Ballast instalation diagram

Discussion in 'Boat Design' started by JoshTruman, Apr 24, 2019.

  1. JoshTruman
    Joined: Dec 2018
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    Location: Lithuania

    JoshTruman Junior Member

    upload_2019-4-24_21-37-43.png
    Good day, I have a small matter...
    For example: I would like to ballast tanko no WB50 so the procedure should be like that:
    Open seachest valves SC2
    Open valves which are marked by green rectangles
    Start pump.
    But I am wondering what is going in intersection of pipelines marked by red rectangle - is that mean that water will flow in both sides ?
     
  2. RAraujo
    Joined: Apr 2010
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    Location: Singapore

    RAraujo Naval Architect

    Inkedupload_2019-4-24_21-37-43_LI.jpg
    What represents the symbol marked in blue? There should be a valve in that line...
     
  3. JoshTruman
    Joined: Dec 2018
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    Location: Lithuania

    JoshTruman Junior Member

    According to diagram there is orifice
    upload_2019-4-25_6-44-19.png
     
  4. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Yes, water will flow both ways; and no, there should not be a valve in the pressure relief. The vented loop pressure relief serves two purposes. First it prevents water hammer if the pump was dead-headed at startup. And secondly it most likely prevents over-pressurization of the tanks. Since most pump rooms are arranged as low as possible in the hull, the water in the vented loop will rise equal to the head. Since the loop is vented above the main deck, water should never reach the loop in normal operation unless you are discharging a tank or pumping bilges overboard through the loop.
     
  5. RAraujo
    Joined: Apr 2010
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    RAraujo Naval Architect

    Overpressure on the tanks is prevented by the tanks own vent... And the loop is below main deck (even if the vent is above main deck the free end of the pipe is below waterline... Since we do not know the height of the water ballast tanks (which may very well be wing tanks) I believe it does not work.
     
  6. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Not really, the ballast pump is most likely a HVLP centrifugal pump and the tank vent will be small (typically ~1/8th the inlet area) so you can easily pressurize the tank to ~max pump head. <shrug> We don't have all the info or piping diagrams, so this is all just speculation, but I put money on my answer as it is unlikely that the wing tanks extend to the main deck.
     

  7. RAraujo
    Joined: Apr 2010
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    Location: Singapore

    RAraujo Naval Architect

    Check the rules of any classification society - the area of the vent pipe must, at least, 25% bigger than the inlet pipe (precisely to avoid overpressure)...

    For instance Bureau Veritas requires (Pt C, Ch 1, Sec 10):
    c) In each compartment likely to be pumped up, and where no overflow pipe is provided, the total cross-sectional area of air pipes is not to be less than 1,25 times the cross-sectional area of the corresponding filling pipes.

    And I never said that the wing tanks extend to the main deck (although they can - think of the upper wing tanks of a bulk carrier or the wing tanks of an oil carrier)
     
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