oxygen concentrators

[Tman]

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.

[Tman]

I forgot to put the price in, $125

[waterlaz]

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.

[Jim Gourgoutis]

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.

[waterlaz]

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.

[duanedr]

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!

[EricKeller]

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 :)

[waterlaz]

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.

[nick.graham]

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?

[Doug Fattic]

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.

[nick.graham]

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.

[shirk]

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.

[bateria]

Hi Doug
I've done it! In the end I bought a refurbished Oxy Concentrator from the UK and it works perfectly with my Harris 15-4 torch and Propane.
Thanks so much for your great help.

Next step will be the Fluxer.

[Doug Fattic]

Great! I'm Glad the system is working for you!

[bulgie]

Anyone use theirs with a "gas economiser"? And is that the right word for the hook you hang your torch on to shut it off? We used to call it the gas miser, but if you google on that, all you get is hits related to gas mileage of cars...

I just got an Invacare Platinum 5 lpm off Craigslist for $100. I understand I will need a "dongle" or short piece of hose to fit the barb fitting on the Invacare and then connect to my oxygen hose to the torch. Source for that, or make it myself?

I've been reading this thread for years but I'm sure I don't remember everything I learned. Does the following sound right?

(?) Don't turn the oxygen off? I guess this means don't connect it to my gas miser -- can I connect just the propane hose to the miser? Yes I can determine this myself if no one knows off the top of their head, just thought I'd ask here first.

(?) Don't use a flashback arrestor on the O2? I gather it's not needed with a concentrator and may reduce the flow rate too much. Definitely correct me if I'm remembering that wrong!

(?) How about reverse-flow check valves? Same deal, not on the O2 side?

Not concentrator related but I'll ask here since I have your attention: I plan to switch to propane, but I still have Acetylene, and enough gear (torches, regulators, hoses etc) to run both. I have a Smith AW1A and a Meco Midget. Can anyone think of any big reason why one of those would be better for propane, or for acetylene?

I have Paige tips, and an AT61 for the Smith, so I can run either torch on propane. I also have acetylene tips for the Smith. I don't have acetylene tips for the Meco yet but I might buy them, so I can leave the Meco on the acetylene. This is based on the assumption that I will switch to propane for most everything, keeping the acetylene around for special projects like gas-welding that need it. With propane as my main setup, I'll want the Smith there because I like it better, more used to it. But I'll listen to any reasons you think the Meco would be better on the propane and Smith on acetylene.

One last question, anything I need to know about using my gasfluxer with propane?

Grateful for any tips, tricks, or pitfalls to avoid!

Cheers

[Thomas Norton]

Mark, I just finished my course with Doug Fattic. In fact I am leaving his place in a few hours and heading for home. I also have an InvaCare unit and brought it here to use. I made up the fitting you are talking about. I can post a pic after I get home and unpack my truck.

[Doug Fattic]

In the medical oxygen supply world there is a plastic piece that on one end is a size B female welding hose fitting and on the other a barb what increases in size so it will accept any size of clear oxygen supply hose. This is what converts the barb on the concentrator to fit a welding hose. In the Welding world, Western Enterprises makes a brass 2 piece barb/size B fitting. Their barbs are for a specific ID ø size hose so you have to pick the right size barb to fit your concentrator hose. This is what Tom did and he can tell you what size hose (that can be bought at Lowe's) fits the barb on his unit.

[Doug Fattic]

How about reverse-flow check valves? Same deal, not on the O2 side?

I have both check valves on the end of all of my torch handles. That keeps both hose lengths even. They don't seem to effect the flow of either gases enough to be a problem. It does take a second or two for enough propane to get through the flashback arrestor and check valve and out the end of the tip for it to light after I open up the tank after it has been turned off.

[bulgie]

Thanks to all, especially Doug for all your help over the years, you are a saint.

I have a medical-supply place that does oxygen whatzits just down the hill, I'll see what they have tomorrow.

Cheers,
Mark

[jclay]

I have a Smith AW1A and a Meco Midget. Can anyone think of any big reason why one of those would be better for propane, or for acetylene?

My Midget required higher pressure than the AW1A for a given lug brazing flame size; maybe 50% higher. While its not a problem for use with compressed gas cylinders it might be a problem for the oxygen generator.

Hot tips for the Midget:
1) Get the longer (9" or 7") tip tube
2) Rotate the tip tube so that it is in plane with the valve body
3) Put the valve body flat in the palm of your hand so that your fingers can manipulate the valves

I sold my Midget and AV-jet torches and kept the AW1A because I (very) occasionally needed to use a cutting head; they're not available for the Midget and I didn't have one for the AV-jet. As for brazing though, I vastly prefer the Midget. If I gripped the perimeter of the Midget's valve body with the tips of my fingers and had the plane of the tip tube perpendicular to the plane of the valve body I wouldn't like it one bit. Gripping the slippery, small diameter round body of the AW1A is difficult, particularly with durable rubber hoses....so I don't. I grip the torch by the B/A adapters, which approximate a flat plane....like the Midget! I do like the tool-less tip changes but it's no big deal. I suppose none of it is really. They're all good torches, but to my way of thinking the Midget is best in terms of brazing operation.