On Wednesday, February 24, 2021 at 5:19:34 AM UTC-8, Tango Whisky wrote:
The point is that with welding oxygen, there is no tracability that a an empty storage cylinder hasn't been left open which would enable moisture to enter. At 30 °C in a dry climate that would be 10 g/m3 water content. Take that content to -10°C and would freeze you valve solid shut (without even to take into account expansion cooling).
On the medical cylinders we use in Switzerland, we have a small valve inserted into the valvo of the cylinder which shuts of the cylinders below a pressure of 5 bars.
Le mercredi 24 février 2021 Ã* 10:03:46 UTC+1, Darryl Ramm a écrit :
On Tuesday, February 23, 2021 at 9:47:53 PM UTC-8, wrote:
At the Cowley wave camps, there's the odd day when record attempts are made to 30,000+ It gets really cold up there as in -30C - actually surface temperature at night a week or so ago.

My welding supplier advises ABO for that kind of height and temperature, and I'm inclined to believe him. But the turnaround time for ABO cylinders is really slow here.
Your welding supplier is confused. **there is no difference** This is the perennial noise that comes up on r.a.s every few years. All the O2 in these uses comes from cryogenic fractional distillation. The cyrogenic process freezes out all moisture. All those cylinders are filled from the same liquid oxygen source. Oxygen distribution systems are inherently dry. If they had moisture in them we'd have a boat load of safety issues in handling and distribution.

I don't understand specific concerns about -30C or flight above a certain altitude. If there was a water contamination problem folks would often be having problems at lower altitudes anywhere around freezing temp. Or do you use ABO at all altitudes? Lots of gliders fly in wave in cold conditions using welding oxygen and how many are falling out of the sky or having problems with oxygen supply. I'm aware of not one case of moisture contamination in a glider oxygen system. Does anybody know of one? I'm aware of shattering cannula tubes because of the cold, and all the usual stupidity of not running on cylinder valves, or taking off with low pressure or not knowing how to operate O2 systems etc...and fires during transfilling glider oxygen... all those stories and not one about moisture contamination. Many many places at least in the USA that refill oxygen for gliders use industrial oxygen.... and the number of problems are???

Refillers should be pumping down oxygen cylinders prior to refilling. It's in the fill procedure for suppliers I've talked with. They know how critical low contaminants including water are with industrial gases, and they don't want to be compressing 2,000 psi oxygen with some potential mystery gas. If the valve is open they may want to inspect the cylinder for corrosion. You can always ask your local refiller what they do. Lots of folks are going to tell you you need medical grade for medical and AVO for aviation, in the best case they might they *think* there is a safety reason or might think they would be in trouble for supplying you with industrial oxygen, or they might just want to charge you more money.

I think it must be time to talk about the dangers of sanding corrosion off lift pins...