Just as an aside, partial pressure is the gas fraction times the *absolute* pressure, not the *gauge* pressure. (Being pedantic about physics isn't picking nits too egregiously, eh?)pescador775:
Emptying a tank ...
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It is great to read all the facts related to pressure...but no one really said if you should leave tank empty or full when storing...
We always fill them in the OFF season. Always ready for when and if they get rented out. The LDS air source is dry. If you do have moist air...in an Aluminium tank you do not worry about rust, just maybe a bad taste, then drain it get it VIP and refill, in steel..your going to have to get a cleaning done...depending if rust did form.
Nitrox tanks are drained. Refilled with air and ready for a fill of O2.
So Tank full when stored or empty or partial???
My tanks are full and been sitting for two months...time to go ICE diving...
We always fill them in the OFF season. Always ready for when and if they get rented out. The LDS air source is dry. If you do have moist air...in an Aluminium tank you do not worry about rust, just maybe a bad taste, then drain it get it VIP and refill, in steel..your going to have to get a cleaning done...depending if rust did form.
Nitrox tanks are drained. Refilled with air and ready for a fill of O2.
So Tank full when stored or empty or partial???
My tanks are full and been sitting for two months...time to go ICE diving...
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Who stores tanks? Don't you use them all the time?
I leave mine full. I rarely go much more than a month without using them. I recently purchased two steel HP100, so my AL80s will become a tad lonely. I still plan on leaving them full and using them primarily on shallower, warmer, 3mm wetsuit type dives.
YUP..they have some nasty battle scars...I am shaking off a freaking bad sinus thing...finally gone..now time to draink the ol tank..
Thalassamania:Who stores tanks? Don't you use them all the time?
Scared Silly
Contributor
When storing cylinders for longer periods, it is best to store them with 100-200psi. Why? First, without beating the dead horse PP02 discussion I will just say there are fewer 02 molecules that can potentially oxidize in the inside. Second, if a fire were to occur where the cylinders are stored there is lower chance of a cylinder explosion. The latter is typically the major concern.
The other option is to store the cylinder completely full. Though there will be more O2 for oxidation and at a higher pressure the oxidation process has been shown to be faster than at a lower pressue. Second if a fire were to occur it is the hope that the gas would heat up fast enough to blow the burst disk before the heat destroys the structural integraty of the cylinder.
So in general the guidelines are near empty or full but not in between. As in between, they chance of explosion is greater.
For the last one - frost forms when water condenses on a cold surface. No water no frost. As such, if the cylinder is filled with dry gas there will not be frost on the inside. That said, if you drain a cylinder and frosts forms on it, do not remove the valve until it warms back to room temperature. Though the chance of room air mixing with the gas in the cylinder is low but when you stick your face up to it you can exhale into it.
The other option is to store the cylinder completely full. Though there will be more O2 for oxidation and at a higher pressure the oxidation process has been shown to be faster than at a lower pressue. Second if a fire were to occur it is the hope that the gas would heat up fast enough to blow the burst disk before the heat destroys the structural integraty of the cylinder.
So in general the guidelines are near empty or full but not in between. As in between, they chance of explosion is greater.
For the last one - frost forms when water condenses on a cold surface. No water no frost. As such, if the cylinder is filled with dry gas there will not be frost on the inside. That said, if you drain a cylinder and frosts forms on it, do not remove the valve until it warms back to room temperature. Though the chance of room air mixing with the gas in the cylinder is low but when you stick your face up to it you can exhale into it.
Sharky1948
Contributor
scarefaceDM:
Based on the below discussions, assuming your LDS pumps dry air, there seems to be no basis for one or the other. Though higher pressure raises the dew point and increases ppO2, it would seem that would increase the likelihood of oxidation. But, if the LDS pumps dry air, this is a moot point. I guess the only thing we concluded was not to store them empty and particularly not with an open valve!
Sharky1948
Contributor
Not to pick a fight, but if my tanks are subjected to a fire, I would probably retire them. High temperatures will change the tempering of steal and the annealing of aluminum. Better safe than sorry!
Probably?!?
Sharky1948
Contributor
For a very brief encounter of the firey kind, I might have them hydroed. OK...it would have to be looking at the fire across the street.ClayJar:
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