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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#41
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
Thanks for clearing it up.... That sucks even worse.
Rob Fraser Competition Engines Chicago, IL. "Siggy" wrote in message . .. Lung cancer. |
#42
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
* wrote:
wallster wrote in article ... I was watching Discovery channel's "American Chopper" last night. In the past, I've read threads about the disregard of welding helmets while tack welding, eye protection while grinding, etc. Last night they out did there lack of safety by filling a balloon with acetylene, setting it on the ground, pouring gas to it and lighting it. No disclaimer regarding safety either. Hopefully some yougster won't think that was cool and try it at home. The fact that filling a balloon with acetylene is really dangerous (static electricity and kaboom... off with those fingers, hand, face...) then lighting gasolene (indoors too!) WOW!, makes jackass look like brain surgery. I posted a warning on the the shows forum board. Did anyone else see this show? walt While I certainly do NOT condone such activity, I find it somewhat puzzling that this subject was never brought up when the late metal master "Roy" used to set off upside-down coffee cups full of acetylene on the American HotRod program. Maybe everbody was hoping Boyd might be walking by when one went off????? I havent Seen the Chopper episode but in the hotrod episode roy makes it obvious hes up to no good, Having never had highschool to teach me that trick i thought that was the O2 that blew up the coffee cup that forcefully So yes i've been led astray but i'm also smart enough to not do it in my shop. |
#43
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
On Tue, 17 Jan 2006 15:20:49 +0000, David Billington
wrote: When I was a student one of the others on the course filled his lunch bag with OA mix and lit it. Bang, the lecturer and others went in to see the kid standng there dazed but unhurt. The lecturer didn't bother to tell him off for being that stupid, he reckoned he learned a lesson and wouldn't do it again. The instructor in my first gas welding class was giving the orientation lecture in a gymnasium- sized shop. We were gathered around a steel assembly table. While giving us the standard safety lecture he was fiddling with a Styrofoam coffee cup. He poked a hole with a pencil and set it top down. A bit later he lit his torch, adjusted for a nice neutral flame, and then wiped the flame out. He held the flowing gas to the pencil hole and then relit the torch. He said, "Now, listen!" and held the torch to the hole. Fortunately, I had no class immediately after, because it was several hours before I could hear clearly again. A more graphic demonstration of the extreme explosive power and brisance of a perfect oxy-acetylene mix would be hard to imagine. That was the sharpest CRACK I have ever heard, and I have been within 50' of a lightning strike that converted the top six feet of a telephone pole to toothpicks. -- --Pete "Peter W. Meek" http://www.msen.com/~pwmeek/ |
#44
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
See my other post for more detail. In summary: Pure acetylene at 15-ish
pounds doesn't "burn", a process which does indeed require oxygen. Instead, it "deflagrates", a process of chemical breakdown that has no need whatsoever for oxygen to be present in order to happen. (presence of oxygen may in fact inhibit deflagration in some cases) The only commonality between the two processes is that they both generate a lot of heat. I read your other post. Thanks, very informative. But, I have a question. If acetylene "defagrates" at around 15 psi, how do they get it into my tank at 250 psi or more? |
#45
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
Dave Lyon wrote: See my other post for more detail. In summary: Pure acetylene at 15-ish pounds doesn't "burn", a process which does indeed require oxygen. Instead, it "deflagrates", a process of chemical breakdown that has no need whatsoever for oxygen to be present in order to happen. (presence of oxygen may in fact inhibit deflagration in some cases) The only commonality between the two processes is that they both generate a lot of heat. I read your other post. Thanks, very informative. But, I have a question. If acetylene "defagrates" at around 15 psi, how do they get it into my tank at 250 psi or more? I am sure someone will correct me if I'm wrong, but I think that is the reason for the acetone and matrix in acetylene tanks. It helps to stabilize the acetylene and prevent(or at least limit) this problem. JW |
#46
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
"jw" wrote in message ups.com... Dave Lyon wrote: See my other post for more detail. In summary: Pure acetylene at 15-ish pounds doesn't "burn", a process which does indeed require oxygen. Instead, it "deflagrates", a process of chemical breakdown that has no need whatsoever for oxygen to be present in order to happen. (presence of oxygen may in fact inhibit deflagration in some cases) The only commonality between the two processes is that they both generate a lot of heat. I read your other post. Thanks, very informative. But, I have a question. If acetylene "defagrates" at around 15 psi, how do they get it into my tank at 250 psi or more? I am sure someone will correct me if I'm wrong, but I think that is the reason for the acetone and matrix in acetylene tanks. It helps to stabilize the acetylene and prevent(or at least limit) this problem. JW OK, I've done a little research (very little) This is what I've found from http://en.wikipedia.org/wiki/Deflagration Deflagration is a process of subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Deflagration is different from detonation which is supersonic and propagates through shock compression The best I can tell, deflagration IS combustion. Combustion REQUIRES an oxidizer of some sort. If I'm still wrong, please point me to a site where I can learn more. |
#47
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
"Peter W. Meek" wrote in message ... On Tue, 17 Jan 2006 15:20:49 +0000, David Billington wrote: Snip A more graphic demonstration of the extreme explosive power and brisance of a perfect oxy-acetylene mix would be hard to imagine. That was the sharpest CRACK I have ever heard, and I have been within 50' of a lightning strike that converted the top six feet of a telephone pole to toothpicks. The neutral flame is so important to the db level. What's that? I can't hear you.... Tom |
#48
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article mctzf.740907$xm3.31868@attbi_s21,
"Dave Lyon" wrote: See my other post for more detail. In summary: Pure acetylene at 15-ish pounds doesn't "burn", a process which does indeed require oxygen. Instead, it "deflagrates", a process of chemical breakdown that has no need whatsoever for oxygen to be present in order to happen. (presence of oxygen may in fact inhibit deflagration in some cases) The only commonality between the two processes is that they both generate a lot of heat. I read your other post. Thanks, very informative. But, I have a question. If acetylene "defagrates" at around 15 psi, how do they get it into my tank at 250 psi or more? Dissolved under pressure into the acetone soaked into the cylinder media. As I understand it, your standard acetylene cylinder only has a couple teaspoons worth of "free" acetylene at high pressure in it at any given moment - an amount insufficient to sustain a deflagration reaction to the point where it could be dangerous. When you draw that amount, however much it is, out of the tank, the pressure in the tank drops, allowing more acetylene to "boil" out of the acetone, rebuilding the pressure, lather, rinse, repeat until there's no more acetylene (or at least not enough to be useful) left dissolved in the acetone. Even if that small amount of "free" acetylene was enough to get a small deflagration reaction going, the resulting pressure increase makes it self-damping, since the rising pressure forces more more acetylene into solution with the acetone soaked into the cylinder media, keeping it from being able to participate in and help perpetuate the deflagration reaction. The "boiling" process isn't the result of heat, but a drop below the pressure needed to keep the acetylene dissolved in the acetone - Kind of like taking water to very low pressure. At the right pressure for the temperature, you can get a "full rolling boil" going in a container of water at any temperature above freezing. You won't be able to *COOK* anything with it, but it'll look exactly the same as the pan of water boiling away merrily on the stove at 212 degrees F. Acetylene "boiling" out of solution to replace what you've tapped out of the cylinder is exactly the same mechanism in operation, just working on different materials. Additionally, acetylene cylinder are *NOT* hollow cylinders, the way oxygen and other cylinders are - If you were to break one open somehow (HIGHLY not recommended outside of properly equipped facilities - unless you *WANT* to die) you'd find that it's almost entirely filled with a highly porous block of something that looks much like concrete. This "rock sponge" is what soaks up the acetone that the acetylene dissolves in, preventing you from getting spits and spurts of raw liquid acetone coming out the end of your torch. Gaps and voids in it are a certifiable Very Bad Thing(TM), which is one of the (if not the main) reasons that dropping an acetylene tank any distance is a Bad Thing(TM) and grounds for having that tank pulled from service and stored someplace "bomb-proof" until it's been inspected and tested to be sure the "stuffing" is still intact and working as intended. If you ever get handed a cylinder that "rattles when rocked" (something *INSIDE* the cylinder rattling, not "stuff attached to the cylinder") immediately hand it back - *GENTLY* - and demand another one. The "rattler" almost certainly has damaged media in it, and is unsafe. It's unlikely, due to the pre-fill inspection, that you'll ever get one, but "unlikely" and "impossible" aren't equal. Unlike oxygen or other tanked gasses, filling an acetylene cylinder is a fairly time-intensive task - They don't just hook it up to a supply and open both valves then wait for the pressure to equalize - They have to let the fresh acetylene into the cylinder at a relatively slow rate so that it gets a chance to dissolve into the acetone. Depending on the size, filling one properly is a process that can take anywhere from a couple hours, to several days, or even longer for really monster-sized ones. Failure to fill properly can easily result in a bomb that's ready to go off at any moment, in response to any (or no apparent) provocation. Which is why, when you take an acetylene cylinder in to be refilled, the most common practice is to simply hand you another one, and put the one you brought in over with the rest of the "needs to be refilled" ones, rather than filling your cylinder "while-u-wait". If you want *THE SAME CYLINDER* back, you're going to have to wait for a while. But since the places that fill them have to inspect, certify, etc. etc. etc. every cylinder that goes through, "This other randomly selected cylinder of the same capacity" is effectively identical to "The cylinder I own and brought in to be filled", even if it isn't actually the same cylinder. Which means, in effect, that when Joe Sixpack "buys an acetylene cylinder", he's not really buying the cylinder itself - he's buying the right to use any single member of a "pool" of who-knows-how-many of that size cylinder, any of which is effectively identical to the one he "bought". -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#49
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
"jw" wrote in message ups.com... Dave Lyon wrote: See my other post for more detail. In summary: Pure acetylene at 15-ish pounds doesn't "burn", a process which does indeed require oxygen. Instead, it "deflagrates", a process of chemical breakdown that has no need whatsoever for oxygen to be present in order to happen. (presence of oxygen may in fact inhibit deflagration in some cases) The only commonality between the two processes is that they both generate a lot of heat. I read your other post. Thanks, very informative. But, I have a question. If acetylene "defagrates" at around 15 psi, how do they get it into my tank at 250 psi or more? I am sure someone will correct me if I'm wrong, but I think that is the reason for the acetone and matrix in acetylene tanks. It helps to stabilize the acetylene and prevent(or at least limit) this problem. Deflagration is what you _see_ but not what happens. Deflagration merely describes a "burning with a flame" situation, but doesn't describe what's occuring chemically. It first polymerizes, then dissociates, often explosively. Dissolving in acetone prevents the polymerization that starts the reaction. But I've always wondered HOW THE HELL they keep that little bit of acetylene in the neck of the bottle and in the pipes up to the first stage of the regulator from undergoing the same reaction? magic abounds.... LLoyd |
#50
Posted to rec.crafts.metalworking
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American Chopper episode got even more reckless
In article , Don Bruder says...
... Acetylene "boiling" out of solution to replace what you've tapped out of the cylinder is exactly the same mechanism in operation, just working on different materials. Not *exactly* boiling, which is phase change from liq. to gas, but rather it's the acetlyene coming out of solution, more like CO2 when you open up a soda bottle. The acetone's not supposed to boil, and of course if the soda bottle is shaken up before opening the acetone can bubble out into the regulator, not good. Additionally, acetylene cylinder are *NOT* hollow cylinders, the way oxygen and other cylinders are - If you were to break one open somehow (HIGHLY not recommended outside of properly equipped facilities - unless you *WANT* to die) you'd find that it's almost entirely filled with a highly porous block of something that looks much like concrete. This "rock sponge" is what soaks up the acetone that the acetylene dissolves in, preventing you from getting spits and spurts of raw liquid acetone coming out the end of your torch. Gaps and voids in it are a certifiable Very Bad Thing(TM), which is one of the (if not the main) reasons that dropping an acetylene tank any distance is a Bad Thing(TM) and grounds for having that tank pulled from service and stored someplace "bomb-proof" until it's been inspected and tested to be sure the "stuffing" is still intact and working as intended. If you ever get handed a cylinder that "rattles when rocked" (something *INSIDE* the cylinder rattling, not "stuff attached to the cylinder") immediately hand it back - *GENTLY* - and demand another one. The "rattler" almost certainly has damaged media in it, and is unsafe. It's unlikely, due to the pre-fill inspection, that you'll ever get one, but "unlikely" and "impossible" aren't equal. They used to use asbestos fiber for the filler, somebody told me that for a while it was diatomaceous earth. There's a lot of half-truths and nonsense circulated about acetylene because most folks don't understand how the molecules behave. Clearly the ullage space above the filler is not full of liquid, though it has acetone vapor in it. But the front end of the regulator probably isn't saturated with that, so why doesn't the 200 psi gas there decompose? The answer is that the mean free path length is too short. Another source of excitement is when you suggest that folks shouldn't use pure copper tubing to manifold acetlyene cylinders. "But my regulator's made of BRASS and brass has COPPER in it, right?" Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
#51
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
Don Bruder wrote:
Additionally, acetylene cylinder are *NOT* hollow cylinders, ...... Unlike oxygen or other tanked gasses, filling an acetylene cylinder is a fairly time-intensive task ...... want *THE SAME CYLINDER* back, you're going to have to wait for a while..... Don, snipped fascinating post - thanks for that Its no wonder acetylene is getting expensive. How much of a performance hit is using oxy-propane instead ? Steve |
#52
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article aAtzf.740928$xm3.441347@attbi_s21,
"Dave Lyon" wrote: "jw" wrote in message ups.com... Dave Lyon wrote: See my other post for more detail. In summary: Pure acetylene at 15-ish pounds doesn't "burn", a process which does indeed require oxygen. Instead, it "deflagrates", a process of chemical breakdown that has no need whatsoever for oxygen to be present in order to happen. (presence of oxygen may in fact inhibit deflagration in some cases) The only commonality between the two processes is that they both generate a lot of heat. I read your other post. Thanks, very informative. But, I have a question. If acetylene "defagrates" at around 15 psi, how do they get it into my tank at 250 psi or more? I am sure someone will correct me if I'm wrong, but I think that is the reason for the acetone and matrix in acetylene tanks. It helps to stabilize the acetylene and prevent(or at least limit) this problem. JW OK, I've done a little research (very little) This is what I've found from http://en.wikipedia.org/wiki/Deflagration Deflagration is a process of subsonic combustion that usually propagates through thermal conductivity (hot burning material heats the next layer of cold material and ignites it). Deflagration is different from detonation which is supersonic and propagates through shock compression The best I can tell, deflagration IS combustion. Combustion REQUIRES an oxidizer of some sort. If I'm still wrong, please point me to a site where I can learn more. Whoever wrote that piece is wrong to use the word "burning" or "combustion", as well as in what they state deflagration to be. In fact, the only thing I can see there that matches with what I was taught in chemistry class is the "subsonic" part. Deflagration IS NOT combustion, DOES NOT require oxygen, and CAN happen in materials not normally thought of as "flammable" or "explosive". Combustion, or even detonation, MAY come as an "after-effect" of deflagration, depending on the presence of oxygen and what the breakdown products are, but they aren't the same thing. Deflagration is the *BREAKING* of a molecule's bonds (such as the double-bond in the acetylene molecule - see "Note 1/ASCII art" below) resulting in some other compound(s), each of which may or may not be "deflagratable", flammable, or explosive in its own right, plus bond-energy released in the form of heat. Combustion/detonation (AKA "Oxidization", whether at high or low speeds) is the combining of oxygen atoms with atoms/molecules of some other compound, *FORMING NEW BONDS*, resulting in heat, various oxides, and water, depending on what the fuel is. To an observer, the "macro-result" - the overall effect at the scale we humans are equipped to observe directly - of deflagration is quite similar to, possibly indistinguishable from, combustion, but lacking a need for any oxygen to sustain the reaction. At the molecular, "micro" level, which we humans aren't equipped to observe directly, the two processes are completely different, and might even qualify to be called "complete opposites". Deflagration requires no oxygen, and unless the material deflagrating is known, might produce any number of unpredictable "other stuff" molecules that don't necessarily include any "-oxide"s or water, and may be flammable/explosive materials in and of themselves. Combustion, on the other hand, whether "just a regular speed burn", or the high-speed shockwave of detonation, absolutely requires oxygen, which combines with the fuel in the classic "oxidization" reaction to release energy in the form of heat, and for a "perfect mix" of hydrocarbon fuel and oxygen, results in a nicely stable, slightly warm mixture of CO2 and H2O. (Note 1/ASCII art) An acetylene (C2H2) molecule - Each "/", and "\" is a molecular bond, the "=" is the double-bond. C is a carbon atom, H is a hydrogen atom: H H \ / C=C / \ H H When C2H2 deflagrates, it splits the double-bond, resulting in two CH2 molecules - each about as stable as a manic-depressive on LSD, and about as "freindly" and "choosy" as a pre-paid whore - plus energy in the form of heat. Since there are two bonds on each of the carbon atoms going begging, each of the resulting CH2 molecules is desperately looking for something to bond with. Add 4 atoms of hydrogen, and the CH2 molecules will snatch 2 atoms each, transforming into two molecules of methane - CH4 - which *IS* flammable/explosive in the presence of oxygen and igition source. Add 6 atoms of oxygen (in the form of 3 molecules of O2) instead, and you end up with a nice stable CO2 and H2O molecule for each half of the "broken" acetylene molecule, plus more heat (from breaking the three O2 bonds to allow each atom of O to go its own way) to "tickle" the parent reaction. -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#53
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
Sorry to be picking on details, but the chemistry teacher in me , can´t
resist it. Acetylene has a tripple bond between the carbons, not a double bond. The tripple is what makes it so reactive. Each of those bonds are relatively weak and so prone to break. As for the O/A explosions, my chimistry teacher in high school did it with a glass beaker wrapped in a towel. One heck of a bang and the beaker was just dust. Henning Don Bruder wrote in : (Note 1/ASCII art) An acetylene (C2H2) molecule - Each "/", and "\" is a molecular bond, the "=" is the double-bond. C is a carbon atom, H is a hydrogen atom: H H \ / C=C / \ H H |
#54
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
"Peter W. Meek" wrote in message ... On Tue, 17 Jan 2006 15:20:49 +0000, David Billington wrote: When I was a student one of the others on the course filled his lunch bag with OA mix and lit it. Bang, the lecturer and others went in to see the kid standng there dazed but unhurt. The lecturer didn't bother to tell him off for being that stupid, he reckoned he learned a lesson and wouldn't do it again. The instructor in my first gas welding class was giving the orientation lecture in a gymnasium- sized shop. We were gathered around a steel assembly table. While giving us the standard safety lecture he was fiddling with a Styrofoam coffee cup. He poked a hole with a pencil and set it top down. A bit later he lit his torch, adjusted for a nice neutral flame, and then wiped the flame out. He held the flowing gas to the pencil hole and then relit the torch. He said, "Now, listen!" and held the torch to the hole. Fortunately, I had no class immediately after, because it was several hours before I could hear clearly again. A more graphic demonstration of the extreme explosive power and brisance of a perfect oxy-acetylene mix would be hard to imagine. That was the sharpest CRACK I have ever heard, and I have been within 50' of a lightning strike that converted the top six feet of a telephone pole to toothpicks. -- Many years ago, a friend hooked a baggy to the overflow tube of a motorcycle battery while it was charging. The resulting filled baggy was ignited with a string/match time fuse. Similar results. Bob |
#55
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
"Steve Taylor" wrote in message ... Don Bruder wrote: Additionally, acetylene cylinder are *NOT* hollow cylinders, ...... Unlike oxygen or other tanked gasses, filling an acetylene cylinder is a fairly time-intensive task ...... want *THE SAME CYLINDER* back, you're going to have to wait for a while..... Don, snipped fascinating post - thanks for that Its no wonder acetylene is getting expensive. How much of a performance hit is using oxy-propane instead ? Steve My question also. Does propane require a different tip or torch? Can the same hoses be used for propane? Bob |
#56
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article ,
henning wright wrote: Sorry to be picking on details, but the chemistry teacher in me , can?t resist it. Acetylene has a tripple bond between the carbons, not a double bond. The tripple is what makes it so reactive. Each of those bonds are relatively weak and so prone to break. As for the O/A explosions, my chimistry teacher in high school did it with a glass beaker wrapped in a towel. One heck of a bang and the beaker was just dust. Henning Don Bruder wrote in : (Note 1/ASCII art) An acetylene (C2H2) molecule - Each "/", and "\" is a molecular bond, the "=" is the double-bond. C is a carbon atom, H is a hydrogen atom: H H \ / C=C / \ H H How'd I end up with "double" in this post, when I know damn well it's a triple? sigh At least I was consistent, I guess (I *KNOW* that I've already posted that it's a triple bond in other messages in this thread, too... The mind is the first to go?) -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#57
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
"Don Bruder" wrote in message ... In article , henning wright wrote: Sorry to be picking on details, but the chemistry teacher in me , can?t resist it. Acetylene has a tripple bond between the carbons, not a double bond. The tripple is what makes it so reactive. Each of those bonds are relatively weak and so prone to break. As for the O/A explosions, my chimistry teacher in high school did it with a glass beaker wrapped in a towel. One heck of a bang and the beaker was just dust. Henning Don Bruder wrote in : (Note 1/ASCII art) An acetylene (C2H2) molecule - Each "/", and "\" is a molecular bond, the "=" is the double-bond. C is a carbon atom, H is a hydrogen atom: H H \ / C=C / \ H H How'd I end up with "double" in this post, when I know damn well it's a triple? sigh At least I was consistent, I guess (I *KNOW* that I've already posted that it's a triple bond in other messages in this thread, too... The mind is the first to go?) -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info Wow, this is pretty interesting stuff. Obviously old hat to a lot of you guys, but it's new to me. I am the type of guy that likes to experiment with stuff that I don't know very much about. While I don't have any plans to mess with my acetylene, it's possible this thread saved my wife a terrible mess to clean up. Thanks for taking the time to explain things in such detail. |
#58
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article 66zzf.498961$084.27952@attbi_s22,
"Dave Lyon" wrote: Wow, this is pretty interesting stuff. Obviously old hat to a lot of you guys, but it's new to me. Idunno about "old hat", but chemistry has always been one of my favorite areas of learning. Call me a well-educated amateur in the field - far from clueless, but in all honesty, likely just as far from expert. I am the type of guy that likes to experiment with stuff that I don't know very much about. Welcome to the "elephant's child" club. (If you don't get the reference, see Rudyard Kipling's "Just So Stories", and the tale of how the elephant got his trunk.) While I don't have any plans to mess with my acetylene, it's possible this thread saved my wife a terrible mess to clean up. Uh, yeah, that's one fairly sane way to look at things chuckling Thanks for taking the time to explain things in such detail. So where do I send the tuition bill? -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#59
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
So where do I send the tuition bill? I'll just stick it in the pile next to all my other bills. |
#60
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article CQzzf.499013$084.345445@attbi_s22,
"Dave Lyon" wrote: So where do I send the tuition bill? I'll just stick it in the pile next to all my other bills. Well, at least it'll have company -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#61
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
Its no wonder acetylene is getting expensive. How much of a performance hit is using oxy-propane instead ? Steve My question also. Does propane require a different tip or torch? Can the same hoses be used for propane? Bob Yes, same hoses and regulators with propane. Cutting torch will require a new tip. The tip is an entirely different design. Propane seems to take longer heating and the cutting kerf will be wider as best as I can remember. It will also use more oxygen. |
#63
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article , Don Bruder
wrote: (Note 1/ASCII art) An acetylene (C2H2) molecule - Each "/", and "\" is a molecular bond, the "=" is the double-bond. C is a carbon atom, H is a hydrogen atom: H H \ / C=C / \ H H When C2H2 deflagrates, it splits the double-bond, resulting in two CH2 molecules Nearly right! Acetylene is C2H2, O.K., but has a triple bond, containing LOTS of potential energy, which is released when the triple bond breaks. ASCII art _ / \ HC---CH \_/ NO oxygen is needed, as you say. Deflagration occurs when a decomposition reaction supplies enough heat to maintain or accelerate the decomposition which cannot escape fast enough to prevent the temperature of the system from increasing. When I had my workshop fire, the fire brigade kept my acetylene cylinder cool by hosing it with water for 24 hours, to ensure that any acetylene decomposition reaction did not self-accelerate to deflagration. Thank goodness! MY house and our neighbours' houses were not destroyed! Evenn if some of the acetylene in the cylinder did decompose, the heat loss exceeded the rate of generation and deflagration was prevented. Detonation occurs when the speed of propagation of the reaction through the substance or mixture exceeds the speed of sound in the unreacted material. G.H.Ireland. -- _ _________________________________________ / \._._ |_ _ _ /' Orpheus Internet Services \_/| |_)| |(/_|_|_ / 'Internet for Everyone' _______ | ___________./ http://www.orpheusinternet.co.uk |
#64
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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Acetylene chemistry (was American Chopper episode got even more reckless)
In article ,
"Dixon Ranch" wrote: Its no wonder acetylene is getting expensive. How much of a performance hit is using oxy-propane instead ? Steve My question also. Does propane require a different tip or torch? Can the same hoses be used for propane? Bob Yes, same hoses and regulators with propane. Cutting torch will require a new tip. The tip is an entirely different design. Propane seems to take longer heating and the cutting kerf will be wider as best as I can remember. It will also use more oxygen. Yep, AT LEAST twice as much. Dont believe me, though... Do the math: Acetylene, C2H2, needs 2 oxygen atoms (2 bonding sites per atom) per carbon (four bonding sites per atom) for 4, plus 1 for every two hydrogen atoms (1 bonding site each) is 1, which makes 5 atoms of oxygen per molecule of Acetylene to burn neutral - Since oxygen comes "naturally packaged" in bundles of 2 atoms, that means we're going to need to mix two molecules of C2H2 with 5 molecules, or 10 atoms, of oxygen to achieve a "true neutral" flame - one that puts out nothing but heat, water, and carbon dioxide. A molecule of propane, C3H8, needs the same 2 per carbon for 6, and 1 for every 2 hydrogen for 4 makes 10 atoms or 5 molecules of oxygen to achieve the same result. All told, you'll go through oxy twice as fast with propane as with acetylene. Start cutting, or running an oxidizing flame, and you'll run through it even faster. Of course, looking at it from the flip side, you're going to burn half as much propane as you would have acetylene for the same tank of oxy, but if I'm not mistaken, oxy-propane doesn't burn as hot as oxy-acetylene, so you have to use more of it to get the same heat (not sure on the BTU numbers - I'll have to look 'em up. I *KNOW* they differ, just not by how much) which makes me think you're likely going to be doing good if you pretty much break even when you get to the bottom line of the refilling bill. Another factor: How much does propane cost in *YOUR* area? Out here in Kali-fornicates-ya, the last refill of my little grille-tank - standard 5 gallon jobbie - set me back a fairly stiff-seeming 14-ish bucks. D'OH! Proofreading the math just made me realize why/how I mangled the acetylene triple bond into a double bond in my other post! Brain fart of epic proportions! PROPER drawing of acetylene: _ / \ H-C---C-H = C2H2 = Acetylene \_/ ^^^ = triple bond NOT H H \ / C=C = C2H4 = Ethylene, not Acetylene! / ^ \ H | H '- = double bond as in polyethylene twine tying your hay bales, or ethylene glycol for the car radiator. Good grief... How did I overlook a screwup *THAT* big and basic!?!? And *YOU* missed it too, Teach!!! Guess that helps me not feel *QUITE* so bad... -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#65
Posted to rec.crafts.metalworking
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American Chopper episode got even more reckless
In article ,
jim rozen wrote: In article , Don Bruder says... ... Acetylene "boiling" out of solution to replace what you've tapped out of the cylinder is exactly the same mechanism in operation, just working on different materials. Not *exactly* boiling, which is phase change from liq. to gas, but rather it's the acetlyene coming out of solution, more like CO2 when you open up a soda bottle. Right. Maybe a poor example. But the mechanism is the same: A drop in pressure. Depressurizing water at an arbitrarily selected temperature to below the vapor pressure of steam at that temperature makes it boil into steam (albeit cold steam) while depressurizing acetylene-saturated acetone to a point below the vapor pressure of acetylene allows it to come out of solution, leaving the even-lower vapor pressure acetone in liquid state. The acetone's not supposed to boil, and of course if the soda bottle is shaken up before opening the acetone can bubble out into the regulator, not good. Absolutely correct. That's also the prime reason you don't use an acetylene cylinder that's been laying on its side for more than a few minutes without first standing it up and letting it "settle" for an hour or so - Liquid acetone (with dissolved acetylene) may still be pooled at the valve if you hook up too soon. Most definitely a "not good" thing. They used to use asbestos fiber for the filler, somebody told me that for a while it was diatomaceous earth. I've also heard of compressed burlap *WAY* back in the long ago, packed fiberglass, glass beads like in the resin-columns of water softeners, and a whole slew of other porous, tightly packable materials. Pumice-stone is the one I was first introduced to and am most familiar with. -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#66
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
Don Bruder wrote:
D'OH! Proofreading the math just made me realize why/how I mangled the acetylene triple bond into a double bond in my other post! Brain fart of epic proportions! PROPER drawing of acetylene: _ / \ H-C---C-H = C2H2 = Acetylene \_/ ^^^ = triple bond NOT H H \ / C=C = C2H4 = Ethylene, not Acetylene! / ^ \ H | H '- = double bond I was interested primarily in the hazards involved in handling of my welding tanks. Like deflagration? Sounds like a cool clueless newbie trick waiting for a chance to happen. Thanks for the clue... I don't have a mean old-timer looking over my shoulder ready to swat me on the back of the head when (I didn't say if) I do stupid shop trick. So it makes sense to read what I can and try to understand the "why" behind the "what". Hey Don? So ok, the third bond is relatively weak and easily broken. But - I think I lost track of a couple of hydrogen atoms (in the text?) Would you do a big favor on request from a clueless newbie? Go back and edit that file over and post it again? With careful counts and the proper bond illustrations et al? I'd like to save it and share with other clueless newbie. It just might help me not blow myself up some day...g? Thanks all, Richard |
#67
Posted to rec.crafts.metalworking
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American Chopper episode got even more reckless
On Wed, 18 Jan 2006 23:34:22 GMT, "Dixon Ranch"
wrote: Its no wonder acetylene is getting expensive. How much of a performance hit is using oxy-propane instead ? Steve My question also. Does propane require a different tip or torch? Can the same hoses be used for propane? Bob Yes, same hoses and regulators with propane. Cutting torch will require a new tip. The tip is an entirely different design. Propane seems to take longer heating and the cutting kerf will be wider as best as I can remember. It will also use more oxygen. OK for heating, but an oxy-propane flame doesn't work well at all for welding -- at least not for welding steel. It may melt the steel, but the chemistry is somehow wrong and it makes a very porous mess. |
#68
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
Don Bruder wrote:
Can be/is. See the rest of the thread. I don't bother if many are wrong. :-) At 14.5 PSI or so, pure acetylene doesn't take much more than a "dirty look" to get a sufficiently large quantity of it to deflagrate. Do yourself a favour: Look at your acetylen bottle. Open it. Look at the primary pressure. It will be around 8bar (116psi). Still living? Now look at the scale of the primary pressure gauge. There will be a red line. It is a 18 bar (260 psi). Don't tell me, that the pressure regulator is filled with acetone. Even the bottle isn't filled completely with acetone. Only about 2/3 of the bottle are. That's because you are allowed to use them tiltet (as long as 30 deg (IIRC) out of the horizontal). Now this means, that the acetylen _has_ pressure of 116 psi inside the bottle and the first half of the pressure regulator. The same quantity at 15 pounds of pressure is all but guaranteed to do so before you even get a chance to apply the dirty look. Nonsense. What's INSIDE the cylinder is almost all dissolved in acetone Almost! It doesn't matter how much is dissolved. There is free acetylen in the bottle with at least 116psi. Those 116psi depending on the temperature and thus of the dissolving ability of the acetone. There is another reason why the ballons explode. I think it is UV-radiation. Acetylen _is_ sensitive. No doubt about that. Nick -- Motor Modelle // Engine Models http://www.motor-manufaktur.de DIY-DRO - YADRO - Eigenbau-Digitalanzeige |
#69
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
""Nick Müller"" wrote in message ... AL wrote: Doesn't acetylene combust spontaneously at around 15psi? Can you get 15 psi by squeezing the baloon? Can't be. The red line at my acetylen bottle's pressure regulator is at 8 bar (116psi). Does it have to be in the presence of oxygen? No, it can disintegrate without O. And if it is getting into contact with copper, it will ignite earlier. Brass up to 60% (IIRC) copper is OK. The reason that acetylene does not explode at the high pressures in a bottle is because it is actually dissolved in acetone. As the gas is used the pressure in the bottle drops and more gas comes out of solution to replace it. Tom |
#70
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
"Nick Müller" wrote in message
... | Don Bruder wrote: SNIP | Do yourself a favour: | Look at your acetylen bottle. Open it. Look at the primary pressure. It | will be around 8bar (116psi). Still living? Now look at the scale of the | primary pressure gauge. There will be a red line. It is a 18 bar (260 | psi). | Don't tell me, that the pressure regulator is filled with acetone. Even | the bottle isn't filled completely with acetone. Only about 2/3 of the | bottle are. That's because you are allowed to use them tiltet (as long | as 30 deg (IIRC) out of the horizontal). Now this means, that the | acetylen _has_ pressure of 116 psi inside the bottle and the first half | of the pressure regulator. This thread got me wondering how the bottles get filled at the gas plant. Is the pure acetylene pumped into an upright bottle containing the existing acetone, or is the depleted acetone solution removed and replaced with the mixed solution in an inverted bottle? Or something altogether different? |
#71
Posted to rec.crafts.metalworking
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American Chopper episode got even more reckless
In article ,
=?ISO-8859-1?Q?Nick_M=FCller?= says... Don't tell me, that the pressure regulator is filled with acetone. Somebody *always* says this. They're right of course. The inlet stage of the regulator has no liquid acetone in it. Why doesn't the acetlyene decompose in the regulator then? Basically because the passage dimensions are too small. The mean free path length for them at room temperature is quite long, they do not develop enough kinetic energy to get over their activation curve to disassemble while inside the regulator. The tank dimensions are much longer so there's statistically a very good probability that one fast one will light off the reaction. Basically you are depending on boltzman statistics to keep your O/A rig from going boom. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
#72
Posted to rec.crafts.metalworking
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American Chopper episode got even more reckless
jim rozen wrote:
Basically you are depending on boltzman statistics to keep your O/A rig from going boom. This is also an explanation for the numbers on the bottle. They are the numbers for the Big-Boom-Boltzmann-Lottery drawn every week. Nick -- Motor Modelle // Engine Models http://www.motor-manufaktur.de DIY-DRO - YADRO - Eigenbau-Digitalanzeige |
#73
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article ,
Mr G H Ireland wrote: In article , Don Bruder wrote: (Note 1/ASCII art) An acetylene (C2H2) molecule - Each "/", and "\" is a molecular bond, the "=" is the double-bond. C is a carbon atom, H is a hydrogen atom: H H \ / C=C / \ H H When C2H2 deflagrates, it splits the double-bond, resulting in two CH2 molecules Nearly right! Acetylene is C2H2, O.K., but has a triple bond, containing LOTS of potential energy, which is released when the triple bond breaks. ASCII art _ / \ HC---CH \_/ Aye... I noticed that screwup when I started doing the "chemical math" to figure out how much more O2 would be needed to run a torch on propane rather than acetylene. Somewhere further down the line in the thread, I posted nearly the same piece of corrected ASCII art. I think the initial screwup came from my drawing the molecule, thinking "that doesn't look right!", remembering that carbon has four valences to bond to, and then "correcting" my original artwork to match that fact, forgetting that I was drawing an acetylene molecule in the process. sigh Sometimes the trees get in the way of the forest. Or is that the forest getting in the way of the trees? Either way, a definite "screwed the pooch" on my part. NO oxygen is needed, as you say. Deflagration occurs when a decomposition reaction supplies enough heat to maintain or accelerate the decomposition which cannot escape fast enough to prevent the temperature of the system from increasing. Yep. On the money. -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#74
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
I once read part of prefill inspection each empty Acetalene cylinder
is weighed so they know how much acetone is missing. Missing acetone is added while filling with acetylene. |
#75
Posted to rec.crafts.metalworking
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American Chopper episode got even more reckless
On 19 Jan 2006 10:34:47 -0800, jim rozen
wrote: In article , =?ISO-8859-1?Q?Nick_M=FCller?= says... Don't tell me, that the pressure regulator is filled with acetone. Somebody *always* says this. They're right of course. The inlet stage of the regulator has no liquid acetone in it. Why doesn't the acetlyene decompose in the regulator then? Basically because the passage dimensions are too small. The mean free path length for them at room temperature is quite long, they do not develop enough kinetic energy to get over their activation curve to disassemble while inside the regulator. The tank dimensions are much longer so there's statistically a very good probability that one fast one will light off the reaction. Basically you are depending on boltzman statistics to keep your O/A rig from going boom. Jim Thank you! That question has puzzled me for decades. It also explains why the calcium carbide depth charges I once made did not go boom at 30 feet but just kept sinking. |
#76
Posted to rec.crafts.metalworking
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American Chopper episode got even more reckless ,a lil offtopic
yes but back in the 20's and 30's they used to fill kids ballons with
hydrogen and the kid or the lucky lady that her gent bought her a balloon ,would be walking along until some prankster would have a lit cigarette and touch the balloon and have a nice pop go off ,never hurt anyone but it was a scare ,after WW2 they replaced hydrogen with helium and the pramksters had no more fun |
#77
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
I still wonder about deflagration: how is it possible for acetylene to exit
the acetone/pumice in the bottle, and travel up through the valve and to the regulator, at over 160psi, without deflagrating? Never heard a good explanation of this. |
#78
Posted to rec.crafts.metalworking,sci.engr.joining.welding
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American Chopper episode got even more reckless
In article ,
"Willer" wrote: I still wonder about deflagration: how is it possible for acetylene to exit the acetone/pumice in the bottle, and travel up through the valve and to the regulator, at over 160psi, without deflagrating? Never heard a good explanation of this. That's been covered several times in the thread by other posters. Part of it is the tiny amount of "free" acetylene involved, and part of it is that the open spaces between "the inside of the cylinder" and "the high pressure side of the regulator" aren't large enough to allow the acetylene molecules to "get a good running start", so that when they bang into each other, they don't have enough energy to trigger the initial breakdown and get the process started. I can *NEVER* remember the proper term for the mechanism involved, but at least two others in the thread have used it. -- Don Bruder - - If your "From:" address isn't on my whitelist, or the subject of the message doesn't contain the exact text "PopperAndShadow" somewhere, any message sent to this address will go in the garbage without my ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info |
#79
Posted to rec.crafts.metalworking
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Acetylene chemistry (was American Chopper episode got even more reckless)
On Wed, 18 Jan 2006 17:43:23 -0800, Don Bruder
wrote: In article , "Dixon Ranch" wrote: Its no wonder acetylene is getting expensive. How much of a performance hit is using oxy-propane instead ? Steve My question also. Does propane require a different tip or torch? Can the same hoses be used for propane? Bob Yes, same hoses and regulators with propane. Cutting torch will require a new tip. The tip is an entirely different design. Propane seems to take longer heating and the cutting kerf will be wider as best as I can remember. It will also use more oxygen. Yep, AT LEAST twice as much. Dont believe me, though... Do the math: Acetylene, C2H2, needs 2 oxygen atoms (2 bonding sites per atom) per carbon (four bonding sites per atom) for 4, plus 1 for every two hydrogen atoms (1 bonding site each) is 1, which makes 5 atoms of oxygen per molecule of Acetylene to burn neutral - Since oxygen comes "naturally packaged" in bundles of 2 atoms, that means we're going to need to mix two molecules of C2H2 with 5 molecules, or 10 atoms, of oxygen to achieve a "true neutral" flame - one that puts out nothing but heat, water, and carbon dioxide. A molecule of propane, C3H8, needs the same 2 per carbon for 6, and 1 for every 2 hydrogen for 4 makes 10 atoms or 5 molecules of oxygen to achieve the same result. All told, you'll go through oxy twice as fast with propane as with acetylene. Start cutting, or running an oxidizing flame, and you'll run through it even faster. Of course, looking at it from the flip side, you're going to burn half as much propane as you would have acetylene for the same tank of oxy, but if I'm not mistaken, oxy-propane doesn't burn as hot as oxy-acetylene, so you have to use more of it to get the same heat (not sure on the BTU numbers - I'll have to look 'em up. I *KNOW* they differ, just not by how much) which makes me think you're likely going to be doing good if you pretty much break even when you get to the bottom line of the refilling bill. Another factor: How much does propane cost in *YOUR* area? Out here in Kali-fornicates-ya, the last refill of my little grille-tank - standard 5 gallon jobbie - set me back a fairly stiff-seeming 14-ish bucks. D'OH! Proofreading the math just made me realize why/how I mangled the acetylene triple bond into a double bond in my other post! Brain fart of epic proportions! PROPER drawing of acetylene: _ / \ H-C---C-H = C2H2 = Acetylene \_/ ^^^ = triple bond NOT The scrappies around here run air/propane for cutting, with the air supplied by the compressor on the PayLoader they use for moving the scrap around. H H \ / C=C = C2H4 = Ethylene, not Acetylene! / ^ \ H | H '- = double bond as in polyethylene twine tying your hay bales, or ethylene glycol for the car radiator. Good grief... How did I overlook a screwup *THAT* big and basic!?!? And *YOU* missed it too, Teach!!! Guess that helps me not feel *QUITE* so bad... |
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