Foundry: How to Build a Burner (Natural Gas)





Introduction: Foundry: How to Build a Burner (Natural Gas)

I'm fairly new to the whole casting bit, just got my foundry up and running a month ago. It took me about six months to figure out how to build a natural gas burner, do to the lack of instruction on the web, so I figured I'd throw in my two cents and show how I made mine.

What I'm posting is what I've learned through trial and error. If anyone has more information or ideas I'd appreciate it if you would let me know.

That being said, I'm not responsible for the actions or ideas of anyone that reads this. There is always a risk when working on "diy" projects, especially those that involve fire. Please practice safety when engaging in any type of casting or metal work.

Step 1: Background

Just a bit of background to explain why I made the burner the way I did.

First off I'm a college student, (i.e. broke) I had to use what was readily available to me, so propane was out of the question.

The natural gas line that I had access to was only 5 psi @ 3/4", so I needed a forced air system.

I had bought the foundry (minus the burner) from a blacksmith shop I go to on the weekends, so the inlet diameter on mine was preset at 1.5" with a 1" hole going into the brick work. It's inside diameter is 10" with a 12" depth. The crucible I have is an A10 (7 5/16" inside height, 5 11/16" inside top, and 3 3/4" inside bottom; holds about 1.5 L)

Step 2: Materials


50-150 cfm (i used a Dayton 11TDR3 squirrel cage)

3/4" ball valve (for natural gas line-in)
3/4" nipple (flared/not flared, depends on your ball valve)
3/4"-1/2" reducer
1/2"x6" nipple (variable)
1/2" end cap
2"-1" bushing
1"-3/4" bushing
2' T-pipe
2"x10" nipple
2"x6" nipple (variable)
2" floor mount
2"-1 1/2" reducer
1 1/2"- 3/4' bushing
3/4"-18" pipe (I had to go back and add a coupling and 3/4"x4" nipple so go with 24")
1 1/2" -1" reducer
1 1/2"x5" nipple
plumbers tape or pipe dope (for sealing the pipes)

You will also need a drill, 1/8' drill bit, vice, welder, and an angle grinder; not to mention the skills and equipment to use them properly.

Step 3: Assembly: Gas Inlet

This is based off what I had to work with. Obviously, if you have a 1/2" natural gas outlet you don't need the 3/4" nipple or the reducer.

3/4" ball valve (for natural gas line-in)
3/4" nipple (flared/not flared, depends on your ball valve)
3/4"-1/2" reducer
1/2"x6" nipple (variable)
1/2" end cap
2"-1" bushing
1"-3/4" bushing

Measure the distance (on the inside) of the 2" T-pipe from one end to the opposing side of the "T" in the pipe. The goal is to get the 1/2" pipe with the end cap, have a final placement centered at that distance in the long portion of the T-pipe when the bushing and everything is screwed in.

Mark on the 1/2" pipe the distance needed. (I used a 6" pipe, but you could go longer if you want.)

If you can find a 2"-3/4" bushing use that, if you can't, do what I did and find its equivalent.

Clean and weld the 1/2" pipe (at the mark) to the 3/4" bushing that your going to use. Make sure its centered. use tact welds and a vice as needed.

Drill a 1/8" hole in the center of the 1/2" end cap and secure tightly on the end that is going into the T-pipe. use plumbers tape or dope

Use plumbers tape or dope on the other end of the 1/2" pipe and screw into the reducer, or 1/2" ball valve.

If using the reducer like I did attach to 3/4" nipple, then attach that to the ball valve. use plumbers tape or dope.

Secure the assembled part to the 2" T-pipe. use plumbers tape or dope.

Step 4: Assemble: Outlet Nozzle

3/4"-18" pipe (I had to go back and add a coupling and 3/4"x4" nipple so go with 24")
1 1/2" -1" reducer
1 1/2"x5" nipple

Use a vice to hold the 1 1/2"-1" reducer (wide side down) in place. Then use the angle grinder to make four equally spaced cuts (as close as you can is fine) about 1"-1 1/2" from the top (1" side). These vent holes provide extra air and helps to control the flame.

Dry fit the 1 1/2"x5" nipple on to the reducer, slide the 3/4" pipe in till its about 1/2"-3/4" (on the inside) from the end of the 5" nipple. Then mark the 3/4" pipe where it lines up with the 1" side of the reducer. This directs the flame further into the foundry keeping the nozzle cooler and it also helps prevent back pressure in the nozzle.

Clean and weld the 3/4" pipe (at the mark) to the 1" side of the reducer. Make sure it's centered. Use tact welds and a vice as needed.

I originally made mine a little too short and back pressure (from the reduction into the brick work) was heating up the nozzle, so I had to add a coupling and a nipple to compensate.

Step 5: Assembly: Fan Mount

This is for attaching the fan to the burner.

2"x6" nipple (variable)
2" floor mount

The blower I had didn't have any ducting to reduce it down to the 2" pipe so I improvised. I got some (specifically 4) 4"x6" roof flashing, cut a 2" hole in the center and bolted them to a 2" floor mount.

I attached a 2"x6" nipple on to the floor mount, then screwed that in to the middle spot on the T-pipe. This right angle to rest of the burner assembly provides air turbulence inside the mixing chamber, creating a better fuel-to-air mixture.

Use plumbers tape or dope on all the pipe fittings for this part.

Step 6: Assembly: Mixing Chamber and Completion

Gas Inlet
Nozzle Outlet
Fan Mount
2' T-pipe
2"x10" nipple
2"-1 1/2" reducer
1 1/2"- 3/4' bushing

Mixing Chamber
Screw the 2"-1 1/2" reducer and the 1 1/2'-3/4" bushing together, make sure to use plumbers tape or dope. If you can find one use a 2"-3/4" reducer instead.

Attach the 2" end of the reducer to the 2"x10" nipple. Use plumbers tape or dope.

This will create the mixing chamber when attached to the 2" T-pipe.

Attach the Gas Inlet to one side of the T-pipe and the Mixing Chamber to the opposite-- if not already done so. Make sure to use plumbers tape or dope for these connections.

Attach the Fan mount so that it is perpendicular to both the Mixing Chamber and the Gas Inlet-- if not already done so. Make sure to use plumbers tape or dope for these connections.

Screw the 3/4" end of the Nozzle Outlet into the 3/4' end of the Mixing Chamber. Make sure to use plumbers tape or dope for these connections.

Test all the connections for air leaks with soapy water before hooking up to a any kind of gas line. Always practice safety when ever using the burner.

Happy melting =)

Step 7: Meltings and Additional Info.

It takes about 1-1.5 hrs to warm up the foundry to the point where it will start melting aluminum and for the crucible to get red hot.

...also great for marshmallow roasting =D



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    I'm writing to you to ask a question

    I have a 25KW boiler, with 11 flames and gas Flow rate 2.7 m^3/h, I want to know how much air litter needs for combustion?

    Thanks a lot

    2 replies

    10 parts air to 1 part gas or 2 parts oxygen to 1 part gas

    Hi, you're going to have to employ some basic chemistry to figure out an exact ratio. Essentially, how many mols of gas to O2 do you need. Falling short of that in sure you can find a chart of calculator somewhere in the Internet.

    Good this helps, good luck!

    For the gas inlet, what's the the reason for having the end cap with the 1/8" hole? I get that it will increase the exit velocity of the gas and probably help mixing; but wouldn't it mix well enough if you just attached the valve directly to the mixing chamber?

    2 replies

    In a word, "blowback". the pressure caused by the 2"-1" reduction can overpower the PSI of the gas inlet if the hole were any bigger. for this reason alone, I highly recommend an anti - blowback valve, it is designed to stop air tracing itself back through the gas line. I would also recommend taking a look at my V2 instructable, it is more streamlined and more efficient. Natural Gas Burner V2.

    Pretty cool, a diy power burner. While 5psi doesn't sound impressive, it's dangerous in the hands of a weekend warrior. Most people don't have access to this type of pressure. The pressure in most homes is about 1/3psi. Are you running 5psi thru this bad boy? Not to rain on your parade, it just seems crazy to me. I've seen 1,000,000 BTU boilers running on under 1psi!

    2 replies

    The place that I'm at is a bit older so 5 psi may have been a standard when it was built, but I have no way of knowing that for sure. Also with a quick bit of research, it looks like average NG psi seems to very by region...

    Most of the time, when using the burner, I have the control valve about half open; otherwise the flame is blown out by the fan. If I had to do it again I would probably go for one that only went up to 100 CFM.

    If you have access to the plans for the 1,000,000 BTU burner please share; I'd be interested in seeing how they are built.

    Delivery pressure varies from by region, true, even by city. All houses, buildings, etc have step down regulation which reduce the pressure typically to 1/3PSI. gas appliances also have a step down regulator which usually reduces the pressure to 1/6PSI.

    Chances are, you probably are only getting 1/3PSI. At the main shut off for your house there should be a regulator. It should say how much pressure its delivering.

    Don't have any plans for any 1,000,000 BTU burner.

    this is very intresting. im not gonna use this (no offense) cause i prefer more athentic means but the design is quite functinal. what are you using for crucible?

    7 replies

    Ceramic graphite I believe, i have a few of them lying around.

    My brother and I have recently made a few tweeks (I havent posted it yet) that really beefed up the burner It will get the foundry hot enough to start meltin in 15min.

    jedi, could you give an explanation of the tweaks you made ? This would be very usefull. Thankyou.

    Ok so when I said we made a few tweaks we almost nearly redesigned the whole thing; for the better I might add. cheaper with less parts and more efficient. I meant to go back and update, but I got carried away with other things.

    We replaced the T section with a 2"x8" nipple and welded a 1/2" black pipe to it. a 90 degree sits at the end of the of the black pipe in the middle of the 2" nipple the 90 is attached to an black nipple terminating at a 1/2"-1/4" reducer (the brass tip).

    Depending on your need (forge/foundry) the nossel for the outer pipe can be changed out. I have to collect some pics to make a new tutorial. I'll get on it this week end.

    Thankyou so much for answering.
    I gave some steps ahead and bought a Jacuzzi water cilinder from a deposit of scrap and it costed me only 4 US$ :) Its big enough to make a nice furnace. Already took it to a machinist here and asked him to make cuts and holes on it, and also to place iron bars down on it to make it moveable something like yours. Unhappily I dont have all the tools needed to it ( yet ) so I thought would be better to get some things made for someone more experienced then I.

    I´m very concerned about the gas thing, hope I can get it to work at least reasonably with Butane gas.

    I saw your pictures in and I will be waiting for any news that you post.

    Sorry for take your time.

    And thanks again.

    Yes, I see.
    Its a little expensive to me this burner. I think I will try to keep it as cheap as possible. Will you still publish your changes here ?

    I'll probably wright up a new one based on the amount of changes we made

    Hi there. I like a lot your instructable, and like more the clean aspect of the result.
    I suppose the natural gas you use is Butane, not propane, right ?
    I only have access to Butane ( the one used in kitchens ) in tanks, so I think I could give this setup a try.
    I just need to know if yes, this is butane gas.

    Congrats, nice work.

    1 reply

    Sorry for the late reply...Butane is the fuel source I designed this thing to work off of a 5 psi gas line, the one originally used for the barbeque.

    The first fan I got was a little too powerful at 150 cfm though it will produce a good 18" long flame it occasionally blows out the flame; but I think that has to do more with the nossel size vs the foundry inlet than the fan. You might be better off with a fan some where in the ballpark of 100 cfm.

    This is a great step by step blog on how to make a burner. I had a little trouble with the plumbers tape, but got it figured out. Thanks a lot for the help.