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Ribbon burner overheat?


Axioner

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Hello all,

First time poster with a question. I wanted to switch from my dirty coal forge to propane, so I made a ribbon burner following Frosty's NA Ribbon burner build, using the same dimensions and everything. The forge heats up fine and runs fine for the first hour. After about an hour is starts backfiring, or detonating inside the mixing chamber. I didn't put any baffling inside the black itself as it sounded like it wasnt necessary from Frosty's write up. I suspect detonation is result of the ribbon burner nozlettes heating up themselves as can be seen in the attached photo. It's odd that only some of them heat up though. Any guesses as to what I did wrong, or how I can fix this? My forge is a 30lb propane tank with 2" kaowool coated with MIzzou and ITC-100. The burner itself is a block of Mizzou with a coating of ITC-100 on the face. Would switching to forced air once it is up and running help mitigate this issue? Thanks in advance!

Hot burner.jpg

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Welcome aboard Axioner, glad to have you. If you put your general location in the header you'll have luck hooking up with members within visiting distance.

How easy is it to take the burner off the forge? I've never seen one do that either, it makes me wonder if the outlets at that end aren't burning inside the block or too close. burning back in the block happened when I had too many outlets in the block and the fuel air mix velocity was too low but no so low it burned back immediately.

I'm thinking there is a little crud or an obstruction at that end slowing the fuel air supply a little. 

Did you clean the outlets or just melt the crayons out? I just melted the crayons out then burned the residue over a dozen charcoal briquettes thinking that'd do it. I discovered ash was inhibiting flow in some outlets so I blew them out with an air hose. From the block back into the plenum and finally out through the T inducer. 

I don't know if that's what's going on with your burner but it's the only possibility I can think of off the top of my head. Something in the burner is obstructing but not stopping the fuel air flow through the outlets.

The general or most common solution to overheating and back firing is to turn up the burner so there's enough fuel air mix flow to keep the block below the mix's flash point. 

Frosty The Lucky.

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Hi Frosty,

I'm from north-central BC in Canada, so not likely anyone in visiting range ;) . As for your questions, after melting out the crayons I used a drill bit by hand and reamed each hole until i felt the bit bottom out on the back of the metal inducer block, so the holes themselves should be clear. I then did this again after coating the face with TIC-100 to make sure that none of that had dripped into the holes creating a plug. The block is held in by 4 set screws though, so its very easy to remove and confirm. I'll do that later today. For my set up I have a Hi-PSI regulator running off a 100lb propane tank, with a 3/8ths line run to the forge, which tapers down to the MIG tip that is used as the jet in the T inducer. As I said, I copied your final dimensions exactly as far as I know. Even when running full open on the regulator, the best I get is a light orange heat, not quite yellow. Is this typical of propane or should I be able to do better than that? I'll post a bunch of pics, perhaps that will help. Also, this issue is happening as full open, so there is no more pressure fuel i can add. When it is first warming up, the flames lift off the block at full throttle, but once the forge is up to heat, they are maybe 1 inch blue flames sitting nicely on the block at full throttle. Thanks again!

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Here are some pics I took just now. I also ran a drill bit through each nozzlette and made sure there is nothing bouncing around in the inducer box that could plug holes. I also ran some weld wire through the welding tip to make sure it was clear too, just to cover the bases. The first pic shows the forge running at full throttle, which doesnt seem hot enough with almost no visible flames. I've also attached a short video of the burner running at *very* low pressure, it was my first test run of the burner after it was cast and baked.

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We aren't going to remember where you are after opening another post. There are a lot of members in BC and if they don't know you're around they'll pass you by. That and we'll pester you if location seems important. 

Sounds like you got the block cleaned out pretty well, well enough maybe maybe not, I can't say.  Sounds good though. The general consensus among the experienced gasser builders is to use Plistex or Matrikote kiln washes rather than ITC-100, they're more effective and WAY less expensive. 

Mine don't get as hot as single outlet 3/4" T burners either. However I think maybe distributing it so evenly means I don't have the HOT spots my old style forges did. I haven't really spent much time tweaking NARBS for performance but other guys are. Mine reach low yellow without much trouble and if they were in a more closed forge might drive higher. 

The description of your flames sounds good mine are less than 1" when hot and look okay. 

Maybe just pull your burner a little farther back from the chamber? Does the plenum get hot? I can touch mine but no way are you going to hold your hand on it more than a short second. 

I don't think we need to flood the thread with pics but a couple more might reveal the secret. (shhhhh!):rolleyes: How about one right after lighting it and another when it starts burning back for both ends of the spectrum.

Frosty The Lucky.

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Looking at your first photo of the operation it appears that you have greatly differing flowrates coming out of different ports in your multiport burner.  If we assume the forge is at a relatively even temperature the walls should radiate the same IR back to each port of the burner block and the flow pattern should convect a similar amount of heat to each port as well.  Of course this is just an ideal case, which clearly is not happening here.  It appears to me that the lower flowrates for the perimeter ports are leading to less cooling by the air/gas mixture and overheating of said ports, allowing pop-back.

I have several theories about this, which I have not had adequate chance to test, or even research adequately:

  1. The lack of a baffle and lower fuel/air mixture flow quantity is resulting in more of the flow exiting the burner in the central section, starving the exterior, and resulting in localized overheating.  I suspect more fuel/air flow may be required for your specific forge configuration.  I would open the needle valve fully and adjust the regulator for stable operation once the forge gets up to temperature.  Then I would raise the regulator around 5 psi and modulate the needle valve to fine tune the burner.  Note that you still may experience problems with pop-back when trying to switch from a high-fire, screaming hot forge to a lower setting.  This is one of the issues I have with a NARB system (with forced air you can run the air without gas at a low rate to cool down the forge while keeping the burner at an acceptable temperature).
  2. I believe that the optimal length of the small ports in any multi-port burner is much shorter than the length most people use.  If I recall correctly, the port length in the Joppa Glassworks burner is only around 1/2" long, at most.  Dudley has made these burners for at least 30 years, and likely knows what he is doing.  Again I theorize that the longer ports in most NARB are providing too much friction, which may be slowing the fuel gas mixture down too far.  It also results in a proportionally longer section of refractory that can get heated by the forge.  This longer hot section may be prone to preignition.
  3. It is possible that the port pattern for these burners should be reconsidered.  Ports on the burner "interior" are cooled by fuel/gas flow on all sides.  Those on the burner "perimeter" are not.  Take a look at a typical Giberson multiport burner head (also note the integral baffle due to the port locations):  hex_facehole.jpg

Again, these are just theories and I am certainly open for discussion 

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Assuming that the "nozzlettes" are pretty much identical in all dimensions I would conclude that one of 2 things is happening: 1) More heat is reflected back up at the burner in the areas where they are glowing inside (not that likely), or 2) you have less fuel/air flowing through those openings.   Since they seem to be in a group I'd guess it has to do with how the mixture is swirling inside your plenum before exiting the holes. 

If anything is somehow diverting more of the mixture to one side or the other of your plenum, it could cause this effect.  Unfortunately there could be several causes of this.  If your mig tip is not aligned well axially in relation to the mixing tube, that could cause more of the mixture to exit the tube on one side than the other.  It would also tend to make it burn a little richer (less air induced) which could also limit your maximum temperature achieved.   If there is any obstruction, burrs, etc. where the mixing tube enters the plenum, that could divert the flow as well.  If there are dents, bumps, etc. on the opposite wall of the plenum from the mixing tube that could also affect the flow, although I think they'd have to be more than just tiny imperfections.   If the end of the burner block inside the plenum is irregularly shaped or tilted in relation to the plenum that could also cause some uneven flow through the ports.

If it were me I'd start with the T portion of the burner and try to ensure that the mig tip is aligned well with the mixing tube before moving to anything else.

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  • 1 month later...

Axioner. I cant help you with the burner but I just wanted to let you know that I am near by. There are a handful of smiths in Prince George. Another few in Vanderhoof. I am in Fort St James. I am sure there are a few of us in each community up north. There is a Prince George Blacksmith Guild on Facebook. 

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Good Morning Axioner,

Welcome to this world, only in Canada, eh!!

The ribbon burners work better with a small air blower (old Hair Dryer). With the multiple burners in a ribbon burner, I have found they work better not being Atmospheric. Play with it, take an old Hair Dryer and move it around your Air Intake, when the Dryer is on Low. You will notice a difference. I have a few ribbon burner Forges and yes I can make them work with Atmospheric Burners, but they work better, easier with a little air help. It is just a function of the number of burner nozzles versus the quantity of Air that gets in through your burner head.

CanIRON XIII in 2021 (Fergus Ontario), has just been officially cancelled, due to Covid 19.  Monitor www/CanIron.ca for details.  There is talk of doing something else via On-line Demonstrations, for 2021.   Manitoba Blacksmith Guild just did "ManIron", last month, October 2020, with 9 Demonstrators. Everyone stayed home. France, South Africa, USA, Canada, Russia were the countries of the Demonstrators. All On-Line. There is a recording of 8 hours of Demonstrators, available on the Facebook page of the Manitoba Blacksmith Guild.

Good Luck with your burner and Forge.

Neil,      Vancouver Island Blacksmiths Association

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  • 2 months later...

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