O/A: Torch drawing acetone?

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I've heard that if you use any more than about 1/7 of the gas capacity of your acetylene tank in a short span of time (single welding session, maybe) that you may start to have acetone delivered through the hose into your torch.Okay, but what I'm wondering is: how could you tell if the torch was delivering some acetone into the flame?  What would the flame do, or look like?And this may or may not be related, but a number of times I've noticed that at the beginning of an O/A welding session the flame (both inner cone and outer flame) seems longer, and then (after a while) seems to shorten up - even when I add more acetylene and balance it (for a neutral flame) with more oxygen using the torch valves.  Still stays pretty short.  What causes this? Seems to occur even when there is plenty of gas left in the acetylene bottle.
Reply:if your tank is layed down, and then you stand it back up and hook up your gear you can get acetone out of it.  I've always heard, if a acet. tank is layed down when you stand it back up let it set twice as long as the time it was layed down. Is the pressure changing on your gages when this happens? could be a worn diaphragm in the regulator?  I've seen regulator pressures back off over time as you're using itMiller Maxstar S modelVictor Journeyman torchB&D 4 1/2 and 7" Grinders"You want me to weld that?  I thought you said I wasn't safe with a Caulking Gun?"
Reply:Anytime my flame changes or the sound changes, I clean the tip. Tip cleaners aren't files, pick one that fits easily.Last edited by Craig in Denver; 03-31-2009 at 08:49 PM.9-11-2001......We Will Never ForgetRetired desk jockey. Hobby weldor with a little training. Craftsman O/A---Flat, Vert, Ovhd, Horz. Miller Syncrowave 250
Reply:Thanks, Smoky Joe.  No, I avoid laying my acet tank over, at any time.Also, Craig:  I do clean my tips, usually before I do any welding or brazing.The more I think about it, the more I think the two points I raised are separate, not related.  So they are:1.  How can I tell if I've used enough actylene that acetone will come through the hose?  (That is, how can I tell from the flame at the torch tip?)2.  Why do the O/A flames shorten (both the inner and outer flame)?As suggested above, the answer to #2 might be that the regulators are gradually coming out of the original fine-tuning I give them for working pressure, so they may need to be adjusted during the welding session.
Reply:Originally Posted by Joel_BCI've heard that if you use any more than about 1/7 of the gas capacity of your acetylene tank in a short span of time (single welding session, maybe) that you may start to have acetone delivered through the hose into your torch.Okay, but what I'm wondering is: how could you tell if the torch was delivering some acetone into the flame?  What would the flame do, or look like?And this may or may not be related, but a number of times I've noticed that at the beginning of an O/A welding session the flame (both inner cone and outer flame) seems longer, and then (after a while) seems to shorten up - even when I add more acetylene and balance it (for a neutral flame) with more oxygen using the torch valves.  Still stays pretty short.  What causes this? Seems to occur even when there is plenty of gas left in the acetylene bottle.
Reply:Is your acetylene cracked open enough?  What size tanks?
Reply:You can get a rough idea of the flow requirements of your most commonly used tips. That and the size of your tank will tell you the probability of drafting acetone. For instance a tip that uses 6 scfh at maybe 6 psi, and you have a 120 cubic foot tank, there's no need to sweat. With that info you can narrow it down to tips that have a good chance, ones that you'd have to run for extended periods and ones that don't stand a chance.Last edited by Sandy; 04-01-2009 at 12:49 AM.
Reply:I think the reason your flame changes slightly(from neutral) when you adjust it is because you hands are on the needles valves and when you let go they realeas slightly, more pronounced as the torches age or are abused by over tightening.
Reply:Acetone in an OA system can result from drawing to much acetylene and from the filling station at the supplier over filling the acetylene tank with acetone.  The Acetone is in the tank to keep the acetylene molecule separated.  Acetylene is very unstable at pressures over 22 psi in a free state.The easiest way to tell if you have acetone in your torch is to look at your hose connections.  It take a lot of acetone to work it way all the way to your torch, it leaves a reddish brown residue every where.  If you have acetone in your hose and torch it has damaged the regulator also and it is only a matter of time before it fails.  Your second question about the torch flame going from neutral to oxidizing is caused by a decrease in acetylene flow.   This can be caused by many things. 1-Acetylene cylinder can not keep up this demand for gas.  Because an acetylene tank can only delivery 1/7 of its capacity an hour, it is very easy to drawn to much, which will reduce the flow rates.  Note: The 1/7 rule applies to cylinder at the time of uses.  For example, a cylinder that original had 140cf of acetylene is half full, it now only has 70cuft of acetylene and you can only use 7 cuft per hour. 2-You have a gas restriction somewhere.  Flash arrestor and check valves are a good place to start.  It possible it is your regulator, however, all regulators fail open, meaning they delivery to much gas, but there could be a blockage. Hope this helps!OAdoctorwww.regulatortorchrepair.com
Reply:I was taught that once you have run acetone through the system you have to have your regulator serviced.Gordie -- "I believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."
Reply:OADoctor,You may wish to go back and verify your comment about draw rate on an acetylene tank.  In the example you listed, a 140 cu. ft. tank at half full, you can only draw 1/7 of 70 cu. ft.Using this same logic, at 25% full, you could draw only 5 cu. ft./ hr. which would not even supply a Smith 0 cutting tip.I think you're wrong in your assessment.  The supply of acetylene from a given size bottle is determined by the TOTAL volume of a given size cylinder.  This has to do with the rate the liquid acetylene "boils off" to become a gas within the cylinder.Also, per your comments, last time I checked my math, 1/7th of 70 is 10 not 7.I see a lot of WRONG answers from the rookies on these boards.  Coming from someone supposedly "in the business", this advice is particularly grevious.  Bad advice in the area of OA can get people seriously hurt.In summary, this was a BS/dangerous posting and should be removed.PS Been using OA since the days when we mixed calcium carbide in a hopper to produce our own acetylene gas.  Also, if you check, there are some sources who now recommend a draw rate of less than 1/10 of cylinder capacity, not the old established rate of 1/7.I know where I'm NOT having my O/A gear serviced.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:PS Been using OA since the days when we mixed calcium carbide in a hopper to produce our own acetylene gas. Also, if you check, there are some sources who now recommend a draw rate of less than 1/10 of cylinder capacity, not the old established rate of 1/7.
Reply:Response  to SundownIII: I was given the information when I was employed by a welding supply company in the early 90's. I was attending a Victor Equipment School for gas apparatus.If an acetylene cylinder has a full capacity of 140CF.  When it is half full it only has 70cf in the tank. (I humble apologize for the the math error, you are correct, 1/7 of 70 is of course 10cf) If you are using a heating tip that draws 15 cuft per hour, it will not over draw the cylinder when it is full, but when the tank is half full it will if it is  used in a continual manner.  The 1/7 rule everyone uses is for continual uses. (Air Products by the way, the manufacturer of Acetylene gas, states that the intermitted withdraw rate is 1/10 and the continual rate is 1/15 of capicity, see this link, http://www.airproducts.com/nr/rdonly...fetygram13.pdf ).   As for my post being dangerous, I think you are grossly out of line.  If I am wrong as you suggest, the only thing that will result in following my advise is someone will not use a cylinder for large cutting or heating jobs that is not totally full, which only increases the safety of the OA operation.  It may result in an increase cost of operation but will in no way be dangerous.   I have seen too many time heating tips and cutting torch that have flashed back because an acetylene tank was used that was to small.  Acetylene burns at an extremely fast rate, and if there is not enough volume of gas being delivered to the flame it will burn back in the torch or heating head.  Anyone starting a job that requires  a lot of heating or cutting would be playing it safe to use a full cylinder.OAdoctorwww.regulatortorchrepair.com