Oil Burner Comparisons for melting Iron (Siphon-nozzle/drip/Ursutz)

Discussion in 'Burners and their construction' started by PatJ, Aug 9, 2018.

  1. PatJ

    PatJ Silver

    Some observations I have made about these guys melting iron:

    1. At least two of these guys elevate their crucibles considerably in the furnace with taller than normal plinth block under the crucible, and/or an extension on the bottom of the crucible (ironsides).
    This seems to jibe with the fact that the top area inside the furnace is much hotter than the bottom, since the fuel is mostly completely combusted towards the top of the furnace, and is thus most likely at its hottest temperature.

    2. Porisitymaster does a myth-bust on the statement "very clean iron should always be used for iron melts".
    This statement is a total myth, and porositymaster deliberately showed me how he melts very dirty and very rusty iron, ie: stuff that looks like he got it off the bottom of the ocean, and it produces perfectly cast parts. Porositymaster does do a frequent skim as the melt goes along, and this may not be necessary at all when using clean iron.
    I use to spend a lot of time and effort trying to clean my scrap iron before I used it, and it was all wasted effort.

    3. I do add ferrosilicon to my melt, and I think all three of these guys do the same.
    The ferrosilicon makes the parts machinable, and prevents hard spots (sometimes called chills, although this term also has other foundry definitions so don't be misled).
    Note that I have melted and cast iron without ferrosilicon and also produced cast iron parts that were easy to machine.
    When I did not use ferrosilicon, I used a multi-cavity mold for both larger and smaller (and respectively thicker and thinner parts).
    The thin parts from the same melt/pour/mold were un-machinable, and the thicker parts (perhaps 3/4" thick) were perfectly machinable, so it relates to part thickness and almost certainly rate of cooling too.

    3. Higher mass furnace = slower iron melt and more fuel used for the same amount of iron melted, when comparing the siphon-nozzle and drip-style burners.
    The Urstuz-type burner (one that works correctly), the furnace mass seems to be less important because the average hot air combustion stream temperature inside the furnace appears to be much higher than a siphon or drip style furnace, and the result is a very fast melt with minimal fuel usage.
    As mentioned above, porositymaster actually turns his Urstuz burner down from its maximum so as not to damage his crucibles, so there is a point where too much heat is not useful, and also indicates that there are limits on how fast you can melt a given amount of iron when using the crucible melting method.

    4. Another notable thing is that both ironsides and porositymaster start with an initial charge of iron in the furnace (in the case of porositymaster, the initial charge is with as much iron as can be fit into a crucible without jamming it), and then add iron as the melt progresses.
    My experience with melting iron has shown that if you drop a large chunk of iron into a molten pool of iron, it can solidify the entire melt (not a hard solidification, but definitely a transition from liquid to soft solid), and this can throw off the entire melt in a very detrimental way.

    For my next iron melt, I am going to follow ironside's routine of adding small and relatively think pieces of iron to the melt as the melt progresses, and I think this is one of the secrets of making iron melts successful.
     
    Last edited: Aug 11, 2018
  2. PatJ

    PatJ Silver

    I will try to make a video of the startup of my Delavan siphon-nozzle burner to show how quick and easy it is, and demonstrate that the only variable that really needs to be tweeked is the combustion air flow (once you calibrate your fuel flow to a fixed rate).
     
  3. PatJ

    PatJ Silver

    Lets talk about fuel flow rates.

    I have often wondered about what is an optimal fuel flow rate for an oil burner used to melt iron.

    Using a somewhat typical (for the examples above) furnace size of approximately 13"-14" inches inside furnace diameter, and 14"-16" inside height furnace height, and lets say a #20 crucible, then that gives a fixed amount of combustion volume inside the furnace (with the crucible and plinth in place), and a fixed amount of surface area for the inside of the furnace (including the exposed part of the floor, the walls and the ceiling of the lid).

    Much of the work in heating a crucible in the crucible-style furnaces that we use is done through the transfer of heat radiating from the wall of the furnace to the crucible, and perhaps not so much direct transfer of heat from the combustion gasses.

    When you spray a coat of ITC100 on the interior surfaces of a furnace, there is a noticeable increase in the iridescence of the furnace interior walls, and according to the manufacturer of ITC (perhaps a biased opinion) the increased radiant heat of the furnace wall lowers the amount of fuel used, and decreases melt times.

    What I have observed with oil burners seems to be that there is a maximum fuel flow level that can be introduced into say a 14" dia, 15" tall furnace, and that can be completely combusted before the exhaust stream exits the furnace lid. Any fuel and combustion air flows above this point seem to actually make the furnace run cooler.
    I have experimented with diesel fuel flow rates between 2 and 10 gal/hr.
    The higher fuel/air flows (say above 4 gal/hr) actually seem to make the furnace run cooler and extend the time it takes to melt iron, or even prevent the iron from melting at all.

    I think the explanation is that for a given interior surface area in a furnace, there is only so much air/fuel that can be forced into the furnace and completely combusted (as mentioned above), and so fuel/air flows above this level actually cool the furnace. The Navy Foundry Manual as I recall seems to back up this theory.

    When I watched porositymaster melt iron as Soule, I initially assumed that he was making a mistake, since his leaf blower was set to the lowest speed, and his fuel flow was much lower than I expected (perhaps 1.5 or at most 2 gal/hr). Much to my surprise, he melted iron quicker than I have seen anyone except perhaps ironsides melt iron.
    In the iron-melting world, it seems counter-intuitive that less fuel = more heat and a faster, more efficient melt, but I believe this to be true.

    So what fuel rate am I going to try in my new 14" dia, 15" tall (interior) furnace? (Edit: I measured my furnace a minute ago, and it actually measures 13" diameter and 14" tall, interior dimensions).
    I think I will start with 3 gal/hr, and if that works, then I will try dialing it down to 2 gal/hr and compare the results.

    I think that the most you can push into a 14"x15" furnace with complete combustion and efficient transfer of heat from the furnace wall into the crucible is 3 gal/hr or less.

    How can this be verified? (edit: I tried the thermocouples; they melted).
    I think by using the thermocouples I mentioned previously on the outside of the refractory shell, I can try the burner starting at 1 gal/hr, and increase the fuel flow and associated combustion air flow up to perhaps 6 gal/hr, and then plot a curve on a graph showing fuel flow vs furnace temperature.
    My guess is that the curve will peak between 2.5 and 3 gal/hr.
     
    Last edited: Jun 9, 2019
  4. Jason

    Jason Gold

    I totally agree pat. For a given size of combustion chamber, there is a peak temperature. Add more fuel and it comes back down. Take any piston engine. Set the throttle and measure the exhaust. Now without moving the throttle, lean the mixture. The exhaust temp goes up until you hit the peak. Any further reduction in fuel causes the temp to start going down. In the airplane world, we call this lean of peak EGT. It's a simple bell curve. Only so much air and fuel can be pumped or burned through a fixed chamber. Any deviation in either fuel or air results in lower temps and in my case less power. Engine manufacturers have figured out in my world we lean engines to find peak egt. THEN enrichen them 75degrees. This gives us economy, power and engine longevity. I hear people say lean of peak operations is bad for an engine. Not so, if temps go down, consumption goes down and if it will run smooth and individual cylinder temps can be monitored properly, it's a win all around. The best place for us to run our furnaces is slightly rich of peak EGT. Funny how some things never change. I run my furnace like a piston engined aircraft.
     
  5. PatJ

    PatJ Silver

    Furnace Atmospheres:

    The ratio's of fuel and combustion air introduced into a furnace will determine whether the interior of the furnace is either A) Reducing, B) Neutral, or C) Oxidizing.

    Oxidizing Atmosphere:
    An oxidizing atmosphere is when combustion air is introduced into the furnace in excess of what is required to completely combust the associated amount of fuel being introduced into the furnace.
    As I understand it, this condition is generally avoiding in foundry work due to the reaction that the excess oxygen will have with the molten meltal, and the resultant excessive amounts of slag that can be produced.
    Flames do not exit the furnace lid when you are running an oxidizing atmosphere.
    I think the excess oxygen can also be detrimental to the crucible.

    Reducing Atmosphere:
    A reducing atmosphere is when an excess of fuel is introduced into the furnace, and this amount is in excess of what can be completely combusted inside the furnace.
    The result is that a flame is visible exiting the opening in the furnace lid, and the more excess fuel that is added to the furnace (over and above a neutral burn level), the larger this exterior flame will be.
    The danger of running an atmosphere that is too reducing is that hydrocarbons can be introduced into the melt (as I understand it).

    Neutral Atmosphere:
    A neutral atmosphere is when there is exactly the required amount of combustion air introduced into a furnace to completely combust the associated fuel flowing into the furnace.


    Most of the guys who melt iron here seem to run either neutral or somewhat reducing atmospheres.
    In the past, I don't think I have been consistent with the atmosphere, and if the iron does not start melting in about an hour, I have tended to panic and start adjusting the burner sort of in a inconsistent fashion, with expected inconsistent (and often unsuccessful) results.

    I plan on running a slightly reducing atmosphere when I melt (attempt to melt) iron in the future.
     
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  6. Jason

    Jason Gold

    I prefer rich, peak or lean. Easier for me to remember. I peak and then enrichen a little to keep from running oxidized. My early melts taught me real fast what running an oxidizing mix will do to bronze. You'd be better off running really reduced, but the metal would probably melt or take 2 days.
     
  7. PatJ

    PatJ Silver


    I read a book by Charles Lindbergh called (I think) "The War Time Journal of Charles Lindbergh".
    Lindbergh was extremely anti-war, and he worked long and hard to keep the US out of WWII.
    But once WWII started, he realized that it was all or nothing, since a loss to Germany would be catastrophic for the US and the world.

    So Lindbergh started flying unofficially for the US in the Pacific, actually going on some missions against the Japanese.
    When returning from one of the missions, he noticed that his two wingmen were almost out of gas, even when he still had considerable reserves.
    So he questioned them about their carb settings, and discovered that the official settings by the book and required by the military were way too rich.
    He had a hard time convincing the military that the engines could be leaned out considerably, but he finally did convince them, and the result was that all the mixture settings for all US fighter planes were leaned, saving the US millions of gallons of fuel. Some speculate that this had a significant effect on helping us win the war in the Pacific.

    Lindbergh learned about the optimum mixture settings when he flew across the Atlantic solo, and indeed one of the reasons he was able to complete this trip was due to using a minimum amount of fuel per mile traveled.
     
    Last edited: Aug 11, 2018
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  8. PatJ

    PatJ Silver

    Another aside from Lindbergh is that due to his notorriety after his Atlantic solo flight, he was invited to tour (and sometimes fly) with the most advanced airforces in the world, including those in pre-war Germany.
    Lindbergh widely reported when he came back to the US that the rest of the world had nothing analogous to the Axis military hardware, and especially the breath and width of advanced aircraft types, and that was one of the things that supposedly emboldened both Japan and Germany to attack the rest of the world.

    It was quite a long time before the Allies developed fighter planes and tactics that could effectively counter the highly maneuverable Japanese Zero.

    Edit:
    One big break that the US got during the war was when a Japanese Zero crash landed in a bog in Alaska. The plane went in inverted, and basically skidded to a halt in the soft bog, and so sustained minimal damage.
    https://en.wikipedia.org/wiki/Akutan_Zero
    The plane was recovered by the US, repaired, and test flown.
    It turns out that one vulnerability of the Zero was that the carb would cut out during a hard right or left turn, or perhaps turn/dive combination?
    So our pilots were instructed to take a sharp turning dive to evade a following zero.

    I am sure the flying guys here know this story better than I, but that I think is the gist of it.
     
    Last edited: Aug 11, 2018
  9. Jason

    Jason Gold

    If anyone knew how to stretch a gallon of fuel, it was that crazy bastard. Today's regs are 30mins reserve daylight and 45 night or IFR. I prefer at least an hour under ideal conditions.

    People run rich because fuel is cheaper than too lean which damages heads and valves. Too rich, you might run out of fuel and it washes oil off the cylinder rings. Companies recommending 75degrees rich are trying to help engines make overhaul and avoid liabilities. Look at that crash last week near john Wayne. I saw no fire damage in that photo and thought, uh oh, no fuel.

    I might look into that ITC to speed up melts on my next build. I plan to switch to natural gas and will have to learn all over again.:oops::rolleyes:
     
  10. Melterskelter

    Melterskelter Gold Banner Member


    I tried originally to run my diesel siphon neutral to just a bit lean thinking I'd get quicker melt times. Then I decided to go just a bit reducing mix. My melt times were the same either way and are quite predictable following a sequence from mushy metal to ready to pour varying at most by 15 mins and not related to mix. I think I get less dross when reducing. Last night I noted a lot of sparks as I transitioned from solid to liquid metal. Sure enough, I was too lean and sparks diminished dramatically with slightly richer mix. Also noted a color change last night. Rich mix provided a green tint and leaning out reddish and more sparks (oxidation of iron?). I could not see the color variation in daylight. Where the green comes from I have no idea. FWIW.

    Another observation is that my melt seems essentially independent of whether the crucible is fully loaded or only half.

    Denis
     
    Last edited: Aug 11, 2018
  11. PatJ

    PatJ Silver

    I noticed with my heavy furnace (perhaps 700 lbs) that no melting of the iron occurs until the entire mass of the furnace is up to a very hot condition.

    Comparing my furnace with ironsides (low mass, almost no mass), my melting starts 30 minutes later than his.
    I had no idea when I build my first furnace, and to ignorantly assumed bigger (heavier) must be better.

    I have also noticed that the melt seems to be much slower when the scraps are large and thick, and I am guessing that is basically a surface area effect.
     
  12. PatJ

    PatJ Silver

    ITC100 has gotten pretty outrageous in price these days.
    I think the directions are 1/2 water and 1/2 ITC100 (check me on that).

    It generally comes pretty hard in the container, but will changed into a thin slurry once mixed with the water (I use a kitchen mixer).
    I spray it on with an cheap Harbor Freight sand blaster.

    The coat goes on very thin, and that is the idea.
    Don't spray too much; you don't want it to run, like a light coat of watery paint.
    The very thin coat prevents any possibility of cracking of the ITC100, and that is all you need on the walls of the furnace. If you smear on a heavy putty-consistency coat of ITC-100 on the walls, it will simply crack and flake off over time.

    You can also mix a little of it with water to make a putty to fill thin cracks with.
     
    Last edited: Aug 11, 2018
  13. Does anyone use a diffuser disc or anything like a flame can in their burners?. An simple propane burner I made years ago had a large steel washer attached to the end of the copper gas nozzle to give a small area of relatively still air for the flame front to stay. My testing was done in a steel tube in open air and the flame would not stay lit without the washer. It should be possible to lower the combustion in the furnace a bit more than I'm currently seeing with my particular burners.
     
  14. Jason

    Jason Gold

    Yeah, the natural gas ribbon burner I built utilizes a diffuser disc in the box. It's used to spread out the NG in the box so I get a dozen little flames instead of one flame.
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    I am very interested (as I have previously mentioned in other posts) in making a low thermal mass furnace when it comes times to replace my current furnace. I have a couple questions:

    How far does a pint of ITC go when coating furnace liner?

    Can anyone point m to more information about Ironsides' low mass furnace build. I looked a while for his video but could not find one detailing his build. I did find the one hat gives some furnace dimensions but assume there is a more detailed one somewhere?

    TIA.

    Denis
     
    Last edited: Aug 12, 2018
  16. PatJ

    PatJ Silver

    I would guess that the interior of a furnace could be coated with a pint or less of ITC100.

    Also note that if you do repeat iron melts, the interior (especially the upper half of the furnace) becomes coated with slag splatter, so that will negate the effect of any coating.

    Probably the main reason I use ITC100 or ITC 200 is to fill small cracks and imperfections in the refractory, and this will extend the life of the furnace.
    If you do mainly aluminum, an ITC coat makes more sense.
     
  17. PatJ

    PatJ Silver

    Here is ironsides most recent video where he melts iron using propane:



    It is really all about keeping the propane tank warm enough so that it will vaporize the propane fast enough to maintain sufficient pressure to melt the iron.




    I think this is a smaller version of the furnace he is using now? (he will have to weigh in here and clarify), but I think the materials are the same.




    I had one person tell me that the Zircon coating was outrageously priced, but I found some online, and as I recall it was quite reasonable, although I did not save the link.

    It would be important to contain all of the ceramic blanket so you don't get the fibers blowing up in the air. I would wear a respirator if I operated this type of furnace just in case some of the fibers did go up in the air (you don't want to get fibers in the lungs).
     
  18. PatJ

    PatJ Silver

    Here is another ironsides video about him rebuilding his furnace with the ceramic blanket/zircon coating.




    The beauty of the zircon-coated ceramic blanket is that you don't have to deal with purchasing heavy refractory, mixing, ramming and drying it, and then deal with moving a very heavy furnace around.

    And you also don't have to worry about the refractory cracking, although my guess is you will have to give a light zircon re-coat of the furnace interior every so often, and a complete overhaul every so many years (a refractory furnace also has a finite life).

    The downside is the potential for fibers in the air, but ironsides seems to still be kicking so I am guessing the containment thing works pretty well.

    And ironsides mentions that there are different temperature ratings for ceramic blanket, which I was not aware of, but my guess is that there is only one rating that is readily available (check me on that).
     
    Last edited: Aug 12, 2018
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  19. PatJ

    PatJ Silver

    I have toyed with the idea of building an air preheater, which would be a type of heat exchanger to heat the combustion air before it enters the furnace.

    Edit: Here is the preheater test. It was a failure, and I did not get much temperature rise at all.




    I think ironsides has used this method with propane, and I noticed that one of the new furnaces posted here also used a second tuyere to heat the burner tube, in order to get a preheat effect.

    The Utsutz-type burner accomplishes the same thing as a preheater, but does it with a pre-combustion chamber (combust or partially combust the fuel/air before it enters the furnace).

    The reason have not used this arrangement is the concern with degredation of steel when you continuously blast a stream of hot gasses on it, and also due to the fact that burner arrangements that don't use this method seem to work just as well, although I don't have any data on the air preheater arrangement so I am just speculating unscientifically.

    I do recall ironsides mentioning that he knew a guy who used an air preheater, and he was able to get a much hotter (and maybe faster?) iron melt, so I think there is potential there, but with added complexity and perhaps more maintenance.

    One problem with using a siphon-nozzle and preheated combustion air is that if you elevate the combustion air temperature to say 1,000 F, then you may melt the o-ring in the nozzle, and that is one reason I have not pursued it.
     
    Last edited: Jun 9, 2019
  20. PatJ

    PatJ Silver

    If I were going to build a zircon-coated ceramic blanket furnace, I think I would make an outer shell of soft fire bricks to give a rigid structure, and then install the coated blanket inside of the rigid structure.

    This would allow you to make the floor from coated soft fire bricks, or maybe use hard fire bricks on the furnace floor, especially if you are doing a lot of iron work.

    Edit:
    I would build it like this furnace, but with a zircon-coated ceramic blanket liner for the walls.
    That way you could replace the ceramic blanket liner every so often without rebuilding the entire furnace.
    The insulating fire bricks are very lightweight, and insulating, but the will not stand up to oil burner temperatures by themselves.
    I destroyed this furnace the first time I uses an oil burner with it; it was a total loss.

    Also, my furnace photos below show how not to apply ITC100.
    This was in the days when a quart of ITC100 was dirt cheap, and so I smeared it on like putty.
    But a thick coat of ITC100 just chips off in large pieces.
    You have to thin the ITC with water and spray on one or two very thin coats to prevent the cracking/chipping/flaking off.

    I would make the furnace the same as my current beer keg furnace, with inside dimensions of 13" dia, 14" tall.

    Soft fire bricks can easily be cut by hand using a hacksaw or other type blade.
    Use a dust mask if you power cut one.



    Picture 200.jpg


    Picture 205.jpg


    Picture 209.jpg
     
    Last edited: Aug 12, 2018

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