overfilled tank capacity?

[Dan Gibson]

And if you head a little west of there, you routinely see 3600 and could even see 3800-4000

You mean NORTH CENTRAL Florida. And yes, we pump those tanks with "+" ratings to 3400-3600 routinely.

 

[PerroneFord]

A little west of where? Who's doing 4k fills? PM me if you need to.

 

[all4scuba05]

Not being aware of facts is not the same as deception. Fortunately, the poster has been made aware of the facts. It is somewhat unfortunate that the tanks does not meet it's rated spec unless it has the plus rating. I can see where that would be confusing for someone unfamiliar with tanks in general.

So here goes my next question. What's there reason why these tanks can't be labeled as a steel LP85 rated at 2640psi?

 

[all4scuba05]

What is the reason this isn't simply an LP85 rated at 2640 psi?
They don't have an AL80 with with two different pressures. Max pressure is 3000 and that's it. It's not 2000+ with 3000 being the overfill pressure.

 

[dannobee]

I don't have all of the answers, but I know they can "fail" the "+" hydro and still pass the regular 2400 psi rating.

 

[PerroneFord]

The aluminum tank cannot be overfilled. It is not elastic like steel tanks. When it fails hydro, it simply fails.

A steel tank has more elasticity. For some period of time, the tank can withstand being overpressured, and will recover. Thus the plus rating. At some point, it loses some of its elasticity but is still safe to use at a lower pressure. So it fails to earn its plus rating.

As to why it's not simply rated as a LP85 at 2400 psi, and let everything above that be gravy, I don't know. This practice has been going on since probably before my birth. I know I've used tanks from 1971 that had a "+" rating. You'll have to ask someone older than me...

 

[Luis H]

This practice has been going on since probably before my birth. I know I've used tanks from 1971 that had a "+" rating. You'll have to ask someone older than me...

My understanding is that the practice started in WW II (I am not that old, but that is what I have read). Due to the war needs and steel shortage it was determine safe to over-pressurize steel tanks (by the 10%). I have read the rest of the historical details, but my memory fails me.

I have several steel 72’s from 1962 and earlier with the “+”. Most steel 72 (independent of how old) will pass the “+” requirements if the hydro facility bothered to look up and calculate the more stringent criteria.

The steel 72 is also 71.2 cu ft at 2475 PSI, not at its rated 2250 PSI. At 2250 PSI it is basically a 65 cu ft tank.

 

[Packhorse]

Ahh how I love the metric system.
Here we rate tanks in WC (water capacity) in Litres or Kgs (same thing as 1 litre of water weighs 1kg).
So a 10 L tank with 230 bar of pressure = 2300 liters
If your SPG says 65 bar then 65x 10L=650 liters of gas left.
If you used 150 bar or pressure during your dive you used 150bar x 10Liters= 1500 liters.
We dont bother with all this + rating BS. Your tank is stamped with its WC rating and its WP or CP rating (working pressure or contents pressure). As far as I know you can not buy LPs new. 207bar and 232bar and 240 bar tanks are then most common, although the OSH limit for scuba tanks is 227bar.

 

[teknitroxdiver]

Ahh how I love the metric system.
Here we rate tanks in WC (water capacity) in Litres or Kgs (same thing as 1 litre of water weighs 1kg).
So a 10 L tank with 230 bar of pressure = 2300 liters
If your SPG says 65 bar then 65x 10L=650 liters of gas left.
If you used 150 bar or pressure during your dive you used 150bar x 10Liters= 1500 liters.
We dont bother with all this + rating BS. Your tank is stamped with its WC rating and its WP or CP rating (working pressure or contents pressure). As far as I know you can not buy LPs new. 207bar and 232bar and 240 bar tanks are then most common, although the OSH limit for scuba tanks is 227bar.

Right, but while we can look at most tanks and see exactly how much air will be in a full one, you have to know it's size (which isn't stamped on it), and it's pressure rating to find out how much air it holds. Bah...

 

[Leadking]

Every tank we have sold since entering the cylinder market has the cubic foot volume at rated pressure stamped on the cylinder as well as the REE number needed for 10% overfill approval. We undertand the issues and are trying to make it easier for all divers.

Lee
www.seapearls.com