Question Where do you get oxygen cylinders filled?

[coolfilmaker]

I’m investigating different system types and I’m trying to figure out if getting large oxygen cylinders filled with medical grade oxygen is something that isn’t that hard to do or if it’s actually a big pain. It seems like it can’t be that hard because a lot of the nitrox systems I see have them.

 

[rjack321]

This is what I believe to be true. I was told by an Airgas employee that they fill them from the same source. The 67ppm is the max, not a target. Hospitals utilize humidifiers to increase moisture where needed.

This ^^
In theory the medical standard allows more O2 in it than ABO. In practice they are basically the same as they are filled from the same source. Also even at their maximum allowed water content, medical and industrial O2 is so dang dry your booster and/or stick doesn't care and will never notice. You're talking ppm differences between O2 grades here when atmospheric air has water measured in percent aka parts per hundred. So like 4 orders of magnitude higher.

 

[Brett Hatch]

Quick search:

No, aviation oxygen, also known as Aviator's Breathing Oxygen (ABO), is designed to be drier than medical oxygen, with a moisture content of less than 0.01%, while medical oxygen can contain up to 67 ppm of moisture.​

Jim is right.

Google Search

I don't have a dog in this fight, but I'm reading the thread, and thought these numbers were confusing. 100 ppm is 0.01%, and 67 ppm is 0.0067%. So if ABO is under 100 ppm and medical oxygen is under 67 ppm... in what sense is ABO drier? I don't get it

Either way, these numbers are quite close to each other. And a gas with, say, 50 ppm (0.005%) moisture would satisfy both requirements... and be quite consistent with the "they're all filled from the same stuff" theory

 

[The Chairman]

More research, and I found a document from the DOD on Aviator's Oxygen. https://www.airanalysis.com/wp-content/docs/Oxygen-Mil-PRF-27210-J-1.pdf

Moisture. Moisture in Types I and II shall not exceed 7 ppm of water vapor or a maximumdew point of -63.3°C (-82°F) when tested as specified in 4.5.3.4​

So, 7ppm is less than 64ppm. But again, it's the max for either. 7ppm is also fine for medical oxygen.

 

[The Chairman]

More research. lN₂ sits at 72^oK and lO₂ sits at 90^oK.

According to the MilSpec doc above, Aviation Oxygen need only be 95% pure while medical Oxygen must be at least 99.2% pure.

Obviously, medical and aviation can come from the same barrel. Their dewars are huge, so this makes sense.

 

[rjack321]

I don't have a dog in this fight, but I'm reading the thread, and thought these numbers were confusing. 100 ppm is 0.01%, and 67 ppm is 0.0067%. So if ABO is under 100 ppm and medical oxygen is under 67 ppm... in what sense is ABO drier? I don't get it

Either way, these numbers are quite close to each other. And a gas with, say, 50 ppm (0.005%) moisture would satisfy both requirements... and be quite consistent with the "they're all filled from the same stuff" theory

There is no one holy grail moisture standard definition for either medical or aviators. Just to give you an idea of the variability across standards between agencies and different aviation programs...

https://apps.dtic.mil/sti/tr/pdf/ADA041245.pdf

 

[Subcooled]

If I were a legislator, I would impose different tax on medical grade, aviators grade and welding oxygen.
Bureaucracy would be different for all, but corporations might opt for one source for all for cost optimization.

 

[broncobowsher]

Because the limits of moisture in medical are higher, doesn't mean they are at the limits. You can still call it medical even if it has zero water in it. It is just that it could have more in it before being rejected. Doesn't mean that it does.

 

[flymolo]

Quick search:

No, aviation oxygen, also known as Aviator's Breathing Oxygen (ABO), is designed to be drier than medical oxygen, with a moisture content of less than 0.01%, while medical oxygen can contain up to 67 ppm of moisture.​

Jim is right.

Google Search

I’d still be surprised about this since they store medical grade oxygen in steel cylinders. I can’t imagine those would hold up for very long if they were being used to store moist gas.

 

[Capt Jim Wyatt]

I got liquid O2 and aviators O2 from AirGas for many years at the two different dive shops I owned. They told me that they pulled a vacuum on the aviators' bottles before filling them to ensure lower moisture and remove contaminants.

They did not do this on welding grade O2 because it does not matter if it has moisture and/or contaminants.

I always assumed the LOX was moisture free.

 

[sea_ledford]

Quick search:

No, aviation oxygen, also known as Aviator's Breathing Oxygen (ABO), is designed to be drier than medical oxygen, with a moisture content of less than 0.01%, while medical oxygen can contain up to 67 ppm of moisture.​

Jim is right.

Google Search

But 67 ppm is 0.0067%, so medical is dryer than ABO?