Blown Forge Questions

KnuckleDownKnives

KnuckleDownKnives

Time to make the doughnuts..
Joined
Feb 12, 2015
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I'm usually pretty good at finding deals, but this one either doesn't exist or is eluding me. I'm putting together a shopping list to make a blown forge and pricing everything and finding the best prices. Is it me or do the 3" gate valves really jump from $35 for a 2" valve to over $100 for a 3"? the cheapest one I can find is $102.58

Edit: It looks like everything in 3" jumps in price SUBSTANTIALLY...

While I'm on the subject, what are your thought on using a valve like this?

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Pricing everything in 3" is a LOT of money (for me). So far I'm at $706.00 just for the blower, floor flange, gate valve, 3 nipples, reducing tee, street elbow and 8" stainless nipple in 1" for the burner tip. By the time I buy all the gas fittings, kaywool and steel for the rest of the forge I don't have, I'll be well over $1000, and I really want to do a 2 burner forge, plus make it PID controlled, so closer to $2000.00

What are the disadvantages in doing this in 2"? This would almost cut the price in half.
 
You can get a blower kit from High temp tools for $65 bucks. You will still need a blower motor, nipple and floor flange to mount the motor. Not sure why you would want to go to 3", seems like over kill to me and it must be a really big forge if you need two blowers. You could consider a 2" assembly and add a 3" air chamber consisting of a couple of 2x3 reducers and a 6"-8" nipple. This is supposed to give you better air flow and shouldn't cost but a few bucks more.

I have a 8"x16" blown forge with a PID controller that I built for about $400.
 
I was going by Satcy's thread in the stickies. He says try to match the outlet of the blower.

Stacy E. Apelt - Bladesmith said:
** A plain piping floor flange is a good looking and easy way to mount the blower to the burner piping. Just make some sort of "O" ring or rubber gasket and bolt them together. There are many other ways to do it, too. Use whatever seems simplest for you. Try and match the pipe size coming from the blower with the blower outlet size to some degree.
Click to expand...

The blower I was going to go with is a bit pricey but it looks very well built, and appears to have a 4" outlet. I've read so many of the forge build posts I think I'm a little scatter brained right now. And it's was hoping for 2 burners not 2 blowers. I would have to make some sort of manifold.

I'm thinking about going with exhaust pipe and fittings. I can get it all in stainless, nice flowing "Y" and and 90's for less than $100. Granted I would want to tig weld it all up over using clamps since I would be dealing with flammable gas. Welding on a 1/4" bungs for the gas lines would be no problem. And reducing down to 1" I could just take a section of pipe and slit it and weld it up into a cone shape and weld a 1" stainless female adapter in the small end so I can use a 8" stainless nipple for the burner tip and would be easily replaceable.

Of course all of this is stemming from "Try and match the pipe size coming from the blower with the blower outlet size to some degree."

IDK maybe I'm just over thinking this waaaay too much.
 
pleasanthill said:
I was going by Satcy's thread in the stickies. He says try to match the outlet of the blower.



The blower I was going to go with is a bit pricey but it looks very well built, and appears to have a 4" outlet. I've read so many of the forge build posts I think I'm a little scatter brained right now. And it's was hoping for 2 burners not 2 blowers. I would have to make some sort of manifold.

I'm thinking about going with exhaust pipe and fittings. I can get it all in stainless, nice flowing "Y" and and 90's for less than $100. Granted I would want to tig weld it all up over using clamps since I would be dealing with flammable gas. Welding on a 1/4" bungs for the gas lines would be no problem. And reducing down to 1" I could just take a section of pipe and slit it and weld it up into a cone shape and weld a 1" stainless female adapter in the small end so I can use a 8" stainless nipple for the burner tip and would be easily replaceable.

Of course all of this is stemming from "Try and match the pipe size coming from the blower with the blower outlet size to some degree."

IDK maybe I'm just over thinking this waaaay too much.
Click to expand...

If your blower has a 3" discharge, I would just put a 3x2 reducer off of the discharge and run a 2" assembly. Notice, Stacy said "to some degree".
 
Yeah, I think I just overloaded myself with reading this and that..............

If I'm going to put a PID control on this and use it for HT will one burner be good enough? I think I'm just going to sacrifice one of my 30lb propane tanks for the body, so that'll give an Idea of the size the forge will end up.
 
pleasanthill said:
Yeah, I think I just overloaded myself with reading this and that..............

If I'm going to put a PID control on this and use it for HT will one burner be good enough? I think I'm just going to sacrifice one of my 30lb propane tanks for the body, so that'll give an Idea of the size the forge will end up.
Click to expand...

A piece of 10" pipe about 18" long with 2" of insulation would be ideal. If you use your propane tank, just shoot for a chamber size of 4 to 6 inches. You can reduce the chamber size by adding insulation. My forge of this size works really well with one 2" blown burner assembly. I thought of buying one of those high dollar forge blowers, but I find my $75 dollar Dayton squirrel cage HVAC fan works just fine. I have to add that I only use mine occasionally for HT and if I was using it daily, one of the Centuar Forge blowers might be the way to go.
 
The use of PVC for the flange, 3" pipe, and valve, makes the manifold cheap and simple. It doesn't usually need to be metal until after the gate valve. The 3" PVC valves cost about $25.
 
Stacy E. Apelt - Bladesmith said:
The use of PVC for the flange, 3" pipe, and valve, makes the manifold cheap and simple. It doesn't usually need to be metal until after the gate valve. The 3" PVC valves cost about $25.
Click to expand...

Thanks for chiming in Stacy. I want to stay away from plastic. With my current shop I'll have to move it around and knowing me would end up hitting something eventually. Actually after seeing the hightemp tools one for $65. I'm just going to go with that. I saw it there a while back but that was when i was thinking of going the venturi route and forgot about it. I'm going to get the kaywool and some other supplies from there so hopefully I'll be able to do it in one order when I'm ready.
 
I can't imagine having that much money tied up in a forge.
3"?? I think mine is 1 1/2" ID all the way through.
I have to keep mine turned down so I don't melt things.



 
I know it's a venturi and not blown.

But anyone use t- rex burners
This is the most expensive part of my forge build list.
Did not mean to derail a thread and will move if needed
 
Just to add to the info:

Manifolds:
The 3" size I list in some tutorials is for the primary manifold from the blower, and is a max size. It can be smaller on most all forges. Any size above 1.5" would be fine. 2" works quite well. What parts are available is often the deciding factor. After the gas enters the manifold ( usually at an elbow), the secondary manifold is reduced by about 25%. A 25% reduction in diameter equals a 50% reduction in area, so it doubles the velocity. This is the difference of stepping down a 2" primary manifold to a 1.5" secondary.

The mixing Chamber:
A mixing chamber is not a requirement, but increases efficiency. It is just reversing the above situation. An increase from 1.5" to 2.5" will slow the velocity to 1/3 its speed. This allows more time for the gas/air to mix well, and when the mix enters the burner tube ( usually between 1 and 1.25"), the speed of injection into the chamber is quadrupled. All this happens with no change in the total volume passing through the complete burner. About 4-5" long is all a mixing chamber needs, so A 3" nipple and two bell reducers is perfect. A reduce bushing can be put on the burner tube end to make the parts fit if the exact size bell reducer isn't available.

The burner tube:
The burner tube can be black iron pipe, but stainless steel is better. It can be used as-is, or a slight chamfer can be ground/filed inside the last inch as it enters the chamber. I don't find any real difference between the two. Technically, the chamfer decreases turbulence at the exit of the tube, but this really isn't an issue on a blown burner ( It does matter on venturi, which is why a flare is used). The burner tube is normally around 1/2 the diameter of the main manifold. If using a 2" manifold at the blower, use a 1" burner tube, 2.5" -1.25", and 3" - 1.5".
 
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