Overfill of Aluminum Tank

[asmackofjellyfish]

I just bought a Luxfer Aluminum 100 (3300 PSI). The LDS I bought it from says that it can be overfilled by 10% for the first year (a max of approx 3600), after which it can't be overfilled unless I switch to a DIN valve. I've only seen posts on SCUBABOARD which refer to Steel tanks being overfilled.

Does anyone have any experience with this, or can anyone comments on whether this is reasonable to do with an aluminum tank?

Thanks.

asmackofjellyfish

 

[Sherwood SCUBA rep.]

Aluminum can not be over filled. Whoever told you that is wrong. On aluminum the service pressure is what is stamped on the cylinder.

 

[Packhorse]

First I have heard of it. But then I live on the other side of the world. Best bet ask Luxfer.

 

[lakewinni]

The guy is completely wrong. Switching to DIN wouldn't change how overfilling affects the tank either.

 

[Packhorse]

What is strange is the 1st year and then change to DIN. This smells of BS

 

[Firefyter]

Aluminum can not be over filled. Whoever told you that is wrong. On aluminum the service pressure is what is stamped on the cylinder.

I would amend this to say that maybe they should not be overfilled, but the reality is that they are routinely overfilled all over the world. I routinely overfill all of mine by 10% or so.

 

[Jorbar1551]

^ that was your thousand post ^

 

[JahJahwarrior]

You can overfill, they do it for hydrotesting. However, it isn't usually done for everday use. If I know it right, which I might not, some tanks can come with a "+" rating which allows for a 10% overfill. If it doesn't pass hydro within certain even more rigid standards, it will lose that overfill rating. However, that might only be for steel tanks.

Do remember, a tank shouldn't rupture until it's burst pressure, which is more than it's working pressure. However, a tank is not designed to be used at anything more than it's working pressure. If you overfill your tank, well within the limits of your burst pressure but over your working pressure, you stress the metal more and limit the life of the tank. This not only makes it less likely to pass hydro, but more likely to rip open and kill you. The metal is elastic, it stretches when you fill it. It stretches a safe amount under normal filling usually, when filled closer to burst pressure, overfilled, it stresses it more then usual. It's just like bending a paper clip. Paper clips will last for years holding together pieces of paper, but a minute of twisting it well and it will break because of stress. However a broken paper clip is less likely to kill you than a suddenly broken, overfill scuba tank.

 

[PerroneFord]

There is no "+" rating system for Alum or HP steel tanks. This was just bogus.

 

[asmackofjellyfish]

Thanks for all the comments.

I think the rational behind the LDS owner's comment about the DIN was that they can handle higher pressure.