Why do we put oxygen in aluminum cylinders?

[2airishuman]

This might help put it into perspective:

• Reasons to manufacture a neutral, lower pressure, steel cylinder
  • We want it
• Reasons to not manufacture a neutral, lower pressure, steel cylinder
  • Economics (no possibility of a profit)

I get that. On the other hand, there are some really oddball cylinders that continue to be manufactured (we know, they have recent "born on" dates), like AL30s. Before Worthington got out of the business they were making all kinds of odd size steel cylinders with various ratings. I don't know what the minimum number of cylinders is that e.g. Faber would have to make in order to cover the cost of tooling up but I can't imagine it's that large. They make things like the FX-23 for a relatively small market.

 

[KevinNM]

I was more addressing the fire and explosion hazard which is reduced by lower pressure, smaller tanks, and regulators and other gear that cannot be used on other, non O2, tanks and fill whips to transfer contamination.

It doesn't take high pressure. Aluminum will burn in 30 PSI 100% O2.
The Flammability of Aluminum Alloys and Aluminum Bronzes as Measured by Pressurized Oxygen Index

At 150 PSI carbon steel will burn in 100% too.
http://www.magnetomechanical.com/resources/PDF_Manuals2/ASTM/ASTM_STP/Stp910/v2art10.pdf

 

[Bob DBF]

I'm not arguing that all he** won't break loose once there is an accident.

Would a lower pressure in a tank, smaller tank, and only having gear that can be used with O2, and not useable with anything else, mitigate the problems associated with O2? It seems to with medical O2.

The biggest issue with medical O2 fires is that patients continue to smoke while using O2, mostly burning themselves, sometimes starting a larger fire. This is the case using a bottle or an O2 concentrator.


Bob

 

[Patoux01]

Here in Europe we have the M26 valve / thread size for use with rich O2 blends.

Actually, M26 is a moronic thing as it is "for anything higher than 21%". Not "For anything higher than 40%". So it basically does not guarantee much of any safety, because a tank with M26 might not be O2 clean.

 

[cathal]

Actually, M26 is a moronic thing as it is "for anything higher than 21%". Not "For anything higher than 40%". So it basically does not guarantee much of any safety, because a tank with M26 might not be O2 clean.

Having witnessed two incidents where a diver put the O2 on the diluent post and the diluent on the O2 post the M26 is a foolproof control of ensuring this cannot happen.

Separately and I stand to be corrected but does aluminium not have a better reaction to oxidation than steel
i.e. Ali cylinders do not suffer from internal rust as opposed to steel cylinders that are used to carry high % O2 ?

 

[Patoux01]

The M26 doing "a good job" on rebreathers is a side effect. Because there you use pure oxygen, not "any enriched air".

Had the rule been "It's higher than 40%, it needs M26", then yes it'd have been useful and I'd probably have been in favor of it.

 

[cathal]

The M26 doing "a good job" on rebreathers is a side effect. Because there you use pure oxygen, not "any enriched air".

Had the rule been "It's higher than 40%, it needs M26", then yes it'd have been useful and I'd probably have been in favor of it.

Can I ask from where do you get 40%? NASA believe anything higher than 23% is a risk: Oxygen Assessments Ensure Safer Medical Devices

 

[Capt Jim Wyatt]

40% is an arbitrary number the diving industry adopted years ago. I recall some justification for the number, but it was loose.

Can I ask from where do you get 40%

 

[68raggtop]

2airishuman, I have a LP45 that has O2 in it if you want to actually try one. I am in the north metro area. I used it once or twice on a dive, but mainly use it for surface O2 (like a DAN bottle) and it stays in the truck or on a boat. PM me if you want to try it.
Dave

 

[Patoux01]

Can I ask from where do you get 40%? NASA believe anything higher than 23% is a risk: Oxygen Assessments Ensure Safer Medical Devices

The millions of tanks that get filled with N32 should give you more than enough proof that 32% is waaaaaay lower than the danger zone.