Acetylene Burner

Discussion in 'Burners and their construction' started by Joe Avins, Dec 20, 2018.

  1. Joe Avins

    Joe Avins Copper

    Does anyone here use acetylene burners for their funaces? I read mostly about propane and oil (and some about natural gas and electric). I would think that acetylene might be desirable for temperature especially for those melting iron, and also introduce less hydrogen per BTU.
  2. PatJ

    PatJ Silver Banner Member

    That was one of my thoughts when I first started thinking about casting metal, because I had used the heating tip on an oxy-acetylene torch to melt steel and pretty much any other metal.

    I recall even talking to the guy down at the gas store about buying oxygen in tanks to inject into the furnace to make it run hotter with propane.

    But now I know what that is a bad idea, and the reason is that a typical iron-rated crucible is rated for 2,900 F, and good refractory is generally in the 3,000 F range for its rating.
    So introducing oxygen with acetylene or propane will just melt the crucible and the refractory.

    A guy names porositymaster uses an Ursutz burner, which is an external combustion burner (burns diesel outside the furnace and then sends 3,800 F (+ -) into his furnace).
    He has a lot of problems with melted plinths, and if his burner is run on the highest setting, he has very short crucible life.

    So you can imagine increasing the furnace temperature to over 4,000 F, which would be easy to do.
    You would have refractory and crucible failures within minutes.

    If they made such a thing as a 6,000 F rated crucible and refractory (that you could afford to buy), then you would have some possibilities with high temperature burners/fuels.

  3. Joe Avins

    Joe Avins Copper

    OK, I see. I was talking about acetylene with air, not with oxygen. Based on adiabatic flame temperatures (°C) from Engineering Toolbox, it seems that air-acetylene is about as hot as oxy-propane. (If this forum software has a table feature I don't see it, so I can't post the table.) The furnace temp reached is not as high as the adiabatic flame temp, but the differences among the flame temps should be instructive. If oxy-propane is too hot then so is air-acetylene.
  4. _Jason

    _Jason Silver

    The next two concerns are cost and material safety. You burn a fair amount of gas heating up a furnace to melt metal. You would need a large tank of acetylene to get any meaningful usage out of it and those are very pricey, especially compared to waste oil and LPG burners. Further, acetylene can become dangerous if you draw too much out of the tank too quickly or if you store the tank improperly. By comparison, propane is quite a bit more user friendly.

    You are absolutely right that acetylene burns much hotter than oil, diesel, and propane, but for our purposes it is generally held to be unfeasible.

    Just my thoughts.
    Last edited: Dec 21, 2018
  5. PatJ

    PatJ Silver Banner Member

    Here are some flame temperatures I was looking at when I got started in castings.

    Common Flame Temperatures

    Acetylene with Air 4532 F
    Acetelene with pure Oxygen 6296 F
    Natural Gas with Air 3562 F
    Propane with Air 3596 - 3623 F
    Propane with pure Oxygen 4579 - 5110 F
    Wood 3596 F
    Kerosene 3810 F
    Light Fuel Oil 3820 F
    Medium Fuel Oil 3815 F
    Heavy Fuel Oil 3817 F
    Coal 3950 F approx.
  6. Peedee

    Peedee Silver

    Even worse would be a flame out, a few people have had 'lid lifters' with propane that woke them up but a flame out with acet would be a bomb!
    Jason likes this.
  7. Jason

    Jason Gold Banner Member

  8. If you pass hydrogen through an electric arc the molecule splits into ionised atoms and will travel a short distance before recombining and giving up the heat. This will get you a flame of 5000 deg C or 9032 deg that's what I want to see: a furnace that burns hydrogen but takes a multi kilowatt electrical input too :eek:. The hydrogen acts as a flux too so stainless steels and exotic metals like titanium would be possible.

  9. Jason

    Jason Gold Banner Member

    I have a turbo torch... It uses just acetylene. It would be plenty to heat up a very small furnace, but I'd never want the fuel bill. Talking to my neighbor the other day, I told him if he ever sees my house on fire, RUN AWAY! Acetylene tanks are dangerous under ideal situations. I should probably have my head examined for keeping it in the garage.

    It's not the actual flame temp that melts metal, but the VOLUME of heat you can produce quickly to overcome the heat loss of the setup that melts metal.
  10. PatJ

    PatJ Silver Banner Member

    I was silver soldering the other night outside the door to my shop, and I heard a strange noise inside the shop, but was not sure exactly what the sound was.
    I know from experience that any time something in the shop makes a strange noise that cannot be immediately identified, this is not a good thing.
    I ran into the shop quickly to find out what made the noise.

    This time was no exception to the "strange noise = bad" thing.
    The diaphragm on the the oxygen regulator had blown out, and oxygen was hissing out of the regulator loudly.
    For a second, I was not sure which regulator was leaking, and I was not sure whether to run or stay.
    I figured that if I ran, and it was the acetylene regulator, then the shop was going to leave the face of the earth when the heater kicked on, and then the house would burn down, and then the wife would kill me, so I decide to stay and chance going up with the shop (better that than having to explain to the wife why we need a new house).

    Turns out it was the oxygen regulator, and I turned the tank valve off.

    It was what I consider a near miss.
    So this coming week I will be relocating the oxygen and acetylene tanks to the remote shed.

    I don't keep propane inside the shop, but rather keep it in the remote shed along with the burner fuel (diesel).

    So be wise and be cautious about where you store stuff; it can leak when you least expect it.

  11. Jason

    Jason Gold Banner Member

    Pat I had one of those horrible freight oxy/ace torch kits. Biggest piece of shit on earth. The hoses dry rot inside of 2yrs.... Well, last summer I was soldiering some hvac stuff and I finally had it. I turned in the 2 little tanks for a B sized acetylene bottle and bought one of these. Best decision I have ever made. No more O2 at my house. This thing sweats stuff together in a heartbeat with silfos. I put the HF torch kit right in the trash can.
  12. Peedee

    Peedee Silver

    It has stuck with me for over 30 years that someday (hopefully never) some poor SOB from the fire service is going to have to deal with cylinders if something goes wrong. The factory I was in they chained up the tanks at the back of the shop, when the Fire Chief did a random inspection he didn't just make a reccomendation he ripped the hell out the MD explaining, with colourful language, what his boys would have to do to get those things out of there (in front of most of the staff).

    They can't stand in a burning shop just hosing down cylinders to avoid blowing half the street, they have to be dragged out.

    Edit: I wasn't have a dig at anybody in particular, we are all pretty clued up here on what is sensible and what is not, just the images that fire guy painted have stuck with me since I was a spotty teen.
    Last edited: Dec 22, 2018
  13. Petee716

    Petee716 Silver Banner Member

    I assume it was age/deterioration that caused Pat's O2 issue. I've never heard of that happening before but of course I'm not super experienced. So was that a fluke, or do regulators need to be replaced/rebuilt at certain intervals?

    I'm starting to become convinced to get rid of acet altogether and convert totally to propane. Between the cost and material hazard it just doesn't seem worth it. I have a small rig with a 2hr O2tank and a B sized acetylene tank. Those Bs don't last long and are pricey. Whenever I'm deciding on which method to use to cut steel I find myself doing the math on the relative cost of gas vs wheels vs ruined blades. I don't use the rig often but it sure is handy when I need it.

  14. Jason

    Jason Gold Banner Member

    When I dumped my little 2 tanks for 1 B, it was an even swap full of gas. What a deal! I hated getting to a job and was forever running low on one bottle. Now I've only got one bottle to worry about. A plasma torch is on my long list, time will tell. Cutting 2inch holes in stainless is not for the faint of heart.:(
  15. PatJ

    PatJ Silver Banner Member

    The regulators I have are standard Victor units, pehaps 40 years old, but in excellent condition, always kept indoors in a clean dry environment.
    I am still using the 40 year old acetylene regulator, but I replaced the oxygen regulator with a new Victor unit.

    I have always been aware that a diaphragm could fail on a cutting torch rig regulator because the instructions say "open the tank valve slowly".
    Snapping the tank valve open slams the diaphragm, and so in the past I have tried to open the valves slowly.
    The oxygen tank has a lot more pressure than the acetylene, and so that probably stresses its diaphragm more.

    But again, best to store the tanks outside in a remote shed.
    Oxygen is not flammable, but it does accelerate combustion, and so a normal natural gas heating unit in a garage turns into a giant blowtorch with pure oxygen around it, and indeed this is how they lost the first Apollo I capsule (and 3 men) during testing.

    I like using diesel as a foundry fuel because if it leaks, it is not really a big problem.
    You can drop lit matches into a container of diesel at room temperature without combustion.
    In fact, diesel on a paper towel only lights reluctantly.
    Waste oil seems to be even more reluctant to light at room temperature.

    There was one guy who was not using a safety valve on the air pressure regulator that pressurized his fuel tank, and his regulator failed, and it over-pressurized his fuel tank, and blew off one of the fuel lines near the funace, which started a large puddle-fire.
    But a large puddle fire is ok in my book, as long as there is no explosion it is easy enough to put out a puddle fire with an appropriate fire extinguisher.

    I do use a 30 psi safety valve on the fuel tank to prevent an over-pressure situation.
    Be prepared as they use to say in the Scouts.

    Last edited: Dec 22, 2018

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