How to store tanks: Empty or Filled?

[NE_SSI_Diver]

My diving season has temporarily been suspended due to a broken collar bone, so i'll be dry for a least 2 months.
I have 4 aluminum 80 tanks in the garage with psi ranging from 700-1100.
So I ask, is it better to leave tanks with that amount of air or more in the range of 3000?

Thanks!

 

[offroadr1]

That should be fine as long as the valves don't leak. From what I understand you just want to maintain positive pressure.

 

[spectrum]

There is no good reason to refill them at this time.

You might want to bleed them down a little lower in case of a fire. A full tank will get hot and increase in pressure causing the burst disc to safely release the pressure in a fire. One with 500 PSI or less simply does not have a tremendous amount of stored energy. If it's neither then the cylinder could be compromised and burst before the burst disc releases on account of pressure. Don't ask me to document this concern but it's often voiced.

Depending on the tanks there could be very good reason not to store them at full pressure due to sustained load cracking.

Heal well.

Pete

 

[Jim Lapenta]

They'll be fine like that.

 

[NE_SSI_Diver]

Thanks for the quick responses everyone! I guess I just have to find a way to forget about them and diving in the meantime .

 

[windapp]

I would say 3000. The reason is that when you are healed you may get an opportunity to dive on short notice when you can't get them filled.

 

[CT-Rich]

I left a nearly full AL 80 at my parents house. I had done some work for somebody and there was still maybe 2500 psi. several years went by and one day the burst disk blew and scared the sh*t out of my parents. The valve on that tank was crap and I had to have it rebuilt a couple of time in less than five years. I was not allowed to store tanks there ever again, full or empty. minimum of 500 psi will keep the moisture out. The burst disk should prevent an explosive failure in the event of a fire. But keeping it stored for a long period full did not work out for me.

I never got around to getting it serviced and had it scrapped, because even with a new hydro, (hydro+valve rebuild= $$$$ = not worth the trouble and money)a lot of shops don't like to have 30 yo aluminium tanks getting filled.

Steel will last forever, Al tanks will fatigue over time. two or three months wouldn't matter. the problem with bleeding the tanks down is that the rapid drop in pressure can cause the little water vapor in the tank to condense out and that can be bad for the tank. I defer to others with a better background than mine if that is still considered an issue (I learned that as a new diver and some of those tips were less than reliable.)

 

[DivemasterDennis]

Long ago and far away I had to take a "PSI" class before operating the compressors and fill stations at my LDS. As part of that course, developed by compressor manufacturer and a tank manufacturer, I was advised that on should not store a scuba cylinder empty. I was also told that for safety reasons, 300 to 700 psi was a good range. Since the class was all about safety AND preserving the life of the cylinders, I hve followed what I was taught.
DivemasterDennis

 

[Bob DBF]

I left a nearly full AL 80 at my parents house. I had done some work for somebody and there was still maybe 2500 psi. several years went by and one day the burst disk blew and scared the sh*t out of my parents. The valve on that tank was crap and I had to have it rebuilt a couple of time in less than five years. I was not allowed to store tanks there ever again, full or empty. minimum of 500 psi will keep the moisture out. The burst disk should prevent an explosive failure in the event of a fire. But keeping it stored for a long period full did not work out for me.

Sounds like you need a new tech, anyone who rebuilds a valve without replacing the burst disc is not rebuilding the valve. The fact that it has to be rebuilt in less than 5 years proves my point.

Steel will last forever, Al tanks will fatigue over time. two or three months wouldn't matter. the problem with bleeding the tanks down is that the rapid drop in pressure can cause the little water vapor in the tank to condense out and that can be bad for the tank. I defer to others with a better background than mine if that is still considered an issue (I learned that as a new diver and some of those tips were less than reliable. )

In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values are less than the ultimate tensile stress limit, and may be below the yield stress limit of the material.

Practically what this means is that there is no difference to the tank whether it is empty or full, it is the change of state from one to the other that causes fatigue. Both Steel and Al are subject to fatigue and that is why they need to be hydroed, to see if they return to proper size after a specific test pressure. Both type tanks should outlast their owner if treated properly. A lot of misinformation has been made up and repeated about AL tanks after the issues with the 6351-T6 alloy Al tanks.




Bob
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I may be old, but I’m not dead yet.

 

[CT-Rich]

Sounds like you need a new tech, anyone who rebuilds a valve without replacing the burst disc is not rebuilding the valve. The fact that it has to be rebuilt in less than 5 years proves my point.
Bob
---------------------------------------
I may be old, but I’m not dead yet.

I wasn't the only person with a problem with that valve, and it was not the burst disk that was the issue. Although I don't remember what the problem was specifically. This was all many years ago and I decided that I didn't need to send the tank in for a hydro and get the valve done again, spend as much as I would have on a used tank and take the risk that it would end up condemned. I like current steel one one and two 72s alot and they have better bouyancy charcteristics that an AL tank.