When is the cylinder "empty"?

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I'm running a 130 cf actylene cylinder and was curious how low I should let the pressure get before exchanging the tank for a fresh one.  My understanding is that if I draw from a cylinder that is too low, I could pull out acetone.
Reply:Draw it down 'til it won't supply sufficient gas to burn.  Acetone won't be a problem as long as you don't tilt the cylinder.Last edited by Dmaxer; 01-21-2010 at 05:17 PM.Reason: SpellingScottMiller XMT 350 CC/CV w/gas solenoid opt.Miller S-22A wirefeederBernard 400A "Q" gunMiller Spoolmatic 30A / WC-24C-K 200A torch/gas lensWeldcraft WC-18 watercooled torchHypertherm Powermax 30Victor O/A
Reply:If you start pulling a little acetone in your torch you'll see it right away. If you start seeing the flames change color shut it off.Tough as nails and damn near as smart
Reply:The Acetylene tank is a volume related solution. Your greatest concern is when you pull too much acetylene BY RATIO to the volume of the tank. The acetylene is encapsulated with the acetone, and the chemical reaction/ transfer from liquid to gas can only happen so fast. Go too fast, it takes acetone with it, and you have problems. If you are drawing acetylene at a slow rate/ ie at the safe rate for the volume of your tank, then you can run that bottle down until you have no pressure left. You will simply have the acetone left in the tank. Time to refill.Note: as temp goes up, that bottle would again show a little pressure as more of the gas is released. When you can't carry a solid flame, just refill it.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Okay.  Thanks!
Reply:In a lot of ways, this is similar to a soda bottle charged with CO2. When you first open the top, the CO2 pressure is high because much of it is dissolved in the water, so the liquid bubbles as the gas is released, and can overflow the container's mouth; this is comparable to drawing the acetylene out to fast. As the CO2  amount drops, both its pressure and the rate it leaves the liquid also drop until none is left dissolved.In both cases, if the bottle is lying on its side, the liquid will also come out. The obvious difference is that with the soda pop, you normally drink the carbonated 'carrier' liquid; the acetylene tanks are made so straws don't fit in well.
Reply:Take off regulator.Look into little round hole.Turn on valve.Nothing comes out?Its empty.Sorry.
Reply:Originally Posted by WelderskelterTake off regulator.Look into little round hole.Turn on valve.Nothing comes out?Its empty.Sorry.
Reply:Well,I have worked for a government agency (Coast Guard). Our tanks at one location were customer owned but not on an exchange schedule with our gas supplier. They were "U.S. Government" labeled tanks and they would fill them and send them back to us.If we turned in a tank that was completely empty, they would charge us for a tank inspection, if it was due or not. The thought being that moisture or some other substance could find its way into the tank and cause problems. As a habit, I always stop using a bottle when it falls below 100 #s.Miller Syncrowave 200
Reply:Originally Posted by ashley1284I'm running a 130 cf actylene cylinder and was curious how low I should let the pressure get before exchanging the tank for a fresh one.  My understanding is that if I draw from a cylinder that is too low, I could pull out acetone.
Reply:Originally Posted by Ian-MetalSmithWell,I have worked for a government agency (Coast Guard). Our tanks at one location were customer owned but not on an exchange schedule with our gas supplier. They were "U.S. Government" labeled tanks and they would fill them and send them back to us.If we turned in a tank that was completely empty, they would charge us for a tank inspection, if it was due or not. The thought being that moisture or some other substance could find its way into the tank and cause problems. As a habit, I always stop using a bottle when it falls below 100 #s.
Reply:If the acetylene output cannot match the oxy output, then it's high time to refill. Can't be watching the guages the whole time, but having to frequently turn up the acetylene while welding is a sure sign to read the guages and switch tanks.When the pressure in the acetylene tank gets too low then oxygen at a much higher pressure can enter the hose and possibly the acetylene tank. A bomb just waiting for a spark? If there are back-flow arrestors do you trust them at seepage levels?Orion pulse-arc welderStick an O/A too
Reply:When your acetylene bottle gets too low on pressure you start pulling acetone you can see it in the color of your flame and also smell it. My old LWS owner who passed on several years ago and was a pretty sharp guy said that you should replace your acetylene bottle when it dropped to 50# pressure or you started burning acetone. That is about when you will notice the flame color change. I used to purchase steel at a place that changed the acetylene bottle when the fire went out on his torch.
Reply:You will NOT, no matter how low the pressure gets, pull acetone out of an upright acetylene tank.   What WILL happen, as the supply of acetylene drops, you will get more and more of an oxidizing flame.   This will increase your chances of creating a flashback in your torch.  If I'm using a big rosebud, or a large cutting tip, I will generally switch over to a fresh tank, or hook two tanks together, before I start.   Save the partial tank for use with a smaller tip.   If using a 000 tip, you see a sharper cone (more oxidizing), it's absolutely time to replace.