Max Heeling Moment - Crane Lifting

Discussion in 'Stability' started by Niru, Mar 26, 2014.

  1. Niru
    Joined: Jul 2010
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    Location: Philippines

    Niru Mr.

    Good After Meridian!

    Was wondering... why is it in the

    USCG (DHS) part 173 - subpart b - lifting
    173.005 specific applicability

    ...applies to each vessel that -

    a.) .....
    b.) has a max heeling moment due to hook load GREATER than of equal to (see attached pic)

    im having less HeelingMoment value in comparing with the computed HM.
    anyone here familiar with this criteria. Thanks!
     

    Attached Files:

    • HM.JPG
      HM.JPG
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  2. Niru
    Joined: Jul 2010
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    Location: Philippines

    Niru Mr.

    Is there any chance that it should be stated " not greater than the computed value"

    just a guess.
     
  3. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I think what the formula means is that the maximum righting moment of the boat must be sufficient so that, with the heel by a weight, never immerse thedeck. In formula also applies a safety factor that is probably included in the coefficient whose value is 0.67.
    The maximum righting moment of the boat must be greater than the heeling moment dipping deck.
     
  4. Niru
    Joined: Jul 2010
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    Niru Mr.

    Many Thanks Sir!

    from your understanding i did compute a value of

    HMmax = 6950.16 feet - long tons

    versus

    RMmax = 9878.586 feet - long tons

    RM > HM

    Tnx!
     
  5. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I guess you had in mind that the maximum righting arm is obtained by calculating the points of the GZ curve for displacement you're considering
     
  6. Niru
    Joined: Jul 2010
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    Location: Philippines

    Niru Mr.

    well what i did was

    i multiplied the total displacement of the vessel from the max GZ @ max GZ angle.

    RM = Disp x GZ

    HM = was derived from the USG Lifting Criteria

    ?
     
  7. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    What you did seems right.
    My question is that how you calculated the maximum value of GZ.
     
  8. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    The phrase simply says that if the heeling moment due to the hook load is greater than X (meaning that the vessel shall be subject to high heeling moments), then USCG (DHS) part 173 is applicable. Otherwise the heeling moment is small enough to make the application of the Code unnecessary.

    TANSL has reworded this in terms of righting moment, which is equivalent.

    Cheers
     
  9. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    Wait, that is wrong! You cannot use the regular GZ curve for this! Notice that the requirement specifies GM "with hook load included". A hook load is applied at the top sheave which significantly raises effective KG and reduces effective RM by inducing a static list. This is especially true for an over the side lift.
     

  10. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    What Niru has done is absolutely correct as long as, of course, he has correctly calculated the values for GZ curve.
    So I asked in post # 7, how he had obtained the maximum value of GZ.
     
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