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Old 01-24-2007, 02:44 AM #1
dueydog
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Compressed Air Weights per Tank.

How about some compressed air weights???



Enjoy,
Matt
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Last edited by dueydog : 01-25-2007 at 10:08 PM.
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Old 01-24-2007, 07:02 PM #2
sartek
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Care of Univ. of Hawaii Chemistry Dept: Weight of air per liter at STP = 1.20 gr/l

Your tables are a little high but not much (Luxfer 68/4500 comes out to be about 13.1oz using Luxfer's product info)
Hell, I never would have thought to even look up something like this.
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Old 01-24-2007, 07:09 PM #3
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Yeah they seem a little high but still good to know. My 68/3000 weighs just over 7ozs more when full.
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Old 01-25-2007, 01:10 AM #4
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Quote:
Originally Posted by sartek View Post
Care of Univ. of Hawaii Chemistry Dept: Weight of air per liter at STP = 1.20 gr/l

Your tables are a little high but not much (Luxfer 68/4500 comes out to be about 13.1oz using Luxfer's product info)
Hell, I never would have thought to even look up something like this.
http://www.newton.dep.anl.gov/askasc...pediawork.html
http://en.wikipedia.org/wiki/Density_of_air

Standard Planetary Information, Formulae and Constants

molecular "weight" of dry air = 28.964 g/mole

dry air has a "density" of STP = 1.293 g/L.

V = (1)(.082 L.atm/K.mol)(273 K) / (1 atm) = 22.414 L

The info is backed by a Chemical Engineer and many web sites. Maybe he's wrong or maybe I botched it somehow. I'll do some double checking. LMK.

Thanks,
Matt
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Last edited by dueydog : 01-25-2007 at 07:24 PM.
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Old 01-25-2007, 02:53 AM #5
sartek
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I noticed the UofH chem page, the professor did some really crappy rounding.

All i did was break down the mole weight to liters (g/M = g/22.4L)

it makes the math a lot cleaner and faster. after all, density is merely mass/volume
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Old 01-25-2007, 12:18 PM #6
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This is the best technical thread I've ever seen on PbNation.
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Old 01-25-2007, 05:16 PM #7
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Quote:
Originally Posted by sartek View Post
I noticed the UofH chem page, the professor did some really crappy rounding.

All i did was break down the mole weight to liters (g/M = g/22.4L)

it makes the math a lot cleaner and faster. after all, density is merely mass/volume
Could you post the equation used for your solution?
Thanks,
Matt
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Old 01-25-2007, 05:41 PM #8
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Sure.
Dry air is known at 28.964 g/mole
1 Mole = 22.414 L of air
28.964 g / 22.414 L (divide both sides by 22.414 to get g/L)
28.964/22.414 = 1.292 g/L

Luxfer Product Information says P08F (68/3000) tank holds 226 Liters
1.292 g/L * 226 = 291.992 g

28.349 g per ounce
292.218 / 28.349 = 10.299 ounces


P11D 70/4500 (68/4500) is 311 Liters
1.292 g/L * 311 = 401.812 g
401.812 / 28.349 = 14.174 ounces

Luxfer's tank info (Metric): http://www.luxfercylinders.com/produ...s_metric.shtml

Last edited by sartek : 01-26-2007 at 09:21 PM.
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Old 01-25-2007, 07:42 PM #9
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Quote:
Originally Posted by sartek View Post
Sure.

Dry air is known at 28.964 g/mole
1 Mole = 22.414 L of air
28.964 g / 22.414 L (divide both sides by 22.414 to get g/L)
28.964/22.414 = 1.292 g/L

Luxfer Product Information says P08F (68/3000) tank holds 226 Liters
1.292 g/L * 226 = 291.992 g

28.349 g per ounce
292.218 / 28.349 = 10.299 ounces

P11D 70/4500 (68/4500) is 311 Liters
1.292 g/L * 311 = 401.812 g
401.812 / 28.349 = 14.174 ounces

I noticed that Luxfer uses the same volume information for 70/4500 and 68/4500.

It makes a difference when you go down to 3 decimal places. The UofH Chem page info of 1.20 g/L puts the math off considerably.
quick and simple math.
Luxfer's tank info (Metric): http://www.luxfercylinders.com/produ...s_metric.shtml

EDIT: Air volume is ALWAYS measured at STP, so there's no need to consider atmos, except to find the volume of air in the tank first.
1CF = 28.317 Liters
Tank volume * Atmos = Cubic Inches Air Volume
Cubic Inches Air Volume / 1728 = CF
CF * 28.317 = Liters
Excellent. I totally agree with the above, which is closer to my calculations. I was going crazy trying to figure out how you came to this solution...

Quote:
Originally Posted by sartek View Post
Your tables are a little high but not much (Luxfer 68/4500 comes out to be about 13.1oz using Luxfer's product info)
I think for simplicity I would rather use the cubic inch per tank rather than each individual liter capacity of every tank out there. That would get tedious.

The P11D 70/4500 (68/4500) being only 311 Liters is not actually a 68ci tank.
Wouldn't a true 68ci tank have 341 Liters and a 70ci have 351 Liters at 4500psi?


Thanks,
Matt
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Last edited by dueydog : 01-25-2007 at 10:00 PM.
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Old 01-26-2007, 12:17 PM #10
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Old 01-26-2007, 05:52 PM #11
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I'm not sure HOW luxfer got that number for a 68/4500. They were correct on the metric information page for everything else (68ci = 1.114 liters)

311 Liters works out to 62/4500. The only way I can see this being true is if the 68 cubic inches is the water displacement of the tank, not the water capacity, which would explain the "missing" 6 cubic inches being the bottle itself due to the wall thickness.

Luxfer has (rounded) 11.0 CF of air listed with the 311L for that tank. 11.0 CF = 311.487 L

Here's an excerpt I found on Metric vs Imperial measurements of scuba tanks:
Quote:
Metric--with its ever logical approach--measures a tank's capacity in liters of water that fit inside. And since a liter of water also so happens to weigh one kilogram, a tank's capacity may be given in kilograms.
Imperial rates tanks by how many cubic feet of compressed air it can hold at sealevel. That makes the imperial rating much more relative as capacity in cubic feet depends on the tank's rated pressure as well as temperature.
This makes more sense with the 68cubic inches being the displacement, while the 1.1 liter is actual capacity.. the decimal difference would be the 6 inches.

Last edited by sartek : 01-26-2007 at 06:06 PM.
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Old 01-26-2007, 08:43 PM #12
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Quote:
Originally Posted by sartek View Post
I'm not sure HOW luxfer got that number for a 68/4500. They were correct on the metric information page for everything else (68ci = 1.114 liters)

311 Liters works out to 62/4500. The only way I can see this being true is if the 68 cubic inches is the water displacement of the tank, not the water capacity, which would explain the "missing" 6 cubic inches being the bottle itself due to the wall thickness.

Luxfer has (rounded) 11.0 CF of air listed with the 311L for that tank. 11.0 CF = 311.487 L

Here's an excerpt I found on Metric vs Imperial measurements of scuba tanks:


This makes more sense with the 68cubic inches being the displacement, while the 1.1 liter is actual capacity.. the decimal difference would be the 6 inches.
So, based on both descrepencies, your posted weights are incorrect. A true 68ci/4500 capacity tank will hold 15.5 oz of air. Correct?

Also, could you remove them if they are indeed wrong so not to confuse others readers.

Thanks,
Matt
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Last edited by dueydog : 01-26-2007 at 08:47 PM.
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Old 01-26-2007, 09:19 PM #13
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A 68/4500 would hold 15.5oz at absolute maximum capacity, yes. But I wounld't want to tell someone that their tank should weigh 15.5oz heavier after filling a 68/4500 and then have them look at the gauge and see 5000+ psi in their tank.

However - The math I posted IS correct based off the published product information from Luxfer. Carleton does not list a capacity rating, and SCI has a Capacity of 1.15 Liters listed for their 70/4500 tank, which is in line with Luxfer's information.

And you don't really have to worry about the liter capacity of all the tanks out there since it's already published. you can get the information direct from Luxfer or SCI online.

So all you need is the g/L weight, and number of liters.. and you're good.

Last edited by sartek : 01-26-2007 at 09:52 PM.
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Old 01-28-2007, 12:06 AM #14
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great job, added to the ultimate sticky.
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