An early siphon-nozzle burner design

I am putting this here so I can reference it.

This was an early design, somewhat a prototype (thus the very rough features), and it included an adjustable mast (there is a screw with a handle that secures the height), a quick-release on the burner interior parts (the vice-grip releases the internals), and a carry handle on top.

I don't use the PVC ball valve any more; those inevitably melt sooner or later.
The PVC valve could be better used positioned closer to the blower and away from the heat.

I hope to make a more refined version of this burner at some point.

 

Here is a later model burner I built using muffler pipe.
This is the unit I will be using with my new low(er) mass furnace.

I think it is 2.25" diameter, and it is quite a bit lighter than the one above, and flows more air than a 2" schedule 40 steel pipe.
But the main reason I went with a 2.25" diameter muffler pipe is so I could easily fit the elbow fitting into the pipe.

I need to add a carry handle and a stand, and work on the slide-out feature to improve it.

The reason I use the slide-out feature is because I have started to seal the burner tube to the tuyere with furnace cement to prevent blow-back of flames around the tube.
So I leave the burner tube cemented to the furnace at all times, and just slide out the burner interior.

I ended up using three legs on the end of the center air tube to center the nozzle in the tube.
The photo shows two legs, but I added one.

 

This is a photo of the second burner in use.
You can see it on the left side of the furnace.
I was trying a dual-180 degree siphon nozzle burner arrangement.

The dual-burner setup did not produce any measurable improvements, so I have gone back to a single burner arrangement.
Since the left burner was a slave unit, it did not have all the valves that the one on the right had, but I have since added needle and ball valves to the second (muffler-pipe) burner.

I don't use PVC valves for combustion air control any more, since I got a leaf blower that has variable speed.

And I was using a rubber fitting on the left burner to allow retracting the interior, and have changed that to an aluminum sheet metal wrap with clamp on one side only.
It is a snug enough fit that I don't need a second clamp, and can retract without having to un-clamp anything.

 

Whats that nozzle? (nice welding....)

 

Its a Delavan 30609-11, nominal 1 gal/hr, but it can be pushed to 5 gal/hr or more, but the manufacturer recommends a 4:1 range.

I used the tombstone Lincoln stick welder set on 40 amps, and a 1/8" Washington Alloy 6011 rod.
Its not a pretty weld because the rod has to be moved around a lot to prevent a melt-through, but it is a solid weld.

Stick welding thin metal is a bit of an art, but I can do it with the Washington Alloy rod.
I tried a Hobart rod and could not do it with that.

 

Next time you need something like this done, shoot it to me, I'll tig it for ya for nothing. If I had tried that with a stick welder, there would have been nothing left.

 

I have had my eye on a nice tig welder for many years but just can't justify it when I can do it with a stick.
I will keep your offer in mind; thanks.
I need to make up some plausible excuse for the wife why I need one.
She always says stuff like "Yeah but you needed an xyz last month for the same reason".
I am running out of excuses; she is on to me.

 

I saw some adorable welds on heavy aluminium (truck chassis) a few days ago, I actually stroked them during a tour/interview of the plant. Lots of 3phase grunt and a bloody good welder.

The dual burner didn't add anything? I'm not question you but what was your take on why?

 

The problem I was having when using a single oil burner was with excessive melt times for cast iron.
Sometimes the melt would take several hours, and the time was way over what it should be.
Some of that was just my total lack of knowledge about what I was seeing the iron melt do, not skimming slag when I should have, not knowing what was slag and what was molten metal, and not understanding how to tune an oil burner.

I figured dual burners would really speed up the melt times and overcome any shortcomings with a high-mass furnace, but alas it was not to be.

There are some commercial furnaces that use dual burners, and in theory the dual-burner concept is a good one, since it produces a very even flame low in the furnace, but theory and the reality of backyard casting can be two very different things, as I have discovered.
After trying numerous siphon-nozzle burner configurations and fuel flow rates, the conclusion I have reached is that it is not so much about the burner configuration or type, or even how many burners (this applies to a backyard-sized furnace, not a big commercial unit), but rather it is about the mass of the furnace.

A secondary issue is getting a burner tuned correctly to produce maximum heat, and it has always be difficult for me to judge when I have an oil burner producing maximum heat, since I have not figured out a good way to measure the furnace heat (I have contemplated measuring temperatures on the back side of the refractory shell in my new furnace, and I may yet try that).
Oil burners can be very deceiving, and an oil burner that is producing maximum heat does not necessarily look like it is producing maximum heat, because there is no flame coming out the exhaust; the exhaust is perfectly clear; ie: combustion is reaching 100% inside the furnace.
There is a tendency to judge a burner output (by me anyway) by the reflection of radiant heat towards me when the burner is running, but what feels hottest to me is actually unburned fuel coming out of the furnace and then combusting in the air, and so the furnace is running cold with partial combustion inside the furnace (not a good thing).

The final nail in the dual-burner coffin was porositymaster's Ursutz burner at Soule this year.



This burner melts iron like it was butter.
This burner is a good example of complete combustion of the fuel inside the furnace, and it does that because the combustion process actually begins in the burner and is partially complete before it ever enters the furnace.
Even it the Ursutz burner completely combusted all the fuel while it was still inside the burner chamber, it would still deliver a hot gas stream that was in the 3,800 F range into the furnace (3,800 F is a published common flame temperature for fuel oil).
I believe porositymaster's burner could be delivering a temperature approaching 3,800 F into his furnace because when the burner is operated at its full level, it tends to melt the steel tube that goes into the tuyere, and it also ruins a Morgan clay-graphite crucible in very short order.
A Morgan clay-graphite crucible is rated for 2,900 F.

While I would not use an Ursutz burner due to the degradation of the burner metal as it operates, the speed at which it operated (and he did not even have it running flat out during the video above) sort of drove home the point that a backyard-sized furnace does not need two burners to quickly melt iron.

So my low(er) mass furnace will either prove or disprove the "furnace mass is the critical factor" theory.
I am confident that my new lower mass furnace will melt iron easily, judging by the intensity of the heat inside of it while I was drying it out (when I turned the burner to 100% at the end of the dryout session).

Ironside's furnace further drives home the point that a low mass furnace (he uses a high-temperature rigidizer on top of ceramic blanket, for a very low mass furnace) makes it easy to get iron to a hot pouring temperature, and with a single modified drip-style oil burner.

Scavenger uses a high mass furnace with a single siphon-nozzle oil burner, and his melt times and oil usage are higher than ironsides and porositymasters, so that sort of reinforces the point that melt speed and fuel usage are directly linked to furnace mass.

So to make a long story long, you only need one burner for a backyard furnace, unless you build a really big furnace.

Edit:
I am not sure if porositymaster's furnace would be considered low, medium or high mass, but I would consider it somewhat low mass just due to its size and the refractory thickness.
I also suspect that his refractory must be somewhat insulating, else that stainless steel shell would act like the mother of all heat sinks, and clearly it does not (his melt times are as fast any any I have seen posted).
To some extent, porositymaster's iron melts are about the burner performance, not the furnace mass, but I think in his case it is a matter of a high-performance burner and a relatively low mass furnace combined.

Edit02:
Another thing I have noticed with guys who successfully do a lot of iron melts is that they all seem to elevate the crucible quite high in the furnace, using a much higher plinth than I have ever used, and this makes sense because you can see in my furnace dryout photos that there is a large cold spot in front of where the burner enters the furnace, and this is due to the air and fuel not being combusted yet, so creating a cold spot low in the furnace. This effect is clearly visible in the photo below.
So a tall plinth would put the crucible up where combustion was more nearly complete.
With a totally hot furnace, this effect is not as noticeable, but still you are introducing ambient air low into the furnace, and it will be at ambient air temperature.

 

My thinking is 2 oil burners would be a PITA. I'm still considering a dual burner rig for my next setup. Except it will be natural gas through a pair of ribbon burners. The million dollar question is will my NG supply at my house handle it? I recently flamed out my cheapy gas heater in the garage when the house furnace AND the water heater all decided to run at the same time. Whoops... lol

 

I have seen jewelers use dual burners on their small furnaces, but I think that is a matter of being able to use double the output of a standard low-output propane torch, and thus could greatly speed up a melt.



Here is a furnace for sale that has dual burners.
In this case, duel burners are not necessary because one burner can easily produce the same output as two burners.
https://www.ebay.com/itm/Foundry-Furnace-Propane-HD-2-Hi-Temp-2-burner-Melts-Gold-Silver-most-metals/282797247267?_trkparms=aid=111001&algo=REC.SEED&ao=1&asc=20131017132637&meid=e6b8a40e1ec347279687ad1bb5488362&pid=100033&rk=1&rkt=2&sd=282797247267&_trksid=p2045573.c100033.m2042


I just don't think a case can be made for using dual burners in a furnace that is less than or equal to about 15" diameter and 15" tall (interior dimensions), but I have been proven wrong on so many topics, so feel free to debunk this idea.
About the best I can do these days is throw out theories and see if they stick, and find out whether ironsides, porositymaster, scavenger, and others will debunk them.

My theories are just that, theories, but I hope to translate some theory into some serious iron melting in about a week.
Either way I will publish what I learn so that perhaps we can come to some sort of accepted consensus about iron melting and what is the best way to go about it.

 

Food for thought based on the theory behind combustion, not necessarily experience with foundry systems.

1. Our furnaces are basically a combustion chamber, any fuel burned external to the furnace is actually reducing the flame temp in the furnace.
2. the initial volume that the fuel is being vaporized in is at a substantially lower temp then the actual flame temp.
3. the 3800F flame temp is based on combustion with limited excess air. for nozzle type burners it is normally accomplished with flame retention burners. any excess air lowers the flame temp. as it mixes unburned air into the flame.
4. Nozzle burners need room for vaporizing the spray cone that generates the flame, this distance on a Hago or Delevan is about 6" to 10" depending on GPM. A flame retention burner design reduces this by about half. The higher the atomizing air pressure the longer the distance is. that is why we really need to stay with the GPM rating on the nozzle rather then forcing much more then double the GPM. In our crucible furnaces the area is being disrupted by the plinth. A nozzle furnace should have substantially more room at the bottom of the furnace for vaporization and flame breakdown. Ideally we would have combustion chamber prior to the furnace.
   1. the vaporizing is happening external to the furnace with drip style burner the flame is @ the 3800 when it enters the furnace.
5. If you want to see the effect of the furnace mass, check the time between the initial melt and the second melt, the furnace mass will be the difference.
6. Just a terminology clarification. Atomization is a mechanical process of breaking down the oil into smaller droplets. Vaporization is a heat process of converting a liquid into a vapor or gas. This heat is taken from the initial flame and cools it until the oil is completely vaporized. once the oil is vaporized the remaining flame temp will be at the 3800 unless lowered by excess air.

Art b

 

The meter on a residential system should be able to handle about 600kbtuh, The pipe sizing between the meter and the burners is normally the limiting factor. I fire up to about 350 kbtuh without problems even when the furnace and water heater are in operation. That is a total of about 500kbtuh on the meter.

 

I really need to put some temperature probes behind my refractory shell in several places, and at several levels.
That is the only way I know to be able to measure what is going on inside the furnace without having a high-temperature-rated pyrometer.

I did see a furnace the other day that had a swimming noodle inserted at the burner level and wrapped around the furnace (during the ramming of the refractory) to produce the combustion area that Art mentions.
I forget now who's furnace build that was. Anybody remember who did that?
Seemed like a great idea, but I just saw it a few days ago.

I wonder if preheating the oil would improve burner performance.
I know that any liquid spraying tends to have a cooling effect.

The Delevan -11 siphon nozzle is nominally rated at 1 gal/hr, but it is commonly pushed to perhaps up to a maximum of 6 gal/hr by myself and others such as scavenger.
Scavenger has too much success to say that you can't push a siphon nozzle at least 4 times its nominally rated output.

But perhaps operating a siphon nozzle within its rated flow rate makes it more efficient?

I was surprised that porositymaster used his leaf blower on the lowest speed.
That seemed to be counterintuitive, at least to a person with my limited knowledge about thermodynamics.
I tend to make the mistake that bigger is better and more compressed/combustion air and fuel is better and hotter, and that is clearly not the case.
I think porositymaster's fuel flow rate was 3 gal/hr, and I would have guessed that with his very fast melt times, he would be using far more fuel flow, and much more combustion air.

I really had to re-think everything I thought I knew about oil burners after seeing porositymaster's burner in operation.

 

That is a very good point.

I asked porositymaster about that, and his response was that he never does back-to-back melts, and so the initial melt time is all that matters to him.
I feel about the same way.
I don't anticipate doing back-to-back pours; one melt/pour uses about 150% of the daily energy that is in my body.

But I remember that porositymaster did say he could do a second iron melt in like 12 minutes (using a #6 crucible), which seems extremely fast, but I tend to believe what he said.
He is not prone to exaggeration, and everything he told me prior to his melt went off exactly as he said.

 

I didn't intend to say that you can't fire them at a higher rate , its that the vaporization zone gets larger due to the larger droplet size at the higher flow rates. If the furnace has enough combustion area inside it would work ok. the larger rated nozzle shortens the vaporization zone at any given firing rate. a 3 gpm nozzle firing @ 3 gpm will have a smaller vaporization zone then a 1 gpm nozzle firing @ 3 gpm. The actual flame zone would be the same size once vaporized.
The dual burners probably would provide what was being anticipated if the combustion zone for each burner would have been large enough for complete vaporization to happen below the level of the bottom of the crucible.

Art B

 

Thanks, the flame trainer was a guy on AA who went on to start building CNC kits, now well out of casting but had a great set up. Search flame trainer on AA and it should pick it from the archives.

Great discussion.

 

I had to visualize that, but yes it would provide the needed vaporization space below the bottom of the crucible, the balance of the furnace could be the same size as would be used with propane or natural gas, firing at the same BTUH.

 

That is interesting to say the least, and makes a lot of sense now that you point it out.

Something else I discovered is that the pumped nozzles can be purchased with different cone angle, but the siphon nozzles seem to all have a fixed cone angles, which seems to be pretty narrow.

 

I am looking for that swim-noodle furnace design and not finding it.
That design makes some sense though because that is the shape of a volute blower housing that is commonly seen in industry, and so perhaps a good reason to use it?

But I am turning up all sorts of old threads that I have never seen on AA.
I went to the "Burner Engineering" section, in the "Show Threads" box I checked "from the beginning", "Show Thread", and then went to the last page.
There I found a bunch of discussions from 2005 about burners, including glumpy's post from 2005 asking how to make a burner (he has been at the big flame thing much longer than I thought), and a bunch of discussions from Lionel himself.
I was not aware that Lio had ever been active on AA.
His screen name was "imported_Lio".

Lots of information there, and occasionally a post that has visible photos (photos that survived the "pb photo-nuke of 2017" as it came to be known).
Wow, I wonder where all those guys are now and if they still do metal casting.
Anon, einstein, essej, r4z0r7o3, machinemaker, adam zeigler , voyeurger, 4cylndrfury, greencheapsk8 (blast from the past).

Discussions of Ursutz and every sort of burner; its all there, and all pretty well hidden and lost forever.


I will keep looking.