Stability criteria for vessels fitted with deck crane.

Discussion in 'Stability' started by athvas, Mar 2, 2013.

  1. athvas
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    athvas Senior Member

    i'm looking for stability criteria for grab hoppper dredger (self propelled) fitted with deck crane. Is there any specific criteria for operation of cranes to be complied with IMO regulations. (Operation of crane at anchored condition only). Plz help.
     
  2. Tad
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    Tad Boat Designer

    Typically we apply a crane heeling load just like that of a passenger or wind heeling load. A heeling load curve is superimposed on the righting arm curve, and your minimum stability standards applied to the residual area........

    Heeling load = COS(angle) * (total heeling moment)/displacement

    You will need to look at it at various load conditions.

    heelingloadcurve.jpg
     
  3. gonzo
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    gonzo Senior Member

    Typically the static stability will get corrected for sea conditions. Also, does the barge have spuds (legs)?
     
  4. TANSL
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    TANSL Senior Member

    Sea conditions are always dynamic. I do not know what it is, or what is the concept for, "static stability" in objects that are always moving, due to the movement of the sea, due to wind or, even, due to the weight hanging from a crane. Could you, please, explain what you mean?. Regards
     
  5. athvas
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    athvas Senior Member

    No the barge does not have spuds. It's a open top hopper with bottom doors.
     
  6. BMcF
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    BMcF Senior Member

    That was exactly how we went about getting a USN USV/drone support vessel conversion certified. A fairly large knuckle-boom crane was being added on the port deck edge back aft; so a range of additional weights were added to that location during the inclining tests and a table of crane lift v. extension limits developed from that data.
     
  7. TANSL
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    TANSL Senior Member

    Perhaps these notes may help clarify the issue somewhat
     

    Attached Files:

  8. baeckmo
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    baeckmo Hydrodynamics

    The DNV rules for vessels up to 15 m say "Vessels equipped with lifting equipment shall not heel more than 10 degrees when lifting 100 percent load in the most unfavourable position".

    DNV also states that "The lifting gear shall be tested at a load 25 % higher than the safe working load. The SWL shall be stated on the lifting gear and must not be higher than the stability requirements as per above will admit".

    I have used these rules for the design of several working boats and find them reasonable. One thing from my experience though: Some standard cranes have slewing bearings and/or mechanisms that don't cope with max load at a ten degree heeling, so be careful. Select a marine crane or an oversize standard and derate it!
     
  9. gonzo
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    gonzo Senior Member

  10. athvas
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    athvas Senior Member

    Thanks , but the length of the barge is 40 mtrs.
    What is the max angle of heel for vessels more than 15m in length?
     
  11. athvas
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    athvas Senior Member

    Could you plz send me the rule reference of the above. In which Classification rules it is given .
     
  12. Tad
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    Tad Boat Designer

  13. athvas
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    athvas Senior Member

  14. powerabout
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    powerabout Senior Member

    if landlubbers are doing this make sure they have allowed the crane to be loaded but inclined, not something that usually happens on the land but having seen an incline vessel/crane test fail due to this, it clearly has happened once before
     

  15. athvas
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    athvas Senior Member

    Is the above requirement applicable for crane with counter weight. or is there any other requirement for crane with counter weight
     
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