Weight of air?

[Divin'Papaw]

All of the tank specs tell you how much a tank weighs when empty. After looking around, I haven't been able to find the formula to use to approximate how much a full tank weights. How much does compressed air weigh? Is there a common value per cf of compressed air? Does it differ by max pressure (2640 v. 3000 v. 3442)?

 

[victor]

1 cubic foot of air weighs 0.0807 lbs at standard preasure and temperature
there is approx 80 cubic feet of air in a normal rental tank at 2400 psi
so the air in the tank weighs approximatly 6.4 lbs
If you enter at 2400 and exit at 500 then you will be about 5.1 lbs lighter than when you went in.

 

[SparticleBrane]

^ Most rental tanks here in the US are Al80s, thus they have 77.4cf at 3,000psi, not 2400.

 

[victor]

Sorry more used to BAR
Weight of air 77.4 cubic feet = 6.25 lbs
Swing between 3000 psa and 500 psi = 5.2 lbs

 

[xiSkiGuy]

You can roughly say that every 13cf of air weighs one pound. So a E8-130 has 10lbs of air in it when full.

 

[donacheson]

All of the tank specs tell you how much a tank weighs when empty. After looking around, I haven't been able to find the formula to use to approximate how much a full tank weights. How much does compressed air weigh? Is there a common value per cf of compressed air? Does it differ by max pressure (2640 v. 3000 v. 3442)?

Each 13 cubic feet of air (at 1 atmosphere and normal temperature) weighs about 1 pound. Hence, an aluminum 80 holds about 80/13 = 6 pounds of air. For the metric folks, an 11 liter tank filled to 200 bar holds about 2200 liters of air (at 1 atmosphere and normal temperature), which weighs about 2.6 kilograms, or roughly 1.2 kilogram per 1000 liters.

 

[padiscubapro]

Each 13 cubic feet of air (at 1 atmosphere and normal temperature) weighs about 1 pound. Hence, an aluminum 80 holds about 80/13 = 6 pounds of air. For the metric folks, an 11 liter tank filled to 200 bar holds about 2200 liters of air (at 1 atmosphere and normal temperature), which weighs about 2.6 kilograms, or roughly 1.2 kilogram per 1000 liters.

also remember a tank filled with nitrox or trimix will have a different weight than air.. Nitrox is not significantly different but a high He mix will be considerably lighter..

see this thread at rbworld
http://www.rebreatherworld.com/decompression-gas-choices/813-how-much-does-gas-weigh.html?highlight=weight+GAS#post7356

 

[jeckyll]

All of the tank specs tell you how much a tank weighs when empty. After looking around, I haven't been able to find the formula to use to approximate how much a full tank weights. How much does compressed air weigh? Is there a common value per cf of compressed air? Does it differ by max pressure (2640 v. 3000 v. 3442)?

http://www.techdivinglimited.com/pub/tanks.html

That should give you a fair bit of data

 

[donacheson]

also remember a tank filled with nitrox or trimix will have a different weight than air.. Nitrox is not significantly different but a high He mix will be considerably lighter...

True, but probably well beyond the scope of the info Divin' Hoosier needs. <G>

 

[Divin'Papaw]

Great info. Thanks. Everyone has provided me the info that I need, and then some. Thanks again.