overfilled tank capacity?

[all4scuba05]

I'm hoping I'm wrong but I've gotten the impression that an overfilled Worthington LP85 has 85 cf of air. I thought it's 85cf BEFORE the overfill?

 

[piikki]

At 2400 PSI it has something like 77 cuft. Pump it to 2640 and you will have 85 cuft. I am afraid that's how it is.

 

[rubberduck]

I've been researching steel tanks here as well and have learned alot in the past few days.

The LP85 will have 85cf at it's rated pressure (about 2400 PSI). The further above 2400 you go the more gas you'll get. Some people will go above the recommended max PSI to really increase their volume.

At least that's how I understand it.

 

[teknitroxdiver]

The tank size of an LP steel tank is stated at it's +10% pressure, that is 2640 psi. An aluminum tank or a steel with no overfill allowance will be at it's normal operating pressure. To find capacity for any tank and any pressure, do like this:

(Size/op pressure)*desired pressure (that is, / means divided by, * means multiplied)

So if you want to know the gas volume of an LP85 at 3500, that's 85/2640*3500=113cf.

You can also do it by percentages. desired psi/operating psi*capacity
Same example as above: 3500/2640=132.6% of rated capacity. 85*1.326=113cf.

 

[dannobee]

Nope, the rated capacity is with the tank's "+" rating, or at 2640 psi. Only holds 77 cu ft at 2400 psi.

I've been researching steel tanks here as well and have learned alot in the past few days.

The LP85 will have 85cf at it's rated pressure (about 2400 PSI). The further above 2400 you go the more gas you'll get. Some people will go above the recommended max PSI to really increase their volume.

At least that's how I understand it.

 

[all4scuba05]

So its basically a low pressure 77 cf tank that can be overfilled to give you 85cf. what a play on words. The word overfilled makes it sound like I'm buying an 85cf tank that can then be overfilled to an even higher capacity...comercialism at its best

 

[teknitroxdiver]

Exactly. But like you said, they're LPs, so pump 'em good. It is 'generally accepted', mainly in Florida, that if you slowly fill an LP steel you're good to at least 3000, if not 3500.

 

[piikki]

So its basically a low pressure 77 cf tank that can be overfilled to give you 85cf. what a play on words. The word overfilled makes it sound like I'm buying an 85cf tank that can then be overfilled to an even higher capacity...comercialism at its best

That's how bummed I felt when I figured it out. Regardless, I decided to get LP85s since they trim very nice. I am nowhere near Florida, and I can tell you this far the fills I have gotten have given me same amount of air that I get in my slightly underfilled HP100s - every time. (Best one - in place where I get 2900 fill on HP100, I get 3000 fill on the LP85...)

 

[PerroneFord]

Exactly. But like you said, they're LPs, so pump 'em good. It is 'generally accepted', mainly in Florida, that if you slowly fill an LP steel you're good to at least 3000, if not 3500.

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

 

[teknitroxdiver]

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

Otherwise known as 'cave country'.