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  • Making your own mix of argon and CO2

    Is there a way to mix argon and CO2 from separate cylinders without using expensive commercially produced mixers?

    I just bought Hobart Handler 140. My demands are more than modest: occasional welding of mild steel, stainless steel and, once in a while, small aluminum parts. I already own a 20# CO2 tank and buying an 80cft one for argon.

    My idea was to use two separate cylinders (argon and CO2) and mix the gases on demand. This way I'd be able to use pure argon for aluminum and different mixes for steels.

    Will a simple "Y" connector work satisfactory for my modest tasks? Will I need check valves, a mixing chamber, etc.? Have anyone had any experience with a simple mixing setup like this?

    P.S. I realize that I can get by with something like 75/25 and pure argon cylinder or FCAW for mild steel, 98/2 for SS and argon for aluminum, but I'd like to pick your brains about mixing gases.

  • #2
    Originally posted by MichaelP View Post
    Is there a way to mix argon and CO2 from separate cylinders without using expensive commercially produced mixers?

    I just bought Hobart Handler 140. My demands are more than modest: occasional welding of mild steel, stainless steel and, once in a while, small aluminum parts. I already own a 20# CO2 tank and buying an 80cft one for argon.

    My idea was to use two separate cylinders (argon and CO2) and mix the gases on demand. This way I'd be able to use pure argon for aluminum and different mixes for steels.

    Will a simple "Y" connector work satisfactory for my modest tasks? Will I need check valves, a mixing chamber, etc.? Have anyone had any experience with a simple mixing setup like this?

    P.S. I realize that I can get by with something like 75/25 and pure argon cylinder or FCAW for mild steel, 98/2 for SS and argon for aluminum, but I'd like to pick your brains about mixing gases.
    Welcome aboard.

    Nothing is wrong with 100% CO² for mild steel!

    As for mixing, if you use the search function and look for "gas mixers", there's quite a bit of discussion on here. A couple of guys have mixers, but if i recall correctly, others have sucessfully used two flowmeters manifolded into one supply line with some provision for mixing the gases.

    Hank
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    • #3
      Originally posted by hankj View Post
      ....others have sucessfully used two flowmeters manifolded into one supply line with some provision for mixing the gases.

      Hank
      that's the thing, has to be flowMETERs, and they need to be the same model. even then, it's probably a waste of time, just get the gases you need in cylinders, unless you absolutely need to play mad scientist.

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      • #4
        Thank you, Hank!

        Originally posted by Pumpkinhead View Post
        ...has to be flowMETERs, and they need to be the same model.
        Why do they need to be the same?

        Originally posted by Pumpkinhead View Post
        waste of time...unless you absolutely need to play mad scientist.
        As for the whole reason to have a mixer... Ideally, in order to weld mild steel, SS and aluminum more or less properly, I'd need to have three separate cylinders (one with argon and two with different argon/CO2 mixes). Each cylinder will need a regulator/flowmeter, and switching metals would require reconnecting cylinders. By having a mixer, I'll get rid of an extra regulator/flowmeter, extra cylinder and the cylinder disconnection/reconnection chores. So not only will I save space and money (fewer cylinders and regulators/flowmeters), but I'll also save time and efforts by not switching the gas sources. As for the "mad scientist" remark, I see only one drawback that can stem from such a "highly scientific" approach: need to calculate proportions and adjust two flowmeters instead of one. Doesn't sound like a big deal to me.

        Considering the nature of my welding demands and the fact that I already have a CO2 cylinder, I feel that a simple mixer willl be a right choice. But only if such a simple mixer works, of course. And this is what I'm trying to figure out. Personally, I cannot see any problem with a simple "Y" and check valves installed after the flowmeters. But, before commiting, I'd like to hear opinions of those who used similar devices or those who could point to potential weaknesses and dangers of such approach, something that is not obvious to me at this point.

        For example, you said that the flowmeters must be exactly the same. To me it is not obvious. Check valves will prevent backflow effects. Besides, considering the proportions of the gases, CO2 flowmeter, unlike the argon one, must have a pretty good resolution. Yet I'm sure you have some valid reasons to support your statement. And I'd like to hear them.

        Thanks again, guys! I really appreciate your participation and help!
        Last edited by MichaelP; 10-22-2007, 12:19 PM.

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        • #5
          you need to use flowmeters, not flowgauges because a flowgauge is simply a regulator with a fixed orifice, and you adjust the pressure to adjust flow.
          a flowmeter has a fixed regulator (pressure) and you adjust the orifice to adjust flow. thus to make C25, you set Ar at a greater flow than CO2, with flowgauges the carbon dioxide will not flow.
          using two flowmeters of the same model ensures the regs. are set to the same pressure for the column length.
          you will still need a pressure reducing device for EACH cylinder going to the "mixer", whereas utilizing separate cylinders you require a pressure/flow device for each CGA connection number CGA580 for inert gases, CGA320 for the CO2.
          you also mention "properly" in your post, to properly weld SS you would need Helium gas going into you mixer or an additional cylinder. either way you'll need three bottles, one each Ar, CO2, He for mixing, or an Ar, a C25, and a tri-mix.

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          • #6
            Hello Michael, welcome to the forum...ol Punkinhead my have a weird handle, but he knows what he's talking about...the problem with the "Y" scenario, is the the gasses don't mix the way you need them to...they have different densities and when they get to the torch they don't mix properly...that's why they make gas mixers. I worked for an aerospace company, and we tried to get it right...never happened. The Smith unit is well worth the money.
            You are more than welcome to try it...and tell us what you find out.

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            • #7
              Originally posted by Pumpkinhead View Post
              using two flowmeters of the same model ensures the regs. are set to the same pressure for the column length.
              H-mmm. I'm trying to think why this is important... As far as I understand, the flowmeter (floating ball) will show you the actual flow of the gas. If its inlet pressure is reduced or the outlet develops a higher resistance to the flow, the flowmeter will reflect it as a reduced flow. Am I correct?

              There are two things that worry me the most about this setup. First of all, as I mentioned above, CO2 will require a high resolution flowmeter. Something like 0-10 CFH so that I could dispense al low as 0.5 CFH if needed. So I'll need to find this kind of flowmeter. And here comes another concern: will those widely available check valves provide a stable opening with such low flow?

              The more I think about it, the less attractive it becomes.

              Also, what do you, guys, think about using flux cored stainless steel wire instead of GMAW for SS welding with my machine?

              Thank you!

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              • #8
                MichaelP,

                As has been stated, if mixing gases was as easy as simply joining the feeds in a Y, everyone would be doing it. They are not.

                A "proper" mixer will cost you more than you paid for your welding machine. If you intend to weld on various materials (as stated), just get the proper gasses already mixed. The CO2 you have, you will use up welding steel if you do any real welding at all.

                I'd love to be able to "mix" 98% argon (from my 100% argon tank) with 2% Oxygen from my O/A bottle (for spray) but I haven't found a cost effective way to do it "properly".
                SundownIII

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                • #9
                  Originally posted by SundownIII View Post
                  ...if mixing gases was as easy as simply joining the feeds in a Y, everyone would be doing it. They are not.
                  With all due respect, I'd like to quote something I found yesterday.

                  "Another type of mixer, Figure 4-16, may also be used in single stations. This Y-valve arrangement is often used to achieve gas mixtures with proportions different from the standard ones. The valve is installed on the outlet side of the flowmeter, with the gas metered by two separate gas flowmeters.
                  To prevent backflow of the gases and improper mixing, a backflow check valve, Figure 4-17, should be installed between the flowmeter and the Y valve".

                  "Gas Metal Arc Welding handbook" William H.Minnick, 1996, p.45

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                  • #10
                    Anybody can write a book...it doesn't mean they know more than the folks who actually doing the job...the weldors I know, don't' write books...they weld. There is just no way you can be sure if your mix, unless you use a mixer. IMHO

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                    • #11
                      Originally posted by Rocky D View Post
                      ..the problem with the "Y" scenario, is the the gasses don't mix the way you need them to...they have different densities ...
                      Rocky, the difference in densities will cause gases to stratify to a certain degree in a cylinder. So the 95/5 mix will never be 95/5 at your torch if you allow the cylinder to remain stationary and don't use it too much. Yet using cylinders with premixed gases is perfectly acceptable.

                      "Y" connector provides dynamic mixing. Sure the mix will not be as homogeneous as it could be after a precise dispensing and deliberate mixing in a chamber, but it can be more homogeneous and precise than the one coming from a stratified cylinder.

                      Again, these are just my thoughts. I am not a weldor, and I certainly cherish every bit of advice and hands on experience I can receive here. As for the "debate like" type of conversation, I always felt that it's very productive if the goal is to clarify an issue.

                      I worked for an aerospace company, and we tried to get it right...never happened.
                      Rocky, could you elaborate on this, please? What exactly did you try, and how the results were evaluated?

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                      • #12
                        Originally posted by MichaelP View Post
                        Rocky, the difference in densities will cause gases to stratify to a certain degree in a cylinder.
                        nope, once mixed they remain mixed, if not the air we breathe would not be as healthful as it is. i.e. it's not stratifying.


                        This Y-valve arrangement is often used to achieve gas mixtures with proportions different from the standard ones. The valve is installed on the outlet side of the flowmeter, with the gas metered by two separate gas flowmeters.
                        this is what i've been saying, a flowmeter on each cylinder you are mixing.
                        as Rocky has stated a simple wye is not going to mix much.
                        taken all together it supports the "mad scientist" statement of mine, you want to do it, do it, it's your time, money, and experience. just report your results.

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                        • #13
                          You could use a Microwave
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                          • #14
                            MichaelP,
                            I was going to try to attempt this last summer. Everyone I talked to advised against this.My LWS, welding instructor, and several people on 2 forums said that it would NOT work. These gases do not mix correctly in the lines. As stated above if it was that easy everyone would be doing it. I thought everyone that said it cant be done was full of sh!t. I thought it is a very simple idea so it "has to work". I bought a few tanks, regulators and some line. Now all I have to do is some calulations I thought. No matter the flowmeter mixes the welding gas never seemed correct. So from EXPERIENCE it DOES NOT WORK. . So I wasted some money. It would be cheaper to just buy a new bottle and have it filled with whatever gas you need at the time. As for a mixer to correctly mix the 2 gasses. They run about $1,000. So either buy a mixer, or buy some new bottles. The bottles will be the cheaper route. As for the time it takes to change the bottle, just suck it up and change them out.

                            -Ryan

                            Edit: What I tried was mixing 98/2 and couldnt achieve a spray with it. I bought a bottle of premixed 98/2 and I could spray.
                            Last edited by ace4059; 10-23-2007, 08:19 PM.
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                            Originally posted by scab
                            If you are the type of person who gets upset at things breaking brace yourself for possible dissappointment.

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                            • #15
                              Ryan,

                              What kind of flowmeter did you use for CO2? Did you have check valves installed in both lines?

                              So far I wasn't able to locate a flowmeter what would be suitable for the task yet reasonably priced. All I found was over $250 for the flowmeter only.

                              This and all the advice I'm getting here are making me less and less enthusiastic.

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