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Thread: Small Donor Tank / Transfill question.

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    O2 Junkie suprabones is an unknown quantity at this point suprabones's Avatar
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    Small Donor Tank / Transfill question.

    Hello everyone,

    I had a question about doing a transfill from a small donor tank.. A 20cf oxygen tank to be exact. I am going to be filling up a IDA-76 which has a capacity of .47 Liters.. How do I calculate how many fills I can do with that tank before I need to top it off? The IDA-76 max pressure is 150 Bar. The 20cf tank I have is roughly 160 Bar. I am not really looking to get a different tank if I dont have to.. I really dont understand all the conversion factors. If anyone could kindly show me? Thanks in advance.

    -Matt.

  2. #2
    Phil Siswick, Tango PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick's Avatar
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    Re: Small Donor Tank / Transfill question.

    Quote Originally Posted by suprabones  View Original Post
    Hello everyone,

    I had a question about doing a transfill from a small donor tank.. A 20cf oxygen tank to be exact. I am going to be filling up a IDA-76 which has a capacity of .47 Liters.. How do I calculate how many fills I can do with that tank before I need to top it off? The IDA-76 max pressure is 150 Bar. The 20cf tank I have is roughly 160 Bar. I am not really looking to get a different tank if I dont have to.. I really dont understand all the conversion factors. If anyone could kindly show me? Thanks in advance.

    -Matt.
    I used something similar to this - you'll need to calculate that IDA cylinder back to CF and PSI: www.cave-dive.com/Bankmixer.xls.

    Just rerun it, swapping the input pressure for the next fill with the output pressure of the last one and you'll soon get the answer.

    Cheers,

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    O2 Junkie suprabones is an unknown quantity at this point suprabones's Avatar
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    Re: Small Donor Tank / Transfill question.

    Quote Originally Posted by PhilSiswick  View Original Post
    I used something similar to this - you'll need to calculate that IDA cylinder back to CF and PSI: www.cave-dive.com/Bankmixer.xls.

    Just rerun it, swapping the input pressure for the next fill with the output pressure of the last one and you'll soon get the answer.

    Cheers,
    Phil,

    Thanks for the link to the spreadsheet.. It is a very usefull calculator. As for the small 20cf tank, I just went and rented a 125cf tank and ran the analysis on that one... a much better setup.. I will be able to maintain a good pressure on the bottle for quite a few fills. Thanks again.

    -Matt.

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    Re: Small Donor Tank / Transfill question.

    Quote Originally Posted by suprabones  View Original Post
    Phil,

    Thanks for the link to the spreadsheet.. It is a very usefull calculator. As for the small 20cf tank, I just went and rented a 125cf tank and ran the analysis on that one... a much better setup.. I will be able to maintain a good pressure on the bottle for quite a few fills. Thanks again.

    -Matt.
    Hot towels on the donor bottle, cold towels or ice bath for the recipient will have surprisingly good effect.

    My He bottles are painted brown and I'd leave them out in the sun before got my booster.....:)

    Tobin

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    Re: Small Donor Tank / Transfill question.

    Quote Originally Posted by cool_hardware52  View Original Post
    Hot towels on the donor bottle, cold towels or ice bath for the recipient will have surprisingly good effect.

    My He bottles are painted brown and I'd leave them out in the sun before got my booster.....:)

    Tobin
    Works well with O2 cylinders over here they are black, stick them in the door of the garage with the cylinder to be filled at the back.
    Not sure it makes that much difference in rainy old england

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    O2 Junkie suprabones is an unknown quantity at this point suprabones's Avatar
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    Re: Small Donor Tank / Transfill question.

    Quote Originally Posted by cool_hardware52  View Original Post
    Hot towels on the donor bottle, cold towels or ice bath for the recipient will have surprisingly good effect.

    My He bottles are painted brown and I'd leave them out in the sun before got my booster.....:)

    Tobin
    That is a awesome technique.. I never thought about expansion and contraction by heat to get more gas out of and into a cylinder. what kind of temps are going to make a difference?

    -Matt.

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    Re: Small Donor Tank / Transfill question.

    Quote Originally Posted by suprabones  View Original Post
    That is a awesome technique.. I never thought about expansion and contraction by heat to get more gas out of and into a cylinder. what kind of temps are going to make a difference?

    -Matt.

    The More temperature difference the better.

    Depending on the ambient temps I've had good results with soaking towels in the hottest tap water I had easy access to.

    If I was filling small bottles I'd put them in a 5 gallon bucket and add ice.

    One of the other advantages of moving from a 20 cuft supply bottle to the 125 cuft bottle is the rate of cooling. As you drain a 20 it will get cold much faster than the 125, and as it cools it will see a pressure drop.

    In a pinch (like no more He on a Saturday) I've been know to source some dry ice for cooling and heat up some water on the stove to "greater than tap temps"

    Poor mans booster. :)

    Tobin

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    Re: Small Donor Tank / Transfill question.

    You can use the following formula;


    (PS1 * VS) + (PD1 * VD) = (PS2 * VS) + (PD2 * VD)

    PS1 = starting pressure of supply cylinder
    PS2 = ending pressure of the supply cylinder
    PD1 = starting pressure of the diving cylinder
    PD2 = Ending pressure of the diving cylinder
    VD = Internal volume of the diving cylinder
    VS = Internal volume of the supply cylinder

    Dale

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    O2 Junkie suprabones is an unknown quantity at this point suprabones's Avatar
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    Re: Small Donor Tank / Transfill question.

    Quote Originally Posted by cool_hardware52  View Original Post
    The More temperature difference the better.

    Depending on the ambient temps I've had good results with soaking towels in the hottest tap water I had easy access to.

    If I was filling small bottles I'd put them in a 5 gallon bucket and add ice.

    One of the other advantages of moving from a 20 cuft supply bottle to the 125 cuft bottle is the rate of cooling. As you drain a 20 it will get cold much faster than the 125, and as it cools it will see a pressure drop.

    In a pinch (like no more He on a Saturday) I've been know to source some dry ice for cooling and heat up some water on the stove to "greater than tap temps"

    Poor mans booster. :)

    Tobin
    I like the poor mans booster.. I think however I would just get like 2 heating pads and wrap the bottle with the pads and then throw some towels around all that to keep it all warm :)

    -Matt.

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