# Oxy/Acetylene mixtures



## triples (Mar 25, 2009)

Hi Guys,

Im quite new to the frame building game and just wanted some advice on mixture settings. For some reason I'm using a alot more acetylene than oxygen. Currently running 50psi on both.
What do you guys run?

Cheers


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## Blaster1200 (Feb 20, 2004)

triples said:


> Hi Guys,
> 
> Im quite new to the frame building game and just wanted some advice on mixture settings. For some reason I'm using a alot more acetylene than oxygen. Currently running 50psi on both.
> What do you guys run?
> ...


Are you sure? Are you sure you're not running 5 psi? If you had your regulator set at 50 psi on your acetylene...well...really bad things can happen.

There's also more to it than what you have your regulators set at.


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## swift (Apr 3, 2007)

Duck!!!

That's a dangerous pressure to be running acetylene at. 15psi max!


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## triples (Mar 25, 2009)

Yes definatly at 50psi. Thats what it said to set it at in the manual. What pressure should the oxygen be at?


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## Blowout (Dec 31, 2003)

*What manual are you reading?*

I seem to recall that all that Acetylene is spontaneously explosive at pressures above 15psi. Acetylene regulators should only go up to 15psi anyway, at least all that I have seen (Smith, Victor, Weldmark, Harris) have a giant red area at 15psi with big "Danger" warnings about exceeding that pressure.

I use oxy-propane now, but If I recall correctly, I have had good luck for brazing and welding thinwall at 10-15psi oxygen and 5-7psi acetylene or so.


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## Blaster1200 (Feb 20, 2004)

triples said:


> Yes definatly at 50psi. Thats what it said to set it at in the manual. What pressure should the oxygen be at?


Does the gauge on your regulator look like the one on the left? (note the red zone past 15 psi)


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## triples (Mar 25, 2009)

No nothing like that. I'm will check it when I get back to the workshop. Maybe I'm confusing myself with kpa. But im 99% certain it's psi as we don't use kpa over here. But now I look at the picture maybe it is kpa.
I will get a picture this afternoon and post it up.


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## dbohemian (Mar 25, 2007)

4 to 5 pounds on both regs. You only need o2 pressures of up to 15 for cutting. Any more than that and fine setting your torch will be way harder than it need be.

I bet you are not at 50. I don't think you would even be able to light your torch easily with those.

Dave B


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## triples (Mar 25, 2009)

Ok just checked it out and I was wrong. It's in kpa only. So I was running 50kpa in both.
Thats only a tad over 7spi.

Any other suggestions why I would be using too much acetylene?


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## triples (Mar 25, 2009)

Blaster1200 said:


> Does the gauge on your regulator look like the one on the left? (note the red zone past 15 psi)


Not quite. It has a red line at 150 kpa but nothing the one you pictured.


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## rocwandrer (Oct 19, 2008)

start with a big feathery blue flame. turn the oxy up / the acetylene down until the feathery tip just disappears, leaving the inner cone. just for fun turn the oxy up some more for a second. hear that? see the inner cone change? bad. turn it back down.


with 2 same physical size tanks, brazing only, with your flame set like this, you will use up the acetylene much faster than the oxygen.


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## NorseRider (Feb 9, 2004)

Pressure settings depend on the construction type of your torch as well as the tip size you're running. If you're running an equal pressure torch (and not an injector type torch) you should run... equal pressures on both according to tip size. 7 PSI is quite a bit above the pressure required by tips used for framebuilding.

Truls


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## Francis Buxton (Apr 2, 2004)

I believe most guys run 3-5 psi on both A and O. 

Just for reference:

PSI KPA
3 21
5 35
7 48


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## rocwandrer (Oct 19, 2008)

couple more comments:

On my regulator, the pressure the regulator reads at zero flow rate is a lot higher than the pressure it reads while I am brazing. I have found that I know what to set the regulator to in order to get the pressure I want while flowing, rather than dumping gas to the room while adjusting the regulator. I aim for around 7 psi on each (slightly higher on the acetylene side), but the pressure reading while brazing is below 5 psi...

I also find if I set the regulator pressure too high, adjusting the mix is still pretty easy, but the flame mix will change slightly while I am brazing (and this is with a nice AW1A Smith torch.)


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## dru (Sep 4, 2006)

If you are using a lot of line, like I do, you should add a few PSI because the pressure will drop by the time the gas reaches your tip. I have 50 ft of line BTW. I normally run around 5 or 6 PSI on both my regs.

Drew


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