Oxy propane neutral flame???

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Hi all.  I'm new here.  Great website.  I've been welding for several years, but I've never touched an oxy propane rig.  Can someone please explain to me how to tell if I have a true neutral flame?  I saw a great video by smith torch company where a guy goes through lighting an oxy propane torch, but  I can't really see the inner flame in the video.  Is the goal to add enough oxygen to where the inner flame "shrinks" to where it cant get any smaller, regardless if more oxygen is added?  I'm a bit confused.   I've seen where there is a ton of explanations about the desired flame look with oxy acetylene, but not oxy propane. MAny simplification is appreciated.  Thanks.
Reply:It doesn't have the shielding effect of acetylene.  What do you want an explanation about single flame, cutting, or multiflame/rosebud?Might as well experiment.  Not sure neutral applies so much since I don't think there is a carburizing sp? flame with propane to be half way between that and oxidizing.Fran
Reply:Originally Posted by fran...k.It doesn't have the shielding effect of acetylene.  What do you want an explanation about single flame, cutting, or multiflame/rosebud?Might as well experiment.  Not sure neutral applies so much since I don't think there is a carburizing sp? flame with propane to be half way between that and oxidizing.Fran
Reply:I remember that video linked perhaps half a year ago.  I tried to make those star effects and it didn't work for me.  I can't see running that much gas roaring like that when I know what size flame with a low acetylene consumption tip would work for that material.The video is fine if you choose to follow it.  It is rather out of the usual technique in that the instructions for my apparatus have you adjust with the cutting oxygen lever depressed.  Unless using a three hose torch with seperate regulators for oxygen preheat and cutting oxygen you won't have a perfectly neutral flame in both instances, cutting flow and none.  This is due to the drag in the hoses and passages of the torch, less oxygen when the cutting stream is occuring.  I like the auto torch feature of some harris torches which likely intensifies this phenomenon.  That smith stuff is tip mix which might make a difference.There is plenty of stuff to search up on here I suspect that is why no one else is typing.  I am not a propane advocate for stuff of that thickness.  Thicker stuff with mechanized torch movement would be something besides acetylene.My way and the way the guys at a shipyard they built submarines do it (Was a long time ago and all I can say is it wasn't acetylene not sure what)  Make the flame with the cutting oxygen depressed pretty much as short as possible. Too much oxygen the blue gets paler and it hardly gets any shorter.   The one piece solid copper dedicated propane tips won't be as short as the two piece ones.  This for me often seems to create too much oxygen during the preheat mode as noted above resulting in kind of scabbing over and not getting a cut until essentially melting.  So a bit more fuel needs added to fix this.If you get some dedicated propane, not for acetylene low pressure propane stuff you won't have to go up on the knobs (multiple times) like the guy in your video.Is natural gas an option?   I guess it might depend on what pressure it under at the meter. I generally have two set ups the harris one on natural gas and the esab group ones on acetylene with the propane tank near them.  I think I use the propane with air mostly.  The natural gas for me seems essentially the same as propane though I am on a collection pipeline which has more btu per cubic foot than after it is processed.The video doesn't show the length of the flame in air with the cutting oxygen depressed vs not depressed does it?Last edited by fran...k.; 03-23-2013 at 11:00 PM.Reason: spelling
Reply:I made the switch to OP a while ago.  I like it.    the key to the neutral flame is in fact the "star" pattern.  Don't pay too much attention to the color of the inner flame or feather as one would for OA.  OP is different because it is a different "chemistry" of gas than acetylene.  Yes, with OP you light the propane first and crank it up until the base of the flame "jumps" away from the torch tip.  If it jumps, retard the propane a bit.  Next step is to add 02.  Add enough 02 until all the flames (inner and outer) both shrink to their smallest possible size.  Next, add more propane, again watching it so that it doesn't "jump".  Usually at this point, the propane is mixed enough with the 02 and it will not jump.  Again, add more 02 until the flame(s) shrink.  At this point, its really loud.  I love it at this point because it reminds me of a fighter jet's afterburner.  Sorry, got off topic. Next, add more propane again, followed by the 02.   I usually do the above steps at least 3 times and I believe in that video you linked, the guy did the exact same thing.  Finally, to get the neutral flame "tuned in," you need to place the torch tip 1/2" (not any closer) to the work piece and tune for neutral.  If the star "legs" are too short, add more propane or reduce the oxygen.   If they are too long, add more 02 or reduce the propane.  Remember:  legs too short, "shorten" (reduce)  the 02 flow.    Legs  too long,  "lengthen" (add) more 02 flow.    Sounds corny, but thats how I remember it.  When in doubt and if you totally screw it p,  cut off 02 first, then the propane. Restart the process all over again.  Play with the "star pattern" legs on some steel, until you learn how to fine tune it.  I think that within 5 minutes of playing with it, you'll be a pro at getting a neutral OP flame.  I don't even think about it anymore.  I just light it and go now.  It's like riding a bike. "Hey I didn't come to look and learn, I came to turn and burn.... If I can't light up, I'm gonna light out!"-JodyIdealarc 250 "Fatman"MM 252MM 211 "Little boy" Victor Torches
Reply:Sounds to me that by the time you have the flame adjusted, I could have the piece cut with OA.Miller 252Miller Bobcat 225Lincoln MigPak 1801959 Hyster forkliftHarris OA torch
Reply:Originally Posted by WeldRiteSounds to me that by the time you have the flame adjusted, I could have the piece cut with OA.
Reply:Moonshine, this is one of the root causes as to why so many people have bad experiences when trying to switch from oxy/acetylene to oxy/propane, or some other alternative fuel source.  Not enough textbooks and manuals take the time to explain how to judge the flame of alternative fuels, but they'll almost always describe the use of acetylene.So you have a formal resource, the practice of setting a reducing, neutral, or oxidizing flame for various fuel gases is discussed in AWS C4.3, Recommended Practices for Safe Oxyfuel Gas Heating Torch Operation (~$50 from AWS).Setting a flame with propane is not as difficult as most people make it.  It is different than acetylene though.  You open your fuel and light it, adjusting until you get a stable flame pushing out of the torch.  Then you slowly open your oxygen.  The flame can be judged based on the shape and color of the inner primary flame (or flames for a rosebud).  When the primary flame is long and has a feathered border, it's reducing.  As the primary flame becomes short and well-defined, it is neutral.  The oxidizing flame looks really similar to a neutral flame, except the difference is that the oxidizing flame will have a slightly shorter primary flame and the primary flame will become a brighter/lighter (whiter) color blue.  Practice going through the full range of reducing, neutral, and oxidizing while slowly turning the oxygen knob a few times.  You'll get the hang of it.Once you know how to judge the oxy/fuel ratio - it's just a matter of getting used to setting the fuel flow high or low enough with the torch knob so that the flame is stable (not pushed too far from the torch, and on a rosebud, there will be a ring formed by the back ends of all the primary flames) but is pushed out from the torch tip enough so the combustion is happening outside the tip.Setting a propane flame should not take any more time than an acetylene flame.I don't use oxy/fuel cutting equipment.  I mainly stick to oxy/propane brazing with single flame and multi flame nozzles.  Always read your entire equipment manual in case there's something special about adjusting your cutting torch.  If you don't have a copy, you can find most online.Also, remember that in acetylene, the primary flame has lots of BTUs of heat, so people are used to applying the primary flame to the work.  In propane, the secondary flame has all the BTUs of heat, so you want to apply the secondary flame to your work surface to really apply some heat.  Lots of people make the mistake of treating a propane flame like the primary flame of acetylene, they put the propane flame too close to the work, and they come away with a bad experience where they think propane is lacking in heating power.  Propane has a large and high BTU secondary flame which is great for applying lots of even heat to chunky assemblies - which is great for brazing or preheating for cutting on thicker metal.Have fun and be safe.
Reply:Originally Posted by Bob AndersonMoonshine, this is one of the root causes as to why so many people have bad experiences when trying to switch from oxy/acetylene to oxy/propane, or some other alternative fuel source.  Not enough textbooks and manuals take the time to explain how to judge the flame of alternative fuels, but they'll almost always describe the use of acetylene.So you have a formal resource, the practice of setting a reducing, neutral, or oxidizing flame for various fuel gases is discussed in AWS C4.3, Recommended Practices for Safe Oxyfuel Gas Heating Torch Operation (~$50 from AWS).Setting a flame with propane is not as difficult as most people make it.  It is different than acetylene though.  You open your fuel and light it, adjusting until you get a stable flame pushing out of the torch.  Then you slowly open your oxygen.  The flame can be judged based on the shape and color of the inner primary flame (or flames for a rosebud).  When the primary flame is long and has a feathered border, it's reducing.  As the primary flame becomes short and well-defined, it is neutral.  The oxidizing flame looks really similar to a neutral flame, except the difference is that the oxidizing flame will have a slightly shorter primary flame and the primary flame will become a brighter/lighter (whiter) color blue.  Practice going through the full range of reducing, neutral, and oxidizing while slowly turning the oxygen knob a few times.  You'll get the hang of it.Once you know how to judge the oxy/fuel ratio - it's just a matter of getting used to setting the fuel flow high or low enough with the torch knob so that the flame is stable (not pushed too far from the torch, and on a rosebud, there will be a ring formed by the back ends of all the primary flames) but is pushed out from the torch tip enough so the combustion is happening outside the tip.Setting a propane flame should not take any more time than an acetylene flame.I don't use oxy/fuel cutting equipment.  I mainly stick to oxy/propane brazing with single flame and multi flame nozzles.  Always read your entire equipment manual in case there's something special about adjusting your cutting torch.  If you don't have a copy, you can find most online.Also, remember that in acetylene, the primary flame has lots of BTUs of heat, so people are used to applying the primary flame to the work.  In propane, the secondary flame has all the BTUs of heat, so you want to apply the secondary flame to your work surface to really apply some heat.  Lots of people make the mistake of treating a propane flame like the primary flame of acetylene, they put the propane flame too close to the work, and they come away with a bad experience where they think propane is lacking in heating power.  Propane has a large and high BTU secondary flame which is great for applying lots of even heat to chunky assemblies - which is great for brazing or preheating for cutting on thicker metal.Have fun and be safe.
Reply:Originally Posted by MoonshineMetalsOne thing we noticed is that because the primary and secondary flames seem to be "lighter" in color, we have to "tune up" without goggles on and in a darker area first.  Then we move over to the cutting piece if need be, once the neutral is set in our minds, "perfectly."  We also discovered what nobody on the Internet or manual so far has thus suggested; that is to acquire a final neutral with the cutting lever fully depressed.  That seems to get better and cleaner cuts.
Reply:Originally Posted by rlitmanYep.  With the lever depressed the oxygen pressure changes a little, and that changes the mix ratio of the pre-heat flame.  This is just as true for oxy-acetylene as it is for oxy-propane.I've actually found that a mask for oxy-acetylene is way too dark for oxy-propane. The flame is must less bright (because it contains less inandescent carbon), so I've found that my sunglasses were actually comfortable with oxy-propane.  I use shade 5 goggles with O/A.  With O/P shade 3 might be ok, or might even be a little dark.  With shade 5 goggles on, I really cannot discern the different between a neutral and oxidizing flame.
Reply:So long as you're protected from the sparks getting around them, that should be fine for cutting.I wear glasses, and it is hard to find goggles that fit comfortably over them, and harder yet to find something in a shade acceptable for oxy-propane, but for me, oxy-propane was just a fun experiment to play with.  I used it to do some copper brazing.  I really don't torch cut much.  That's what I use my plasma for.BTW, if you were doing serious heating with oxy-propane, you might still need to go as dark as shade 5,  The flame is nearly invisible through a shade 5 lens (it looks like an oxy-hydrogen flame), but the "sodium flare" off the heated metal can be painfully bright.