How long a tank can remain fully filled?

[Davidstealey3]

if you take your valve off, that means you have had to drain all the air out of the cylinder after your dive, and now you need to have it vip again to have it filled.

just some food for thought, as long as you end your dive with some air in the tank, and the water pressure from the depth you are at does not exceed the air pressure in the tank you should not have to worry about water in the tank form diving. i would be worried more about moisture from the compressor at the dive shop and from getting hot fills when you get your tanks filled

 

[oxyhacker]

Note too that they kept the tanks heated to a little over 100 degrees F for the full time. It was a torture test, as it was intended to be, not a simulation of what happens to a tank in real life.

It's also worth noting that while the report on the 3% O2 tank that killed the guy said it had been sitting in a hot shed for 3 months since he last used it, it didn't say that was when it was last filled - it may have been festering for years.

The test that Doc references did show very substantial corrosion within 3 months. But when you look at the test, they:

"used 6 new DOT-3AA uncoated 4130 high-pressure steel cylinders for the test. They put 500 milliliters of either fresh or salt water in the cylinders."

Now, 500 ml is a 16 oz beer or a bit more then a pint, if you are

 

[Web Monkey]

The test that Doc references did show very substantial corrosion within 3 months. But when you look at the test, they:

"used 6 new DOT-3AA uncoated 4130 high-pressure steel cylinders for the test. They put 500 milliliters of either fresh or salt water in the cylinders."

Now, 500 ml is a 16 oz beer or a bit more then a pint, if you are going to get a pint of water into your tank, well there is a very long discussion we need to have. Let's just say that this study is way out at the end of the bell curve of abuse and is into the BS test category.

It's not impossible (or even amazingly unlikley). An SB user was complaining last year about routinely corroded tanks from bad boat fills around Catalina Island.

Terry

 

[paddler3d]

I've always heard that you do not necessarily want to store the tank long term with a full fill. Reason being you're placing undo stress on the valve.

Anyone hear this one?

 

[Randy43068]

I've always heard that you do not necessarily want to store the tank long term with a full fill. Reason being you're placing undo stress on the valve.

Anyone hear this one?

No. It doesn't seem that likely to me that it would cause undue stress on the valve. I'd think using it would place more stress and strain on it than just sitting with pressure on it.

 

[Randy43068]

basic question here I guess:
if an HP tank is fully filled (3400 psi), how long can it remain there and is it ok to use it after a long period ?
thx

Just out of curiosity, why do you ask?

 

[stargost]

Just out of curiosity, why do you ask?

There were 3 reasons behind my questions:
1/ could I let my (HP) tank fully filled in my garage for a couple of months (or more for winter time) without overall risk for it (tank, valve) or maybe environment.
2/ Assuming there is suddenly a good five opportunity not allowing to go back to LDS for filling, is it possible (not that I'd plan this in purpose, mostly just in case)
3/ I looked at buying additional used tanks, whether AL, or LP/HP steels, and found one which stayed filled for probably couple of years if not more, fully filled. Not that I would not have done VIP and hydro after buying, but i was curious about potential damaged or not.

As usual, question was answer far beyond expectations !

Thanks

 

[Randy43068]

There were 3 reasons behind my questions:
1/ could I let my (HP) tank fully filled in my garage for a couple of months (or more for winter time) without overall risk for it (tank, valve) or maybe environment.
2/ Assuming there is suddenly a good five opportunity not allowing to go back to LDS for filling, is it possible (not that I'd plan this in purpose, mostly just in case)
3/ I looked at buying additional used tanks, whether AL, or LP/HP steels, and found one which stayed filled for probably couple of years if not more, fully filled. Not that I would not have done VIP and hydro after buying, but i was curious about potential damaged or not.

As usual, question was answer far beyond expectations !

Thanks

Well, were I you, I'd keep them filled as long as the time horizon is a few months, for a couple of reasons. ( few months is about 6 to 12 for me in an aluminum )

1) it's recommended to store them either empty OR full in the unlikely chance they in a building when it burns down.
2) if you get the chance to dive, you're good to go. Grab a bottle or two and you're out the door.

 

[Gilldiver]

if you take your valve off, that means you have had to drain all the air out of the cylinder after your dive, and now you need to have it vip again to have it filled.

just some food for thought, as long as you end your dive with some air in the tank, and the water pressure from the depth you are at does not exceed the air pressure in the tank you should not have to worry about water in the tank form diving. i would be worried more about moisture from the compressor at the dive shop and from getting hot fills when you get your tanks filled

Drain tank, take valve off, look in tank:

If dry, put new O-ring on valve, put valve back on, transfill 50-100 psi from another tank, get filled.

If wet, Rinse out with clean HOT water, get the tank as hot as your tap water can (120-130F), drain tank, while inverted, blow clean air into tank for 30 - 40 seconds, check for wetness, if wet, (it will not be) invert and blow some more air into it, When dry, put new O-ring on valve, put valve back on, transfill 50-100 psi from another tank, get filled.

This is not Rocket Science.

 

[Gilldiver]

It's not impossible (or even amazingly unlikley). An SB user was complaining last year about routinely corroded tanks from bad boat fills around Catalina Island.

Terry

Wet fills seem to be a much bigger problem in the west and south then in the Northeast, but it does happen. But that is what the yearly is all about, catching corrosion before any major amounts occur.

If you question the dryness of a fill, then take a look. Maintain your tank just as you would your BC or regulator.