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How much air does an LP85 hold at 2400 PSI?

Discussion in 'Tanks, Valves and Bands' started by CaveSloth, Sep 23, 2019.

  1. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
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    It is what you just said. liters * bar to et total liters of gas in tank. the point i think is that not all tanks are equal,,,, like the S80 and the C80. both 80's but one is like 12 ltrs and the other is like 10 or 11 liters. tank factor will reflect the difference.
     
  2. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
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    thats part of hte problem i America. no one sells tanks as anything other than xxx cf , psi and material. al80 ,,, hp steel 100 etc. you will probably never see in a shop a tank labeled as a 13L 200 bar tank only as a AL S80.
     
  3. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
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    I wouols suspect tha if the tank was marked other than an increment of 5 then it is probalby accurate. so if you have an lp76 adn it has a service pressure of 2400 then you multiply the 76 by I think 28.5 to convert form cu ft to liters and then divide that by the bar of the tank. for a 2400 tank that is about 163

    76 x 28.5 is 2166 ltrs then ltrs / bar 2166 / 163 equals 13.2 liters water volumn. you have a 13 liter tank.

    ifyouwant to do this iperial then 2400 / 76 and that is 31.6 pai per cuft. if they put 2000 psi in the tank to top it off then you bought 2000 / 31.6 cu ft.
     
  4. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
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    you filled 7# and got 2400 psi thats 342 psi for pound of gas. full tank is 3550 so you have 10.3 pounds of gas in the tank air is 8# per 100 cuft so

    10.3 / 8 = 1.29 units of 100 cuft you have a tank with 129 cuft in it.
     
  5. Lorenzoid

    Lorenzoid idling in neutral buoyancy

    # of Dives: 500 - 999
    Location: Atlanta, USA
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    So the Europeans sort of have what we would call HP and LP versions of a 13L tank? And being rule-abiding, I am guessing they don’t make a habit of filling tanks beyond their service pressure.
     
  6. Storker

    Storker Divemaster

    # of Dives: 100 - 199
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    Almost, but not quite.

    The most common tank sizes - at least around here - are 7, 8.5, 10, 12, 15 and 18L. Fill pressures are 200, 232 and 300 bar. 200 bar is getting obsolete, 232 bar is rather popular since it provides a good balance between capacity and weight - and since compressibility still isn't much of an issue if you PP blend - and 300 bar tanks are preferred by those who appreciate a slightly more negatively buoyant tank.

    Typical rec twinsets are D7x300 or D8.5x232, but I've seen D4 and D6 as well
    Typical rec singles are 10, 12 or 15L, in 200, 232 or 300 bar (except 15x300, which is a true beast to schlep)
    The typical tech twinset is D12x232. D15 and D18 are only for those with extreme gas reserve requirements, and quite a few of those are switching to rebreathers nowadays.

    And it's generally steel. Al tanks are almost only used as ponies or stages due to them being largely neutrally buoyant (plus a little, minus a little, depending on how full or empty they are).
     
    KWS likes this.
  7. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
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    overfilling is not an issue in this. If I have an al 80, you dont know what tank I have because it comes in a 10 and 12 liter version (C80 or S80 and its not even an 80 to boot). The Europeans have say a 15ltr/232 ( made up tank) and with that marking there is no doubt what you have. by those 2 numbers you now the volumn. working pressure and capacity. the over fill is just a ratio adjustment to the capacity due to PSI change. Just looking at those numbers i can say one has +/- 200 surface minutes of breathing and still not fall below say 500 psi or so. The european markings are much more functional for those calculations. imperial is comfortable to americans to use but but when you say you again have an 80 cuft AL tank you dont really know what you have. tank factors are really easy to do in metric.

    Another example is the lp121 by oms .... inverse to the S80 that tank has 125 in it adn not 121 cu ft.
     
  8. Storker

    Storker Divemaster

    # of Dives: 100 - 199
    Location: close to a Hell which occasionally freezes over
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    We absolutely do. Nothing made up there.

    Perhaps the most popular single around here is the 12x232. I once had a 15x200, but these days I use 10x300 because that allows me to carry some 4-5kg less on my belt (a couple kilos less compared to a 12). They have slightly higher nominal capacity, but nearly exactly the same real capacity (just a smidgen less than 100 of your cubic feet) . If you need more gas than that, the most common alternatives are D8.5x232, 12x300 or 15x232.

    In warmer waters, I've typically used 12x200s. Most people use less gas while diving wet, and I guess those dive centers don't see much point in scrapping a bunch of perfectly usable tanks. Steels, when properly maintained, can last for decades.

    There are quite a few who prefer a small twinset over a single for balance and comfort. I prefer singles, because it's easier to stow an extra single in my boat than having to go to shore for a refill during my SI.
     
    KWS likes this.
  9. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
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    Thanks for that. I was trying to emphasize the format of the tank designation knowing only about US tanks, and was trying to avoid someone saying that there is no such tank and going off topic. just the 12/300 by its self tells the whole story. If when we in the US when buying a AL S80 knew we were buying a 77/3000 it would be easy for us also. There is a lot that is so much easier to do in metric. I often wish compuers would display both imperial and perhaps metric on an alternate screen. Working depth in bar for math is so much easier.
     
  10. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
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    Let me ask why most tanks are steel. is that because selected thermal protection makes steel the most practical. In the states or carribean it is AL that rules the waves but we need little if any thermal protection depending on the area. Ignoring the cave divers,,,I would guess that our north east and west divers use a lot of steel. Lots of dry suits.
     

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