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 écritÂ*:
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.