Rust inside tank and O2 level

[skdvr]

I have read about this before but I could not find the post... It must have been before the big bang...

Anyway my question is about rust in a steel tank and how it would affect the O2 levels if you did not know there was rust in there. I have heard that if there is rust it will deplete the O2 to the point where you could not beathe it and be OK, but I seem to remember in the previous post someone who is a lot smarter than I am on the subject explained that is not the case. That it could be completely rusted and sitting for a long time and still be OK to breathe. Just looking for some feedback...

Thanks
Phil

 

[Ann Marie]

The University of Rhode Island did a study of cylinder internal corrosion that revealed that following three months of storage, a corroded cylinder (steel) contained only 15% oxygen, a near-deadly deficiency.

 

[Sideband]

"Near deadly"? If I recall correctly, you need 18% O2 (at surface) to support life. Anyone breathing that would at least be unconscious in short order.

I'd think at the point where the %O2 got that low the tank would be unusable because of the amount of steel that would have been effected.

 

[DennisW]

I would have to read the study. Flash rust on steel actually stops further corrosion from taking place. Therefore if there was flash rust only, then the O2 levels would not change enough to make a difference.

 

[skdvr]

The University of Rhode Island did a study of cylinder internal corrosion that revealed that following three months of storage, a corroded cylinder (steel) contained only 15% oxygen, a near-deadly deficiency.

OK, I guess I was wrong about what I had read before... Thanks for clearing that up. 15% is certainly NO GOOD...

Phil

 

[Scared Silly]

What you need to be looking at is not so much the O2 percentage but the O2 partial pressure. I have breathed air that had a pressure of less than 350mm Hg or 70 mm Hg for the partial pressure of the 02. At sea level normal is 760 and 159 mm Hg respectively. If you convert what I was breathing I was getting about 45% less 02 than at sea level (equivilent of about 10% O2 at sea level). Obviously I did not die but many would if they tried this with out proper acclimatization - but this is an extreme case.

Breathing 15% O2 at sea level is approximately the same partial pressure wise as going to 10,000 ft and breathing air with 21% O2. Some people will do fine others will pass out and few might die. We see this regularly when flat landers come skiing in the hills (most get to lower altitudes before they die though as they think they are having a heart attack. The O2 levels for pilots before requiring supplemental O2 is around 12,500ft (around a 13% O2 equivilent as sea level).

As was said 15% at sea level is not good, probably give you a big ol headache, make you dizzy, feel nauseated, etc. If you pass out you will probably not die but because you are in the water you will probably drown.

Oh, yeah those who dive at extreme depths typically use a Hypoxic Trimix. But they do not start breathing that at the surface. But use a "travel gas" until they are at the acceptable depth for their mix.

Other items haled air from the body around 17-18% O2 - good enough for CPR.

 

[Luis H]

The University of Rhode Island did a study of cylinder internal corrosion that revealed that following three months of storage, a corroded cylinder (steel) contained only 15% oxygen, a near-deadly deficiency.

I have a copy of that report at home. I don't recall all the details, but they used about a pint of salt water into the tanks and filled them to pressure. They also kept them at a very warm temperature to simulate absolute worst condition. IMHO a relatively extreme test, very useful information, but needs a bit of interpretation.

 

[skdvr]

What you need to be looking at is not so much the O2 percentage but the O2 partial pressure. I have breathed air that had a pressure of less than 350mm Hg or 70 mm Hg for the partial pressure of the 02. At sea level normal is 760 and 159 mm Hg respectively. If you convert what I was breathing I was getting about 45% less 02 than at sea level (equivilent of about 10% O2 at sea level). Obviously I did not die but many would if they tried this with out proper acclimatization - but this is an extreme case.

Breathing 15% O2 at sea level is approximately the same partial pressure wise as going to 10,000 ft and breathing air with 21% O2. Some people will do fine others will pass out and few might die. We see this regularly when flat landers come skiing in the hills (most get to lower altitudes before they die though as they think they are having a heart attack. The O2 levels for pilots before requiring supplemental O2 is around 12,500ft (around a 13% O2 equivilent as sea level).

As was said 15% at sea level is not good, probably give you a big ol headache, make you dizzy, feel nauseated, etc. If you pass out you will probably not die but because you are in the water you will probably drown.

Oh, yeah those who dive at extreme depths typically use a Hypoxic Trimix. But they do not start breathing that at the surface. But use a "travel gas" until they are at the acceptable depth for their mix.

Other items haled air from the body around 17-18% O2 - good enough for CPR.

Good points made. Thanks for the post. I did not even think about the altitude analagy, that makes a lot of sense.

Thanks again.

Phil

 

[skdvr]

I have a copy of that report at home. I don't recall all the details, but they used about a pint of salt water into the tanks and filled them to pressure. They also kept them at a very warm temperature to simulate absolute worst condition. IMHO a relatively extreme test, very useful information, but needs a bit of interpretation.

I would like to see the report. I would be interested in reading all the conditions that they subjected the tanks to.

Thanks
Phil

 

[Bob3]

... The O2 levels for pilots before requiring supplemental O2 is around 12,500ft ...

Yep, FAA allows "up to" 30 minutes at 12-5 before supplemental O2 is mandated.

Wet air or water in a steel tank is bad news - I've heard of folks passing out after letting a tank sit over winter (several months) with "bad air" inside.
I'd like to see a good quotable source that I could refer to; having stats to rattle off is always better than "I heard about ..."