Mycelium

Burner chuffing

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Greetings IFA,

I've posted here once before with my initial attempt at building a pair of Venturi burners (that were rather crude). After several months of diversions and learning new skills (basic machining and TIG welding) I've looped back around to attempt #2 with better results but still not quite functional.

Forge body:

Standard 20lb propane tank lined with 2" of Kaowool coated with a refractory stove paint and a Unicast 3000 bottom.

Burner:

Propane line hooks up to 1/8" brass fittings that are T'D inside the 2" pipe nipple. There is a grub screw that allows me to adjust the position of the gas line. I have a very crude

A 0.023" (I have tried 0.030" and 0.035" but the 23 seems to produce the most stable flame) MIG tip is used as the injection orifice and the tip of it is about 0.4" from the throat of the 2" to 3/4" bell reducer (still had the threads on the inside which I could machine off if necessary).

The burner pipe is 6" long and there is a 3/4 to 1" reducer on the end as a flare. The flare is currently pulled back into the Kaowool liner.

Propane source:

Standard 20lb propane tank with a 0-30psi adjustable regulator and standard flexible line (not ideal I know but once I have the burners working I'll look at hard plumbing).

 

Does it work? Kind of.

It will light and I can get the flame to burn in the flare. I can even heat steel up to forging temp.

However after about twenty to thirty minutes of run time the burner starts to chuff which so far as I can tell is the flame chasing up the burner tube ( carefully peering down the back end of the burner confirms this). 

After reading numerous threads on others experiencing this problem there are several things that can cause this:

1. Regulator freezing up and causing the gas pressure to drop off

- I have tried running the forge with the tank in a bucket of water and still only get about a half hour of run time before things start chuffing.

2. Back pressure from combustion gases cause turbulence and interfering with the propane/O2 mixing.

- Once the chuffing starts I have tried opening the forge up entirely and it seems to help initially but still ends in things chuffing.

3. IR radiation off the opposite wall heating up the flare and the burner pipe causing the propane to ignite in the tube.

- I do have my flare pulled back into the Kaowool though the rim of it is still exposed. I suppose I could get in there with some extra wool and paint to cover up the rim a bit better.

I am not entirely sure how to proceed in troubleshooting. Suggestions are appreciated.

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2 hours ago, Mycelium said:

Standard 20lb propane tank with a 0-30psi adjustable regulator

That is your major problem. There is not enough surface area for the liquid propane to turn into a gas fast enough at high pressures. Putting the tank in water will help with freeze up only.

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So I need to be running off a bigger tank or a different reg?

On 8/14/2019 at 4:57 PM, timgunn1962 said:

Turning the pressure up often works.

I have tried that and it doesn't make any difference that I am capable of detecting.

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Alright, I'll see of I can russle up a bigger tank. My local makerspace has a big tank for the oxy-propane torch.

I've not had a reason to examine it's fittings closely but I might be able to hook up to that for a test run.

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I can run a pair of 3/4" Ts off a 20lb. tank for a couple hours before they start to slush up, that's not your problem.

Who's burner plans did you use or is this something you came up with yourself? 

The things that jump out at me is that long nipple on the intake end. The only practical reason I've ever come up with is to move the jet farther away from the mixing tube. You're eliminated that possible benefit by putting the supply so far down.

On top of that you have a stack of fittings evidently intended to put the jet INSIDE the mixing tube.

It's burning rich in the pics because it can't possibly induce enough intake air, cranking up the psi won't do it the propane stream can't expand enough to make a difference just going faster only means more fuel in the mix.

You might try losing all the fittings below the cross pipe except the bushing with the jet screwed into it. See if that leans it up. The next step I'd try is cutting off as much of that nipple above the cross pipe as I could. 

Remember trouble shooting rule #1. Change ONE thing at a time, test, observe the results, compare to the previous test, take notes and only then make another change. I prefer making several small changes over making one big one.

Try searching out Ron Reil's burner plans I believe they're archived on the ABANA site and follow his plan as close to exactly as you can. Ron and I don't make the same kind of burner but his work well and is a design proven by a good 30+ successful years.

If you want to make a T burner the plans are in the propane burner section of IFI.

Frosty The Lucky.

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I've read through Ron's website a few times actually. As for the running of the gas line through a pipe nipple rather than the bell reducer I've seen in a few places I decided to opt for that as it would be easier to dis/assemble.

Adding the extender fittings actually improved the performance of the burner. With just the bushing that the MIG tip threads into I was lucky if I could get the flame to stay in the flare for five minutes let alone 30 before it started to chuff. The tip isn't quite in the throat of the reducer though. It's maybe half into the body. I haven't tried it with just one of the spacer fittings (there are two). Maybe its a matter of meeting in the middle. TBH, where that fuel injector nozzle needs to be in relation to the burner pipe is what I've been haziest on in the whole build.

Chopping off the back half is definitely another good idea.

I will however test one things at a time and dropping a fitting before I go chopping anything.

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The rule of thumb for jet hold back from the throat is 1/2 the mixing tube diameter. Eg a jet for 3/4" tube should be held back 3/8". This is the departure point and will need adjusting for your build. 

When I build a 3/4" T, the 1" x 3/4" T has about 2x the air intake port size and I run my jet around 1/2" - 9/16" back. My T burners draw a huge amount of combustion air which allows me to run 0.035" contact tips for jets without running high pressure. This results in a LOT more fuel air at a lower velocity. 

There are fundamental differences between a Linear burner like yours and a Jet Ejector like I build. I don't know why they're so much different but they are. The important basics are the same though, a good flame is a good flame and the adjustments are the same in principle. 

Frosty The Lucky.

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Ooookay. I found time to tinker today. First thing I tried was varying the number of fittings between the injection fitting (MIG tip) and the T fitting it is plumbed into. 

I tried running with only one spacer fitting and it gave a unstable burn. The flame would catch in the flare but would start chasing up the mixing tube within 5 minutes.

I opted to go back to two spacer fittings (no spacer fittings also behave unstably last week) which had at least given me a 20 minute burn last weekend. After this I actually broke out the calipers and figured out that with the two spacers and two turns of the pipe nipple the injector nozzle was pretty damn close to 3/8" from where the bell reduces down to 3/4". So that spacing is on spec.

Next thing I tried was hacking a section of off the back of the pipe nipple. Initially this did improve the quality of the flame. Certainly a leaner flame only now the burner won't run stable for more than five minutes and once it's hot I can't get the flame to catch in the flare :/

Additionally I picked up a gauge for my regulator. I ended up with a 0-60psi (the hose fitting guys were out of 0-30) only to discover that the line pressure is actually way way lower than that. More like 1-5psi making the gauge almost useless. The only way we could get a noticable spike was to put a finger over the MIG tip and it would jump to 10psi even with the reg set to 30. I also tried cranking the reg up and down with the burner running and I have to get very close to 0psi before there is a noticable dip in the intensity of the flame. Anything above that spot doesn't seem to affect the flame too noticably.

At this point I'd run out of time and had to pack it in. I guess I might as well hack the rest of the back off the pipe nipple just to see if it improves things? Unfortunately I don't think I'll be able to tap the bigger tank at the makerspace so I don't currently have an option for trying a different bigger tank.

 

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Good Morning,

Some propane tanks have a volume limiter. What size jet are you using? No pressure means you have low flow or too big of jet.

If you are checking the burner without putting it into a Forge, you aren't getting actual results.

If you have a question PM me.

Neil

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Oh hey Neil,

I am using a 0.023" jet as this has given the best results thus far.
I do indeed have the burner hooked up to a forge. It was just easier to photograph off the forge right after I cut the back open.

Is there a way to determine if my tank has a flow limiter? and if so how does one source a tank without one?

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On 8/15/2019 at 12:02 PM, Frosty said:

The rule of thumb for jet hold back from the throat is 1/2 the mixing tube diameter. Eg a jet for 3/4" tube should be held back 3/8". This is the departure point and will need adjusting for your build. 

When I build a 3/4" T, the 1" x 3/4" T has about 2x the air intake port size and I run my jet around 1/2" - 9/16" back. My T burners draw a huge amount of combustion air which allows me to run 0.035" contact tips for jets without running high pressure. This results in a LOT more fuel air at a lower velocity. 

There are fundamental differences between a Linear burner like yours and a Jet Ejector like I build. I don't know why they're so much different but they are. The important basics are the same though, a good flame is a good flame and the adjustments are the same in principle.

This is good stuff, Frosty; you should post it on one of the permanent burner threads, to preserve the advice in a handy place.

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I think it's all in the thread with my original T burner plans. 

Heck, I found out recently I can edit my original PDF on the T build. I could clean the above up some and include it. I need to start working on the plan revision. I just never remember to do it. 

I sure wish I'd done something differently felling that tree.:(

Frosty The Lucky.

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Should I be seeing the same line pressure as what my regulator is set too? I would assume so but maybe this is a counter intuitive thing at there's going to be a pressure drop in the line?

Despite my best efforts googling I can't find any useful source of information on trouble shooting high pressure propane setups. It's all BBQs and residential tanks with none of the articles providing any real information.

Maybe I'm just using the wrong search terms.

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33 minutes ago, Mycelium said:

Should I be seeing the same line pressure as what my regulator is set too? I would assume so but maybe this is a counter intuitive thing at there's going to be a pressure drop in the line?

No, they aren't that accurate, If regulator and gauge are within 5lbs. I'd be surprised. At best they're approximations and seeing as the manufacturers don't think anything's wrong you aren't gong to find problem solving tips. 

You want a high pressure regulator NOT a BBQ regulator. Search, "Propane Warehouse" and look at their adjustable propane regulators, the 1-30 psi reg is about $40. and shipping. This is what you're looking for. They are taller from diaphragm to adjusting knob, the knob being on a shaft and not integral to the regulator body. 

The ones next to them on the page are BBQ and Shrimp pot cooker regs and not so appropriate for the amount of propane a forge burner requires.

They aren't ranked by output volume but a typical forge burner rarely uses 20 psi. but draws enough volume to freeze up a 40 lb. tank in a couple/few hours. 

Frosty The Lucky.

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It's definitely the tank. Might be that it's low but regardless I borrowed another tank and now the burners running a high enough pressure to blow itself out. Going swap out the 0.023 for something bigger to see if I can stabilize the burn.

 

Edit: I am running a 0-30 high pressure reg already.

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Was it empty? If not you probably have one with the safety valve thingy that prevents sudden a propane draw. You can sometimes get around them by opening the flow slowly with the 1/4 turn shut off valve. 

I can just flick my old tanks on but the new 20 lb. tank shuts down if I don't take a few seconds to open the shut off.  The 40 is okay and my 100 lb tanks were old when I bought them. 

Okay, that problem solved, next one please? Tuning's just a matter of reading and tweaking. We'll have you roaring in no time.

Frosty The Lucky.

 

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It was xxxx near empty. Just enough in there for the burners to light but not able to supply the necessary pressure to run hot hot.

Working great now! Thanks everyone for the troubleshooting help : )

Some tweaking will definitely be necessary. I'll have to get in there with some extra Kaowool and refractory paint to protect the flare. I ran it for 40 minutes or so last night and the flare defs got up to an orange heat.

Also had a go at beating out a knife shaped object. Rather crude but felt like an appropriate way to celebrate.

Now for the hard part. Learning to blacksmith :P

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Yep, you gotta have propane to make one work.

Frosty The Lucky.

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The last photo shows the flame impinging on the on an outcropping in the burner port, and being interfered with; cutting away that chunk of material would probably do a lot  for efficiency.

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