First burner - Troubleshooting

Discussion in 'Burners and their construction' started by MadMechanic, Sep 29, 2022.

  1. MadMechanic

    MadMechanic Copper

    Hello all,

    As I mentioned in my member introduction, I am trying to get my first casting furnace up and going so with that comes building a burner.

    About a year ago I attempted building my first burner based on some designs I had researched online. It didn't work. I'm going off memory here but I seem to recall that I could get it to light just on propane but as soon as I started to open the choke to allow for air it would quickly stop working. Unfortunately I don't have any video of it's behavior at this time and I need to get my propane tanks refilled before I can try to give it another test run.

    However, before I do that, I think it would be a good idea to run my design by all of you and see if there is a fundamental design issue that needs to be addressed first.

    This is intended to be a naturally aspirated burner, I do not want to introduce forced air at this time.

    Here is a SolidWorks model of my design exactly how I built it with 1 minor omission: the 3D model does not show a choke plate whereas the real burner does have a choke plate.

    burner cross section.PNG

    burner cross section profile.PNG

    The main body, from left to right, is comprised of the following parts:
    1-1/4 steel pipe - 4" long
    1-1/4 to 3/4 steel pipe reducer
    3/4 steel pipe - 8" long
    1-1/4 to 3/4 steel pipe reducer
    1-1/4 steel pipe close nipple
    1-1/4 steel pipe tee
    1-1/4 steel pipe plug

    The 1-1/4 pipe plug is drilled with a through hole that closely fits the 1/4 brass pipe (listed below) and is crossed drilled and tapped for a set screw to secure the pipe in place.

    The propane injector is comprised of the following parts:
    .030" MIG contact tip
    1/4" tube brass compression fitting
    1/4 pipe brass tee
    1/4 pipe brass tube - 6" long (propane gas feed)
    1/4 pipe brass plug

    The brass plug is drilled and tapped 5/16-18 thread and a length of threaded rod is installed and secured on both ends by jam nuts. This rod carries the choke plate and allows me to thread the choke plate in and out to adjust air flow, or at least that's the theory.

    Does anyone here see any glaring design flaws with my burner? Anything that I should address, change or improve before I test again? I believe that after I gave up testing my burner I had read that the 3/4 steel pipe is too small, but I don't recall where I read that and what the reasoning was.

    For my gas regulator, I have two choices. The first regulator I bought is a Bayou Classic 5HPR-40 adjustable regulator that I got on Amazon and adjusts from 0-40 psi.

    Bayou Classic.jpg

    This is the regulator I used when I tried testing my burner. Unfortunately I don't recall what I had my pressure set to but I also wouldn't be surprised if I had it set incorrectly. This regulator does not come with a gauge but it has a port for a gauge to be added easily, which I did.

    The second regulator I purchased is a SUA Welding Technologies LPG adjustable regulator, max inlet pressure 400 psi, max outlet pressure 15 psi.

    SUA Reg.jpg

    I have not used this regulator yet. It is a very nice/professional looking welding style regulator with dual gauges (inlet and outlet pressures) and fits to a standard 5 gallon propane tank via CGA-510 fitting.

    Of these two regulators, which one would be recommended and why? Also, what should my starting pressure be set to?

    *For safety, I also have a 12ft long, braided stainless steel propane extension hose that goes between the tank/regulator and the burner.

    Thank you for any help you can provide.

    Last edited: Sep 29, 2022
  2. rocco

    rocco Silver

    That second regulator looks like an acetylene regulator, they all max out at 15 psi. But not to worry, they also work equally well with LPG, in fact, it's what I use. I tend to run mine at around 10-12psi, but what setting will work best for you depends on your exact set-up and a little experimentation will be required to find the sweet spot. That said however, I'm also using a .030 mig tip orifice so 10-12psi is probably a pretty good starting point.
  3. FishbonzWV

    FishbonzWV Silver

    Welcome MM,
    I run a 3/4 burner in both of my furnaces, an A6 and an A10 size. It's plenty for aluminum. I ran mine NA for a couple of years before adding a blower.
    When you do an outside the furnace test, the burner needs a flare on the end. Get rid of the 4" nipple on the reducer. The reducer will act as the flare. Remove the flare when you put it in the furnace.
    I have a 1" nipple welded to the furnace body as the tuyere and the 3/4" pipe slides into it. But, if the nipple is threaded it squashes the pipe down and the 3/4" will be too tight. You can ream the nipple or just buy one an inch longer and cut the threads off.
    On a NA burner a choke is not needed. You lean the flame out by varying the gas pressure.
  4. MadMechanic

    MadMechanic Copper

    This is all good information and feedback.

    Thank you for this. When I bought the SUA regulator it was listed as a propane regulator for Oxy-Propane torch setups, the box just says "L.P.G." on it, but I wouldn't be surprised if it works for acetylene (or if acetylene is the original design purpose). Thank you for the pressure information, I will plan to use the SUA regulator the next time I go to test the burner.

    Ok, so if I'm understanding you correctly, I should remove the 4" section of 1-1/4 pipe on the business end of the burner and test again in open air? Then, when I get the furnace setup, take the reducer off and run it straight from the 3/4 pipe?

    I didn't know that an NA burner doesn't need a choke. It seems like every burner design I have seen/read about online has a choke plate, even if it is being run NA. I guess I also figured I needed a choke plate after watching the BigStackD casting channel on YouTube, he runs all of his furnaces/burners NA and all of his burners have choke plates of some sort.

    Without a choke plate though, how do I make sure to avoid the propane flowing backwards through the burner body during start-up and spitting flames out the back? Or is this a non-issue/concern?

  5. The limited experiments I did with propane and light amounts of forced air from a small squirrel cage blower into a 4" bore pipe showed the need for a still area of airflow near the propane nozzle for flame retention other wise the flame blew out every time. I found a 1" diameter steel "Panel beater's washer" with a 1/4" hole placed right around the nozzle would give enough still air that the flame could burn stable and close to the nozzle tip. You may need something similar at any rat
  6. FishbonzWV

    FishbonzWV Silver

    That's correct.
    I make a flare in the wall of the furnace. It just seems like the right thing to do.
    I don't find it necessary to run one.
    Non-issue. I have had the flame burn in the tube when the gas pressure was too low.
    Last edited: Sep 29, 2022
  7. rocco

    rocco Silver

    I don't run one either. I use the pressure regulator setting to tune the burner, I suppose if you had a non-adjustable regulator, a choke might be desirable.
    BTW, my very first burner, many years ago, used a fixed low pressure regulator and a blower, with that burner, it was absolutely necessary to have some means of controlling air flow, for that I used a variac to power the blower. I used that because I happened to have one already so that's what was most convenient me but if had not had one, I would have rigged up some type of throttle and/or diverter valve.
    Last edited: Sep 29, 2022
  8. mytwhyt

    mytwhyt Silver

    The burner should run just fine with a 3/4" tube, or an even smaller 1/2" tube.. That's what I used on my small aluminum furnace. You can see in my burner thread.. I started large, and by mixing and matching fittings I can switch to different size tubes...
    Small aluminum propane furnace.. | The Home Foundry

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