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OxyAcetylene welding

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  • OxyAcetylene welding


    Well, it’s been a while since I posted to this forum.

    So, I am learning oxy-acetylene welding and cutting skills using a Harris setup. As for the welding, I am using a #5 welding tip but am not sure what the pressure settings (oxygen and fuel) are for this size tip. Earlier, I tried 20 PSI oxygen and 5 PSI acetylene, but I would rather have more certainty. I looked on the Harris website but could not find this information anywhere, which is disappointing.

    Thank you for the advice, this is a great forum and it has been helpful in the past.

  • #2
    8-12 lbs acetylene and 15-20 on the Oxy............these numbers are based on the size of the tip your feeding..........the larger the tip gets the more fuel & Oxy it needs through the regulators........larger tips also means welding and heating larger parts.


    • #3
      Ok...the disclaimer is always follow the manufactures recommended set up and shut down.
      As you've discovered, it's at times written pretty vague.

      I thought, save some typing and find a video link, you see the crap out there?

      Try this.
      With regulator adjusting screws loose, torch valves in a closed position, open slowly (not that it matters much which first) the Acetylene cylinder valve. When the gauge stops rising reading bottle pressure, open the cylinder valve further a full 1 to 1 1/2 turns of the valve further.
      While you could open it all the way, it's a double seating valve, it rarely leaks and most expect as a fuel gas if things go south to close it quickly after the oxygen which if things went south would be increasing the effects while the Acetylene supports it burning.
      Open the oxygen valve slowly, when high pressure gauge reads bottle pressure, open fully reseating the valve.

      Now, before I go on understand this. I could say set both pressure to 5 and 5 and you'd think balanced? Fact is most O2 gauges don't allow for that accuracy in the increment reading, and other factors come into play.
      The big risks are low Acetylene gas pressures, or excessive high O2 pressures.

      Open the Acetylene torch valve three twists. The idea is to open the valve fully and three twists of the wrist comes close.
      Slowly screw in the Acetylene adjusting screw until you hear or feel gas escaping from the tip. When you do, stop and close the torch valve. This has purged this line, and regulator.
      Do the same to the oxygen. Open the torch valve and slowly increase pressure by screwing in the adjusting screw. When you hear or feel it exiting the torch, close the valve.

      If you've done it slowly you should have enough, if your heavy handed, or using a really small tip size possibly to much?

      Understand, due to construction, mixer design, orifice size, not to mention hose size and length, regulator type and construction, cylinder pressures, gas pressure requirement can vary on the gauges. As well, if you are setting to allow for a working range of flame volume for a given size of torch tip.

      Let's continue, keeping in mind it's late, I'm tired, and I'm not going to fluff the conversation much as I go on, but if you want to balance the gas pressure now for welding, brazing, heating, this is how you do it.

      Open the acetylene valve, and light the flame. Once lit, open the valve again three twists, fully open, increase probably or decrease maybe, the gas pressure by screwing in or out the regulator adjusting screw until the flame, is no longer smoking, jumping away the width of the tip. This is the maximum Acetylene gas pressure for this time. Setting enough regulator pressure to ensure adjustment out the smoke range, allowing for a marginal increase if greater heat volume is required below the next tip size up offering greater flame volume.

      Once the Acetylene gas pressure is adjusted, close the Acetylene valve on the torch until the flame shrinks in size enough to attach to the tip, starting to smoke, open the torch valve again increasing gas flow until it once again stops smoking and that's the base or minimal setting.

      Slowly add Oxygen by opening the torch valve to this setting. Adjust to a neutral flame by open the oxygen torch valve. If adjustment can't be obtained, increase regulator pressure. If adjustment was obtained, open the Acetylene further and adjust again the oxygen until a neutral flame. The goal is both valves fully open and adjusted to a neutral flame.

      When this happens, your regulators are adjusted to provide balance pressures no matter what they say for readings, and you've adjusted to maximum gas flow for that tip size.

      Now, close the oxygen all the way close, Acetylene is or should be jumping away, the width of the tip or so, it will be reduced to smoking, increased out of the smoke range and oxygen once again added to achieve a neutral flame.

      You need a bit more heat volume add a bit of Acetylene, and a bit more Oxygen adjusting to a neutral flame. If you had to much you don't reduce into a smoke range you switch to a smaller tip.

      Tips work best with a soft flame. Out of the smoke range to slightly above. After that gas pressure starts to show as flame pressures.

      Anyways...I said I wasn't going to give you a lot of fluff and I didn't. But your 20psi oxygen and 5 psi acetylene were a bit out of balance. If any of this makes sense it should help with that? If it doesn't, well, 5 and 5 works because it takes less explanation.


      • #4
        Smith’s setting is 10 both oxy acy
        That’s my go to up to #9 tip
        Unless cutting or using rose bud never needed over 10 it’s more about proper tip size per material


        • #5
          This information really helps a lot! Thanks!


          • #6
            Special thank you to Noel for doing all that typing!


            • #7
              Heavy Metal Welder 76, it was my pleasure to be of help. Your very welcome, and thank you for the acknowledgment.

              I mentioned I was leaving out the fluff. I did. I didn't say anything about single or two stage regulators, injector or balanced pressure torches, I didn't mention the importance of checking o rings, leakage checks, torch and tip design, check valves and flash back arrestors, cylinder valves and cylinder construction, gas properties and gas safety, flame types and there purposes, techniques and application.
              For this I apologize.

              I commend you for asking. I went looking on line to see what the world wide web had to offer and frankly, disappointment was my discovery. I can see why you did ask for assistance in clarifying the confusion out there.

              But I gave you the basics of how to balance the gas pressures for oxygen/acetylene gas fusion welding, brazing, soldering and heating. With an understanding of this set up procedure for adjusting gas pressures, you won't be screwing regulator pressures to the readings of a gauge as you will the gas exiting the tip.
              Asking the question, why do we need reverse flow check valves and flash back arrestors? My response is too reduce the risk of back fires and flash backs because we have bad teachers.

              While you didn't ask, I'm also going to say, setting gas pressures for oxy fuel cutting is a bit of science as well worthy of greater explanation for understanding the process.
              To prove the point, set your pressures, light the torch and adjust the flame. Now, if your cutting tip is clean, with the oxygen lever squeezed, increase or decrease Oxygen regulator pressure and notice the reaction to the length of the cutting stream?

              There is a very good reason why some call it a gas axe.

              Oxygen, seemingly in abundance, is wasted because for some reason folks read a chart that say's something and they think gospel and gold? Another example of enough knowledge to function and to be dangerous.
              Then, when it isn't doing what they want or think/expect for results, more is better so up goes the pressure?

              Typically, excess oxygen pressure, or increasing oxygen cutting pressures excessively, will reduce the cutting stream length. Gas pressure turbulence. More isn't better.
              Oxyfuel cutting is about rapid oxidation and slag elimination. Heat input to sustain the temperature, and a focused forceful stream to eliminate.
              With understanding, the amount of preheat flames, orifice size of the preheat flames, increases the volume of heat energy to sustain the temperature for rapid oxidation to occur. The longer in length the cutting stream is, the greater the effectiveness for slag elimination. Other wise it's a wider kerf and slag build up because of excessive heat and poor slag elimination.

              Once again, I left out some fluff. My bad. I'm thinking though, smarter is sure better then dangerous. Good luck with your endeavors.


              • #8
                Sorry, but I couldn't find my file to copy and paste, but here's the long hand version. Hope it helps.