Oxy-Acytelene Welding help needed!

[John Coloccia]

A leak must have crept into my setup from the time I checked it for leaks (just before starting the project) to a couple of hours into a project. I noticed my torch spitting, and immediately shut things down. I went over to my acetylene tank and noticed it was down to about 50psi. This was a new tank!

I only have about and hour, maybe slightly more, welding time on this tank. Clearly, I've exceeded the safe withdrawal rate of the tank, by quite a bit.

It's all shut down now, but I'm not sure what to do. Nothing's gone kaboom. Is it safe to disconnect everything and have the tank picked up, or should I not even touch it? I know acetylene is unstable without enough acetone, but I don't know if that means it would have already gone boom or it can go boom at any time or with some movement.

I'm guessing that since it's at 50psi just sitting in the tank, there's not a whole lot I can do to it just moving it that it wouldn't have already done on it's own, but I need some advice from a real pro here.

[David Freed]

I have worked with or around oxy-acetylene setups for over 30 years and I have never heard of an unsafe withdrawal rate. Of of all the different people I have worked with nobody has mentioned it. I did some searching and found this.

http://www.thermadyne.com/IM_Uploads...20guide_lo.pdf (http://www.thermadyne.com/IM_Uploads...20guide_lo.pdf)

On page 14 in the middle of the page it talks about a fusible plug in all cylinders that will not allow the cylinder to explode. Read the whole paragraph for yourself, but I think it would be safe to move the cylinder outside and call the gas company.

At one place I worked, one of the guys told about the flame flashing back (that probably isn't the right term) up the hose and the cylinder itself caught fire. He said the flames were almost touching the ceiling and the cylinder had a high pitch scream. Of course everyone "ran for their life", but he said it just burned itself out. They couldn't go back to work for a little while though, because the shop was full of smoke.

[John Coloccia]

I have worked with or around oxy-acetylene setups for over 30 years and I have never heard of an unsafe withdrawal rate. Of of all the different people I have worked with nobody has mentioned it. I did some searching and found this.

http://www.thermadyne.com/IM_Uploads...20guide_lo.pdf (http://www.thermadyne.com/IM_Uploads...20guide_lo.pdf)

On page 14 in the middle of the page it talks about a fusible plug in all cylinders that will not allow the cylinder to explode. Read the whole paragraph for yourself, but I think it would be safe to move the cylinder outside and call the gas company.

At one place I worked, one of the guys told about the flame flashing back (that probably isn't the right term) up the hose and the cylinder itself caught fire. He said the flames were almost touching the ceiling and the cylinder had a high pitch scream. Of course everyone "ran for their life", but he said it just burned itself out. They couldn't go back to work for a little while though, because the shop was full of smoke.

If you take too much out of the cylinder at once, some of the acetone comes out with the acetylene. Theoretically you can take so much acetone out that the acetylene (under high pressure) becomes unstable and goes boom. 1/7 capacity was the old number. The new one is 1/10. So if you have a 140 cubic foot tank, you can safely withdraw 20 cubic feet per hour (or 14 if you like the new spec better). I practically drained the whole darn thing in an hour!

I decided to just disconnect everything and move it. When I thought about where the tank was sitting, it was basically outside my bedroom window, two floors down....where my wife is sleeping. So move it I did. While I was at it, I found the leak. My shiny new Smith regulator is leaking from the body somewhere.

I'm still curious if generally it was safe to move it or if there's some other procedure to follow.

[Chris Parks]

No reg will pass enough Acetylene to include Acetone in normal operation, that is a fact. The only time a reg will get Acetone through it is if the bottle is laying down during use or has been laying down and at least 30 minutes has not been allowed since it has been stood up. The 30 minutes is to allow the Acetone to settle into the porous material that holds it in the bottom of the bottle. There is a fusible plug and this melts if in a fire and prevents an explosion by allowing the gas to escape in a semi-controlled manner but I still would not like to be around. If in doubt at any time first close the bottle valve and then release the hose pressure by opening the acetylene control on the hand piece BEFORE closing the reg valve. This means the hose has no pressure in and the reg is not loaded. After welding both hoses should be relieved of all gas in this manner and the regs closed. Leaving a reg open and opening the main bottle valve is a sure way to damage the reg gauges as they are slammed on by the gas pressure.

[Ed Jolin]

Good question, John. I've also heard and read of the 1/7th rule, but now that you ask, they never tell you what to do once you've significantly exceeded that rate...

I would call my gas supplier and ask. I would also ask whether getting acetone in regs/hoses would cause concern for damage.

Alternatively, since it's they're probably not open on Sunday, Hobart has a good welding forum, as does weldingweb.com. (no affiliation w/ either)

I'm interested in what you find out!

[Scott T Smith]

If you take too much out of the cylinder at once, some of the acetone comes out with the acetylene. Theoretically you can take so much acetone out that the acetylene (under high pressure) becomes unstable and goes boom. 1/7 capacity was the old number. The new one is 1/10. So if you have a 140 cubic foot tank, you can safely withdraw 20 cubic feet per hour (or 14 if you like the new spec better). I practically drained the whole darn thing in an hour!



According to what my welding supplier told me a few years ago, the statement above is correct.

Unless you have a leak, about the only time that you need to worry about flowing too much acytelene is if you are using a rosebud tip with a small tank - especially if it is a larger rosebud. Rosebuds typically require a lot of acytelene pressure and flow, and can evacuate the tank too quickly. Most other tips won't flow enough gas to cause a problem.