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What 's the rules for purging .

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  • What 's the rules for purging .

    HI everybody

    What are the basic rules for back gasing , I just presume that at the bigining you let more argon in just to let the air out and after that you back off on the CFM of argon , and what about the size of hose in and the size of the exit hole ???????
    I am welding a davits , round 1 inche .065 SS316 .



    SPOOLMATE 3035

  • #2
    Rules for purging???

    Lets see eat something then hack it back up.


    • #3
      Other than initially giving the argon a minute or so to displace the oxygen in the purged area i don't think there are any "rules"

      I have done it 2 ways. I use a "Y" fitting at the argon tank that has knobs on it. I'll turn the knob for purge open while i get myself ready to weld, by that time it's good and purged.

      The other way i've done it is to place the "Y" on the outlet of the welder (where it supplies gas to the torch hose) and then i'll leave the knob open and will just tap the pedal to kick in the "post flow" a few times to purge anyair out then i start welding (i did this in an attemp to save on argon, but didn't see any gains) now i'm back to having the "Y" on the tank and just opening it when needed.

      BUilding a back gassing set of plates and tools is a really fun project to do as well. I built a small table that you can lay you r parts on, cover any open areas and place your argon line in the side, this thing is AWESOME!

      I havent' got to messing with any brass or copper ones, i can't seem tofigure out how they work and haven't seen the really expensivfe type in person, so i just make due with what i can build and take examples from other peoples home made back gasssing parts.
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      • #4
        with the crap that i do at work i have to use NF Nitrogen-oil free - which is mad expensive (and great for filling your tires!!) purge with the nitrogen and I have to moninter the discharge for less then 1% O2 and then and only then.. can I rock and roll... its a pain in the ass...

        especially when you finish a run and realize you started your purge with a tank that was 200PSI full and didnt catch it..

        that makes for a very very very long night!


        • #5
          I added a purge switch to my Miller MIG. It opens the gas valve without feeding wire or energizing the gun.

          I sometimes also use it to put inert (enough) C25 gas in varnish cans before closing them. Keeps them from skinning over.

          Here are some details:


          • #6
            I understand how to purge the inside of a pipe, but how do you purge the backside of flatstock when welding?


            • #7
              Since argon is heavier, the inlet needs to be at the bottom and the outlet above it, so it will fill like water and push the oxy out the top.
              RETIRED desk jockey.

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              • #8
                Originally posted by Brianstick View Post
                I understand how to purge the inside of a pipe, but how do you purge the backside of flatstock when welding?
                what i have always done is have someone hold the purge hose on the back of the piece and move it with you as you weld...seemed to work pretty well when i had to do some 16 ga. stainless ductwork
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                • #9
                  Aluminum foil, & masking tape makes a good dam in a pinch, for the backside of flatstock.
                  Warning to young ladies:
                  If you wear loose clothes, beware of the machinery. If you wear tight clothes, beware of the machinist.