Aluminum tank, filled when new,,,,

[Machrihanish]

Hi all, I bought an 80cbft tank used.
The tank was purchased, filled then stored for a number of years, 4, maybe 5 years. Could the air still be good in it and what would make it go bad?
If the air went/is bad how would someone go about cleaning it?
Mach

 

[RonFrank]

Hi all, I bought an 80cbft tank used.
The tank was purchased, filled then stored for a number of years, 4, maybe 5 years. Could the air still be good in it and what would make it go bad?
If the air went/is bad how would someone go about cleaning it?
Mach

If the tank has gone four years, it needs a vis. If it's been five years, it needs a vis, and a hydro.

I would not breath it. Both a vis and a hydro are going to required the tank to be emptied, and the valve pulled.

You are saving all of $5 by breathing this tank. Is that worth the risk that the air could be bad? I can't think of a reason why it would go bad, but why bother. Take the tank in and get it serviced. You will need to anyway because even if you just want to sell it, the value is going to be MUCH lower if it's out of hydro and vis.

 

[Jimmer]

If it was stored for 4 or 5 years, it defnetly needs a visual inspection and possibly a hydro. So take it to a shop and they'll inspect it, and clean it if needed.

 

[Colliam7]

The tank was purchased, filled then stored for a number of years, 4, maybe 5 years. Could the air still be good in it and what would make it go bad?

The air is probably 'good', it is probably breathable. Hypothetically, if there was an enormous amount of oxidation, and the interior is filled with aluminum oxide, there could be a slightly lower than normal oxygen content, But, why jump in the water and depend upon it, when a fill is inexpensive, and you will probably need a hydro / vis anyway, followed by a fill?

If the air went/is bad how would someone go about cleaning it?

The tank may or may not need to be 'cleaned'. But, if it does (e.g. because of aluminum oxide buildup), it is easy to do. Part of the same process that is used in oxygen cleaning - a slurry of glass beads with a dilute Simple Green solution is put into the tank, and the tank is then put on a tumbler - will accomplish this. Most shops can do this easily, and clean the valve at the same time, in case there is any particulate matter that has built up as a result of oxidation, and gotten into the valve when the tank is drained.

 

[DA Aquamaster]

The practical issue is whether you use the tank before you take it in for inspection or hydrotesting or whether you just dump the air that is in it and take it in immediately.

The air is probably just fine and oxidation will not occur unless there is water in the tank. As long as it does not smell/taste funny I would not worry about it. The remaining consideration is the timing of the inspection to give you the most utility from the tank as a turn around time on the hydro could be as long as 2-3 weeks. If you are going to do a dive now and then have a month or two before you start diving a lot, use the tank. If on the other hand you are not diving until the start of the season, dump it and have it tested/inspected now to avoid anyloss of use of the tank during the season.

 

[pescador775]

Storage of air/gas in a steel tank can raise questions. For example, if there is water in the tank the cylinder strength could be compromised, rust binds oxygen and therefore may make the contents hazardous to breath.

Water/corrosion inside an aluminum tank which has been stored for X years will generate a funky odor. Normally, corrosion from fresh water (condensate) is spotty and will not impair the cylinder integrity and oxygen content is not altered enough to cause a hazard.

It is unusual for salt water to be present inside a tank but this is the most hazardous condition causing severe rust/corrosion. All these conditions are exacerbated by NITROX (high O2).

Generally, an unknown tank should be inspected by draining the air/gas and pulling the valve.

 

[Walter]

Check the O2 content just to be on the safe side, but I'd bet the air is fine.

You don't have to have the tank inspected to use it, just to have it filled again.

 

[Machrihanish]

Thanks all,