O2 concentrators/compresser

Factual Questions
1

I use oxygen for my work (glassblowing), and I would like to find a way to make my own. The problem is, that I need more LPM, and a higher PSI than a single O2 concentrator could provide. I would like to get a few, string them together with hose and put the output into an air compresser (and then into a tank of some kind I guess). However, I seem to remember something about how you can’t use a regular air compresser for pure oxygen. Something about the oil used in the AC and it being a fire/explosion hazard. Or maybe it has something to do with the corrosion that O2 causes. Or maybe it’s that the corrosion leads to the fire/explosion risk?

Also, is it bad for the O2 concentrater to create that kind of backpressure (the O2 pushing into the compresser as a bottleneck)

2

what you are proposing is a fire hazard. don’t do it.

3

What percentage O[sub]2[/sub] do yo need? And at what lpm do you need it delivered and for how long?

4

Gee, thanks </sarcasm> any further details you feel are worth offering?

@ iggy - I would guess ~90%, I really don’t know about the LPM

5

oxygen promotes fire and explosion, you want to carefully control where it can go.

the more piping/hose with the gas is more of a hazard. you want a cylinder and just the amount of hose you need.

having oxygen in unnecessary contact with combustible material is a fire hazard.

6

Did you not see the place where I said that I work with oxygen every day? I am well aware of the fire triangle, I don’t need a lot of don’t-try-this-at-home worrying. I am not even going to try this until I am absolutely sure it’s safe. That’s why I posted this here, and why I’m going to do more research into oxy-safe compressers, and more research into the concentrators, etc.

7

what I need to know about is whether the backpressure will hurt the concentrators, and what it is about the compresser that makes it unsafe for use with oxy. Is it the oil? Some other part? What is different about an oxy-safe compresser?

8

It might.

I work with them occasionally at my job, and they don’t put out much pressure at all, and don’t have anything to deal with any back pressure that might be generated. They are designed to just push the oxygen directly to a nasal canula, so they don’t output high pressures and aren’t designed to ever experience any back-pressure (well, medical O2 concentrators, that is…not sure if there are non-medical ones.)

Is there any reason you want to make your own other than just use tanks?

Edit: There are some models of O2 concentrators that are made to fill up mini-O2 tanks instead of going right to a patient, so they must have something in their design to deal with backpressures, right? But the tanks are really small and still don’t have much pressure, so I’m guessing still woudn’t meet your needs.

9

the main reason is expense - If I wanted to use those big green tanks, it would cost me 25$ every 1-2 days. I currently use oxygen from a big tank of liquid O2, and that costs me about 2$/hour. Using concentrators i am pretty sure I could get that number waaay down, I’m thinking 20c/hour or less. Also, having my own supply would mean no downtime - currently if I run out on a friday, I have to wait several days before a new tank can be delivered

10

those mini-tanks might actually be a possibility! Especially if I had a few extra tanks, so one could always be filling while I use the others. I will look into them and find out how long they can put out oxy at ~20 psi

11

Have you looked at Sundance Art Glass? They have some good advice on oxicons and stringing them together. I assume you’ve got a monster torch and work boro, still I think 15 LPM should do. I have a small torch for soft glass and only need 5 LPM but I’ll tell ya, making my own oxygen and using natural gas is about the best thing ever…no more tanks!

12

I have designed oxygen systems for chemical plants where typically the oxygen is separated cryogenically to 96 - 99.5% and then pumped as a liquid to high pressure and finally vaporized to give high pressure oxygen.

It would have really helped if you mentioned the final pressure and the flow (do not understand if the LPM is at low pressure or higher pressure) you were looking for - since we do not have that, here are some considerations I would go into :

1> Buy a compressor rated for oxygen service. Look at the Oxygen booster compressors (if they meet your pressure/flow needs) at http://www.rixindustries.com/oxygencompressors.html

2> Since you are going to header a lot of Oxygen concentrators together, make sure you are using good check valves if there is a concern that you can have one concentrator flow into the other one. If possible - use the fewest concentrators. Also - keep in mind to have a good size manifold.

3> Look into the velocity and pressure and see if you can use exempt metals (again knowing the flow/pressure would have helped here). You can look at a good guide on oxygen piping here : http://www.eiga.eu/fileadmin/docs_pubs/Doc_13_12_Oxygen_Pipeline_and_Piping_Systems.pdf

4> Pay special attention to valve internals to make sure they do not react with Oxygen. Use large radius bends and fittings to avoid local areas of high velocity.

5> Understand cleaning for oxygen service - you need to remove all residues / paint etc - here is an industrial guide, hope you can use the concepts from it : http://www.asiaiga.org/docs/AIGA%20012_04_Cleaning%20of%20Equipment%20for%20Oxygen%20Service.pdf

6> Have a purge system - so you can purge out the system once you are done. If you are going to use compressed air - ensure there is no oil in the compressed air.

7> Look into cooling the oxygen (if needed) after the compressor. Look into providing a volume after the compressor. Understand how you will control flow from the oxygen concentrators - provide block valves , so you isolate individual oxygen concentrators.

8> Since you will have a lot of oxygen concentrators putting out a lot of N2 purge gas - make sure you are doing this in a well ventilated area otherwise the air you breathe may become deficient of Oxygen

I think you are taking the right approach of understanding the risks and mitigating them by good design. Oxygen deserves utmost request - and please understand the complete risks. The above are only some considerations - there are others that need to be understood and solved.

Oh I forgot - please use a flow meter rated for oxygen service or take a regular flow meter (check if the materials are suitable for O2) and calibrate it.

13

Home oxygen concentrators are capable of 90%+ purity at around 5 lpm.

am77494 already noted Rix Industries as a manufacturer of an oil-less compressor that is favored for oxygen application.

These are very expensive machines and it will take quite some time to recover your cost in such a setup.

14

I think you can beat the cost if you research it well. Scuba diving compressors are oil free too but I do not know if 150psi or so pressure will be adequate for you. You can also buy pressure regulators etc for scuba diving. – Again - I have no experience doing this - you will need to research to ensure it is safe and operable.

Some other oil free AIR compressors may be purchased from Hookah and GAST.

15

am77494 pretty much has it. It sounds like home concentrators don’t provide enough oxygen fast enough for you. I’m not sure how much availability there is between home scale and massive industrial scale. There are some companies making accoustic chillers that rather efficiently condense oxygen. Check out Q-drive. I think they’re owned by Chart now.