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Thread: oxygen concentrators

  1. #41
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    Default Re: oxygen concentrators

    Doug, he is local here in Western South Dakota and is on Craigslist. His prices are good but firm. I do not know if he will ship, I would be able to help folks. Hours were all in the 20's at the ones I looked at.
    Trent Knight, riding since the 83 Coors Classic warped me.

  2. #42
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    Default Re: oxygen concentrators

    I forgot to put the price in, $125
    Trent Knight, riding since the 83 Coors Classic warped me.

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    Default Re: oxygen concentrators

    I am experiencing problems with my DeVilbiss 525 KS oxygen concentrator. The compressor doesn't work constantly. Instead it does this on and off thing like a refrigerator. It doesn't stop pumping oxygen.
    However, when this happens I am not sure whether the pressure or oxygen purity varies but the flame changes from being oxidizing to reducing and back. This makes brazing harder and increases the risks of flame blow-out.

    I suspect that this is not normal behaviour and that operating the concentrator like that can further damage it. Googling the problem didn't help.
    I am not afraid of taking the thing apart so if anyone has any good ideas besides paying someone else to fix it for me, I would be glad to know them.
    Evgeniy Vodolazskiy (Eugene for English-speaking =)

  4. #44
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    Default Re: oxygen concentrators

    Quote Originally Posted by Doug Fattic View Post
    Jon, you bring out important points on the output of an oxygen concentrator and tip size preferences. This morning I went out to the shop and tried using large tips with my concentrator to find their limits. I have a Smith AW1A torch handle. This is a small “aircraft” size torch handle. I attached the AT-61 mixer elbow designed for propane (the AT-60 is for acetylene) that has a threaded end that allows for different sizes of tips to be exchanged. I put on a NE154 tip that is marked 36. This 36 number represents the drill size 36 which has an orifice of .1065”. My oxygen concentrator is a DeVilbiss model 515s and has a stated output of 5 liters per minute. In actuality I bought a DeVilbiss because others have indicated its actual output is closer to 8 lpm. It worked okay but the concentrator was at its limit of supplying enough oxygen. In fact if I turned up the propane beyond what is intended for that tip size I ran out of oxygen. At that volume it sounded loud like a jet engine. I didn’t like the the shape of the cone of the flame. It was like a frayed bulb on the end.

    I also tried the oxygen output with my Victor setup. In this case I used their acetylene W-J-6 welding nozzle with propane as the gas. The Victor size 6 tip is also .106” in diameter. Just for clarity this is an all-in-one unit that does not have interchangeable tip possibility. You change the whole unit from the torch handle if you want to change tip size. The mixer part of this unit is more like a propane one in that it has 6 supply holes just like their UN-J mixer elbow designed for propane. For comparison purposes a W-J-4 has 4 supply holes. Obviously there is more oxygen needed to match the larger amount of burnable gas with a bigger tip. Neither the Smith NE154 tip (which is designed for propane when using it with the AT-61) or the W-J-6 (which is designed for acetylene) has the recess on the end of the tip that helps keep a propane flame attached like what is on the Victor TEN tips (to be used with their UN-J mixer elbow) or the propane tips made by TM Technologies specifically for propane that fit the Meco Midget torch handle. However if you carefully adjust the flame they still work okay. This flame pattern on the W-J-6 was very nice and pointed. Again my concentrator supplied enough oxygen but it was at its limit.

    As Jon has pointed out, some pros prefer a big tip/flame for brazing. They can get in and out with their huge flame very fast. The advantage is that the heat effected zone going up the tube is minimized because it takes less time to braze a joint. A big flame can also reduce alignment distortions. I have found that it is not possible for 99% of beginners to use a very large tip. Things happen too fast for them to recognize how to respond quickly enough. However too small a tip can be problematic too. That requires a more precise heating pattern and many have trouble heating something like a lug evenly if the flame is small. For several reasons I don’t like using a big flame and prefer something like a Victor #3 for lug brazing. This is just personal preference and isn’t related to better or worse.

    In summary, my DeVilbiss 515s rated as 5 liters per minute (but actually has a higher output) can run a tip orifice size up to .106” (a Victor #6). The actual limit is a Victor #4 if the propane is tuned up to maximum. If an experienced brazer like Jon wants to use bigger tips, they would need to get a bigger concentrator or use acetylene with a smaller concentrator or use oxygen tanks.

    Just for a reference point. I prefer a Victor #4 for bottom bracket shells and fork crowns when using propane. Students do better with a #3. I typically use a #3 when doing lugs and dropouts. For Braze-ons I use a #2. And I’ve found I have better control with a #1 tip then a #2 when fillet brazing with propane. In fact tip size doesn’t make too much difference with me because I can make adjustments with whatever.

    Doug Fattic
    Niles, Michigan
    If you need more O2 flow for a bigger torch tip, you can gang multiple oxygen concentrators together to feed a single torch. The bench-top torches that lampworkers use make huge flames and need lots of oxygen, and some of them have 3-4 oxycons running at the same time. ;)



    There are also "industrial" oxycons that produce more pressure, e.g.
     

  5. #45
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    Default Re: oxygen concentrators

    I had some issues with my devilbiss 525 ds oxygen concentrator that I believe I've managed to solve^W overcome.
    Prior to my fix it has been making some very loud noises and oxygen purity was not consistent.
    Upon inspection I found out that the noise was coming from a safety valve on the compressor that is supposed to relieve extra pressure.
    It may very well be that something else is causing the problem that results in increased pressure.
    However, all other components seemed to be working fine. At least to the point that I could test them.
    Therefore, I've decided to just go for it and adjust the safety valve to allow for higher pressure (a better idea might have been to replace the valve altogether).

    Anyway, since that tweak my oxygen concentrator has been working flawlessly and I am happy with what I did so far.
    Just sharing this, maybe someone will find it useful.
    Evgeniy Vodolazskiy (Eugene for English-speaking =)

  6. #46
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    Default Re: oxygen concentrators

    Quote Originally Posted by shirk View Post
    Just picked one of these up for $52 from an estate auction. It has roughly 4500 hours on it and works perfectly. I'm hoping to play with it a bit more this weekend. Doug, as always, thanks!

  7. #47
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    Default Re: oxygen concentrators

    I wish people wouldn't post the cheap prices they got an oxygen concentrator for, because that is keeping me from just spending $300 and getting it over with :)
     

  8. #48
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    Default Re: oxygen concentrators

    I just wanted to state the obvious here. But since it took me a couple of years to figure out... :D

    Don't place your oxygen concentrator in tight corners. I've struggled with various issues like low oxygen concentration and overheating enough to take my concentrator apart a couple of times and try to fix it.
    And all I had to do was just give it some "fresh air" as it was just chocking on that endless loop of nitrogen.
    Evgeniy Vodolazskiy (Eugene for English-speaking =)

  9. #49
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    Default Re: oxygen concentrators

    Getting set up to braze at home and considering using an oxygen concentrator with acetylene. Question for those who use this setup: what happens when you turn the valves off at the torch? Presumably the concentrator is designed to produce constant flow. Would turning the valve off cause a problem for the concentrator unit? If taking a short break from brazing, what’s the procedure for shutting down briefly? Does the machine need to be turned off?
     

  10. #50
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    Default Re: oxygen concentrators

    I don't turn off the oxygen knob on my torch handle. I just let the concentrator run all the time I might be brazing even when the flame is turned off. Concentrators are designed to run 24/7 for a long time. Medical patients need for oxygen doesn't stop so neither does the concentrator. Most concentrators have some kind of warning signal when the oxygen gets shut off that is an irritating sound. There is no need to turn off the concentrator any time you stop to do something else during the time you are brazing. I don't turn off the control knob on my torch at any time either when I shut the flame off for a short time or when I am finished brazing entirely.
     

  11. #51
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    Default Re: oxygen concentrators

    Quote Originally Posted by Doug Fattic View Post
    I don't turn off the oxygen knob on my torch handle. I just let the concentrator run all the time I might be brazing even when the flame is turned off. Concentrators are designed to run 24/7 for a long time. Medical patients need for oxygen doesn't stop so neither does the concentrator. Most concentrators have some kind of warning signal when the oxygen gets shut off that is an irritating sound. There is no need to turn off the concentrator any time you stop to do something else during the time you are brazing. I don't turn off the control knob on my torch at any time either when I shut the flame off for a short time or when I am finished brazing entirely.
    Thanks Doug. I learned to turn off the oxygen first when turning off the torch (vs. fuel first), so I was coming at it from that perspective. Wondered if it would cause a problem for the concentrator.
     

  12. #52
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    Default Re: oxygen concentrators

    I turn off both the fuel and oxygen when I shut down my torch, then I open the oxygen back up. My unit will run for a short period with the oxygen on my torch off before an alarm goes off.

    Same goes for my start up procedure.

    I turn on the concentrator and let it run till the low oxygen light stops blinking and turns green. Then I'll turn off the oxygen and open up my propane to light the propane first and then bring in the oxygen. If I leave the oxygen closed too long here again the alarm will sound.
    Brian Earle
    North Vancouver, BC
    Built a few frames in my garage.

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