How to store filled scuba tanks

[NAM001]

I doubt there is any risk of rupture at this point. 6061 is good material. The only issue i se is that the higher the tank presure the faster they corrode. IF they are really cold then i would either leave them alone or vent them fown to 100 psi or less. NOt turning a valve for 4 years is not a real big + for the venting process and gettng a goosd seal afterwards.

 

[TMHeimer]

I have heard that really cold temps. doesn't hurt the tanks themselves, no danger that is. Im' no expert on what may be affected such as the o ring, etc. By bitter cold are you talking 0 Fahrenheit or like -40F? (where I used to live, and was told by someone not to fear tanks outside in -40)

 

[SubAquatix]

Ok, this seemed obvious to me, but hey, I'm not an engineer or anything.
- drop them down to under 300 psi. This is enough pressure to account for some leaking, while at the same time keeping anything from coming into the system. Additionally, this reduces the stress on any metal, threaded seat and valve system, that might occur from long term exposure to such stress.
- lay the tanks on there side. Just a good practice and avoids damage to the tank or valve since you can't knock it over.

 

[Hickdive]

Don't lay tanks on their side for long term storage

IF there is any moisture inside then corrosion can occur which will be at the thinnest part of the cylinder wall rather than the thickest part at the base.

If knocking them over is a problem then put them somewhere they can't be knocked over or secure them to a wall or other solid structure.

 

[kombiguy]

You know what's weaker than a burst disk?

The last few thousandths of an inch of aluminum and paint covering up a neck crack.

Especially when the tank hasn't been emptied or inspected in years.

There's a reason it's called "Sustained Load Cracking"

flots

Yeah, I should have made clear that we were discussing a cylinder, in a fire, rupturing before the burst disk, due to the heat of the fire causing the air inside the cylinder to expand. SLC is a different animal altogether, and yes, can cause a cylinder to rupture before a burst disk.

 

[Belzelbub]

I can't even imagine a scenario where an aluminum tank would rupture before an ultra-thin copper disk.

I've heard that advise as well. It was always in relation to a fire. Theory was that the burst disc is set to give at a certain pressure. When full, a tank exposed to a fire will reach that point rather quickly, and the bust disk would give like it's designed to do.

When the tank is not full, it will take longer for the pressure to reach burst pressure (pv=nrt). While the pressure is increasing, the tank is also getting real hot. So the theory is that the temp weakens the tank itself, so it could rupture before the disk bursts. Theory seems plausible.

I always store my tanks full. During a hiatus from diving, they stayed like this for a couple of years, and kept their air.

 

[Searcaigh]

I always store my tanks standing up.

When I lived in Jeddah (Saudi Arabia) they were stored upright outside in my yard with temps frequently hitting 45 Celsius + (113F), never had a burst disc out of the 16 tanks I owned at the time.

Currently I store all my tanks upright indoors, although only temperature controlled when there is somebody at home, but during the summer when sometimes nobody around the temps hit 50C+

I also had a couple of years with no diving due to flying frequently for business and kept them full during that period (2002-03) had no issues with the air in them, which I used when I dived again in 2004, although some of my tanks did require hydro etc., I used them first then had the testing done when I put them in to be filled after the dives.

 

[KeithG]

If you start at 1000 psi and it looses pressure and your at 200 psi for a long time tanks will prob have humidity in it.

can we stop spreading old wives tales?

"humidity" can only get into your tank if the gas inside the tank is at ambient pressure AND the valve is open. Otherwise your tank is a sealed container. Full of dry air. At positive pressure. Nothing can get in. It will still only contain whatever was in there to start with.

Think of your tank as a clean room. ISO Cleanroom Standards | Federal Clean Room Classifications They use air pressure differential to keep the nasty stuff out. A differential air pressure of 0.03 to 0.05 inches water gauge is recommended between spaces. 1 inch water gauge ~ 0.0360911906567 PSI. Clearly, it does not take much residual pressure in your tank to keep things out.

 

[flots am]

I don't believe sustained load cracking is a recognized problem with modern aluminum materials. If they were my tanks and still full, I would drain them over a hour or so under water.

Sustained-load-cracking characteristics of aluminum-lined NGV cylinders

It's kind of dense, and not specifically SCUBA, but apparently it's still a problem in some types of cylinders. I wouldn't bet my life on it being impossible on a SCUBA cylinder, especially one that has an unknown past and hasn't been inspected for years.

flots.

 

[redacted]

Sustained-load-cracking characteristics of aluminum-lined NGV cylinders

It's kind of dense, and not specifically SCUBA, but apparently it's still a problem in some types of cylinders. I wouldn't bet my life on it being impossible on a SCUBA cylinder, especially one that has an unknown past and hasn't been inspected for years.

flots.

Per ref report, known 6351 problem. none observed with 6061.