redneck23ms
Contributor
how long is a tank of air good for? i'm getting a pair of hp120's filled next week but may be a while before i use them. is it common practice to get them emptied and refilled after a certain period of time?
how long to trust a filled tank?
- Thread starter redneck23ms
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Herb-alaska
Contributor
I fill my tanks as fast as I empty them. I try to keep them filled and ready to go all the time. I would have not problem diving a tank that was filled last year. You actually want to keep the tanks filled at about 500 psi or completely full to ensure that you do not have moisture issues and also in the event of a fire a full tank will heat and expand to blow the burst disk before the tank is affected while a tank at 500 will allow the tank to heat up with out risk of it exploding.
so keep your tanks full and ready to dive. This of course applies to air and nitrox fills only. I personally would never keep a full o2 tank around the house the risk of a big bang if the valve was damages is just to great.
halocline
Contributor
If the fill is clean and dry, and the tank is in good shape, indefinitely.
swimmer_spe
Contributor
I hope so, I have not dove on my tanks since the summer, and wont till sometime in May.
Kharon
Contributor
I always fill my tanks at the end of the diving season so they're ready for the "break the ice" dive in early spring. My pony get filled at the vis and the last dive of the season I breathe it down to 500 psi for the next vis. I don't think compressed air has a use by date as long as the tank is clean - since it's been vis'ed that should be the case.
Depends on your assumption of risk.
Aluminum tanks do not affect the air contained inside of them, even with severe corrosion. The same cannot be said of steel tanks if moisiture is present.
The process of rusting consumes oxygen. How much oxygen is consumed depends upon the ambient temperature and the amount (and type) of water present. Salt water is much more corrosive than fresh.
There is one documented case of a diver who died from breathing a corrosion-induced hypoxemic gas mixture (2% to 3% oxygen in the tank). His cylinder did not have a current visual inspection. The cylinder was severely corroded and had been sitting unused for 3 months with only 500 PSI in the tank. The corrosion was severe enough to consume nearly all of the oxygen in that tank, and he died when he jumped into shallow water to retrieve an outboard motor.
So.... if you have no moisture in your cylinder then halocline's answer "indefinitely" is correct. But you don't know whether or not you have moisture unless you drain your tank and look inside.
So.... the general scuba cylinder expert recommendation is to re-analyze the oxygen content if your steel tanks have been stored for 3 months or more.
If you really want a detailed answer, check out this thread. There is no real good data to answer your question definitively, every anwer you get is anecdotal or speculative. There were some small studies done almost 40 years ago under extreme conditions, and industry professionals have gleaned some basic recommendations based on those studies. But the studies were so small as to be statistically worthless.
But, short of a statistically-significant, double-blinded, placebo controlled study.... the consensus of experts is as good as it gets.
Similar threads
