Gas Cutting

[Oldhand]

I hardly ever post on this forum but I'm going to chime in on this. Acetylene becomes unstable above 15# when in a gaseous state. It is desolved in acetone when it is still in the bottle and is stable. Acetylene should never be used from a bottle laying on it's side as that draws acetone from the bottle. Acetylene shouldn't be be used from a bottle that has been laying down until it has stood upright for 30 minutes.

Oxygen by it's self is not dangerous. It promotes rapid combustion of flammable materials though is why you have to be careful. Never use oil or grease around high pressure oxygen as it can lead to an explosion as seen in the video.If you just have to lubricate something on an oxygen regulator use soap. Clean and dry is best.

When cutting I always set my regulators at 10# acetylene and 40# oxygen and use that unless I'm cutting metal over 1/2" thick. It saves steps back and forth to your bottles. Those little valves on your torch are regulating devices as long as your tip is not plugged and can be used to set your flame. You can feather your cutting oxygen lever for the thickness of metal you are cutting also. I cut 16 guage to 1/2" plate with a 00 tip and those pressures. Above 1/2" I'll increase tip size and oxygen pressure for the thickness of the material. I'll also increase acetylene pressure when using a #4 cutting tip or a big scarfing tip.

The pressure in a bottle of acetylene varies a great deal with the temperature. I have seen a full bottle register 375# pressure on a summer day when the temperature is over 100 degrees. I've also seen a full bottle only show 140# when the temperature is around 20 degrees. Acetylene bottles are filled and measured by cubic feet, not pressure. Oxygen bottles are filled to 2200# pressure maximum and doesn't vary a lot by temperature.

That's the way I've always used them. Actually, don't remember ever having the acet. over 9-10.

Used to braze a lot of carbide tipped tooling, cutting plate, etc.

 

[Peanut]

i bet that would make a boom! we used to put the oxygen in styrofoam cups and put a cig lighter to it. oxygen is the best acelerent there is. i was gonna rig up a small bottle to a briggs engine and slowly crack the vavle and use it as nitro but a buddy beat me to it and said his motor just exploded . the good news is he said before it blew . thats the most rpm's that little engine ever seen. i'm sure with the right mixture of oxygen in the line it would run for a while but there's it would be interesting to try a car engine with it. i bet it would probably increase the gas mileage because it would fully burn all the fuel not to mention it would probably use less fuel to get the explosion needed to push the piston down.

 

[OldMasterTech]

Hi all,
These new Plasma cutters are incredible to use and watch in action.
They cut through 10mm plate like a knife through butter !
However, what happens when you need to do a job outside or in the field ?
Call for the gas bottles is the cry ! [Oxy-acetylene or Unsaturated hydrocarbon if you're a boffin]
Once you've lugged the heavy things to the job what pressures do you use for cutting ?
I always have a 5/45 mix and was wondering what pressures you all prefer ?
This is usually fine for anything up to 10mm plate I find although for box I reduce the mix down to 4/40.
Cheers !
Jon

Instead I took a heavy duty plastic pallet, covered it with a half-sheet of 1" plywood, then mounted my Miller Bobcat, a vertical compressor and my Miller Spectrum 75 plasma cutter on it.
Now I can slide the whole assembly into the RTV bed and hit the woods or the field or wherever I left the broken item. If I'm heading to a swampy spot I just leave the pallet assy. right on the forks of the tractor instead of using the RTV.
Took two weekends to build & wire because I ran the output of the Bobcat into a surplus 100 amp circuit breaker box and did a nice (to code) wiring job on all components.
The torches are retired to the corner of the shed where they are ageing quietly........

 

[Red Beard]

Well said Doubleh!! Anyone who has trouble believing you better do some reading!! The aceteline pressure is for real. Some rigs use a blow back valve to keep an explosion out of the aceteline tank ( when the torch pops ). Don't they also use, or used to use corn cob media with the acetone in the tank? The oxygen only mixes with combustable materials ( plastic, asphalt, clothing, skin, metal, ect. ) to make or allow them burn, although that does make oxygen very dangerous also.

 

[Peanut]

for the blowback we used to keep a bucket of water when doing alot of highpressure washing.when you hear the pop and then the wistle it's time to drop it in the bucket. the best thing to be safe with when useing oxy/acetelene is to make sure your not around grease . and never let the hoses come into contact with grease or oil. if you have a shop then mount your bottles outside with a shutoff valve inside to shut them down .we had to hoses go up into flames because we had them coiled up on a rack inside the shop and you guessed it the vavle was outside near the tanks.when working in a shop never have 100' of hose rolled up if you only use 25' of it . when i'm running my welding truck i take all the hose out and the welding lead out too so that way there is nuthing that can arc out or pinch the lines.i do leave the oxygen bottle in the truck and i elevate the gas bottle about 2" at the cap . the gas is really unstable if you drop the bottle or it gets a sudden jolt from something.in my truck i have it set up for stick/fluxcore and mig so i end up toting 3 bottles lead/hose and that huge thernydine wirefeeder.i also have an aluminum wirefeered that i use my spoolgun with for welding aluminum but thats another bottle.lol sometimes it takes a little under an hour to setup everything and another hour to take it down. i do see alot of scrap guys running down the road with the gauges still on but they have the valves off .i would never run with the caps off but i think it's just a peace of mind because most of the caps on them bottles han easily be knocked off by a tap of a hammer they really don't hang onto them bottle to good.