Where do you store your tanks when your not diving?

[nellamit]

I generally try to dive at least once a month so I usually keep my tanks full so I'm ready to go.

[arcFlash]

NorthlandDivers: I'll bite. Why empty?

[mcdiver]

Hey Arcflash,

I was told by a buddy who works as a fire fighter that if you have a scuba tank that is full and is caught in a fire, it could be a potential problem should something "blow." All that air compressed at 3,000 psi, look out.

[NorthlandDivers]

If you store tanks full for a long period of time it puts added stress on the tank as it is always stretched.  Over time it could make a difference in the elasticity of the metal  which could make a difference on passing a hydro.

[arcFlash]

I contacted Luxfer as I didn't agree with the assumption that Sustained Load Cracking (SLC) was an issue. Luxfers site states that SLC isn't an issue with the new alloy and test of up to 8 years under load did not produce SLC. Basic metallurgy supports this. Work hardening from the elastic deformation during fills would most likely do more long turn harm than storage. Having said that, Luxfer recommends storing empty (20 - 200psi) for general safety reasons with no comment on SLC or failing hydro.

The reply:
Thank you for visiting Luxfer's web site.  Please see the explanations below regarding scuba cylinder storage;

Short term:  Tightly close the cylinder valve.  Leave some pressure in the cylinder (200-300 psig).  Secure cylinder and assembly from rolling loose, tipping over or falling.  Store at room temperature in a dry place.

Long Term:  Prior to prolonged storage, the valve should be removed from the empty cylinder.  Wash the cylinder internally and externally with fresh tap water, then thoroughly dry (inside and out).  Install the valve using a small amount of Dow 111 lubricant in the threads following the manufacturer's recommended valve installation procedures.  Replace the O-ring if the manufacturer recommends it.  Store valved cylinders at room temperature in dry conditions either upright or horizontal, but NEVER inverted, with some positive pressure in the cylinder (not less than 20 psig).

Please also keep in mind, storing several fully pressurized 3000 PSI cylinders can be cause for concern in the event of  a fire or other events of Mother Nature.  If the cylinders are heated during a fire or tossed around in the event of a hurricane or tornado, the cylinder can become a high pressured vessel.  You may want decrease the concern by having the minimum amount of fully pressurized cylinders on hand.  If I can be of further assistance, please do not hesitate to contact me.

[LRRP02]

to the question bout pressure in tanks when storing them. steel no problem with 100 lbs of air but alum I would store them full. reason is that at 500 psi if you did have a fire the burst disc would not blow in time as the alum will degrade to the point of rupture before the pressure would get to the point of blowing the burst disc. for a fire fighter putting water on the tanks the explosion would very possibly injure them.