True pressure acetylene becomes unstable at

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I already know what the real pressure acetylene becomes unstable at. The industry safety standard is 15 PSI but who elese knows the true pressure. Just thought I would ask and maybe see what information people can share on it. --Gol'
Reply:Maybe this is a question better left unanswered so that we don't end up with a bunch of guys that don't know any better pushing the limits and hurting themselves or others. DaveI am what I am, Deal with it!If necessity is the Mother of Invention, I must be the Father of Desperation!
Reply:Hence its being disolved in acetone and kept in agamassan filled cylinders for safe storage and use.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:15 pounds is what I read everywhere so why go further?
Reply:15 it CAN BECOME UNSTABLE, but MAY NOT, defintely more shock sensitive at 15 psi.Ive actually had acetylene up to 25 psi, on accident, i was extremely careful shutting the rig down and bleeding it off.Ive heard spontaneous combustion will occur above 25 psi, and it will combust for sure above 30 psi, i dont have the desire to find out though.
Reply:Why would you ever want to go more than 15 psi anyway?   I have had, on occasion, a diaphram in the regulator crack, in use, believe me, it's not a pretty sight.   Course, shut down ASAP.   If you need more heat, just put a bigger tip on, or a bigger rosebud, and use the appropriate sized tank or tanks hooked together.   Cranking up the pressure, is kinda like running a 120v mig on 480 three phase .....
Reply:Subjects like this don't have a simple answer; in this case, what happens depends greatly on the conditions. Different metals and even different surface conditions of the same metals can have different catalytic properties and of course the temperature, the presence of other gases (especially oxygen) and the size of the cavity holding the gas will all have an effect.Acetylene (C2H2) doesn't need  to react with anything else; it has a high energy triple bond between the carbons and when conditions are 'wrong', the molecule comes apart, mostly liberating free carbon, hydrogen gas and lots of heat which causes an explosive increase in the pressure.When oxygen is present, it  can be even worse. Consider the fact that when your torch tip overheats and pops, the volume of gas is very small and also well contained yet the noise is very loud.
Reply:if you need more pressure than 15psi, try MAPP gas.  It doesnt burn as hot, but it has the same volility as water when stored in a pressurized cylinder.  also requires different torch tips."Real power is an arcair hand torch with a piece of 3/4 inch carbon and 1500 amps.  You feel like Zeus throwing a lightning bolt."
Reply:go1lum---just as example how powerful acetylene is (and dangerous)when I was living in a small town in Wyoming two bored workers at a bentonite plant filled a 25 gallon trash bag with acetylene from a handy torch,put it in the middle of the warehouse floor and lit the bag on fire.Our heroes sat on a stack of bagged product to watch the show.The concussion was heard two miles away in town---knocked them both out briefly---and blew out numerous windows.Amazingly they were not fired --- but had to spend their own time cleaning up the mess!!
Reply:Instrumentation and Analytical Science - Google Books Resultby P. A. G. Payne, Institution of Electrical ... - 1989 - Technology & Engineering - 437 pages”As the acetylene evaporates from the acetone solution, and passes out of the reducing valve, it warms slightly as the Joule-Thompson coefficient is negative ...” Most pressurized gases have a positive Joule-Thompson coefficient.  When such a gas passes through a restricting orifice (i.e., a valve seat or hole in a pipe), its temperature decreases.  The temperature of a gas with negative Joule-Thompson coefficients increases as it passes through the orifice.  Pressurized hydrogen (another gas with a negative Joule-Thompson coefficient) will sometimes auto-ignite when it exits an orifice into an atmosphere that contains oxygen (e.g., air).   As a previous response to your post pointed out, there are many variables involved that could influence whether a one-time pressurization of acetlyene ignites and explodes.  15 psi is probably the lowest pressure that auto-ignition of acetylene was observed during a series of tests under controlled conditions.As for you knowing the actual pressure at which acetylene auto-ignites, please don't share it with us.Last edited by Teddco; 08-30-2008 at 08:59 PM.TeddCoHTP Microcut 400 & Invertig 160DC  Smith Dual Guard MD-510 OA Rig  Lincoln SP135+  Hobart Stickmate LX 235/160
Reply:C2H2 is generally considered to auto-ignite at 28psi at 70 degrees F.Never seen it, but I have seen a leaky hose fill a small space and ignite...scary.
Reply:Originally Posted by 4sooth.Amazingly they were not fired --- but had to spend their own time cleaning up the mess!!
Reply:From one of my welding books on the chemistry of welding from 1916.Acetylene free of being absorbed in acetone ( or water) known to be safe at 2 atmospheres absolute (14.7 gauge) and is considered safe at pressures above this to a limited degree. At 40 atmospheres absolute it becomes very unstable and auto-ignition is possible depending on the environment. This book goes into detail on design and function of acetylene generators, and the pumps used to raise the pressure to bottle the gas. I dont know why anyone would EVER need to go over 15 psi gauge, especially considering most of the giant shipyard torches could originally operate off on a generator...at about 2-5 psi of fuel pressure.
Reply:Originally Posted by Broccoli1Union job
Reply:I heard a story once about a welder years ago at my old job getting sick and tierd of the crows hanging around the mill site. i guess  one of the loader operators would feed the birds bread on his coffee break and it was the sort of thing that would make his day. The welder also wanted to get even with the loader operator for something, not sure what it was, so he decided he would get "2 birds with one stone". He took a garbage bag filled it with acetylene and put his trouble light inside with the bulb broken and filiment intact. then with 100 feet of extension chord and a half loaf bread to bait the bag he sat out and waited for the a bird to land, an audiance formed, a crow landed, he pluged the light in, and the witnesses told me there was alot of feathers floating around.  Please dont do this. its dangerous.  kinda hard not to laugh about it though lol.Nothing Ever Got Done By Quitting, Never Give Up.
Reply:http://www.doli.virginia.gov/infocen...acetylene.htmlThis link shows what happens when you have a leaking acetylene tank stored in your vehicle and a dome light switch or electric door lock solenoid arcs.TeddCoHTP Microcut 400 & Invertig 160DC  Smith Dual Guard MD-510 OA Rig  Lincoln SP135+  Hobart Stickmate LX 235/160