How long can air sit in a tank?

[captain]

Where I worked we had emergency SCBA's mounted through the plant. They got checked for pressure once a week and only got refilled if used or every 5 years at hydro time. I have used scuba tanks that have been filled for years.

Where do you draw the line, one day, one week, one month, one year, one decade.

 

[Shftrdog]

As long as there was no mositure in the tank it will be fine.

 

[mathauck0814]

Where I worked we had emergency SCBA's mounted through the plant. They got checked for pressure once a week and only got refilled if used or every 5 years at hydro time. I have used scuba tanks that have been filled for years.

Where do you draw the line, one day, one week, one month, one year, one decade.

Personally, my tanks don't sit very long. But I would probably say if I hadn't dove in a few months I'd dump and re-fill (if for no other reason than to remind the dive shop guys that I'm still alive). Also sometimes I don't write what's in them (I know, I know) and don't have the analyzer handy... out goes the gas and me to the fill station.

 

[Tigerman]

Where I worked we had emergency SCBA's mounted through the plant. They got checked for pressure once a week and only got refilled if used or every 5 years at hydro time. I have used scuba tanks that have been filled for years.

Where do you draw the line, one day, one week, one month, one year, one decade.

But you probably knew how the tanks had been maintaned and where they where filled. They where also not going to be used under pressure, I assume?

Personally my reason for not just using the mentioned tanks is not time, but the fact that they are used, with unknown history since the last checkup and theres gas in them of unknown origin which means you have no idea what contaminants could be in them or even know for sure what gas it is..

 

[captain]

But you probably knew how the tanks had been maintaned and where they where filled. They where also not going to be used under pressure, I assume?

Personally my reason for not just using the mentioned tanks is not time, but the fact that they are used, with unknown history since the last checkup and theres gas in them of unknown origin which means you have no idea what contaminants could be in them or even know for sure what gas it is..

I do not know where the company sent them out for hydro and refilling. What does "used under pressure" have to do with air in the tank.
I know some of my vintage diver friend who have used tanks filled decades ago after a quick smell and O2 check.

 

[Tigerman]

It has to do with the fact that you get more of everything with each breath?

 

[Brendon]

It has to do with the fact that you get more of everything with each breath?

Why dont you just say your talking about Daltons or Henry's law... Assume that you are talking to fellow divers on this forum...

 

[j yaeger]

...i haaaaaaaaate partial pressures!!!
(trying to be impartial here)
have fun
yaeg

 

[Tigerman]

Why dont you just say your talking about Daltons or Henry's law... Assume that you are talking to fellow divers on this forum...

Because I dont remember the names of all kinds of laws of physics, but remember what theire about? (Well, not all of them of course, but more than what I recall the name of off the top of my head)

 

[Doc Harry]

How long?

If the fill is clean and dry, and so is the cylinder, and the fill pressure is within rated limits -- then air can stay in a cylinder indefinitely and it will be good as the day it was filled.

Start adding moisture and corrosion to the picture, and there are a variety of possible outcomes, especially with steel cylinders.

Corrosion in aluminum cylinders doesn't affect the quality of the breathing gas, but severe corrosion can get so bad as to weaken the wall strength enough to place the cylinder in danger of rupture. Modern standards and practices -- designed to prevent such problems -- make the latter outcome very unlikely (but not impossible).

Corrosion in steel cylinders is a much more concerning issue for two reasons: steel cylinders have thinner walls and rust formation consumed oxygen. The thinner walls of steels cylinders can withstand much less pitting and corrosion before they are at risk of rupture. Also the formation for rust (iron oxide) consumes oxygen from the breathing gas. So it is always best to analyze the gas for oxygen content before use.

Of course, you don't know whether or not you have moisture and corrosion in your cylinder unless you drain it and look inside.

So it's a matter of personal risk assessment.

For instance -- I inspect, maintain and fill my own cylinders. I know the quality of my filters and I know the quality of my breathing gas. I am very careful to avoid "wet fills." So I an inclined to use my cylinders without a second thought even if they have been stored for several months. I do a quick check of the oxygen content just be sure, and off I go.

Now if I had an unknown cylinder and it was being filled by someone else -- then I would proceed with caution. I would probably have them drained and inspected before I used them.