oxygen concentrators

[Doug Fattic]

An oxygen concentrator might be one of the options to consider when buying a brazing outfit. For those not familiar with them, they are the units that supply patients (usually elderly ones) with nearly pure oxygen when their lungs are no longer working at full capacity. They are a small machine about the size of a suitcase that separates out the nitrogen and carbon dioxide in the air to supply nearly pure oxygen (pure enough for brazing anyway). They have a clear plastic hose that runs to a patient’s nose. They are heavily regulated in the medical industry and cost thousands of dollars if buying them outright or rent for hundreds a month. However there are used ones sold on the open market at modest prices for non-medical purposes like glass flame-working or brazing. They are popular with those that make jewelry.

Someone might consider this option is for reasons of safety, convenience and cost. Because it is not a highly pressurized tank, it isn’t going to turn into a missile or bomb if something goes wrong. There is no need to transport them to the store for refills (only possible during open hours) and the cost to run them is only the electricity they use and an occasional filter change. Because they have a built in flow meter, they don’t require a regulator saving that expense. Their biggest disadvantage is that they have to run for a minute or 2 before they produce enough pure oxygen or it will blow out the flame.

Probably the biggest market for concentrators is for people that live in big cities where the purchase and transport of oxyacetylene tanks are restricted or are a long way from a welding supply store. Furthermore some rental or home insurance policies are not friendly to potentially hazardous tanks. This unit solves those problems.

They are made with various amounts of oxygen output. The smallest ones at 5 liters per minute work fine with torches usually used for brazing. Their units of life is measured in hours used and designed to run for several years continuously.

There are many companies that sell refurbished ones. I bought mine from M&M Medical Repair in Beaverdale, Pennsylvania. They have all kinds of makes and models in stock. They are a supplier to other retailers as well. A 5 lpm unit costs $300 and comes with a 3 year warranty. I paid $30 for shipping to Michigan. The Rio Grand Jewelry company (they have online sales) sells a brazing version for $425. DotMed.com is an auction house for all kinds of medical equipment including concentrators with hundreds advertised at various prices. It is common to find them in the classifieds for $75 to $200.

Oxygen concentrators don’t typically need to be modified for brazing. On mine, the oxygen output has a brass size B fitting. All I need to do is plug it in, screw the end of my hose onto the fitting, turn it on and wait a minute or 2. After I light the flame, I adjust the flowmeter so its output matches the orifice size of the tip.

Concentrators differ a bit on what kind of fitting is at the end of the output. They have some kind of plastic barb to hold the clear hose that carries the oxygen to the patient. On my Devilbiss unit that plastic barb unscrews from a brass B fitting. The same fitting that is on the output of a oxygen regulator. On other models that only have a plastic non-removable barb, one would have to make a transition piece to convert the plastic ending into a brass A or B welding hose fitting. That could be done with a brass unit from Western Enterprises that has a barb on one end that fits into a short piece of clear hose and an A or B fitting on the other to connect to a hose going to your torch.

I want to be clear I’m not suggesting a concentrator is the best way to go for everyone. What I am saying is that it is a very good option to consider for safety, convenience and cost reasons. It combines nicely with propane that can be chosen for the same reasons. We are all different in what we like or don’t. And our choices can be influenced by where it is most convenient to buy what we want.

Doug Fattic
Niles, Michigan

[shirk]

Doug's info on using a concentrator with propane was the tipping point for me finally buying a brazing rig. I've been wanting to build a few frames for years but had not bought the needed supplies. I was watching craigslist for a used brazing set-up but they were all huge torches or more than I initially wanted to spend.

Thanks again Doug for sharing all your hard earned info.

[David Tollefson]

That's the same oxy concentrator unit that I have. Never a hiccup. Like you, it was what made it so much more accessible for me. I owe a great debt of gratitude to Doug for all the information he's shared.

Doug, if you're ever in the Seattle area, ring me up. I owe you a round or two.

[Jonny Cycles]

Doug,

Thanks for all the great info on oxygen concentrators. I just went through the process of getting a new torch and tanks and referenced this thread - http://www.velocipedesalon.com/forum...ane-30480.html extensively while doing so. I was interested in the idea of an oxygen concentrator, but the flow rate became the main sticking point for me.

My previous setup was oxygen propane. After starting out using a smaller tip I quickly gravitated to using a larger tip, in fact ultimately settling on the largest tip I could find which was a tip with a 0.125" opening, and sometimes a rose bud. I often ran them both at the max flow of propane and oxygen I could get w/out the torch blowing out. (ok ok....I turned it down a bit for bottle mounts and cable guides). Would I wish this tip size on a newbie? No. Is this size required to build a frame? No. Is a bigger flame better? It's debatable, but it worked better for me. Others may not have the same experience but I know many builders do prefer a large tip.

My point is: Consider having the ability to run large tips. If not now, maybe sometime in the future at least to try it. The book that comes with my Smith AW1A torch doesn't give the oxygen flow rates for a oxy-propane setup with a 0.125" tip or a rosebud, but it does list the oxygen consumption for a 0.106" tip used with propane: 38 scfh, or 17.9 LPM. While 20 LPM concentrators are available, they are a bit of an investment.

Acetylene makes it a bit easier. For acetylene I would want the ability to run at least a 0.06" tip. The oxygen flow rate listed for these is a bit more reasonable at 8 LPM. 10 LPM oxygen concentrators are easier to find and quite a bit less expensive.

[Doug Fattic]

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

[bambuko]

...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)...

Doug, from when I was doing my reasearch on the subject I seem to remember that flows higher than nominal were less pure oxygen?
So you might be getting 90% oxygen at 5 lpm, but less than that at higher flow?

[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.

[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.

[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.

[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

[bastia]

I have a visionair 5 from airsep.
I did not open it (at the moment). The schematics of the visionair 2 and 3 indicate a mixing (?) tank / a assy (?) tank and in the two cases a regulator. I think that my oxycon have a (little) tank too.
Add a tank is a good idea to test/solve the problem, but technically I wouldn't really know how to add a tank (which oxygen container to use).

[Doug Fattic]

bastia, i'm wondering if you can put in-between your concentrator and your torch handle (on your oxygen hose) an air carry tank. These are small (mine is 7 gallons) tanks designed to get filled with pressurized air from a compressor and take it somewhere to fill up a flat tire (or whatever). I wouldn't use typical quick release connectors to connect the output hose to the tank (these QR connectors are used in almost all air tools so they can easily be connected and disconnected from the air line) because they require more pressure to operate properly than a concentrator can provide. I'd just connect the oxygen air line directly into and out of the tank. This I would assume help smooth the air output flow. The disadvantage of course is that you would have to run the concentrator long enough to purge the tank of ordinary air until it became full of only oxygen.

As I understand it (maybe) a concentehtrator has 2 pistons (or whatever they are) working together. One is on while the other is off and repeat. This is what causes the pulsing as they go back and forth. I think my Devilbiss has a "bladder" that is like a tank that smooths out the air flow between pulses before the oxygen leaves the unit.

Here is my air carry tank.
IMG_7662.jpg