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.
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