T fitting is just above the gate valve. Then there is a short iron nipple a 90° elbow and the burner tube. Do not use galvanized iron for the burner tube. However below the elbow is should be fine as that should not be getting hot.

The term "burner tube" is a misnomer. There should not be any combustion within it. It's just an injection tube. If you have any combustion within the tube, it will get hot and maybe even glow red, you probably don't have enough air pressure going through the burner. A stainless steel flair on the end of the burner tube will help protect the black iron from being burned away. I solved that problem by leaving the end of the tube within the wall of the forge.

Doug
.
 
Thank you Doug, very useful stuff.

I spent hours last night doing more research (the internet is so amazing!) and I'm feeling a bit more knowledgeable today. I feel like a plan is coming together.

Bob
 
I like my forge allot. Let me know if I can add to your thread here.
The burner has a flair on one end but the flaired end isn't in the fire, it is at the cold end and is made to funnel and speed up air flow much like a Venturi type burner. The blown forge needs just a bit of back pressure at the burner so the burner I provided is smaller diameter made from schedule 40 steel.

The blower for the 12" body only needs to be 65 cfm and have an an adjustable intake door. It's a good match for this small body forge.
 
Thanks Bruce and yes, feel free to add anything. I will get some pictures up as soon as I get organized. Ordered my regulator, hose, gauge assembly today. Did you use the quick disconnect in lieu of a ball valve shutoff?

Bob
 
RangerMadeKnives said:
Thanks Bruce and yes, feel free to add anything. I will get some pictures up as soon as I get organized. Ordered my regulator, hose, gauge assembly today. Did you use the quick disconnect in lieu of a ball valve shutoff?

Bob
Click to expand...
I use quick connects, the same ones used on air tools.
 
This is not specifically related to my forge build but, I just had to show it off somewhere...my first anvil. UPS brought it today; driver was not impressed.

Bob

Untitled by Bob, on Flickr
 
You must log in or register to reply here.
Back
Top