Pipe Volume Math Question

Discussion in 'Computer Support' started by Jimi, Mar 18, 2007.

  1. Jimi

    Jimi Guest


    I am filling a pipe with glycol.. The pipe is 1/2" (inside diameter).
    I need to know how many imperial gallons per 100 feet this pipe will hold so
    I can figure out how much glycol to buy.
    Thanks for any help on this. Jim
    Jimi, Mar 18, 2007
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  2. Jimi

    SJP Guest

    3.397301 Gallons
    SJP, Mar 18, 2007
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  3. Jimi

    Robb Guest

    Ask a scientist, or try this formula.

    Question From:
    Sammy, Age 8.

    My Dad and I are going to build a sail boat using PVC pipes for flotation.
    Is there an easy way to caculate how many 8 foot long, eight inch diameter
    pipes we will need to support our weight and keep the boat floating?


    The weight that the pipes will support is the weight of the water they can
    displace minus the weight of the pipes themselves. To calculate this, you
    need to know the volume of the pipes, the weight of the pipes, and the
    density (weight/volume) of water.

    Fresh water has a density of 1 kg/liter. Salt water has a higher density.
    The volume of the pipes can be calculated from their diameter and length
    by the formula

    V = L pi r^2, where
    L is the length of the pipe, 8 ft = 96 in.,
    pi = 3.14159,
    r is the radius of the pipe, 4 in.

    So the volume of a pipe is

    V = (96 in)(3.14)(4 in)^2
    = (96 in)(3.14)(16 in^2)
    = 4823 in^3

    Now you need to convert cubic inches to liters. 1 cubic inch = 0.01639
    liters, so

    V = (4823 in^3)(0.01639 L/in^3)
    = 79 L.

    So, in fresh water, an 8-ft length of 8-in diameter PVC pipe can float 79
    kg minus its own weight.

    [attrib lost, from the 'net]
    Robb, Mar 18, 2007
  4. Jimi

    Old Gringo Guest

    Old Gringo, Mar 18, 2007
  5. Jimi

    Whiskers Guest

    First-form maths!

    The volume of a cylinder (a pipe is a cylinder) is (22*r*r*h)/7 where r is
    the radius (half the diameter) and h is the height (or length, if you
    like), and 22/7 is pi. Make sure that you use the same units (either feet
    or inches) for both radius and height!

    1 imperial gallon is 277.4193 cubic inches or 0.160544 cubic feet.
    Whiskers, Mar 18, 2007
  6. It is amazing that anyone does these calculations in imperial measure now.
    Geoff Pearson, Mar 18, 2007
  7. Jimi

    Mike Easter Guest

    Numerator = cross-sectional area of pipe cm^2 x pipe length cm x ImpGal
    Denominator = conversion units for ImpGal cm^3

    Values: 0.5 " ID = 0.25" radius = .635 cm
    Xsec = pi x r^2 = pi x .635^2 cm^2

    100' = 30480 cm = 3 x 10^4 cm
    ImpGal = 4546.09 cm^3 = 4.546 x 10^3 cm^3

    Numerator = pi x .635^2 x 3.048 x 10^4 cm^3 x ImpGal
    Denominator = 4.546 x 10^3 cm^3

    I get 8.49 Imp Gal

    It seems like 100 feet of 1/2 inch pipe could hold something less than
    10 gallons of liquid.
    Mike Easter, Mar 18, 2007
  8. Jimi

    philo Guest

    but i'd purchase 3.397302 gallons , just to be on the safe side.

    I think it's a school math problem though
    philo, Mar 18, 2007
  9. Jimi

    Whiskers Guest

    Perhaps he's got these old pipes and hasn't heard that shops now have to
    sell stuff in litres?
    Whiskers, Mar 18, 2007
  10. Jimi

    Whiskers Guest

    I think you let your decimal point slip a bit somewhere in there.

    My method:

    22*.25*.25*1200/7=235.7142857142857143 cubic inches

    235.7142857142857143/277.4193=0.8496679420439951881 imperial gallons
    Whiskers, Mar 18, 2007
  11. Jimi

    SJP Guest

    I've changed my mind on my previous answer and reckon its 0.8493253 Gallons
    SJP, Mar 18, 2007
  12. Jimi

    Mike Easter Guest

    I'm trying to figure out why anyone would be filling 100 feet of 1/2"
    pipe with glycol, presumably ethylene glycol.
    Mike Easter, Mar 18, 2007
  13. Jimi

    Mike Easter Guest

    1 cm of that pipe will hold 1.27 cc, that sounds right, and a meter 127
    cc and 30 meters would be 3810 cc, so I think your answer is better than
    mine. I must've misplaced a decimal somewhere.
    Mike Easter, Mar 18, 2007
  14. Jimi

    Mike Easter Guest

    Aha! There it is. 100' = 3048 cm = 3 x 10^3 cm
    pi x .635^2 x 3.048 x 10^3 cm^3 x ImpGal
    Now it gets 0.849
    Mike Easter, Mar 18, 2007
  15. Jimi

    Mike Easter Guest

    Right there.
    That sounds pretty close. ;-)
    Mike Easter, Mar 18, 2007
  16. Jimi

    Robb Guest

    Then is my volume calculator borkd?
    I get 235.62 cubic inch = 0.849324351255694 gallon [UK]
    Robb, Mar 18, 2007
  17. Jimi

    Whiskers Guest

    To stop it from freezing?
    Whiskers, Mar 18, 2007
  18. Jimi

    Willard Guest

    Willard, Mar 18, 2007
  19. Jimi

    Jimi Guest

    Jimi, Mar 18, 2007
  20. Jimi

    Whiskers Guest

    Copy/paste from Kcalc; odd when being lazy makes it easier to get answers
    to a silly degree of precision than to get a rough aproximation. Let's
    say 'a bit less than 4 litres' to keep things sane :))

    My value for pi is approximately 0.04% on the high side - but it's better
    to have a drop left over than being a drop short, and differential thermal
    expansion and manufacturing variations are probably going to swamp that
    Whiskers, Mar 18, 2007
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