Emptying a tank ...

[ianw2]

"… without beating the dead horse PP02 discussion I will just say there are fewer 02 molecules that can potentially oxidize in the inside.."

Finally, some words of reason and logic!

"…(t)he 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 pressu(r)e…"

Good point!

"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.

THANK YOU! I was beginning to wonder what the heck was going on with all this water getting IN to tanks! Man, if I drained a half a cup of water from my tank (as others have mentioned or claimed), I’d be back at the LDS raising h@[[

 

[pescador775]

Ian, the remarks by silly are not relevant to most divers, those who have confidence in the quality of air/gas fills. No water, no oxidation. There is one useful comment among the several, that is of storage pressure and (aluminum) tanks. In the very rare event of fire, it would be better to have stored the tanks nearly empty. Aluminum tanks which are stored half full are likely to burst before the plug blows. This is because the heat treated aluminum is compromised at relatively low temps, around 400F. The tank will explode when heated above that temp. Storing an aluminum tank full is not injurious in any way and should also be safer in a fire than a tank which is partially full. Oh, yes; to give credit where due, the drain procedure mentioned by silly is correct.

 

[do it easy]

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!

Not picking a fight either , but the reasoning is not to protect the tank, but the property, people, and firefighters around it during a fire.

 

[Sharky1948]

Not picking a fight either , but the reasoning is not to protect the tank, but the property, people, and firefighters around it during a fire.

Got it! I missed the point!

 

[Packhorse]

Someone give this man a medal.

Chilling beer is New Zealands second favorite pass time!

http://www.asciimation.co.nz/beer/

 

[CompuDude]

Better still put a couple of beers under the towel and hood and you have a beer chiller!!

I have had this discussion on another forum and was quite suprised by a couple of posters who said they have drain half a cup of water from a fast drained tank!!
I sugested this was more the fault of a dodgy comperssor.

This was my OP on the subjects

My LDS was discussing this issue with me recently, and said that most of the time it comes from getting fills on boats. Wet tanks get water pushed into them by boat crews rushing to fill tanks as fast as possible for the next dive, and within a year, with a lot of dives under those conditions, you can easily end up with a cup or so of water in your tank. Big problem!

 

[DEEPLOU]

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.

One of the best answers yet.

But I can't take sides on whether to store full or "empty". Thus: half my tanks are full and the other half have abt 500psi.(empty)

 

[Codyjp]

so if you really had a half of a cup of water in your tank wouldn't you get a reg/mouthful of water when you turned upside down while diving? I don't buy that this is possible.

 

[do it easy]

so if you really had a half of a cup of water in your tank wouldn't you get a reg/mouthful of water when you turned upside down while diving? I don't buy that this is possible.

There is usually a snorkel tube in the valve to prevent exactly this. It's essentially a short straw so that the valve doesn't draw from the lowest part of the tank when it is inverted.