All of this is great we now know every
thing about oxygen but where can we get our mountain high bottles filled ,in Melbourne?
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Geoff Vincent
Sent: Saturday, December 24, 2005
11:01 AM
To:
[email protected]
Subject: [Aus-soaring] Oxygen
sources and use
Most of the subscribers to this thread have got the
facts at least partly right. The moisture specification, i.e. maximum
level permitted under the quality criteria published by BOC and Air Liquide is
as follows: Welding oxygen 100 ppm, medical oxygen 67 ppm, aviators dry
breathing oxygen 10 ppm. All these marketed "grades" of oxygen
come from the same production process and are thus identical in composition and
in the cylinders as delivered all have a moisture content less than 10
ppm. That means, irrespective of the labelling on the cylinder, all meet
the ADBO spec of 10 ppm moisture.
However, if you decant oxygen from a supply cylinder, irrespective of it's
label, to your glider oxygen cylinder it is certainly possible to introduce
extraneous moisture during that process: e.g. minor amounts contained in
un-purged air in the transfilling apparatus (absolutely insignificant in the
general scheme of things); liquid water sitting in the fittings on the supply
cylinder - a potential major problem (I've seen this actually happen when
a fresh G-size cylinder with no plastic seal cap was brought in from outside
storage and the transfiller was screwed in without the fitting being inspected
or cleaned); condensation in the transfilling apparatus, another
potential major problem. Clearly all of these problems can be
avoided by having sound inspection and purging procedures and housekeeping
practices.
I have been using commercial (welding) oxygen in my own glider for several
years in both Mountain High EDS and Avox A8A constant flow regulator systems
with absolutely no adverse impacts. Why on earth would you expect any
adverse impacts anyway? The delivered oxygen "grades" are
identical, irrespective of labelling, and if your transfilling procedures are
up to scratch then the oxygen in your glider cylinder will meet your
physiological requirements when needed.
Just one word of caution though - how confident are you that the gas supplied
in the cylinder labelled oxygen (whether from a gas supplier's cylinder or from
your glider cylinder re-filled by a supplier) is actually oxygen? What if
it actually contains nitrogen, argon, or any of the other compressed gases
supplied by BOC et al? How would you know? Believe me, shit happens,
nothing is fool-proof. This aspect is my greatest concern.
By profession I happen to be an industrial chemist/chemical engineer/process
engineer with over 45 years experience and understand the properties of oxygen
reasonably well. As a life-saving precaution I do a simple series of
checks whenever I am using a fresh oxygen supply cylinder for the first
time. Firstly, check and double-check the cylinder colour coding (black
for industrial oxygen), label (oxygen, O2) and UN number (1072). Secondly,
crack the valve very slightly and sniff the contents. Despite oxygen
being described in the literature as an odourless and tasteless gas it has a
distinctive slight odour. Thirdly, and most importantly, I make use of oxygen's
unique ability to support combustion. Crack the valve very slightly and offer
up a smouldering 5mm diameter cotton wick. The wick will burst into flame
if the gas is oxygen, but will not flame if the gas is anything else. To
the uninformed this latter check may sound hazardous but in reality it is quite
safe. Only if all these checks are positive do I proceed with transfilling.
Geoff Vincent
PIK 20B
VH-GAX
