twin pacs?

[Sea Otter crew]

Anders,

Tackar så mycket,

Chris.

I have found my beloved double sevens (7 liters) at a site in the UK, www.divingshop.com

I have tried to convert this into the US equivalent but it doesn't work out; qnybody knows?

 

[Sea Otter crew]

should read, anybody knows?

Chris

 

[Sea Otter crew]

OK Guys,

I have found the what a 7 liter bottle is in US standards, it is a 77.8 or 78 cu ft bottle and as i have the answers on my other questions I think this thread is closed?

Safe and Happy diving,

Chris on S/Y Sea Otter.

 

[JimC]

A 7l tank filled to 206 bar (3000psi) holds 50cf of gas.
A 7l tank filled to 186 bar (2640psi) holds 45cf of gas.

 

[Sea Otter crew]

Thanks Jim C,

I am learning every day something new, couldn't just figure out how the US numbers were calculated, but now i know.

Safe diving,

Chris.

 

[JimC]

UK tanks are mesured in how much internal volume they contain. Expresed in liters of water. US tanks are mesured in how gas they hold at there rated service presure while at 15deg C. Expresed in cubic feet.

Convertion is rather simple.

First you have to change to metric:

80cf / 0.035cf/L = 2285.7L (typical AL80)
3000psi /14.538psi/bar = 206.8bar (typical AL80)

Now adjust that volume to 1bar:

2285.7L / 206.8bar = 11.1L
------------
Going the other way we can simply plug in the values we know and solve for cf@rated presure.

7L * 206bar * 0.035cf/L ~= 50cf


I much prefer the UK system as it tells you an absolute volume. Not a number which varies with temperature, and is normaly not even close to the actualy volume. Most AL80's hold 77.4 to 77.7 cf.

 

[Sea Otter crew]

Hi Jim,

Thanks for the calculation demo,
yes I agree the UK/European system is a bit simpler, but I think it is good for us Europeans to know the other system as well, especially like us, sailing people, when we come closer to the US for diving on our "grand tour".

regards,

Chris.