Gas Cutting

[joncowcare]

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

 

[PBinWA]

I bought a new OA cutting torch and a full set of tips last winter. I haven't had a chance to use them yet. I've been too busy working this year and nothing has been done.

So right now my pressures are 0/0!

I did buy a tank cart with big wheels which will make lugging the tanks out to the field less of an issue.

 

[shinnlinger]

I see you asked this 2 months ago, but for reference purposes I will say I set my acetylene at 5-8 psi and my oxygen at 25-40 depending on the thickness of the steel. The thicker the metal the more I give it.

I will also say acetylene likes your clothes so make sure you don't let an unlit torch blow acetylene on your shirt and then light up. More than one boatbuilder has lost his life cutting in close quarters because of this.

On a more positive note, the new "dry cut" saws are awesome at cutting steel and are a lot less $$$ than a plasma cutter. I have a DeWalt chop saw that I won't reccomend because of the erganomics of it but the technology is great. Metabo, MIlwaukie and a few others make hand held circular saw models that are more portable and I bet their is a lithuim Ion model coming soon to a store near you.

Shinnlinger

 

[Bindian]

I see you asked this 2 months ago, but for reference purposes I will say I set my treasure and my oxygen at 25-40 depending on the thickness of the steel. The thicker the metal the more I give it.

I will also say acetylene likes your clothes so make sure you don't let an unlit torch blow acetylene on your shirt and then light up. More than one boatbuilder has lost his life cutting in close quarters because of this.

On a more positive note, the new "dry cut" saws are awesome at cutting steel and are a lot less $$$ than a plasma cutter. I have a DeWalt chop saw that I won't reccomend because of the erganomics of it but the technology is great. Metabo, MIlwaukie and a few others make hand held circular saw models that are more portable and I bet their is a lithuim Ion model coming soon to a store near you.

Shinnlinger

Shinnlinger,
I might be wrong, but what I remember from my high school farm shop teacher is that acetylene starts to become unstable over 5 psi. Is that true?
hugs, Brandi

 

[shinnlinger]

Brandi,

15psi is what is eched in my mind, but just make sure I will double check
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After a quick jump on the web.

"Gaseous acetylene under pressure may decompose with explosive force. Never use acetylene at pressures in excess of 15 psig. "

Phew, I wouldn't want to give bad advice, or worse, dangerous advice. Thanks for asking. But it is good to reinforce that a SMALL turn of the regulator can result in a BIG problem.

 

[Doc]

Good info guys. Rep points for the research Shinn.

(and at first I thought we had a thread about cutting gas .....totally different! )

 

[Bindian]

Brandi,

15psi is what is eched in my mind, but just make sure I will double check
..........................................................................................
...........................................................................................
...........................................................................................

After a quick jump on the web.

"Gaseous acetylene under pressure may decompose with explosive force. Never use acetylene at pressures in excess of 15 psig. "

Phew, I wouldn't want to give bad advice, or worse, dangerous advice. Thanks for asking. But it is good to reinforce that a SMALL turn of the regulator can result in a BIG problem.

Shinnlinger,
Okay. Thanks for the updated lesson.
hugs, Brandi

 

[Peanut]

Shinnlinger,
I might be wrong, but what I remember from my high school farm shop teacher is that acetylene starts to become unstable over 5 psi. Is that true?
hugs, Brandi

what do you mean unstable??the pressure of your gas has all to do with what size tip your useing.000 tips don't need as much gas or oxygen as a size 1 or 2 tip

 

[Bindian]

what do you mean unstable??the pressure of your gas has all to do with what size tip your useing.000 tips don't need as much gas or oxygen as a size 1 or 2 tip

Peanut,
Unstable, you know, as in not being stable. Or as Shinnlinger stated in post #5 here................
"Gaseous acetylene under pressure may decompose with explosive force. Never use acetylene at pressures in excess of 15 psig. "
.....................hugs, Brandi

 

[Peanut]

i think your talkin about the torch as for as the gas pressure the bottle is filled to i think 500 or 1000 lbs of pressure and i never had one go bad on me nor did i have one decompose with explosive force. now i did see a guy blow his torch up by turning the gas wide open but that was a o-ring blow out and had nuthing to do with the gas breaking down it's just that the gas side of a torch is not supose to handle high pressure like the oxygen side is. now when we use a rose bud to heat stuff we light the rose bud and then crank it open to have enough gas to burn the rose bud properly.

 

[Bindian]

i think your talkin about the torch as for as the gas pressure the bottle is filled to i think 500 or 1000 lbs of pressure and i never had one go bad on me nor did i have one decompose with explosive force. now i did see a guy blow his torch up by turning the gas wide open but that was a o-ring blow out and had nuthing to do with the gas breaking down it's just that the gas side of a torch is not supose to handle high pressure like the oxygen side is. now when we use a rose bud to heat stuff we light the rose bud and then crank it open to have enough gas to burn the rose bud properly.

I am talking about regulated line pressure. You crank that regulator too much and the acetylene can blow by itself from static friction.
I was taught oxygen at 40 psi line pressure and acetylene never over 5 psi line pressure in high school farm (FFA) shop.
hugs, Brandi

 

[Peanut]

no down here i done had my buddy work the bottles for me and this is no joke we would drill out the tips i think they was a 6 or 7 size tip maybe bigger but i would run through a bottle of oxygen in 15 minutes. we done this for a few days then we ended up getting a few liqid bottles of oxygen and we would run through one of those a day the acyteline would be cranked up too but as long as you had it flowing and there wasn't any restrictions in the torch you was ok. now i know what your sayin and yes the gas is highly flamable but we never had one blow up on us. they even say not to lay the bottles down or it will cause an explosion but when we would do raod jobs the bottles were always laid down in the truck infact if we didn't have anything to tie them up with at the shop we would lay them down so that way if you pulled the hose they couldn't fall over and break the valve off. you can get a static ignition whitout any pressure and still have it explode. when i was workin our biggest fear was to get a oxygen leak now that is real deadly. i was in a engine room workin above my buddy and his torch had a leak"oxygen" well he layed it down on top his bucket and my tacker struck arc the sparks fell into it and BAM!!! i huge flash of bright white light no flame just a huge bam and then light. it totally shredded his bucket and blew every toll stright up and into the grating under us. so to me the oxygen is more scray than the gas. now i agree unless you know what your doin keep the gas level in the white and stay out the red zone to be safe.

 

[Peanut]

here is a video about the oxygen

http://www.youtube.com/watch?v=NwFRYlJQ6RQ&feature=player_embedded#

http://www.weldingtipsandtricks.com/welding-accidents.html

 

[Bindian]

no down here i done had my buddy work the bottles for me and this is no joke we would drill out the tips i think they was a 6 or 7 size tip maybe bigger but i would run through a bottle of oxygen in 15 minutes. we done this for a few days then we ended up getting a few liqid bottles of oxygen and we would run through one of those a day the acyteline would be cranked up too but as long as you had it flowing and there wasn't any restrictions in the torch you was ok. now i know what your sayin and yes the gas is highly flamable but we never had one blow up on us. they even say not to lay the bottles down or it will cause an explosion but when we would do raod jobs the bottles were always laid down in the truck infact if we didn't have anything to tie them up with at the shop we would lay them down so that way if you pulled the hose they couldn't fall over and break the valve off. you can get a static ignition whitout any pressure and still have it explode. when i was workin our biggest fear was to get a oxygen leak now that is real deadly. i was in a engine room workin above my buddy and his torch had a leak"oxygen" well he layed it down on top his bucket and my tacker struck arc the sparks fell into it and BAM!!! i huge flash of bright white light no flame just a huge bam and then light. it totally shredded his bucket and blew every toll stright up and into the grating under us. so to me the oxygen is more scray than the gas. now i agree unless you know what your doin keep the gas level in the white and stay out the red zone to be safe.

Uh.......any time you transport high pressure bottles the caps suppose to be installed. Sounds like y'all were an accident looking for a place to happen.
hugs, Brandi

 

[Doubleh]

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.

 

[Peanut]

Uh.......any time you transport high pressure bottles the caps suppose to be installed. Sounds like y'all were an accident looking for a place to happen.
hugs, Brandi

who said anything about transporting them with their caps off??? although i see old scrp trucks runnin down the road with the gauges on the bottle we never did that. i'm talkin about the bottles being in the back the truck or on it we would lay them down and scrap them to the side of the welder or bind them down but we always used them both laying down in the truck.

 

[Peanut]

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.

oxygen by itself is very dangerous let some pure oxygen into a cup that is upside down and light it it works just like a flash bang grenade.

these guys lost their life because of pure oxygen.

http://www.youtube.com/watch?v=_Ih_yxmOJaI

 

[Peanut]

and here's pure oxygen buring too. this stuff is way more deadly than the gas atleast you can smell the gas but if you don't see he oxygen leak your dead if you make a spark.

http://www.youtube.com/watch?v=D7QpSfvyOek&feature=fvw

 

[Doubleh]

and here's pure oxygen buring too. this stuff is way more deadly than the gas atleast you can smell the gas but if you don't see he oxygen leak your dead if you make a spark.

http://www.youtube.com/watch?v=D7QpSfvyOek&feature=fvw

Take your torch, turn on only the oxygen, take your striker and try to get it to burn. Good luck.

 

[shinnlinger]

If you are ever bored on the 4th of July, go get some helium balloons and attach them to a plastic trash bag and fill it with oxygen and then a whistle of acetylene. Then attach a wick, light and release.

Make sure it is a long wick because you will blow out windows and have the police visit unless you do it at night.