Conversion of Cylinder sizes

Simon Ciantar · 14th January 2006, 11:12

Hi all,

To begin posting on this forum I decided to tackle a very simple subject but which bugs me when trying to follow some treads here

How do you convert cubic feet to litres ?as most of you guys seem to use this unit when talking on cylinder capacity Im used to using 10, 12 , 15 ltr cylinders etc...

thks

Simon

***EBT*** · 14th January 2006, 11:47

Short version; 1 liter = 0.035 314 667 cubic foot

Long version. Take Metric tank, multiple capacity (ie 12L) by pressure (ie 232 bar), to get Litres of free gas (2784 in this case). Multiple by 0.035314667 to get the US equivalent; 98 Cuft (give or take small change).

Obviously in the other direction you take the cuFt/0.035 etc then divide by rated pressure. For a standard alu 80 (runs at 3000 PSI/207 Bar);

(80/0.035314667)/207=10.9 Liter.

/Zak

decoweenie · 14th January 2006, 11:49

Quote: (Originally Posted by Simon Ciantar)

How do you convert cubic feet to litres ?

This is a rough calculation...

Convert cf into free liters using: cf * 28.3 = free liters
Convert rated pressure into bar using: psi / 14.5 = bar
Convert free liter at pressure into displacement: free liter / bar = L

For example, 80cf 3200psi into Metric equivalent:

80cf * 28.3 = 2,264 free liters
3200psi / 14.5 = 220 bar
2264 free liters / 220 bar = 10 L

As said, just roughly...

macdiver · 14th January 2006, 12:27

Is there a table somewhere that gives equivalent tank sizes typically used in discussions (e.g. al 2 liter = 13 cu ft )? The above conversion factors are great for calculating accurate numbers but I usually see 2, 3, 7, 10, 12, and 15 liter tanks mentioned not 11. So is the above a 10 or a 12? or is it an 11 that just isn't as common?

edited due to typo

MAD · 14th January 2006, 12:55

Alternatively try the Gas Management Program (GMP)

Should be available at:-

GMP

Does all this simple sort of stuff as well as blending calculations.

A spot on piece of software..

Rgds

Mark

.

***caveseeker7*** · 14th January 2006, 13:47

Quote: (Originally Posted by macdiver)

Is there a table somewhere that gives equivalent tank sizes typically used in discussions (e.g. al 2 liter = 13 cu ft )? The above conversion factors are great for calculating accurate numbers but I usually see 2, 3, 7, 10, 12, and 15 liter tanks mentioned not 11. So is the above a 10 or a 12? or is it an 11 that just isn't as common?

Part of the problem is that different tank pressures are common in the US (usually lower). A 3 liter tank here has 19 or 20 cuft, whereas in Europe you can get some with 29 cuft.

Then different materials and wall thicknesses. The same size tank in alu or steel will have different liquid capacity (L) ... and maybe pumped to a different fill pressure. And there are overpressure fills (+ rating in US) ... .

Last but not least, 80 cuft doesn't mean that you can actually get 80 cuft into the tank. Here in the US vendors liberally round up sizes. Said tank usually holds 77.4 cuft.

If you look at manufacturer's or distributor's websites for US tanks you'll frequently find the liter capacity listed.

Rough guide:
steel/alu 13 cuft = 2 L
steel/alu 19 cuft = 3 L
steel 27 cuft = 4 L
steel 45 cuft = 7 L
steel 66/72 cuft = 10 L
steel 98 cuft = 15 L
steel 131 cuft = 20 L

PITA like everything else they measure here.

leadking · 14th January 2006, 14:13

liters is the liquid internal volume of a cylinder (61 CI or .053 CF)

U.S. measurement are total CF of gas at maximum rated pressure. In the case of 3AA cylinders include the 10% overfill.

Westwinds · 14th January 2006, 16:16

OMS shows their steel cylinder conversions as follows:

Air capacity (cuft) - Liquid capacity (L)
130cuft - 17L
100cuft - 13L
80cuft - 10L
65cuft - 8L
45cuft - 7L

http://www.omsdive.com/cyl_spec.html

Westwinds.

Simon Ciantar · 14th January 2006, 21:14

thks folks

that pretty much what I was after

Simon

2002scubasteve · 8th August 2007, 03:36

I have used the conversion formula given here cuFT/0.035/rated pressure,but I don't understand that a tank with lower pressure holds more liters? Example: a 95 steel tank with 2400psi(165.474bar) holds 16.40 liters.
same tank at 2650 holds 14.85 liters according to this formula. How can this be?

14th January 2006, 11:12	#1 (permalink)
Simon Ciantar New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: May 2005 Location: Malta Posts: 38	Conversion of Cylinder sizes Hi all, To begin posting on this forum I decided to tackle a very simple subject but which bugs me when trying to follow some treads here How do you convert cubic feet to litres ?as most of you guys seem to use this unit when talking on cylinder capacity Im used to using 10, 12 , 15 ltr cylinders etc... thks Simon
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14th January 2006, 11:47	#2 (permalink)
*EBT* Apprentice Luddite Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: UK, Brighton Posts: 1,855	Re: Conversion of Cylinder sizes Short version; 1 liter = 0.035 314 667 cubic foot Long version. Take Metric tank, multiple capacity (ie 12L) by pressure (ie 232 bar), to get Litres of free gas (2784 in this case). Multiple by 0.035314667 to get the US equivalent; 98 Cuft (give or take small change). Obviously in the other direction you take the cuFt/0.035 etc then divide by rated pressure. For a standard alu 80 (runs at 3000 PSI/207 Bar); (80/0.035314667)/207=10.9 Liter. /Zak __________________ Eagles May Soar, but weasels don't get sucked into jet engines! Rebreather World Terms of service Real diving t-shirts for real divers Last edited by EBT : 14th January 2006 at 11:52.
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14th January 2006, 11:49	#3 (permalink)
decoweenie Crash Test Dummy Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Feb 2005 Location: Cairo Posts: 5,510	Re: Conversion of Cylinder sizes Quote: (Originally Posted by Simon Ciantar) How do you convert cubic feet to litres ? This is a rough calculation... Convert cf into free liters using: *cf 28.3 = free liters Convert rated pressure into bar using: psi / 14.5 = bar Convert free liter at pressure into displacement: free liter / bar = L** For example, 80cf 3200psi into Metric equivalent: 80cf * 28.3 = 2,264 free liters 3200psi / 14.5 = 220 bar 2264 free liters / 220 bar = 10 L As said, just roughly... __________________ "...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..." - Rebreather World PM Last edited by decoweenie : 14th January 2006 at 12:34. Reason: spell it out
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14th January 2006, 12:27	#4 (permalink)
macdiver New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Dec 2005 Location: new jersey Posts: 5	Re: Conversion of Cylinder sizes Is there a table somewhere that gives equivalent tank sizes typically used in discussions (e.g. al 2 liter = 13 cu ft )? The above conversion factors are great for calculating accurate numbers but I usually see 2, 3, 7, 10, 12, and 15 liter tanks mentioned not 11. So is the above a 10 or a 12? or is it an 11 that just isn't as common? edited due to typo
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14th January 2006, 12:55	#5 (permalink)
MAD Rebreather World Writer Current Rebreather/s: Inspiration Classic Evolution Home Build Other Rebreather/s: Home Build Join Date: Feb 2005 Location: Northampton Posts: 71	Re: Conversion of Cylinder sizes Alternatively try the Gas Management Program (GMP) Should be available at:- GMP Does all this simple sort of stuff as well as blending calculations. A spot on piece of software.. Rgds Mark . __________________ 1007 dives and finally I'm a novice... www.divejunkie.com
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14th January 2006, 13:47	#6 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,325	Re: Conversion of Cylinder sizes Quote: (Originally Posted by macdiver) Is there a table somewhere that gives equivalent tank sizes typically used in discussions (e.g. al 2 liter = 13 cu ft )? The above conversion factors are great for calculating accurate numbers but I usually see 2, 3, 7, 10, 12, and 15 liter tanks mentioned not 11. So is the above a 10 or a 12? or is it an 11 that just isn't as common? Part of the problem is that different tank pressures are common in the US (usually lower). A 3 liter tank here has 19 or 20 cuft, whereas in Europe you can get some with 29 cuft. Then different materials and wall thicknesses. The same size tank in alu or steel will have different liquid capacity (L) ... and maybe pumped to a different fill pressure. And there are overpressure fills (+ rating in US) ... . Last but not least, 80 cuft doesn't mean that you can actually get 80 cuft into the tank. Here in the US vendors liberally round up sizes. Said tank usually holds 77.4 cuft. If you look at manufacturer's or distributor's websites for US tanks you'll frequently find the liter capacity listed. Rough guide: steel/alu 13 cuft = 2 L steel/alu 19 cuft = 3 L steel 27 cuft = 4 L steel 45 cuft = 7 L steel 66/72 cuft = 10 L steel 98 cuft = 15 L steel 131 cuft = 20 L PITA like everything else they measure here. __________________ Cheers Stefan "It is still a good day if you are on the green side of the grass! Su amigo Roberto!" Sponsor Lou in Race For Life!
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14th January 2006, 14:13	#7 (permalink)
leadking New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Nov 2005 Location: Minneapolis Posts: 56	Re: Conversion of Cylinder sizes liters is the liquid internal volume of a cylinder (61 CI or .053 CF) U.S. measurement are total CF of gas at maximum rated pressure. In the case of 3AA cylinders include the 10% overfill.
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14th January 2006, 16:16	#8 (permalink)
Westwinds Supporting Member Current Rebreather/s: Inspiration Classic Evolution Other Rebreather/s: Join Date: Jan 2005 Location: Ontario, Canada Posts: 89	Re: Conversion of Cylinder sizes OMS shows their steel cylinder conversions as follows: Air capacity (cuft) - Liquid capacity (L) 130cuft - 17L 100cuft - 13L 80cuft - 10L 65cuft - 8L 45cuft - 7L http://www.omsdive.com/cyl_spec.html Westwinds. __________________ Located in Canada
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14th January 2006, 21:14	#9 (permalink)
Simon Ciantar New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: May 2005 Location: Malta Posts: 38	Re: Conversion of Cylinder sizes thks folks that pretty much what I was after Simon
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8th August 2007, 03:36	#10 (permalink)
2002scubasteve New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Aug 2007 Location: Fort Worth, Texas Posts: 1	Re: Conversion of Cylinder sizes I have used the conversion formula given here cuFT/0.035/rated pressure,but I don't understand that a tank with lower pressure holds more liters? Example: a 95 steel tank with 2400psi(165.474bar) holds 16.40 liters. same tank at 2650 holds 14.85 liters according to this formula. How can this be?
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