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Imperial to Metric tank capacity

Discussion in 'Tanks, Valves and Bands' started by elmagnoon, May 6, 2007.

  1. elmagnoon

    elmagnoon Solo Diver

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    Is there a table of Imperial tanks and what their capacity is in metric?

    For example what's a Luxfur S80? Is it a 10 Litre?
    I have the following and would like their capacity in Metric


    Luxfur S080N
    Luxfur S040
    PST E130


    Thanks
     
  2. dsteding

    dsteding DIR Practitioner

    # of Dives: 200 - 499
    Location: Seattle, downtown
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    Metric capacity depends on working pressure. To get volume of gas you multiply the working pressure (in bar) by the volume of the tank (in liters). This gives you the total liters of gas in the tank. 1 cubic foot equals about 28 liters, so you then divide by 28 to get capacity in cubic feet.

    Not being terribly familiar with working pressure of metric tanks, I can't convert your volumes to metric.

    A quick search of the archives yielded this table that explains the liter/pressure difference (netdoc was using PSI here as a result of where the thread was going):

     
  3. Charlie99

    Charlie99 Solo Diver

    # of Dives: 500 - 999
    Location: Silicon Valley, CA / New Bedford, MA / Kihei, Maui
    7,966
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    http://www.luxfercylinders.com/products/scuba/specifications/us_metric.shtml give specs for Luxfer cylinders in metric. The most common AL80 is the S080, which is 2kg positve buoyancy when empty. It's fill pressure is 3000psi or 207 bar. Water volume is 11.1 liter.

    I don't have a metric table for the PST cylinders handy, but

    130cu ft at 3442psi is 130cf * 28.4 l/cf = 3692l at 232 bar = 15.9 liter cylinder.
     
  4. elmagnoon

    elmagnoon Solo Diver

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    Thanks for the replies. They're very very helpfull though I'm still digesting the numbers.

    Qustion for Charlie99:

    If an E130 holds 130 cubic feet of comressed air and a S080 holds 77.4 cubic feet. The E130 holds approximately 68% more compresed air than the S080.

    Would I be able to apply the same comparsion in metric and say that an S080 with 11.1Litres @ 207 bar= 2297.7 Litres of air, then an E130 @ 232 bars will hold 68% more = 3860 Litres of air. Which brings the E130 closer to being a 17 litre tank.

    Does that make any sense?
     
  5. Charlie99

    Charlie99 Solo Diver

    # of Dives: 500 - 999
    Location: Silicon Valley, CA / New Bedford, MA / Kihei, Maui
    7,966
    146
    0
    Per this PST spec sheet it is a 16.6 liter tank. http://www.pstscuba.com/PST Scuba Product Specification Sheet.pdf (pdf)

    ========================
    There are some weird things about converting back and forth ---

    3442psi converts to 237bar if you use 14.5psi per bar. I think that discrepancy is that EC rates fill pressure at a lower temp than does the USA.

    Particularly at higher pressures, each additonal atm doesn't add additional free gas equal to the water volume (Van Der Wals effect. Departure from ideal gas).

    Rather than bar * size to get free gas, technically is should be atm * size. Another 1.325% error.

    It's really 28.3 liters per cubic feet, not the 28.4 that I used (12 cubed * 2.54 cubed / 1000).

    Put all of this together and it adds up. The S080 actual free volume of 77.4cu ft is 2192 liters, not the 2297.7 you came up with by multiplying 11.1l * 207bar.

    Of course, this all is in the noise compared to the variations in RMV. :)
     

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