Cuft to liter conversion

[spoolin01]

This liter conversion stuff is great... if there is any accuracy to the liter specs. Is there? Unless 12 liters means 12.0, you don't get a very accurate number for your cu ft calcs.

 

[Charlie99]

This liter conversion stuff is great... if there is any accuracy to the liter specs. Is there? Unless 12 liters means 12.0, you don't get a very accurate number for your cu ft calcs.

It's about as accurate as calling a 77.4 cu ft tank an Aluminum 80.

In other words, it's more than accurate enough considering how much my SAC varies.

Charlie

 

[Firefyter]

I wonder how those guys feel getting warned about a pi$$ing match they got into over 7 years ago? (If they ever come back.... they haven't been online in over a year...)

 

[spoolin01]

It's about as accurate as calling a 77.4 cu ft tank an Aluminum 80.

In other words, it's more than accurate enough considering how much my SAC varies.

Charlie

Agreed, it's a matter of what you do with the information. I just had a dweeby quibble with multiplying 12 to get a four-digit cu ft conversion when more accurate capacity info is available. Probably (hopefully) not the point of the posts in the first place.

 

[nitrox-bob]

Ed,
I suspect there's some confusion resulting from the wording of your question: "Anyone know the formula to convert cubic feet to liters for tanks?"
If what you are asking is "Anyone know the formula to convert cubic feet to liters?" the answer is; one cubic foot = 28.31685 liters.

 

[ttrtilley]

Using the ideal gas law to calculate the water capacity of a tank given the air capacity and pressure results in too low a value that gets worse with increasing pressure.
For a 16.6 liter tank that holds 130 cubic feet at 237 bar, we calculate a water volume of only 15.5 liters. We need to multiply by about 1.07
For the same tank which holds 104 cubic feet at 182 bar, we calculate a volume of 16.2 liters which needs to be multiplied by less than 1.03

Does anyone have a formula that does better than Boyle's law?
I want an empirical formula and am willing to assume that the given air capacity and pressure are accurate.
To soothe the flamers, I do not intend to use this underwater

Dr. Google tells me:

Compressibility factor of air at 300 Kelvin [a pleasant temperature].
Bar: 1 5 10 20 40 60 80 100 150 200 250 300 400 500
Z: 0.9999 0.9987 0.9974 0.9950 0.9917 0.9901 0.9903 0.9930 1.0074 1.0326 1.0669 1.1089 1.2073 1.3163
[sorry, but tabs seem to be broken]
Fitting a parabola to the 150 200 250 values [the data are not quadratic, but anything should be better than Boyle]

Z = .00000182x*x - .000133x +.9864

Never having seen "compressibility factor" before, I will recklessly try volume = Z*Boyle's_volume.
Z(237)=1.057 and Z(182)=1.022 which are a tad small (assuming accurate data

These much improve the volume estimates above to 16.4 liters and 16.5 liters respectively.
That's probably good enough.

Is anyone familiar with compressibility factor?

 

[redacted]

No.

In the year 2009 people should not care about any imperial units of measurement: feet, yards, chains, bull-roars and other such historical oddities.

America - the Stone Age called: they want their measurement system back...

We may not be metric yet; but we are inching our way towards it.

 

[Tigerman]

It's sort of an apples & oranges comparison.
Liter ratings are for unpressurized volume, while CF ratings are for how much gas a cylinder holds when pressurized.
For example, a LP steel 11 liter tank is a 72 CF tank, while a standard AL 11 liter tank is an 80 CF tank, and a HP steel 11 liter tank is a 95 CF tank (approx).
Add to that that the CF rating on a tank isn't necessarily exactly at its working pressure (for example, a standard AL 80 has a working pressure of 3000 psi, but to get 80 CF in there you have to pump it to 3100)(holds 77.4 CF at 3000).
-----------
On the one hand, the liter rating is a more accurate measurement of the actual inner volume of the tank - but as we breathe air, the CF rating is more useful in expressing how much gas the tank holds when it's full.
Rick

Not entirely accurate.. Its pretty easy to work out the breathing air of a Steel 15L at 200 bar, given the fact that 1 bar is almost exactly 1 atm..
15L*200 = 3000 liters of air.
If you then calculate your sac in liters/minute as well..

 

[sibermike7]

There are 28.3 litres per cubic foot.

To find out how many litres of air a "metric tank" holds multiply its size or WC by its pressure in bar.

So a 12 litre tank X 200 bar = 2400litres. 2400/ 28.3 = 84.8 CF.

I think that is what the OP really wanted to know. However, that was so long ago ...
Good/simple answer. I am diving a lot in Europe and can use either system and I like things about both. Measuring tanks with liquid volume tells me the physical size of the tank. I want to know what volume of air is in it, as P-horse wrote, it is simple math when I know the pressure. However, if I travel to the States and wanted to rent a similar size tank, I would need to know how to convert. I understood exactly what the OP meant with the question that he asked though it was many moons ago. Is that scary?

 

[Kindly 'Ol Uncle Hoot]

Hello,

Anyone know the formula to convert cubic feet to liters for tanks?