New tank owner...

[scubadobadoo]

If I get my tanks filled at the start of winter and don't use them until the start of summer, can the air become stale or go bad? If so, how long might this take? I have Al 80's. Seems like a silly question but I seem to recall this coming up when I did my equipment specialty, but I can't remember the answer. Thanks in advance.

 

[Brian Gilpin]

No not likely.

 

[ID diver]

I have not had the air in my cylinders (steel or aluminum) get stale even when they sat around for several months. About the only thing I can think of that will cause the air to go "bad" is in a steel cylinder if you had some water in it and it started to rust (oxidize). The oxidation would use up some of the oxygen in the air. I don't know how long this process would take. When aluminum oxidizes it "covers" the metal and seals the metal from the air (at least that is what I remember) so I don't think you would have the same problem with aluminum.

If you know you are not going to use your cylinders over the winter you might want to bleed the cylinder down to about 500 PSI. This relieves some of the stress on the cylinder (from the gas pressure) and then when you fill it in the spring you know you will have a fresh fill.

My $.02. I am sure you will get plenty of information from the others on the board.

 

[mustfajohnson]

One of the factors you should consider is safety. Aside from all the knocked/dropped hazards, the potential energy in a full cylinder is tremendous. They should be stored upright with a minimum of pressure. Heaven forbid that you have a fire but the heat generated by even a small fire can quickly cause the internal pressure of a fully charged cylinder to exceed its Test Pressure. While the over pressure device "should" keep a tank from having a catastrophic failure I'd rather not have that exposure. Air fills aren't that expensive.

 

[jbd]

One of the factors you should consider is safety. Aside from all the knocked/dropped hazards, the potential energy in a full cylinder is tremendous. They should be stored upright with a minimum of pressure. Heaven forbid that you have a fire but the heat generated by even a small fire can quickly cause the internal pressure of a fully charged cylinder to exceed its Test Pressure. While the over pressure device "should" keep a tank from having a catastrophic failure I'd rather not have that exposure. Air fills aren't that expensive.

Minimum pressure, from my understanding, is 20 to 50 psig.

 

[nativenarcosis]

I have read in extreme cases with AL cylinders that the formation of aluminum oxide on the inside of the tanks could theoretically decrease the oxygen percentage. Go figure if it ever happens in the real world.

 

[Tom Winters]

Scubadobadoo - why drain perfectly good tanks? They're fine pumped full and no, the air will not go stale. Plus if you drain them down and then decide to go for a January dive in the East River, you won't have tanks.
I wouldn't store them right next to a hot radiator all winter though.

 

[scubadobadoo]

So let me understand...no it isn't a problem to keep them full but it may be safer if I drain them to about 300 psi? I do understand that the potential for danger exists. I plan on placing the tanks in the back of a large walk-in coat closet where they will be out of the way for the winter. Any problem with that? Space is an issue in NYC and getting an air fill isn't expensive but can be a real pain the the butt given parking and that's assuming you have a car and aren't lugging dive gear on the subway. Been there, done that. Not fun and boy did I get some looks on the 7 train heading into Queens...

Thanks all for your knowledge and opinions.

Hidiver1, that East River current is a killer and the visibility is too. Boy do I wish it were a safe option though. If I am ever a part of the Mafia dive club I'll try it.

 

[pete340]

if you drain them down and then decide to go for a January dive in the East River, you won't have tanks.

You make it sound like that's a bad thing.

 

[paulwlee]

Don't worry about it.
The air won't go bad, and the tank won't explode.
As long as you get the visual inspections and hydros done there won't be a problem.

Now if you are worried of a fire where you store the tanks, then go ahead and store the tanks with minimum pressure. But I'd worry a lot more about getting into a car crash when you go to get that tank filled for the next dive.