Steel tanks absorb O2?

[LUBOLD8431]

Hmmm... This is interesting. I would recommend that you not use those tanks until you get a complete visual inspection on them. In fact, I would offer to do a thorough investigation of this problem. Please send me the affected cylinders ASAP. I will do my best to identify the problem. It may take up to five years for a complete analysis.

 

[oceancurrent]

Hmmm... This is interesting. I would recommend that you not use those tanks until you get a complete visual inspection on them. In fact, I would offer to do a thorough investigation of this problem. Please send me the affected cylinders ASAP. I will do my best to identify the problem. It may take up to five years for a complete analysis.

Excellent idea!

 

[pgdive]

Hi

I do know that on any given day, a compressor can put out a slightly different % of O2 in the air that it is pumping. Our quarterly air tests are never exactly the same in regards to the 02. They might vary by .01 here or there, but they are still well within the guidelines for modified grade E (O2 compatible) gas. In fact an "air" compressor can fail its test if the O2 percentage climbs too high.

Paul

 

[Soggy]

Since this has absolutely nothing to do with New England, could one of the mods please move this somewhere more appropriate?

 

[oceancurrent]

...I think I will bring the tanks at the dive store, drain them, look into the steel tanks for rust, fill all the tanks to 1000psi with air from the same source, let the their temperature equalize with the environment at home for a few hours, perform a reference analysis, and then let them "age" for three months...

All right, I got the experiment set up. The light stick didn't reveal rust inside the steel tanks other than tiny speckles, which are perfectly normal. All tanks got drained and filled to 1000psi. I let them sit indoors for a few hours and took O2 measurements. All four tanks clocked solid 20.9%.

I will re-analyze the tanks in three months and post the results.

 

[Rick Murchison]

fill all the tanks to 1000psi

I hate to rain on your experiment, but...
It's ok to do this with steel, but you should store your aluminum tanks either full or nearly empty. This has to do with aluminum's inability to retain its strength when exposed to heat. In the event of a fire, a full aluminum tank will blow the burst disk before the tank weakens to the point it will explode. Likewise, a nearly empty tank will never reach a high enough pressure to explode even a weakened tank. But 1000 psi? 1000 psi is just right to have a tank exposed to typical building fire temps weaken enough to explode before the burst disk lets go.
Rick

 

[oceancurrent]

That's a good point, Rick!

Just for the record - I normally store the tanks at 500psi for the winter. I was sloppy this fall (*long story*) and didn't bring the pressure down after the last dives of the season. Since I want to keep the variables as close as possible to the last 3 months, I will let them chill at 1000psi. I know it equals more tank fatigue and somewhat higher risk of exlosion, but we'll hope for the best. ;-)