Storing tanks under pressure, how long?

[Sonic04GT]

I have 2 Worthington Steel 100s. How long can I safely store these filled at about 3600psi before it starts putting stress on the tank or does anything that could affect the life of them?

I normally refill them on my way home for next time, but it has been about a month since I've been diving so they're still sitting in my closet topped off.

 

[captain]

Forever

 

[SDiverJim]

My understanding is that your supposed to store steel tanks full. I'm sure someone more knowledgeable will chime in here.

 

[Scared Silly]

The minute you put any gas in your cylinders they became stressed.

Two issues, storage for accidental explosion due to fire resulting in a increase in pressure. Wisdom is for long term storage they should be full in which case the burst disc will go or near empty in which the cylinder will fail before blowing.

As for the pressure - cylinders are made to be stressed but return to their original shape. This phenomena is know as being on the linear section of the stress-strain curve, modulo some hysteresis. The hydro test looks for exactly that - for the cylinder to come back to (nearly) its original shape.

In other words if your cylinders have been properly maintained they are fine.

 

[elmer fudd]

My understanding is that tanks behave like a spring. What wears them out isn't being stored full or empty, but rather the cycle of filling or emptying them, particularly when it is done rapidly. The other thing that will wear them out is pushing them past their limits. With a spring this would be when you went past it's yield point. Hydro testing basically measures the yield point of your tanks and determines if you still have enough safety margin to keep using them.

 

[domeport]

Forever. the ring will fail before the tank.

 

[Sonic04GT]

Thanks for the information. Read in a magazine somewhere that it's not a good idea to store tanks full, but around 500psi instead, which is what I did when they sat for about a year.

 

[elmer fudd]

Thanks for the information. Read in a magazine somewhere that it's not a good idea to store tanks full, but around 500psi instead, which is what I did when they sat for about a year.

I believe that's due to water condensation. If the tanks have only 1/6 their original air, then they also have 1/6 their original water and less opportunity for rust or corrosion.

 

[captain]

I believe that's due to water condensation. If the tanks have only 1/6 their original air, then they also have 1/6 their original water and less opportunity for rust or corrosion.

As long as the storage temperature does not go below the dew point of the air in the tank it will be fine. I wouldn't store them in unheated spaces in winter temperatures.

 

[Troutmaster]

Did you use the seach function of this site before posting, because there are a BUNCH of threads on this subject.