Hi all How to calculate this? Are there any general formulae? Besides, since a given tip has a given set of OA pressures, which is the acceptable variation range? And, there is some rule of thumb regarding how long should be the flame inner cone as per tip size?
My welding instructor once had to cut up a die show (lower, IIRC) weighing something like 40 tons. He had a helper that would exclusively reload his tanks. Essentially, once the helper had loaded another O2 tank, the rig was switched over and it was then run out as the next O2 tank was ready. Something like 11" thick. Now that's draw.
1/7 is also what I've been taught (more on topic). You can manifold acetylene tanks to increase your draw (two tanks, double the draw, and so on) Does anyone here do work that might cause a tank to run out faster?
That helps with propane tanks, but doesn't apply to the case of acetylene tanks. The reason for limiting withdrawl rates to 1/7th tank capacity per hour is to prevent pulling over acetone from the acetylene tank. The acetylene is stored in solution with the liquid acetone, and it needs some time to come out of solution. If you withdraw faster than about 1/7th tank capacity per hour, you start getting a mixture of acetylene and acetone coming out. That contaminates the flame.
On Mon, 19 Jan 2004 14:17:21 -0500, Gary Coffman vaguely proposed a theory ......and in reply I say!:
Actually from my experience I was joking. The reason, AFAIK, that any of these give trouble, is that withdrawing large amounts of pressure gets them cold. Wrapping them up makes it worse, unless the weather is itself extremely cold.
**************************************************** sorry remove ns from my header address to reply via email
I was frightened by the idea of a conspiracy that was causing it all. But then I was terrified that maybe there was no plan, really. Is this unpleasant mess all a mistake?
I have also been taught that the withdraw rate has to do with pulling acetylene through the rig. Very bad for rubber hoses. Essentially the rig has to be rebuilt. Again, this is coming from my instructor who has actually had to use a manifold while cutting to prevent this from happening. All his theory of this type comes out of operator manuals from Victor...
Check with your equipment supplier, my local dealer has tip charts for all the makes he sells, they're free. They have orfice sizes and gas flows per hour on them for each tip. Also recommended pressures for each tip size and the thickness of material each size can handle. One reason to go with a local dealer for your equipment rather than going mail order(or import) is support.
1/7 of the acetylene tank capacity per hour is the rule. Doesn't become a real problem until you start getting into the larger welding tip sizes or are doing a lot of cutting on heavy steel.
I tend to go one welding tip size larger than the recommended size on the chart, it's easy to crank down the pressure but if you have to increase it until the flame really hisses, the molten puddle gets blown around a lot and you can blow holes in the work, if it's thin. I like a quiet flame and a pool that just sits there waiting for filler additions. I've invested in enough tips that I can do this. The ones that come with the sets are just enough to get you started and into trouble... I also use filler rod of known composition, not coathanger wire.
My rule of thumb until you hit the top two or three tip sizes is that the inner cone of the flame about matches the material thickness. No scientific reasoning behind this, just observation. With the larger tip sizes, the cone doesn't increase in length that much from size to size, it gets fatter and the tip of the cone becomes more rounded. Use the tip chart as a guide.
1/7th of maximum rated capacity per hour. Note that this means it should take 7 hours to empty a cylinder at the rated draw for that size, whatever size that might be. So if you're emptying any size acetylene cylinder in less than 7 hours of use, you're drawing gas from it too rapidly for safety. That's why you need bigger cylinders (or ganged cylinders) to feed bigger flames.