Medical Oxygen Generator for small volume Nitrox?

[kevinstone]

I wouldnt think it's worth the time or money.

 

[Allan C Smith]

Another thing to consider would be gas absorption/deco models. Far as I know deco models don't worry about Argon as its only 1% in air. Maybe they don't need to worry about it at 4% either but who really knows?

Really would like to resurrect this. I was looking at the Nuva air systems as a way of providing 40% o2 for the new Hollis Explorer. wouldn't this be an issue for them as well? Also as a concern the medical grade o2 we use for blending down her can be as low as 80% I wonder how much argon is in that stuff?

---------- Post added January 11th, 2013 at 12:08 PM ----------

Also Seeing Issues with CO2 From these "recreational membranes" Are these systems all as bad as they say? If so I'm starting to understand why we don't have any Nitrox on the island.

 

[CraigAClark]

Really would like to resurrect this. I was looking at the Nuva air systems as a way of providing 40% o2 for the new Hollis Explorer. wouldn't this be an issue for them as well? Also as a concern the medical grade o2 we use for blending down her can be as low as 80% I wonder how much argon is in that stuff?

When you mention the Nuvair system are you talking complete with l.p. and h.p. compressors?

The two units below are a complete PSA system to produce 99% O2 @ 2 scfm to 2250 psi. One unit will produce 93%+/- 3% and larger contains a second PSA that removes argon and other trace gases to achieve the higher purity.

 

[Allan C Smith]

I was looking at the stand alone Nuva air system. Membrane, filter, regulator, heater and Nitrox stick. That I could run through a small, second hand, compressor and use a bank filled by the same compressor for the low pressure side. It would be my understanding that there would be no filtration of trace gasses with this system. Unless the Filter on the low pressure side can some how remove them?

---------- Post added January 11th, 2013 at 01:04 PM ----------

When you mention the Nuvair system are you talking complete with l.p. and h.p. compressors?

The two units below are a complete PSA system to produce 99% O2 @ 2 scfm to 2250 psi. One unit will produce 93%+/- 3% and larger contains a second PSA that removes argon and other trace gases to achieve the higher purity.

View attachment 144551

So it could be speculated that the reason we are getting such low O2% down here is the lack of the second unit removing the remaining nitrogen and Trace gasses.

 

[pasley]

... I think that Argon is believed to be 2.3 times as narcotic as Nitrogen. Therefore, 4% Argon should not be an issue. But who knows?

Don't forget to apply your Partial Pressues formula to the 4% Argon.

 

[nimoh]

Don't forget to apply your Partial Pressues formula to the 4% Argon.

I think the partial pressure matters little since as you are using the bottle deeper you are mixing it. The 4% Argon/96% Oxygen mix, would be considered 100% O2 and not be used below 20' resulting in 6.4% Argon (at 20')

If you are at 70', you will be cutting the mix in half to 2% (i.e. 50% O2), then triple it for the 3 ata and you get 6%

 

[Allan C Smith]

I think the partial pressure matters little since as you are using the bottle deeper you are mixing it. The 4% Argon/96% Oxygen mix, would be considered 100% O2 and not be used below 20' resulting in 6.4% Argon (at 20')

If you are at 70', you will be cutting the mix in half to 2% (i.e. 50% O2), then triple it for the 3 ata and you get 6%

Yeah but if you were using a simi closed Re breather like the explorer the level of argon could increase as you consume O2. Add to that effectively double the amount of argon in the breathing gas and we could have some problems.

 

[CraigAClark]

We are talking about a PSA system on the island? If that is the case, and they are only producing 80% purity it is probably due to a system problem. Generally, 13x molesieve is used in the beds for units that produce 93% +/- 3%. PSA stands for Pressure Swing Adsorbtion. There are usually two sieve beds to keep a constant supply of oxygen flowing out of the system. Low pressure air, 30 psi on small units and around 100 psi (like the one in the system I posted), are fed to sieve beds alternately. Each bed, as it is being pressurized, separates the O2/trace gases from the nitrogen. The O2 moves ahead of the nitrogen. Electronic or pneumatic valves controlled with a PLC stop and start the gas flow through the beds. Just before the nitrogen would "break" through the sieve (which would contaminate the O2) the inlet valve is closed and another valve opens and the nitrogen is dumped from the bed.While one bed is pressurizing, the other bed is dumping. Temperature plays a big part in how quickly the system warms up and begins producing an acceptable purity.

There are a number of factors that can lower purity, depending on how many "bells and whistles" are in the system. If the beds don't have enough seive in them, the seive has been shifted (usually during shipment), moisture has gotten into the sieve bed because air supply pre-filters haven't been changed or it could just be old and needs changing. Control valves can wear and start to leak. I could keep going, but you get the idea. In the system I posted, there is a safety feature, controlled by a fault relay in both the O2 analyzers that will not allow O2 to flow to the receivers unless it meets the minimally acceptable purity. 80% doesn't even come close in the lower purity PSA.

 

[Allan C Smith]

CraigAClark Thanks for the lesson! So in your opinion is the 80% O2 we get down here safe for Nitrox blending? Granted it's safer from and explosion point! But do you think my fears of Co2 and Argon are justified or just down right silly?

 

[nimoh]

Yeah but if you were using a simi closed Re breather like the explorer the level of argon could increase as you consume O2. Add to that effectively double the amount of argon in the breathing gas and we could have some problems.

good point. I was speaking purely of open circuit, and know very little about rebreathers.