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Thread: Tank filling

  1. #1
    Associate Engineer
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    Tank filling

    ipt>
    Hi,

    We have a 2000 litre tank which drains (gravity fed) to two seperate tanks.

    The one outlet pipe (4") feeds both tanks but currently splits unevenly - instead of a T piece, it is more like and S which mean one tank is filled before the other. The difference in height between the two inlets is approx 400mm

    What is happening, obviously, is one tank is filling before the other but what I am wondering is whether to TOTAL filling time would change if we adjusted the pipework to a T piece which should see both tank fill evenly???

    Thanks in anticipation for your help

  2. #2
    Technical Fellow
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    Not sure I follow. A sketch would help. Are you saying that both outlets are at 400mm differing heights or the inlet to the two tanks. The inlet heights would not matter, but the outlets being at different levels by 400mm would certainly affect filling speed and times.

    Even with a T outlet, there is no guarantee of even filling though. You would probably require a valve on one or both outlets to adjust flow.

  3. #3
    Lead Engineer RWOLFEJR's Avatar
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    Not sure I understand the question either.
    But I'll throw this out there... If the two tanks you are filling are same/ same and same elevation. Or they are identical and sitting on a floor. You could either bottom fill them with a tee or just put a pipe between the two to basically connect them and they'll fill to the same level.

  4. #4
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    Tank layout

    tanks.jpg

    Apologies for the confusing explanation - essentially, this is what we have...

  5. #5
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    Say the current set up takes 1 hour to fill, albeit unevenly.

    If the bottom tanks had inlets at the same level, would they fill quicker or will it still take 1 hour to transfer that volume of liquid?

  6. #6
    Principle Engineer
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    When you say unevenly, what is the difference in time of the two fillings?
    Are we talking minutes? Are the pipe sizes from the T equal? Are the 2 tanks equal in geometry?
    And what are the dimensions of each tank?

    The thing that strikes me is the way the outlet is configured. The left tank will fill first because of the jet effect. If you make the T connection identical you should get closer fill times.

    If the small tank geometries are equal, then the fill times should be almost equal and, if not something else id going on.

    And making the height equal shouldn't have much of an affect on the total fill time.

  7. #7
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    Just noticed 1 hour to fill???
    Must be filling concrete mix.

  8. #8
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    IF all pipe sizes from the vertical delivery pipe to the 1000L tanks are the same, IF the 1000L tanks were identical in floor area then the left tank would fill slightly faster due to tiny losses in the pipe bends. Although, a Tee is notoriously bad at directing an even flow through both sides. If you had a dump well (attached pic) at the bottom then the two inlet pipes came from that the chances of even filling would increase.

    Quote Originally Posted by Jordan View Post
    If the bottom tanks had inlets at the same level, would they fill quicker
    Tricky question. If one inlet was at the bottom of the tank and the other at the top, then the tank with the inlet at the top would fill first as it is not pushing against any pressure to fill the tank. If the inlets were slightly offset vertically then the tank with the higher inlet would fill faster.

    Forget about the 2000L tank for the moment. Basically what is important here for equal filling is that BOTH 1000L have...
    the same size inlet pipes
    the same area at the bottom of the tank
    the same height of inlet pipes.

    Square v round shape would not matter. The thing that will mostly dictate the filling rate is the difference in height between the top of the fluid in the 1000L tanks and the top of the fluid in the 2000L tank.

    What you have is a column of fluid in the vertical pipe with a known pressure at the bottom. Similarly, as the 1000L tanks are filling you will have a column of fluid in each of those. In order to fill evenly you must keep the top level of both 1000L tanks close to the same.

    Pressure equals Head X Density so as long as you can keep the Head constant in both tanks they should fill evenly. The driving force for the fluid is the difference in Pressure between the Head in the delivery pipe v the Head in either/both tanks.

    Maybe a Gate valve on the left tank can be used to throttle down any advantage it has.
    Attached Images Attached Images

  9. #9
    Associate Engineer
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    a valve before entry to each tank can solve your problem.

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