Safety Question - Forced Air Burner

Whether or not the needle valve is helpful depends on whether or not the gas “jet” is small enough to offer enough restriction for the regulator to provide the necessary adjustment sensitivity.

A small jet can usually provide enough backpressure to just use the regulator. A big gas jet needs the needle valve.

It’s not a case of one approach being “better” than the other. Both approaches work, they are just different.
 
timgunn1962 said:
Whether or not the needle valve is helpful depends on whether or not the gas “jet” is small enough to offer enough restriction for the regulator to provide the necessary adjustment sensitivity.

A small jet can usually provide enough backpressure to just use the regulator. A big gas jet needs the needle valve.

It’s not a case of one approach being “better” than the other. Both approaches work, they are just different.
Click to expand...



Yes Tim is correct about this, a needle valve and the regulator do *NOT* accomplish the same thing.

It's highly advantageous for tuning to add a needle valve, this allows you to run higher pressure on the regulator, but restrict the flow (creating a better "jet" of fuel injecting). With smaller forges it's not mandatory to have, but it's a nice feature, and I'd never build another without a needle valve. To be clear, you need a regulator regardless, the needle valve adds tunability.
 
A needle valve increases your atmosphere and temp control - in tandem with gas pressure and air gate valve - so much that it's beyond words.
I can think of no situation where I would not have a needle valve as part of the recipe.
Or a shut-off valve.
I have three on my system for safety.
 
Karl B. Andersen said:
A needle valve increases your atmosphere and temp control - in tandem with gas pressure and air gate valve - so much that it's beyond words.
I can think of no situation where I would not have a needle valve as part of the recipe.
Or a shut-off valve.
I have three on my system for safety.
Click to expand...

I highly agree, or do like me and go hog wild. Salem says it just needs a cockpit now.

Photo%20May%2017%2C%203%2038%2013%20PM.jpg


Photo%20May%2017%2C%203%2038%2008%20PM.jpg
 
Personally, I don't see anything unusual about JT's setup. I would add another solenoid at the propane tank, though. What if you drop a hot blade on the propane hose and burn through it. The solenoid at the tank will shut off all gas to the regulator and hose. It only takes a flip of a switch.
 
Stacy E. Apelt - Bladesmith said:
Personally, I don't see anything unusual about JT's setup. I would add another solenoid at the propane tank, though. What if you drop a hot blade on the propane hose and burn through it. The solenoid at the tank will shut off all gas to the regulator and hose. It only takes a flip of a switch.
Click to expand...

Hey Stacy, do you have any knee jerk answers to the following? I don't need much detail. Just making sure I'm heading in the right direction with the re-build.

1.) Should I slightly move the burner to the front portion of the forge body and angle it slightly backwards to create a "reverse swirl" into the forge? Is there an optimal design here?

2.) In the original Indian George design, I had a "jet" where the propane entered the elbow. (a 1/2'' bull plug with a 1/16'' hole in it). Is this necessary? Doesn't seem like it is looking at other designs. May help with holding back pressure during tuning?

3.) For a 16'' x 6'' chamber with additional fire brick floor (I have a 10'' air tank as a shell); should I "y-off" (split) the burner into 2 smaller ports? Or utilize one large swirling burner? Or no big difference either way?

4.) Do you have a pictorial example of your "perfect" DIY forced air burner setup?

Thanks for all yall's help! Makes this build way easier to conquer.
 
1) That setup is becoming popular.
2) The gas just needs to enter the air manifold. I use a Tee with a reducer bushing in one end as an elbow. The 1/4" propane line pipe nipple screws in the bushing.
3) I would just use one burne port.
4) The schematics are in the stickys. some great photos of several that are built on my plans. Here is one thread about building with it:
https://www.bladeforums.com/threads/pid-controlled-forge-heat-treat-oven-plans-wip.1385057/

There used to be some great photos of several that are built on my plans, but the recent changes in hosting have removed many old photos. Fred Rowe's "Vulcans Chariot" and Eric Fleming (I'm pretty sure it was him) had nice ones. Send Fred a PM and ask him to post new photos of the Chariot.

My Illmarinin's Sapmo is in boxes until the new shop is done. When it all gets re-assembled as a "Super Forge" it will make JT weep with tears of envy.
 
Looking forward to seeing it. As to the solonoide on the tank side. I just have a ball valve right after the regulator.
 
Fwiw, if using a solenoid gasvalve.
I think to do it right one should energise the valve thru an airpressure switch. Not simply switching via the PID or sharing power with the blower.
Further, at our shop.
Gashoses and electrical cords in the ”hot zone” are protected sliding a length of aluminum FMC over them.
 
Last edited:
All, once again thanks for the help. I'll post some pictures of the build once I have something worth showing!

Cheers,
James
 
Lieblad said:
Fwiw, if using a solenoid gasvalve.
I think to do it right one should energise the valve thru an airpressure switch. Not simply switching via the PID or sharing power with the blower.
Further, at our shop.
Gashoses and electrical cords in the ”hot zone” are protected sliding a length of aluminum FMC over them.
Click to expand...

Would you care to elaborate on this air switch you're describing?
 
He is saying that the gas solonoide valve should be pilot operated using an air line from the control box. This air would be controlled by another solonoide valve connected to the pid.

I personally don’t think so. These are designed for combustion gasses and are NC so power loss is not a problem.
 
JTknives said:
He is saying that the gas solonoide valve should be pilot operated using an air line from the control box. This air would be controlled by another solonoide valve connected to the pid.

I personally don’t think so. These are designed for combustion gasses and are NC so power loss is not a problem.
Click to expand...

I was thinking something like that. Basically so you're not having an electrical component operate the fuel directly. Sounds overkill for our purposes.
 
Yeah, considering the valve are designed to cycle flammable gasses the way we are using them. I’m fairly positive thy are used on propane and natural gas furnaces.
 
JTknives said:
He is saying that the gas solonoide valve should be pilot operated using an air line from the control box. This air would be controlled by another solonoide valve connected to the pid.

I personally don’t think so. These are designed for combustion gasses and are NC so power loss is not a problem.
Click to expand...
Ha Ha !! Nothing so elaborate...
Connecting a gas solenoid to blower or control power shuts off the gas if power fails, but does nothing if the blower dies. For example seizes or burns out.

Controlling gas solenoid using the blowers air pressure assures gas will shut off anytime the blower is not running regardless of reason.
 
Last edited:
JT, placing a solenoid at the tank just after the ball valve is what code requires. It is also a good way to assure that the gas is shut off.

Lieblad is talking about an air flow detector. These are used on boilers and larger furnace burners. I never heard of one used on a small forge ... until now.
It is a tube placed in the air flow from the blower that detects the increased air pressure, This activates a safety switch in the power to the solenoid and allows the gas solenoid to activate.
The mass air flow detectors used on cars and trucks are cheap, and probably could be placed in the manifold from the blower. You would have to do some research on how the detector sends the signal to see how to connect it to the DC solenoid control line.

If someone is salvaging a blower from a boiler or oil/gas furnace, there is already an MAF as part of the assembly. It is that 4X6" box with the adjustable flap that looks like an air vent (usually mounted on the side of the blower). It has a NO switch built into it.
 
Last edited:
Lieblad said:
Ha Ha !! Nothing so elaborate...
Connecting a gas solenoid to blower or control power shuts off the gas if power fails, but does nothing if the blower dies. For example seizes or burns out.

Controlling gas solenoid using the blowers air pressure assures gas will shut off anytime the blower is not running regardless of reason.
Click to expand...

Ok well that little bit helped as I thought you were talking about some sort of air operated actuator vs an air pressure sensor.

Stacy E. Apelt - Bladesmith said:
JT, placing a solenoid at the tank just after the ball valve is what code requires. It is also a good way to assure that the gas is shut off.

Lieblad is talking about an air flow detector. These are used on boilers and larger furnace burners. I never heard of one used on a small forge ... until now.
It is a tube placed in the air flow from the blower that detects the increased air pressure, This activates a safety switch in the power to the solenoid and allows the gas solenoid to activate.
The mass air flow detectors used on cars and trucks are cheap, and probably could be placed in the manifold from the blower. You would have to do some research on how the detector sends the signal to see how to connect it to the DC solenoid control line.

If someone is salvaging a blower from a boiler or oil/gas furnace, there is already an AFD as part of the assembly. It is that 4X6" box with the adjustable flap that looks like an air vent (usually mounted on the side of the blower). It has a NO switch built into it.
Click to expand...

Actually that's quite easy Stacey. A mass air flow sensor works off a return voltage usually between 1 and 5 volts and a pulse width. You'd probably need to build a pid out of an adrino for a system like this. Shoot just get a fuel injector off a car/truck as well and you could program the pulse lengh and width on it, put a rheostat on it and operate it like a regular oven once the parameters are figured out.


California would probably need an O2 sensor to make it emissions legal :D:D
 
You must log in or register to reply here.
Back
Top