Another melt "learning opportunity"

Will a 1" tube naturally aspirate enough air? Seems I read he smelled of propane when he went inside or was that someone else? If so that is unburned propane:not enough air.

If you've got a lathe and a mill center your jet in your tube. You can see the video posted above a sleeve that is used to limit air with no blower.

Here's my burner, 0.023" MIG tip ($2.00). Shiny part is just a piece of iron drilled through and tapped.



Gauge is off a $5 tire pressure gauge



6 psi propane, burner tube is 1-1/2" and it stays outside of the hot face with no flare.

 

Starting to become clear that I missed quite a few fundamental principles somewhere along the line. Most importantly, the fuel-air mixture is critical to get correct (which, in hindsight, is obvious?), and will vary with different tubing sizes and propane pressures. I can only assume that the folks promoting 'so simple, don't think about it!' are fortunate/lucky with their tubing/pressure choices. And/or I am very unlucky.

Ok, new game plan:

• Must have a propane gauge (did not realize you could just use air pressure gauges!)
• Must be able to adjust air flow (with some kind of collar)
• Must be able to adjust propane flow (regulator, confirmed by downstream pressure gauge)
• Propane injector must be centered in tube/tuyere bore

I should be able to make something akin to what @oldironfarmer posted. Thanks for that! Although I have the tools, don't always have the creative mindset necessary to fabricate from scratch. This is what the hive-mind is for!

@oldironfarmer , your end section there, is that not actually a taper, just...not actually tapered? Like a step up of piping sizes creates a change in pressure because more area, right? Does your burner function exactly the same without that end cap? Trying to determine whether or not I should be including something like that in my design, or not.

Looked at the other designs mentioned, seems like the above principles cover them all. If 10-20psi of propane still isn't enough with this new plan, I'll revisit the Kwiky/diesel route.

 

I just use a straight pipe going into the furnace. The collar on the fire end was internally tapered to help maintain the flame on the tube. The internal taper at the exit helps stabilize the flame. In my furnace I use a cast taper in my burner block to do the same. It would not be a bad idea to internally taper your burner tube, since you have a lathe. Also a good reason to step the end of the burner tube back into your hot face a bit, to make additional flare even though it is a step. I never tried to run my burner outside the furnace without the collar.

My tip holder piece was the end off a joint of oilfield sucker rod. Obviously anything that fills the opening works, or you put the bell reducer on the end (traditional design) with some kind of air control on it.

I light with no air and get a lazy yellow flame, then slowly slide the air open. I run about 10 psi downstream of the valve but I have an 0.023 hole in my tip. If yours is 0.08" a 1/16" drill bit will go in and a 3/32" will not. If you have one, a 5/64" should go in. 0.08" is 12 times the size of mine. I would think you would get by with a couple of pounds of propane, that's all assuming your hole is 0.08". I'm soon to try a 0.035" tip, and then liquid fuel, but I'm new at this too.

Edit: I see Al203 and I were posting simultaneously, so I need to add my burner tube is 1-1/2" O.D. tubing, smaller than I wanted but I am stubborn at using whatever I have if I can make it work. Now my hard refractory burner tile matches. I actually use a ball valve to regulate the propane because I have a long hose from a 200 gallon tank. My regulator on the tank is set at 20 psi.

If you look closely my nozzle tip is just downstream of the air holes. Air slots can get you more air area, and triangular slots can give you a wide range of adjustment. I put a clamp on my air slide but never use it, it stays in place nicely by gravity and makes for quick adjustments. It is larger than the pipe and I find tightening my clamping set screw changes the air setting.

I'm still struggling with air setting. I get a distinctly green flame with less air and have settled on the point where the flame turns full blue. Comments?

 

I will add that the nice thing about welding tips is they screw in and are cheap.

I tried drilling one and broke my drill bit. Not much of a machinist but they aren't soft either. I was quite surprised, I had drilled half way through.

 

Here are some BTU charts for the Hybrid burner.

Not sure exactly what the data means, but the output appears to be somewhat linear, ie: the curve is somewhat straight above a certain gas pressure.

http://www.hybridburners.com/BTU-charts.html

Edit:
Comparing the burner sizes all at 10 psi pressure, the larger burner produces a lot more heat, so I guess the orifice is getting larger as the burner tube gets larger, and with a larger burner tube there is more combustion air, and the fuel usage I guess is proportionally increasing for a fixed pressure.

Edit2:
There is a fuel usage chart on this page for the various Hybrid burners:
http://www.hybridburners.com/products.html

This chart appears to be almost linear (not exactly, but close), ie: for about 4 times more heat, you burn about 4 times more propane.
The largest burner appears to be more efficient than the smallest one., comparing fuel per BTU.

 

For what it's worth, the actual tuyere tube is 2" OD - was just the burner tube that was 1". I have some pieces of stock that can be made to work - 2" mystery ferrous metal, and 1.5" 1014? mild steel.

As for what I want, well, I do want to melt bronze at some point. Iron is kinda scary, but that's also something I wouldn't mind being able to do down the line. For the next year just aluminum.

Does that change anything? Just make a bigger version of what OIF posted? Gonna draw up some ideas in Sketchup.

 

Here's a rough drawing of what I have in mind, based on my limited abilities.

• Light blue tube at left is the tuyere itself (in above pic)
  
• Silver piece slides into the tuyere tube, loose slip fit
• Dark blue piece will be loctited into the silver
• Light blue piece on the right will slip fit into dark blue, have a set screw

Using mig tips will, as you mentioned, allow flexibility in port sizing, and I have a few spares lying around anyways - I think .023 or .030.

Seem reasonable?

 

You will want a burner tube approximately 12" long, or perhaps a little longer, ie: like the Sidearm diagram.
For your sleeve into the tuyere, let that be the flair on the end of your burner tube, and it can be an easy slide into your tuyere tube.

The flair must be close to the inside of the furnace lining; perhaps within 1/2" or slightly less, otherwise you will have flame inside the tuyere tube, and the burner can turn bright red and overheat.

It there is too much clearance between the flair and the tuyere tube, you can get flame blowback, which can heat up the burner tube, and potentially melt the hose.
But the fit does not have to be tight; just a sliding fit, allowing for metal expansion when things heat up.


I don't like to use a pressure gauge up near the furnace, since that area can get very hot sometimes, and the gauge is subject to damage getting banged around with the burner as you transport it..
I use a pressure gauge back at the tank on the output of the regulator.

A acetylene regulator is approved for use with propane, and that is what I use.
This is a deluxe setup, and not required, but works great, especially if you already have one laying around.
It gives you both primary and secondary pressure in one device.
And an acetylene regulator screws directly into a propane tank; no adapter required.



Brass/bronze should not be a problem with this burner.
If your propane tank gets too cold to allow enough vaporization, it can be placed in a bucket of water.

For me, if the propane tank has so much flow that it is always getting too cold and the pressure will not stay up, then it is time to change over to an oil burner, since oil eliminates this problem.
I have not had propane tank cooling problems with aluminum.
You can melt iron with propane and forced air, but you need either a large propane tank, multiple propane tanks, and/or a way to keep the tanks warm to keep the pressure up.
Propane is not a good way to melt iron in my opinion, but it can be done.

For melting iron with an oil burner, you will need 3,000 F (or higher) rated furnace refractory, else the interior of your furnace will disintegrate rather quickly.
Iron is much more difficult and time consuming than aluminum, but once you figure out how to do it, it is achievable (with the right refractory and crucible; iron rated).
Melting iron is hard on the furnace and crucibles, and so your furnace/crucible will not last almost indefinitely as it will with aluminum melts.

 

PatJ is saying your dark blue piece needs to be a piece of pipe or tubing at least 12" long. If you put your gauge on the burner that also gets it away from the furnace.

So far my burner tube stays cool but I may have to plug the gauge hole (or make another burner) as I go to higher temperature materials. since my tank is 30 ft or more away I would have to put a manifold in away from the burner to get a local pressure gauge.

I altered my burner to take an 0.045" tip today. I was wrong, it had an 0.035" tip. Sometimes I have to run with wide open air so I elongated the air holes.



Puts out a lot more heat. Started out at 10 psi and got the furnace very hot. To get similar heat I lowered the propane from 10 psi down to 4 psi. I ran four heats in two hours and made 33 aluminum muffins. Hopefully this will let me melt brass and bronze, maybe copper too.

 

Ah, going back and reading the drawing, it's "9D" for length - that answers my question. The left-most light blue piece extends a good 8" into the furnace. I think maybe the best thing here will be to pick up some pipe with a 2" OD, turn it down to fit inside the tuyere pipe, and then make the "dark blue piece" the same way @oldironfarmer made it.

@PatJ - I'll ensure the gauge is far enough away - thanks to the sand, the outside barely gets even to the point where I can't touch it with bare hands, although I might have a spare acetylene gauge lying around...good to know!

Also, the refractory is indeed 3000F, and I use a graphite crucible. I had planned on getting a dedicated iron crucible at that point, knowing what the heat does to stuff.


Thanks guys, I will update this thread once I have some time to execute on these ideas. Life is busy!

 

I think he is saying he is only going to make a sleeve out of 2" pipe, the "silver" piece in his nice drawing. He didn't mention diameter of his burner tube, so I think your post will help in that.

Like I mentioned earlier, I found my existing nozzle to be 0.035" when I went to change it. I really appreciated PatJ's link to Hybridburners as I had seen that site years ago and had lost the link with a computer crash, didn't know the site name. Having an existing burner with tuyere diameter set I made good use of the spreadsheet to determine BTU expectations. It meant nothing to me before because I didn't have a feel for BTU requirements to get to melting temperature in a reasonable time. For reference, my furnace does nicely at 50,000 BTU/hr and I can easily go to 100,000 BTU/hr.

With my four 3/4" holes for air and 1-1/4" inside diameter (actually about 1.2") I had about 1-1/2 air opening over tube area (it's a bit better because I ignored the increase in hole size due to the curvature). With the additional 1/2" I slotted the air openings it's now about 1.9 times burner tube area.

I had been running full air occasionally so with your suggestion of what air to tube ratio should be I checked and added enough to approach 2x. Thanks.

I have a 200 gallon propane tank so tank freezing is not a concern for me. I also get propane at the best possible price (truck delivery, late summer fillup when they run a promotion). I'm still heading for a liquid burner.



The tank is about 30 feet away, downhill for safety, and I run a hose with propane rated quick disconnects up to the furnace.