REFLECTOR: Oxygen systems

David Staten david.staten at gmail.com
Sat Feb 14 20:43:40 CST 2009


Kent Murley wrote:
>  Just don't use  
> medical grade O2 because that has water vapor added to it (to keep  
> patient's lungs moist) and water vapor at altitude could freeze your  
> regulator.
>
> Kent
>
>   
As Dr Epstien pointed out... and I will concur.. this is a pure, 
unadulterated BS of an old wives tale.

ALL commercial/medical/aviation/welders oxygen is cryogenically 
distilled as a liquid, and either stored as liquid pure oxygen or 
evaporated and compressed into pure compressed gaseous oxygen. TriGas 
and Air Liquide are two of the major suppliers in healthcare and 
industry. Same distillery feeds all streams. Bob on the loading dock 
takes a hose, and reads the manifest and says.. gee.. I need 4 aviation 
bottles, 200 medical bottles and 50 welders bottles today.. and then 
fills them all from the same hose. The inventory they fill from meets or 
exceeds all specifications.

 Moisture in a high pressure oxygen rich environment would cause rapid 
corrosion and compromise of the storage vessel. Not to mention iron or 
aluminum oxides couldn't be all that healthy to breathe either.

Think about what you just wrote..that at altitude the regulator would 
freeze...  the pressure difference between altitude and sea level for us 
non-pressurized folks is less than 6 psi.. 14.7 psi at sea level  to no 
less than 8 psi up high. Do you really think that compressed gas going 
from 2200 PSI to ambient is going to be affected by those 6 extra PSI? 
Did you know that medical oxygen is carried routinely in medical 
cylinders for medical patients in non-pressurized aircraft and they dont 
freeze either? The Universal Gas Law applies here PV=nRT. You can 
calculate the temperature change of the gas as it leaves the regulator 
using that formula. I suspect you will find the temperature change to be 
below freezing no matter if at MSL or at altitude and very little 
difference between the two temp values calculated for the two pressure 
changes.

If you read the specs, and the FDA requirements that were enacted within 
the past 20 years you would know that medical grade oxygen is actually 
more likely to be impurity free. The medical grade tanks have serial 
numbers and are tracked. Medical grade cylinders in medical use are 
required to be taken to VACUUM between fills, whereas a welding cylinder 
that runs empty may be left open to air, which potentially allows 
atmospheric contaminants in.

Any moisture in oxygen is added after the gas leaves the tank and regulator.

Dave
Paramedic for 18 years, Critical Care Nurse for 9 of them, 10 years of 
firefighting and servicing oxygen and breathing air equipment scattered 
in there.. And I stayed in a Holiday Inn once too.


More information about the Reflector mailing list