tank size..........

[stingray1]

Alright.......any mathemetically smart people out there? I've got a question that I hope someone can answer correctly. What does 18 litres convert to in cubic feet? What about 10 litres? And if you haven't figured out that this mathemetical equation deals with dive tanks.........please do not answer.

 

[Drew Sailbum]

Depends upon rated pressure.

Tank measurements such as 10 liters or 18 liters refer to the water volume of the tank - if you pulled off the valve, how much water could you pour inside?

Measurements such as 80cuft are a measure of how much gas the cylinder holds at its rated pressure. A 80cuft tank which has a rated pressure of 3300psi is small physically than one with a rated pressure of 2640psi.

 

[stingray1]

Depends upon rated pressure.

Tank measurements such as 10 liters or 18 liters refer to the water volume of the tank - if you pulled off the valve, how much water could you pour inside?

Measurements such as 80cuft are a measure of how much gas the cylinder holds at its rated pressure. A 80cuft tank which has a rated pressure of 3300psi is small physically than one with a rated pressure of 2640psi.

Thanks. I was just trying to end my curiousity. One of my BC's is a Mares Vector Origin and it's label has a single tank with maximum capacity tank size as 18 litres and it has two tanks with a maximum capacity tank size of 2 x 10 litres. So I was just tring to figure it out. Your explination makes perfect since though. But it still doesn't answer my curiousity.

 

[wedivebc]

Alright.......any mathemetically smart people out there? I've got a question that I hope someone can answer correctly. What does 18 litres convert to in cubic feet? What about 10 litres? And if you haven't figured out that this mathemetical equation deals with dive tanks.........please do not answer.

An al80 holds 11 litres of liquid so at 200 bar (~3000psi) it contains 2200 litres of air which actually amounts to about 77 cuft

 

[WarmWaterDiver]

Thanks. I was just trying to end my curiousity. One of my BC's is a Mares Vector Origin and it's label has a single tank with maximum capacity tank size as 18 litres and it has two tanks with a maximum capacity tank size of 2 x 10 litres. So I was just tring to figure it out. Your explination makes perfect since though. But it still doesn't answer my curiousity.

Be happy to help, but need the pressure the tanks you're using when considered 'full" of compressed gas.

Most (re: Newtonian) liquids are virtually incompressible. The gas volumes tanks are rated in for "cubic feet" are cubic feet of gas at a standard set of conditions (in general - "standard air"). The PADI OW text puts this in perspective when it mentions the volume of air contained in a Al 80 would occupy the volume of a small closet (80 cubic feet) - at 1 ATA.

This is why a HP steel 80 is smaller in actual tank external (and internal liquid) volume than a LP steel 80 for example.

 

[donacheson]

Thanks. I was just trying to end my curiousity. One of my BC's is a Mares Vector Origin and it's label has a single tank with maximum capacity tank size as 18 litres and it has two tanks with a maximum capacity tank size of 2 x 10 litres. So I was just tring to figure it out. Your explination makes perfect since though. But it still doesn't answer my curiousity.

The capacity of scuba tanks is measured in at least two ways: water volume and the number of cubic feet of air at 1 atmosphere and room temperature which can be squeezed (compressed) into them.

There are 28.3 liters per cubic foot and each cubic foot is compressed by a factor equal to the tank's working pressure
divided by (about) 15 psi. Thus, your 18 liter tank, assuming it has a working pressure of 3000 psi, will hold (3000/15)(18/28.3) = 127 cubic feet of air (at 1 atmosphere and room temperature).

An aluminum 80, whose water volume is about 11 liters and working pressure of 3000 psi, will hold about (3000/15)(11/28.3) = 78 cubic feet.

 

[SteveD]

There's two metrics you use with tanks.

Internal volume relates to the amount of water (uncompressable) that the tank can hold. A Luxfer S080 holds 678 cu in, 11.1 liters.

The tank capacity is the measure of the amount of (compressed) air that the tank can hold. Therefore we need to multiply the internal volume by the rated tank pressure. The Luxfer S080 is rated at 3000 psi, 207 bar. So the air capacity is 77.4 cu ft, 2192 litres.

Every tank is slightly different, so to be completely accurate you need to check the manufactures spec sheets. See Luxfer specs at
http://www.luxfercylinders.com/products/scuba/specifications/us_metric.shtml

 

[stingray1]

Thanks to everyone that responded to my post. There is a lot of knowledgable people here. And a lot of valuable information.
Thanks again, your information has helped a great deal.