Safety Question - Forced Air Burner

J. Keeton

J. Keeton

Joined
Nov 15, 2005
Messages
1,201
Hey Blade/Forge-Gurus,

I'm going to be building an improved duplicate of the forge I built in 2005 minus the lame door (Picture Below). My question is in regards to the safety of this system in the event of a power loss while forging.

Question: Does arranging the blower above the propane intake negate the power loss concerns with forced air burners?

Thanks in advance for any input,
James

PC140070 by JK2900, on Flickr
 
I'm just now building a forced air forge myself (my first), so take this with a grain of salt, but I don't think blower position has much to do with it. You'll likely still get gas (and flame) backfeeding into your pipe if I'm not mistaken.

At any rate, you can get a 110VAC, normally closed gas solenoid for about $10 on Amazon prime. Wire it to your blower circuit, and if the power ever cuts out, your gas feed will as well.
 
J. Keeton said:
Hey Blade/Forge-Gurus,

I'm going to be building an improved duplicate of the forge I built in 2005 minus the lame door (Picture Below). My question is in regards to the safety of this system in the event of a power loss while forging.

Question: Does arranging the blower above the propane intake negate the power loss concerns with forced air burners?

Thanks in advance for any input,
James

PC140070 by JK2900, on Flickr
Click to expand...
Firstly, seems odd the orientation what I think is gas input at first elbow from blower. Is gas nozzle pointing toward the blower ?
Anyway, our forges somewhat different piping design. Their gas nozzle much closer and pointed toward the fire.
 
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I highly recommend having the blower below the level of the forge. This keeps the draft going up through the forge and keeping the blower cool. Plus this draft will draw propane up and into the forge
 
I agree with JT, place the blower lower than the forge.

The safety concern is taken care of by putting a main solenoid in the propane line ( usually at the tank). This will shut off the gas if the power fails. It also means you can't accidentally leave a gas line pressurized or open when you leave the shop. Put the switch for the solenoid by the door and shut it off when you shut down the lights.
 
I'm going to be the odd man here and say that blower above is better as propane is heavier than air and in the event the blower goes out the gas will continue down the pipe and into the hot forge and burn off and not into the blower and escape into your shop. I would also not cross over the top of the forge there is no need for the long run of pipe before the cutoff and between the cut off and the elbow, all the fuel and air mixing is done between the gas inlet and the forge.

Then again all of this posted here is just educated speculation, I don't think any of us are really certified in saying if one way is safer than the other with the exception of adding a solenoid to shut the gas off in the event of power loss.

not that we're building anything to any particular code rating this may provide some insight on safety.

Nation Fire Protection Association NFPA 58 Liquefied Petroleum Gas Code
You could read the entire section 2-5.4 Vaporizers, Tank Heaters, Vaporizing Burners, and Gas–Air Mixers
Link to pdf code book.

2-5.4.8 Gas–air mixers shall comply with the following: (a) Gas–air mixers shall be designed for the air, vapor, and mixture pressures to which they are subjected. Piping materials shall comply with applicable portions of this code. (b) Gas–air mixers shall be designed so as to prevent the formation of a combustible mixture. Gas–air mixers that are capable of producing combustible mixtures shall be equipped with safety interlocks on both the LP-Gas and air supply lines to shut down the system if combustible limits are approached. (c) In addition to the interlocks provided for in 2-5.4.8(b), a method shall be provided to prevent air from accidentally entering gas distribution lines without LP-Gas being present. Check valves shall be installed in the air and LP-Gas supply lines close to the mixer to minimize the possibility of backflow of gas into the air supply lines or of air into the LP-Gas system. Gas-mixing control valves in the LP-Gas and air supply lines that are arranged to fail closed when actuated by safety interlock trip devices are acceptable shutdown devices. (d) Where it is possible for condensation to take place between the vaporizer and the gas–air mixer, an interlock shall be provided to prevent LP-Gas liquid from entering the gas–air mixer. (e) Gas–air mixers that utilize the kinetic energy of the LPGas vapor to entrain air from the atmosphere, and are so designed that maximum air entrained is less than 85 percent of the mixture, shall be exempt from the interlock provisions in 2-5.4.8(b), (c), and (d), but shall be equipped with a check valve at the air intake to prevent the escape of gas to atmosphere when shut down. Gas–air mixers of this type receiving air from a blower, compressor, or any source of air other than directly from the atmosphere shall include a method of preventing air without LP-Gas, or mixtures of air and LP-Gas within the flammable range, from entering the gas distribution system accidentally.
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KnuckleDownKnives said:
I'm going to be the odd man here and say that blower above is better as propane is heavier than air and in the event the blower goes out the gas will continue down the pipe and into the hot forge and burn off and not into the blower and escape into your shop. I would also not cross over the top of the forge there is no need for the long run of pipe before the cutoff and between the cut off and the elbow, all the fuel and air mixing is done between the gas inlet and the forge.

Then again all of this posted here is just educated speculation, I don't think any of us are really certified in saying if one way is safer than the other with the exception of adding a solenoid to shut the gas off in the event of power loss.

not that we're building anything to any particular code rating this may provide some insight on safety.

Nation Fire Protection Association NFPA 58 Liquefied Petroleum Gas Code
You could read the entire section 2-5.4 Vaporizers, Tank Heaters, Vaporizing Burners, and Gas–Air Mixers
Link to pdf code book.
Click to expand...

Yes that makes sense "on paper" but here's the issue; when the power goes out, the propane is still being *injected* under pressure, which means an ad-hoc "venturi" is suddenly created. It's not very powerful, but the propane isn't just going to "settle" down into the forge, it's going to draw air and jet to a location based on the other variables of the burner setup.

No, the OP's first forge, the way the propane is coming in directly opposite the air, seems like a bad idea all around frankly. I'd want to see it getting up in directed down from that joint, or at the lower elbow, directed into the forge itself.


I've lost power a lot of times while forging with blown burners. As long as you're close by, it's usually not that big a deal, but I'd highly recommend having a tall ceiling or some fire-resistant material above it, as it usually shoots dragon breath about 6' tall out of the forge, there's not enough air for the fuel, so it flows out seeking air, and goes straight up typically.


If you really want some "piece of mind" for a power outage, it would be extremely easy (unplugging and plugging in cords, after you hit the "buy" button), to connect your blower to an Uninterruptible Power Supply (UPS), the same type as you can get to protect your PC from power outages. Depending on size this could give you a couple of minutes of backup power to shut down the gas, and they typically come with a very loud "alarm" option, letting you know the power is out in case you simply don't notice.

Although another option would be to setup a solenoid on your gas, that's "normally closed" without power, preventing gas flow. Power goes out, gas supply dies automatically.
 
The safest bet for all would be a safety switch to kill the gas. That's probably why the code book says to have a safety valve on both air and gas and doesn't mention placement of a blower. Is is 75% safe up or 70% safe down? Either way it's only partially safe.
 
KnuckleDownKnives said:
The safest bet for all would be a safety switch to kill the gas. That's probably why the code book says to have a safety valve on both air and gas and doesn't mention placement of a blower. Is is 75% safe up or 70% safe down? Either way it's only partially safe.
Click to expand...

Yeah, they're pretty much required here on any kind of gas forge or kiln, if the Fire Marshall is aware of what you're up to. I try to keep a wide berth of anybody in that sort of office. ;)
 
Like I said, putting a solenoid at the gas tank is the simplest and safest method. I believe it is part of the fire code for any external gas tank to have a shut off solenoid (BTW, no gas tanks over 1 pound are allowed inside residential or occupied buildings).

I wouldn't want to risk burning the place down because a hose broke, or the power went out while making damascus. Flip the switch off and the propane stops instantly. The switch should be at the exit door ( IIRC, that is also code).

I think J. Keeton may have accidentally put the elbow with the gas port on backwards. The gas should be injecting down the manifold, not backwards toward the blower. Luckily, it should be a five minute fix to unscrew it and put it back on the right direction.

If someone dropped that forge off at my place, what I would do is unscrew the elbow, remove the vertical black pipe and black elbow, and connect the gas port elbow to the horizontal black pipe ( gas injecting toward the forge). I would then screw the blower manifold pipe and valve into the elbow so the blower is sticking straight up. More than one 90° angle is bad pneumatic engineering.
 
All,

Thanks for the input. I really like the solenoid and/or Power Supply options.

As far as blower placement; it would be easier to mount it under the forge to the base. With the solenoid and/or back up power supply options, I feel like this would be a safe system.

In Regards to the picture of the original design... That was not a mistake. At the time I found/believed that by injecting the gas against the blower would yield a more turbulent environment and aid in mixture. Looking back, it probably wasn't the safest system... but I operated it like that for ~ 2 years. On the second page of the thread below we discussed the new placement.

Here is the original forge's build thread from 2005: https://www.bladeforums.com/threads/the-3rd-time-is-the-charm-my-forge-construction.377055/

Thanks again for all the input and discussion, this really helped. The new and improved 2018 version will be better than the original!

Cheers,
JKeeton
 
Dude you need a shut off valve right there at your gas fitting. And a needle valve, as far as that goes.
Here you see the quick disconnect - then a shit off valve and then a needle valve. If the power goes out I can disconnect the line, throw the shut off or close the needle valve. Triple insurance.
Regardless, you need the needle valve to control your atmosphere with a simple system like this.
And the shorter the piping - the better.
GM2UtSA.jpg
 
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While I have yall here....


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? That seem optimal to me.

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.

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?

4.) Stacy, do you have a picture of the burner you described in this post below. Adding a mixing chamber sounds genius.

Thanks!


Stacy E. Apelt - Bladesmith said:
I have been helping a member with his forge build. I thought I would post some of the info on building the burner.

He had asked about my reference to a "chamber" in the burner.

It is a good idea to have a "bulge" in the burner as a mixing chamber. This is where the gas and air mix to more fully burn in the chamber. It adds a lot to the forge efficiency. You just use a larger piece of pipe and two "bell reducer" adapters. If the burner is 1" pipe, then a 3" piece of 3" pipe is the mixing chamber. Thus, you use two 1" to 3" bell reducer adapters to make the burner go from 1" to 3" to 1" again, and then out into the forge chamber. The bell reducers are standard fittings at plumping supply and hardware stores. Here is a link to what I am talking about. Use the sizes available in your area. The chamber can be any size at least twice the burner pipe size. 2.5 or 3" works great.
http://catalog.industrialpipega.com/viewitems/black-malleable-sch-40-80-fittings/bell-reducers-2

The burner pipe size for a medium size forge could be 1" or 1.25". That mostly depends on what use it will see. If doing regular forging and HT, 1" is plenty. If welding damascus, 1.25 would be great (but the 1" will still do fine). 1" is what I would suggest, unless you plan on making a larger forge in the future, or doing lots of welding. ( The whole burner can be moved from forge to forge for many years of use.) The length of the pipe pieces used to make the burner isn't terribly important as long as it has about an 8" long pipe as the burner tube going to the forge.

If I was to make up a shopping list for building a top notch 1" burner for a 5-6" chamber by 14-16" long forge it would be (starting from the blower):
Blower - 100-150CFM range, preferably variable speed. A fan/light controller will often work as a speed control. DC blowers are super if you find one.
2" floor flange. You need some sort of flange or other fitting so the blower can connect to the burner piping.**
2" closed nipple to connect flange to next item.
2" gate valve. A gate valve is placed here to adjust the blast from the blower. If using a speed control, the valve may not be needed, but a ball valve is still a good idea.****
4" piece 2" pipe.
2" by 1" bell reducer
1" closed nipple.
1" street elbow ( ell) ****
1" tee with a 1"X1/4" reducer bushing in the side port. This is where the gas valve is placed. A 1/4" needle valve is used to control the gas flow. The gas line connects here. Using "quick connect" gas fittings on the gas hose is a really good idea. HTT&R has them, as well as most everything else needed to make a great burner.
3" piece of 1" pipe
1" by 3" bell reducer
3" piece of 3" pipe
1" by 3" bell reducer
8" piece of 1" stainless steel pipe. This is the burner tube to enter the forge. Stainless pipe is recommended here, everything else can be black iron. Buy a spare of this pipe, as it will need replacing eventually.


****If everything was kept linear, the whole burner would be a good 36" long. That will work fine, but takes up a lot of room and is a balance issue. Placing an "ell" in the setup right before the "tee" not only shortens the length of the assembly, but places the blower in a hanging down position below the forge which keeps hot gases from flowing up into the blower when the forge is shut off. A good practice is to always shut off the gate/ball valve when shutting down the forge.
Make a bracket or brace of some sort to support the burner arm and blower, as just hanging it from the forge is pretty unstable. If building the forge on a rolling cart, weld this brace to the cart.
Click to expand...
 
Just MHO if you have an adjustable regulator the needle valve is irrelevant unless your fuel tank is far away. I personally get better results from the adjustable regulator that's within 10' with the hose to the tank. Unless you get a GOOD needle valve the regulator to me works better. I had a cheep one and removed it because it was just another fitting in my system with chances to leak as I left it wide open and use the regulator to adjust the gas flow. I have a low pressure gauge close to the gas orface I use as I know my forge good enough I can set temp by it. I do have a cut off valve close to the burner as well in case of emergencies.
image.jpg
 
Karl B. Andersen said:
Dude you need a shut off valve right there at your gas fitting. And a needle valve, as far as that goes.
Here you see the quick disconnect - then a shit off valve and then a needle valve. If the power goes out I can disconnect the line, throw the shut off or close the needle valve. Triple insurance.
Regardless, you need the needle valve to control your atmosphere with a simple system like this.
And the shorter the piping - the better.
GM2UtSA.jpg
Click to expand...
Is your quick detach fitting just a air line fitting. I use a quick detach fitting on my line as well but it’s some fancy fitting I got from high temp tools way back in the day. I had researched it back then and the word on the street is the air line fitting are prone to leaking and got good for combustible gasses.
 
JTknives said:
Is your quick detach fitting just a air line fitting. I use a quick detach fitting on my line as well but it’s some fancy fitting I got from high temp tools way back in the day. I had researched it back then and the word on the street is the air line fitting are prone to leaking and got good for combustible gasses.
Click to expand...

Curious as well, as that looks like a std air fitting. I also heard teflon wasn't good to use on gas fittings and better to use pipe dope. Granted I have teflon on mine just because s couple fittings aren't tapered threads and that's what I had to use. When I build my next one I want to use all flare/compression fittings what ever these are called. I forget right this min. These are what come on the end of store bought rubber gas lines.

image.jpg
 
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JTknives said:
Is your quick detach fitting just a air line fitting. I use a quick detach fitting on my line as well but it’s some fancy fitting I got from high temp tools way back in the day. I had researched it back then and the word on the street is the air line fitting are prone to leaking and got good for combustible gasses.
Click to expand...
Yes - regular air fitting. I've been running the vertical forge with a blown burner on four different forges since I saw the first Fogg forge at Ashoken 15 years ago. This is the fourth one I've made just like this. Why would they leak? They don't leak on anything else. We're only running low psi and they don't leak with far over 100 psi.
 
Karl B. Andersen said:
Yes - regular air fitting. I've been running the vertical forge with a blown burner on four different forges since I saw the first Fogg forge at Ashoken 15 years ago. This is the fourth one I've made just like this. Why would they leak? They don't leak on anything else. We're only running low psi and they don't leak with far over 100 psi.
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I'd probably stay away from the cheap air couplers. The ones I have in my shop do leak if turned just right, although, yes, they are at about 90 psi.

Milton Industries brand fittings seem to hold up well though.
 
The issue with using air disconnects is not knowing whether the seal is something that propane will corrode or not. More than likely they're nitrile/buna/viton but there's no standard that they have to be since they all hold up to air. There's a chance they're silicone or propylene which have a low compatibility with propane.

Whether that means they'll disintegrate or not I don't know.
 
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