High Pressure Acetylene . . . .

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OK,   Here's a question for all you pro's. out there:They say that acetylene is "unstable" at pressures above 15 lbs.unless it is dissolved in acetone.   Above this pressure, it could actually EXPLODE !HYPOTHETICAL QUESTION:  You're done with the torch.....you close the bottle valves......at this point, you would normally "bleed" the system by opening the torch valves and letting the pressure out of the system.   Let's say you don't bleed it ?   The acetylene bottle valve is closed, the torch valve is closed, and the high pressure gauge on the gas still say's: 200 lbs.   That's telling me that there's 200 lbs. of acetylene in that regulator, (and there should NOT be any acetone in the regulator)........Why doesn't it blow up ?   I'll be the LAST one to let you down !
Reply:OK, let me attempt to remove any doubt of my lack of intelligence here by attempting to answer the question.First, there is little to no likelyhood of explosion because the Acet inside the gague worm is fully contained and unable to combine with oxygen.The common usage of the word explosion is often a misnomer for what actually happens in the exothermic reaction taking place.Acetelene at pressures above 15psi becomes inherintly unstable and seperates into it's components, some of witch will easily combine with atmouspheric oxygen, and self ignite in a very rapid exothermic reaction.Evidently, this was a common occurrence in the days of acetelene lighting systems, so they were reconfigured with the acetelene generator being buried in the yard, with a safety valve that releived the generator pressure at 12 psi.  If somebody wanted to do some searching, there is doubtless an Air Force TM that explains acet generators in great detail since the USAF had them in inventory at least till 1965, but I have no inclination to do the search.To have an exothermic rapid reaction, you need 2 things, fuel and oxygen.  No oxygen is present in the acetelene in the gague worm, so no reaction can take place.Either that made sense, or it didn't.Appreciation Gains You Recognition-
Reply:Franz...That was a wonderful reply......and that's why I asked the question...I don't have Alzheimers just yet, and all my years of being on this rock, I've alway's been told that you need 3 things for a fire: Fuel, Oxygen & heat.   That's why I didn't believe that acetylene would just "blow up" all by itself.....sure, you have fuel....but where's the heat ?  (and, if the torch outfit is working properly, where's the oxygen) ?   The fuel side of an oxy-acetylene outfit has nothing to do with the oxygen side, until it get's to the mixer at the base of the nozzle.Why in the Hell do all the books tell you that acetylene will go "Bang" above 15 lbs. ?I'll be the LAST one to let you down !
Reply:Marko, probably cause the goober who got paid to write the book, and clown who got paid to edit it have never been closer to a torch than seeing the picture that will go in the book.Add in that it's a lot easier to say something will explode than it is to really explain what happens.I always found it amusing, back before smoking became a mortal sin, when nurses and hospital employees informed me Oxygen could explode.They had been told so, and the story got bigger with each telling.Appreciation Gains You Recognition-
Reply:Originally posted by Markopolo Why in the Hell do all the books tell you that acetylene will go "Bang" above 15 lbs. ?
Reply:The decomposition of acet is exothermic. We demo this to students every year. No oxygen is required for a substantial risk with a large volume of free gas. Of course, if there is oxygen available, the initial decomposition will trigger the more energetic combustion of the gas. Note that when acetylene burns in oxygen, the first stage is decomposition, the blue part of the flame bieng colored by excited C2 dimer.The main protection (as I understand it) in the gas space in the bottle and in the regulator inlet is the small volume of gas present, surrounded by a large mass of metal. If, by some quirk of fate, an acet molecue decomposes (and they do), the configuration is such that the energy is absorbed by the metal surrounding the gas and the filler in the bottle before it can trigger other gas molecules to let go. The small volume of gas is critical to this. Also, in the worst case, is all of the free gas goes, there is such a small volume that the bottle, valve, regulator, etc, can more than withstand the shock.see: http://www.esabna.com/EUWeb/OXY_handbook/589oxy3_3.htm
Reply:To add a little more: spontaneous decomposition goes on all th time, at a very low rate. At whatever temperature the gas is at, some of the molecules have less than average energy, some lmore, a few a lot more. Those with a lot more may decompose. I can make it concrete this way: to a molecule, energy is speed-- temperature is just a measure of the average energy the molecules have, which essentially is a measure of average speed. If one of the fast molecules bumps into another one, it may break a C-C bond, releasing energy, kind of like cutting a stretched rubber band. Unfortunately, it al happens at a scale too small to see, and the analogy isn't perfect, but it doesn't change the result.How likely is a problem with modern equipment? Not very. By the early 1920's, the major issues had been worked around, and equioment and bottles manufactured since have made it very difficult to have an accident with acetylene.
Reply:Acetylene is C2H2 above 15 PSi free acetylene will dissassociate into Hydrogen H2 and Carbon C2 Hydrogen is a extremely explosive gas.  Here's the MSDS I downloaded.General Characteristics Health Hazards Material Recommendations A colorless, flammable gas with an odor similar to garlic. Shipped and stored in dissolved acetone. Can decompose spontaneously if pressure exceeds 15 PSIG. A simple asphyxiant Use steel and wrought iron. Avoid copper, silver and mercury. Explosive acetylides can be formed on copper and aluminum bronze. TLV-TWA Flammable Limits DOT Class / Label  2.3----100% 2.1 / Flammable Molecular Weight Specific Gravity Specific Volume 26.04 0.91 @ 70 F 14.5 cu.ft./lb @ 60 F CGA Valve Outlet CAS Registry No. UN Number 510 74-86-2 1001 National Stock Number (NSN) Applicable to Acetylene MIL Specs/ Fed SpecsMSDS for Acetylene --------------------------------------------------------------------------------GradePart # Purity Minimum CylinderSize VolumeSCF Pressure@ 70 F Comments Atomic Absorption400100  99.8% 061023  390145  250250  None Purified400200  99.6% 061023  390145  250250  None  Industrial / Technical  99.5% 061023  390145  250250  None --------------------------------------------------------------------------------General: Acetylene is simplest member of unsaturated hydrocarbons called alkynes or acetylenes. Most important of all starting materials for organic synthesis. Usefulness of actylene is partly due to the variety of addition reactions which its triple bond undergoes and partly due to the fact that its weakly acidic hydrogen atoms are replaceable by reaction with strong bases to form acetylide salts.OSHA Data:Acetylene is a compressed gas that is used as a fuel and is stored in a liquid state. When the valve is opened and pressure is released a portion of the liquid turns to gas. This gas is then used by the device that the cylinder is connected to. Because acetylene is stored as a liquid, the cylinder will only work properly if the tank is used in the upright position. Using, or storing, the tank in any other position can be extremely dangerous. According to the U.S. Department of Labor General IndustryDigest, 1994 (Revised):"Acetylene cylinder shall be stored and used in a vertical, valve-end-up position only." The actual OSHA standard, 1910.253(b)(3)(ii) says,Acetylene cylinders shall be stored valve end up. Because acetylene is extremely sensitive to pressure, it should never be used at more than 15 p.s.i. Many workers have been injured or killed when using oxygen-acetylene welder and cutters because they allowed their rig to subject the acetylene fuel to pressures greater than 15 p.s.i. The actual OSHA standard, 1910.253(a)(2) says,Maximum pressure. Under no condition shall acetylene be generated, piped(except in approved cylinder manifolds) or utilized at a pressure in excess of 15psig (103 kPa gauge pressure) or 30 psia (206 kPa absolute). ... This requirementis not intended to apply to storage of acetylene dissolved in a suitable solvent incylinders manufactured and maintained according to U.S. Department ofTransportation requirements, or to acetylene for chemical use. The use of liquidacetylene shall be prohibited. General Data | Boiling ChartPure acetylene is a colourless gas with a pleasant odour; as prepared from calcium carbide it usually contains traces of phosphine that cause an unpleasant garliclike odour. Acetylene can be decomposed to its elements with the liberation of heat. The decomposition may or may not give rise to explosions, depending on conditions. Pure acetylene under pressure in excess of about 15 pounds per square inch or in liquid or solid form explodes with extreme violence. Mixtures of air and acetylene are explosive over a wide range, from about 2.5 percent air in acetylene to about 12.5 percent acetylene in air. When burned with the correct amount of air,acetylene gives a pure, white light, and for this reason it was at one time used for illumination in locations where electric power was not available, e.g., buoys, miners' lamps, and road signals.The combustion of acetylene produces a large amount of heat, and, in a properly designed torch, the oxyacetylene flame attains the highest flame temperature (about 6,000° F, or 3,300° C) ofany known mixture of combustible gases. The hydrogen atoms in acetylene can be replaced by metallic elements to form acetylides--e.g., acetylides of silver, copper, or sodium. The acetylides of silver, copper, mercury, and gold aredetonated by heat, friction, or shock. In addition to its reactive hydrogen atom, the carbon-carbon triple bond can readily add halogens, halogen acids, hydrogen cyanide, alcohols, amines,and amides. Acetylene can also add to itself or to aldehydes and ketones. Many of the reactions mentioned here are used for the commercial manufacture of various industrial and consumerproducts, such as acetaldehyde, the synthetic rubber neoprene, water-base paints, vinyl fabric and floor coverings, dry-cleaning solvents, and aerosol insecticide sprays. Acetylene isproduced by any of three methods: by reaction of water with calcium carbide, by passage of a hydrocarbon through an electric arc, or by partial combustion of methane with air or oxygen.
Reply:acetylene can polymerize into C6H6 (benzene) at sufficient pressures.the reaction is explosive.oxygen need not be present.A true democracy is two wolves and a sheep voting on what's for lunch.
Reply:YUP, that's one impressive lookin MSDS, but it would be real nice if they included the necessity for OXYGEN to make the "explosion" happen.Hell, they don't even point out that post exothermic reaction the hydrogen will form the dreaded Dihydrogen monoxide, and leave a bunch of carbon floating around in the atmousphere.Appreciation Gains You Recognition-
Reply:Franz: Oxygen is NOT required.
Reply:OK, splain to me how the Hydrogen can produce an exothermic reaction without Oxygen being present.Appreciation Gains You Recognition-
Reply:Anf Hydrogen fusion reactions don't count in this discussion!Appreciation Gains You Recognition-
Reply:*MARKOPOLO IS SITTING BACK, LEARNING MORE THAN HE EVER THOUGHT HE WOULD ABOUT ACETYLENE* !I'll be the LAST one to let you down !
Reply:Originally posted by Franz OK, splain to me how the Hydrogen can produce an exothermic reaction without Oxygen being present.
Reply:I am not a chemist but the bonds between the carbon and hydrogen in acetylene are unstable.  The fracture of those bonds is what creates the energy.The texts I recall indicated that the actual " point of return"  " all is lost"  is around 27 psi.
Reply:While we are on the subject : don't even think about running copper lines around your shop with acetylene in them.  Over time the inside will form copper acetylide which is a totally unstable compound.  Any sudden shock or blow and we have lift off.
Reply:Crithpy, report to the SWAMP forthwith!  Yer just lucky you found a forum where smartasses are appreciated."Over time the inside will form copper acetylide which is a totally unstable compound. Any sudden shock or blow and we have lift off."You mean we weren't going for liftoff?  Next you'll be advising people not to blow up baloons with acetelene + oxygen, and attach firecrackers to them.Appreciation Gains You Recognition-
Reply:Speaking of stupid a guy on halloween eve decided to take home some mix in garbage bags in the back of his Vega.   The event made the news in the suburb of Richmond south of Vancouver BC about 12 years ago.  No injuries to persons but the Vega lost all its windows.  Good ending for a Vega actually.Last week they showed a custom car build and the old bodyman did the styrofoam coffee cup trick for the camera.  A really stupid thing to televise!There are enough injuries and accidents already.
Reply:welp,God has bestowed a certain level of stupidity on mankind in an effort to reduce the gene pool via accidents and any stunt that is preceded by the phrase.... "watch this"which is proof that God created the heaven and the earth and acetylene.A true democracy is two wolves and a sheep voting on what's for lunch.
Reply:Critphy, God did NOT create acetelene, he created Carbide, and mason jars so swamp dwellers could harvest fish from the swamp.Then along came lazy people (probably Democraps) who didn't understand, or want to properly use carbide, and they used dynamite, and got all kinds of stupid government regulations instituted by their rich friends (Kennedys) so poor folks couldn't fish efficiently any more, and would have to go on welfare.It's too damn late for solid logic.Appreciation Gains You Recognition-
Reply:I remember my Ol' man telling me about a game he and his friends used to play when they were kids....back in Pennsylvania.They'd take a paint can, or something similar with a tight-fitting lid.   Put a little carbide in it and wet it, and put the lid on tight. A small hole had been put in the can on the side near the bottom.   One kid would sit on the can, and another would hold a lighted match near the little hole !   Dad said it'd pop them up about 6' in the air !   (and all these damn kids know how to do today is sit in front of a computer) !I'll be the LAST one to let you down !
Reply:I'm not a chemist, But I did stay at a "Holiday Inn" last night.Franz brought up a point. Dihydrogenmonoxide is one of the least publiziced and greatest dangers to mankind that is known. More people die each year due to the various effects caused by this extremely toxic compound, than any other single cause. Death can come in as little as a few minutes when over exposed.Here's an informative webb sight exposing the dangers of this evil substance. I'm sure if John Kerry was informed of the dangers, he would be against it.http://www.dhmo.org/facts.html
Reply:Dammit Jim, you aren't the guy who peed in the hottub last night so we couldn't soak there this morning, ARE YOU?DHMO should definitely be exposed more for the hazard it is, I agree with you on that.Appreciation Gains You Recognition-
Reply:I guess peein in the hot tub is kinda like bringing work home for meOriginally posted by fla jim I'm not a chemist, But I did stay at a "Holiday Inn" last night.Franz brought up a point. Dihydrogenmonoxide is one of the least publiziced and greatest dangers to mankind that is known. More people die each year due to the various effects caused by this extremely toxic compound, than any other single cause. Death can come in as little as a few minutes when over exposed.Here's an informative webb sight exposing the dangers of this evil substance. I'm sure if John Kerry was informed of the dangers, he would be against it.http://www.dhmo.org/facts.html
Reply:Well, a little delay in response (had to... what you call it... oh ya- work. I hate fixing things other people butchered, especialy diesels) but here it goes (any chemists that find errors here, or would care to elaborate where I left out details, please do. It's been a few years):Your question:How can the hydrogen produce and exothermic reaction without oxygen? My response:The hydrogen doesn't produce the major part of the energy in this case. The most energetic portion of the decomposition is breaking of the triple bond between the carbons in the acetylene. Some research does indicates that the decomposition may start with one of the hydrogen bonds breaking as a first step, which will be exothermic, in which case the gas volume will increase, raising pressure (the hydrogen forms a gas, and the acetylide -- CCH -- is a gas, giving an increase in the total molar gas quantity, and the temperature will rise) which feeds the reaction. This is followed by the triple bond breaking, prodicing CH, and the last bond letting go, liberating the other hydrogen atom, which will soom find another free hydrogen and, exothermically, form an H2 molecule. As the temperature increases, the point at which exothermic polymerization occurs may be reached, which opens up a number of possible paths. If the conventional path, as promoted by high-school chemistry teachers and gas suppliers for many years, is correct (the triple bond breaking first), the result is the same.. increase in the molar gas quantity and increase in temperature, but the liberation of hydrogen is only at the end of the process, with no acetylide intermediate.another nice example of an exothermic reaction from decomposition where hydrogen involved and not burning is...... hydrogen peroxide. Decomps to oxygen and H2O. Yes, exothermic, and produces oxygen. And, yes, it is spontaneous. Not terribly energetic on its own, though. (about 700cal/gram- Criminy, you need at least a 20% solution before there is a major risk of the solution boiling from the spontaneous decomposition  ) And no, this is not burning, even though one product is water, as the hydrogen begins the process bonded to the oxygen.Lets look at another one, where there is no water involved at all, known to schoolboys for decades, even back in the days of my youth... Ammonium Tri-iodide. Happy decomposition, triggered by heat, friction, pressure, bright light, sheer spitefulness. Hydrogen (in the ammonia-nitrogen triiodide complex) is involved in the reaction, no need for oxygen during the decomposition  (to iodine and ammonium iodide and nitrogen).There are many other examples.Does this cover it?
Reply:Well sure, if you look at it that way, but since your information wasn't submitted back while we were on that part of the subject, you loose 50% of your grade.We've moved on to ridding the world of the dreaded Dihydrogen monoxide, in the intrest of child safety and future generations now.Does anybody know how to get a federal grant?Appreciation Gains You Recognition-
Reply:enlpck . . . that was very scholarly !   I'm sure that a good number of very "intricate" chemical reactions take place every day in our lives....and 99% of them go un-noticed.   For the "average" person however,  I still think you need oxygen to make something go "KA-BOOM".I'll be the LAST one to let you down !
Reply:Ah, but this has quite a lot to do with eliminating the dreaded dihydrogen monoxide. Note the portion devoted to ammonium triiodide. No dihydrogen monixide, AND, the added benefit of Kaboom!!
Reply:Oh, OF COURSE !....HOW COULD I HAVE OVERLOOKED THAT !  (sorry, i couldn't resist)  I'll be the LAST one to let you down !
Reply:3 beers and a plate of greasy Mexican food results in the endothermic and subsequent exothemic liberation of intestinal gas (tetra-hydro-tri-chiwawa-propane) ...........There's no need for oxygen ...........In fact, by morning, you'll be gasping for oxygen..A true democracy is two wolves and a sheep voting on what's for lunch.
Reply:My lord, does that bring back memories. A crew cab, 5 of us, a hint of.... lunch. Sudenly, one smiling guy in the truck, four of us outside, all doors open, gasping.
Reply:Franz, some posts ago, maybe on the old site, we talked about Redox reactions, i.e. explosive reactions that don't require oxygen. Acetylene will  ignite in the presence of chlorine gas without oxygen.  Or take a piece of sodium in a glass ampule.  Put that into a test tube of carbon tetrachloride (remember the pre-EPA days when we thought that was a great fluid for dry cleaning?), cap it and drop it out the window.  Ka-Boom! (assuming the ampule containing the sodium broke).  And no oxygen there, either.  A classic Redox reaction.  Halon sprayed on light metals like lithium, potassium, etc. will do it also.So, similarly,  any time you break the molecular bonds, which appears to happen somehow when C2H2 is pumped above 15 psi, you're gonna' release energy.  And also in the presence of some metals you may get an exothermic reaction.  After all, that's the principle behind fuel cells.But in retrospect,  I don't claim to be a chemist.  Maybe a chemist out there can give a better explanation.
Reply:OP, There are myriad combinations of ingredients (many reaily available at the grocery store) that will yield very rapid burn rates, please note, I ain't usin the E word, cause I don't need a visit from some Gooburmunt Agent, as my license is expired.Most people would be amazed at what can be done with Peanut Butter, or pool chlorine, but I ain't splainin it on the internet.Back to the original question Acetelene at pressures above 15psi; I still contend cannot yield a rapid exothermic action without the presence of oxygen.  Were it possible, how in hell could acetelene exist in the area of the cylinder above the concretious sponge inside the tank?The ACETONE the acetelene is disolved in is all volumetricly contained within the concretious material. and acetelene gas at high pressure is above that, and all the way into the pressure side of the regulator.  The acetelene gas compound in that sealed environment does not, and aparently cannot break down.When the same acetelene gas above 15psi contacts the atmousphere, the breakdown action will occurr.  That breakdown in the presence of oxygen will make BOOM!Given that we are about the same vintage, you may recall back in the 50s, several manufacturers marketed Acetelene/air torches that connected directly to either a B or MC size PresToLite tank, sans regulator.  All flame control on those torches was accomplished by "cracking" the valve on the cylinder.  Those cylinders were certainly emitting acetelene to the torch at a pressure above 15psi, and yet no breakdown occurred.  Acetelene by itself, may well breakdown the molecular bond, BUT, even if that happens, without Oxygen, NO flame, regardless of speed thereof, will occurr.Discharge of acetelene at more than 15psi to the atmousphere, may well result in molecular delinking, along with oxygenation, yielding the well known KABOOM.This reaction is very similar to an oxygen saturated pillow in a hospital environment meeting a source of ignition.Appreciation Gains You Recognition-
Reply:Before I hook up a new tank I crack open the valve to blow out any debris. So your saying not to do that because it could cause an explosion, right?
Reply:No. Because the pressure instantaineously drops below 15 PSI accross the cracked valve!
Reply:I've always cracked the valves first.  But the spent gas is not under pressure at that point and there is no way for the oxygen to get back into the tank.  But after reading all this and a few things from the army which says not to run pressure higher than 15psi or 29.5psi(depending on which part of the article you are reading) because heat or shock can cause an explosion.  But then I was looking back at acetelene welding.  I'm not sure if my Victor welding chart is accurate.  Does anyone have a victor book with them that says what the recomended psi is supposed to be for a tip of 3 or greater? Who's on first?Common sense in an uncommon degree is what the world calls wisdom.
Reply:after reading this info (commercial) from Linde, you will be the all knowing all seeing Acetylene God on your block.http://www.linde-gas.com/Internation...pdf_acetylene/$file/Acetylene_update.pdfyour knowledge is now boundless and nude virgins will lay before you.Last edited by Crithpy_Critter; 03-28-2004 at 09:18 PM.A true democracy is two wolves and a sheep voting on what's for lunch.
Reply:dammit...the rat bastards won't allow the link...............the virgins will have to wait until I can post it some other way.A true democracy is two wolves and a sheep voting on what's for lunch.
Reply:Crithpy here's your link to acetylene
Reply:Remember:  Oxygen is not the only oxidizer!On the DHMO issue, though, if stray electrical currents were to pass through it, it would separate into a highly explosive gas and a potent oxidizer, not a good combination unless done on purpose.  How is this stuff still legal?