How long is a tank of air good?

[tedtim]

I hate to waste a $5 fill, but since we strive for safety is a somewhat safety-challenged sport, this is probably a good suggestion. Right before diving again, drain it to 500#, then refill it with fresh air.

Well said Don. The cost of a fill is small. If you have any doubt about the quality of the air in your tank, drain it and get a fresh fill.

 

[moneysavr]

My rule on AL 80's is store them with 500PSI valve up!
Air is Air,but you do need a vis, so 1 year will be max,dont dive gas in a tank that you did not have filled ! if you get used tanks have them looked at by your LDS dont take any chance!
Brad

 

[OWSI176288]

remember condensation on the outside probably means condensation on the inside. A no no for dive cylinders unless you don't mind buying a new one fairly soon.

Say What?!?

My understanding is that moisture on the inside of a tank is totally unrelated to any moisture that forms on the outside due to adiabatic cooling.

Any moisture on the inside came from the airfill station used to fill the tank and got in the tank long before you started to drained it. Moisture that forms on the outside when a tank is drained is nothing more then water in the air forming condensation due to the tank cooling.

 

[NSDiver]

containing air that had been stored in a closet for 9 years...no ill effects.

I've been trying to get my dad back into the sport for a few months now (he is finally taking a refresher). Anyway, a few weeks ago he got out his old equipment to check it out and hooked his regulator up to his AL63 that hadn't been filled since 1977. It was FULL - and he said the air was fine.

 

[DandyDon]

My rule on AL 80's is store them with 500PSI valve up!
Air is Air,but you do need a vis, so 1 year will be max,dont dive gas in a tank that you did not have filled ! if you get used tanks have them looked at by your LDS dont take any chance!
Brad

That sounds good, too. Finish a dive with 500#, take the tank home and store it upright. Don't know why Clay liked 1500#?

Say What?!?

My understanding is that moisture on the inside of a tank is totally unrelated to any moisture that forms on the outside due to adiabatic cooling.

Any moisture on the inside came from the airfill station used to fill the tank and got in the tank long before you started to drained it. Moisture that forms on the outside when a tank is drained is nothing more then water in the air forming condensation due to the tank cooling.

Yes that's certainly true. I think what he meant was that if you drain a tank quickly, the metal will chill. If you get condensation on the outside, that means the tank is cool enough to condense any moisture accidentally inside the tank. We hope for dry fills, but how would we know...?

I've been trying to get my dad back into the sport for a few months now (he is finally taking a refresher). Anyway, a few weeks ago he got out his old equipment to check it out and hooked his regulator up to his AL63 that hadn't been filled since 1977. It was FULL - and he said the air was fine.

Oooooo, would you like to breath old air from that tank? Again, we hope for dry fills, but how would we know...?

Test breathing it is one thing, diving it with depth and pressue would scare me. Get a viz, hydro, and new fill. Need to service the Reg, too.

 

[ShakaZulu]

He further suggests that corrosion is a risk that can also decrease Oxygen content and thereby increase Nitrogen percentage. Aluminum may not corrode as quickly as steel, but it still can happen. Clay suggests storing the tanks at half full, to maintain pressure on the tank so as to prevent further problem, and to prevent a diver from using a tank that had been filled at a long-ago, perhaps unknown date.

This is the key right here, how much is your life worth to you??

 

[O2BBubbleFree]

Test breathing it is one thing, diving it with depth and pressue would scare me.

The pressure differential is greatest on the surface and less at depth, so failure is more likely at the surface.

 

[cyklon_300]

cost $1...so, at the time, I guess my life was worth a buck. Adjusted for inflation, it's probably a bit more presently.

fwiw, the air had no taste or odor problems.

 

[Goose75]

Say What?!?

My understanding is that moisture on the inside of a tank is totally unrelated to any moisture that forms on the outside due to adiabatic cooling.

Any moisture on the inside came from the airfill station used to fill the tank and got in the tank long before you started to drained it. Moisture that forms on the outside when a tank is drained is nothing more then water in the air forming condensation due to the tank cooling.

I would have to pull out some old textbooks to figure out the details but your point is how I remember things. The condensate on the outside was pulled from the air outside. The air inside should contain very little moisture so it would be hard for it to saturate the inside of the vessel. If the air inside the vessel has a high moisture content then your fill station is a problem.

 

[lamont]

in a steel tank the inside of the tank could rust and use up some or all of the O2 in the bottle.