Welding Tips and Tricks

So I've started a new job in a big fabrication factory and there's quite a lot of Oxy acetylene rigs all over. I've not had much experience with o/a but I'm confused with the withdrawal rate rules.... We only use the rigs for cutting and they are the biggest cylinders you can get here (320cf) I've been told about changing the tips for different thickness steels but no one there seems to know about the withdrawal rates? What's the safest size tip to use for a cylinder this size? Or could someone explain it simpler terms. I've been searching all over the net and can't find a straight forward answer.

Thanks

The cylinder size has little do with the flow rate of the fuel/oxy. The tip size is best matched to the flow rate of the 2 fuels, and that info is generally available in the manufacturers (tip) catalog for recommendations. The cylinder is nothing more than a reservoir...

As a rule, the thicker the material, the larger diameter the tip is used

You can use what ever sized tip for the metal you are cutting, but it's the pressure that is most important with acetylene. Over 15 psi it becomes unstable. Most manufacturers have a table available for pressure of gasses per tip size, but the last time I checked most ran at 3-5 psi., 20 on the oxygen.

Withdrawal rates can be an issue! Usually if your trying to run too big of a tip off of too small of a tank. Or if the tank gets real cold. It will cause the acetylene to draw out the liquid acetone and it will shoot green fire balls from the tip. This is a very bad and possibly deadly condition! I'll see if I can't find my book with charts and post a few pics.

In heavy demolition, I've never used a gauge setting above 12 PSI on Acetylene. The oxy'acet flame's only purpose is to preheat the surface of the metal ahead of you. Once you're cutting, the burning of steel with pure oxygen is your primary heat source below the surface. The cut limit is controlled by tip size (mainly the cutting orifice, which is pure O2) and O2 pressure. I've run as high as 80-90 on O2. (Higher on natural gas, but that's another topic.) On that 320CF cylinder, you're not going to push withdrawal limits at any practical tip size at 12 PSI or less. I've cut rusty fly-ash covered 2" sections with a #3 tip, and if it's a bit cleaner, a #2 will do fine.

Steve

crouchy wrote:So I've started a new job in a big fabrication factory and there's quite a lot of Oxy acetylene rigs all over. I've not had much experience with o/a but I'm confused with the withdrawal rate rules.... We only use the rigs for cutting and they are the biggest cylinders you can get here (320cf) I've been told about changing the tips for different thickness steels but no one there seems to know about the withdrawal rates? What's the safest size tip to use for a cylinder this size? Or could someone explain it simpler terms. I've been searching all over the net and can't find a straight forward answer.

Thanks

Here you go, this should help.
http://www.thefabricator.com/article/sa ... -knowledge

Knowing the newer 1/10 withdrawal rule, and looking up the flow rate of your torch tip, with get you on the right path.

You'll likely find out that the tank size you're using was chosen because the tip can't overdraw it.

Cheers guys, that would kinda make sense them choosing the biggest bottles as to not to overdraw