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Velocity in a pipe via a pressure test.

  1. Jan 31, 2013 #1
    Okay i'm currently doing a thrust block design for a water supply system. The new line is a 250mm line. The water is fed from water towers where council has said the operating head is about 30m. I've set up my thrust block program in excel and it is all working fine. The only trouble is i'm unsure on exactly what flowrate/velocity of the water in the new pipeline to calculate the thrust.

    Now i was thinking the best way to do it was to solve with bernouli's with two unknown V's.

    and simultainiously solve for v1 = v2a2/a1 and vice versa. but was thinking maybe there might be a better way.

    I do have a pressure test from a current line in the area where the new line is going. The information from the pressure test is as follows:

    65mm line

    Flow rate/second (L/s) Pressure (kpa)
    0 220
    5 185
    10 125
    15 0
    16.5 (open) 0

    So using this pressure test, is it possible to gain the velocity of water in a 250mm line under similar conditions? or do i use the approximate 30m head in there to calc it instead? I may have to go to council and get more info off them but i struggled enough to get the pressure test.

    If anyone can help that would be great! Cheers.
  2. jcsd
  3. Jan 31, 2013 #2
    Sorry i just relised that the pressure test formatting didnt come out right...

    So it was a 65mm pipe

    fully closed valve = 220kpa
    running 5 l/s = 185 kpa
    running 10 l/s = 125 kpa
    running 15 l/s = 0 kpa
    Fully open running 16.5 l/s = 0 kpa

    So what i'm chasing is a velocity in a 250mm line in order to accurately calculate thrust in the pipe. We have an estimated head in water towers of 30m and the pressure test in the above.

    Can any one help?

    Hope this has clarified things a bit.

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