"air" bottle converted to Nitrox

[Couv]

.... What makes us (SCUBA guys) smarter that the Navy, NASA, NFPA, or CGA?

The same thing that make UPS and FedEx smarter than the US Postal Service.

 

[turnerjd]

But that was an oxygen tank. The issue here is recreational nitrox capped out at 40%.

This is where the conceptual problem is...........

When you partial pressure blend, your tank is in effect an oxygen tank.

For PP blending, the tank is emptied (or nearly emptied) and then filled with 100% O2 to a certain pressure depending on the mix you want, usually around 70 bar or so, and then topped off with air. This exposure to 100% O2 is where there is the potential for problems (and of course this risk does not exist for filling tanks from banked nitrox).

Just because there are so few accidents, doesn't mean that there is no risk. It just means we know how to manage this risk. Oil and O2 don't mix. We've known that for probably over 100 years. Anything coming into contact with 100% O2 has to use the correct O2 compatible grease and O-rings. If this is done, then there is almost no risk of an accident. However, if there is oil, or the o-rings are not compatible then there is no absolute instant death guarantee, but the RISK of something going wrong is much greater.

Just remember that the rec mix that is capped out at 40% is the final mix. Sometimes (but not always) to get to this 40% you have to put 100% O2 into your tank first. Your regulator etc will be fine, as it is never exposed to anything greater than the mix in the tank, but the tank might be exposed to more.

J

 

[JohnN]

This is where the conceptual problem is...........

When you partial pressure blend, your tank is in effect an oxygen tank.

For PP blending, the tank is emptied (or nearly emptied) and then filled with 100% O2 to a certain pressure depending on the mix you want, usually around 70 bar or so, and then topped off with air. This exposure to 100% O2 is where there is the potential for problems (and of course this risk does not exist for filling tanks from banked nitrox).

Just because there are so few accidents, doesn't mean that there is no risk. It just means we know how to manage this risk. Oil and O2 don't mix. We've known that for probably over 100 years. Anything coming into contact with 100% O2 has to use the correct O2 compatible grease and O-rings. If this is done, then there is almost no risk of an accident. However, if there is oil, or the o-rings are not compatible then there is no absolute instant death guarantee, but the RISK of something going wrong is much greater.

Just remember that the rec mix that is capped out at 40% is the final mix. Sometimes (but not always) to get to this 40% you have to put 100% O2 into your tank first. Your regulator etc will be fine, as it is never exposed to anything greater than the mix in the tank, but the tank might be exposed to more.

J

All good points. If you go back to the original post, the question was about BANKED gas, not PP fills.

 

[Agility]

another problem is that an oxygen clean tank does not stay clean if it is filled with air from a compressor that does not meet the critaria for clean air. http://www.andihq.com/index.php?option=com_content&view=article&id=68:what-is-safeair&catid=36

 

[turnerjd]

All good points. If you go back to the original post, the question was about BANKED gas, not PP fills.

Yeah, I know, but some of the posts went off tangentially, and I thought that a quick reminder of the why etc... was probably good.

---------- Post added February 11th, 2013 at 05:37 PM ----------

another problem is that an oxygen clean tank does not stay clean if it is filled with air from a compressor that does not meet the critaria for clean air.

and this is where the oil in a normal tank that may cause problems does indeed come from...........