Close to 100% nitrogen in an old tank?

[The Chairman]

The info sounds hinky. Aluminum won't consume O2, although steel can. It would make sense if it were a small bottle for a dry suit.

 

[rjack321]

The info sounds hinky. Aluminum won't consume O2, although steel can. It would make sense if it were a small bottle for a dry suit.

And it takes A LOT of steel corrosion to reduced O2 to dangerous levels. And the problematic O2 %age is even lower the deeper you go. Like so much rust the tank is at risk of rupturing. The cylinder being accidentally filled with argon, helium, or another non-breathable gas seems more likely.

 

[jale]

Hi
Sorry about your friend.
Was not your friend passionate about cars also?
Indeed, some people use pure nitrogen to fill tyres.
I hope you will get an answer.

 

[nadwidny]

Hi All,

Had a friend pass from a diving accident last fall. The coroner just got back to his family with info. I didn't speak to the coroner directly and this information is second hand.

However, I have been told that his aluminum pony bottle was filled with almost 100% nitrogen and I can't make sense of how that would happen?

I believe he hadn't used that bottle for a couple of years but don't know that for sure. Is there anyway anyone could think a pony bottle could accidentally get filled with nitrogen? Or if there is some type of oxidization process on the inside of a tank after a long period of time that could increase nitrogen levels?

I will be following up to see if I can read the report to confirm this information. It would obviously make a lot more sense if it were filled with 100% O2 and he didn't realize it and switched gasses too deep.

Thanks for any information in advance

I used to work at a lab that did air testing for compressed breathing air (scuba stores, fire stations, etc) and have run thousands of air samples. I am always interested in solving situations such as this. I would like to talk more with you. Send me a PM if you would like to discuss this further.

 

[Namreg 58]

I think jale is on the mark. It is common practise among the car racing fraternity to fill their tires with nitrogen as it does not heat up as much as air under racing conditions. Always pays to test breathe your gas before diving.

 

[JohnN]

I think jale is on the mark. It is common practise among the car racing fraternity to fill their tires with nitrogen as it does not heat up as much as air under racing conditions. Always pays to test breathe your gas before diving.

Off topic, but not quite right. Nitrogen is used because it is dry. "normal" compressed air (at least as used to fill car tires) has quite a bit of water in it. When the tire warms up to track temperatures, that water increases the tire inflation temperature to an unpredictable degree (on track days, I used to fill my tires to +- 0.2 PSI)

 

[martincohn]

If it was the gas that caused this accident. Another example of why its so important to test EVERY bottle with an analyzer BEFORE you use it.

I decided it was worth the extra $$$ to be able to test o2, he, and co.

 

[wgw04024]

Did this accident make this forum back when it had happened?

 

[Rollin Bonz]

Sorry for your loss.

I was on a dive boat a few years ago and the
owner told us an interesting story. Cannot confirm or deny it's authenticity or it's plausibility...

He said that he had a regular customer/friend pick up a nitrox fill. Friend doesn't check O2 percent at pick up. Does check it a few days later, and it's a few percentage points lower than it's supposed to be. Customer comes back to complain to the owner. Owner apologizes, no idea what happened, but won't happen again. Next tank, it happens again. Third tank, owner fills himself, promises customer THIS one is good. Few days later, customer checks the tank, O2 percent is low. Returns to the shop. They remove the valve and find a considerable algae growth of some kind in the tank.
They think the algae was oxidizing the o2.

Again, may be total BS, I don't know.

 

[wnissen]

Okay, here’s my calculation:
Pressure (atm) * volume (L) * fraction of 02 (%) * ideal gas moles/L * molar mass of 02 (g/mole) * mass fraction of Al (Al/O2) = grams of Al consumed. That works out to .3 grams aluminum per liter per atmosphere. So a 2L pony at 200 bar would consume 120 grams of aluminum to use all the oxygen. That’s roughly a quarter pound. The number for steel would be more than twice that. Rust is heavy, but it seems unlikely there could be that much lost from a cylinder.