Grain Stabilty Calculation

Discussion in 'Software' started by Dr34m3r, Jul 21, 2014.

  1. Dr34m3r
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    Dr34m3r Senior Member

    anyone can tell which tool can be used for calculating Grain Stability ? Delftship can do it ? or which is the best way ? make a excel spreadsheet ?

    Thanks
     
  2. NavalSArtichoke
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    NavalSArtichoke Senior Member

    It will help us if you tell us a little more about this project -

    What information do you currently have about the stability characteristics of the vessel, that is:

    1. Does the vessel have an existing stability manual?

    2. Does the vessel have a grain stability document?

    Do you have drawings of the vessel, particularly ones which describe the hold(s) where you want to carry grain?
     
  3. Dr34m3r
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    Dr34m3r Senior Member

    1. I have stability manual
    2. I am trying to make that grain stability document

    yes , drawings are available. Tank modeling also done in Delftship.
     
  4. TANSL
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    TANSL Senior Member

    You just have to calculate the variation in the position of the center of gravity of the load on each heel. With this, you can calculate the new position of the total center of gravity and therefore the value of GZ. With a value of GZ for each length, traces the GZ curve and calculate the dynamic stability. These curves must meet the applicable criteria for the type of boat.
     
  5. NavalSArtichoke
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    NavalSArtichoke Senior Member

    Grain in a hold acts in a manner which is different from liquids in a tank, which is why a special grain loading document must be prepared.

    If you don't already have a copy of the IMO publication, "International Code for the Safe Carriage of Grain in Bulk", I would suggest that you obtain this publication right away and start reviewing it.

    There are special stability regulations which grain carriers must meet, in addition to the normal IMO intact stability criteria. To make a Grain Loading Document, you will have to compute the maximum allowable grain heeling moment versus displacement for the vessel.

    In addition, when grain is loaded into a hold, not all of the volume of the hold is initially occupied by the grain. The Grain Code shows how the grain surfaces are trimmed on loading, which is why you need drawings of the hold so that you can calculate the void spaces above the trimmed grain surface. When the vessel gets out to sea, the grain can shift and settle further in the hold, due to the motion of the ship, and you have to calculate the heeling moment caused by this settlement.

    This second part of the calculation, the determination of the grain heeling moments, is what makes the grain stability calculation so difficult and resistant to analysis by most stability programs. There are some out there which claim to do grain stability, like GHS, but I am unfamiliar with the accuracy of their results.

    For more information, google "IMO grain stability" and you should find references to the IMO Intact Stability regulations and the IMO Grain Code.

    If you google "Grain Loading Manual", you can also find a sample grain loading manual which you can download and review.
     
  6. Dr34m3r
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    Dr34m3r Senior Member

    hi

    i have the IMO publications and understood the theory behind it. but was wondering if Delftship or other way to do it. I know NAPA can do it, but its expensive one.
     
  7. NavalSArtichoke
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    NavalSArtichoke Senior Member

    IDK of any free software which can do these calculations, certainly not calculating the grain heeling moments for the individual holds.

    The last time I did such a calculation it was largely by hand, with the aid of some basic NA programs like tank capacity calcs. to run the capacities of the holds at an angle of heel and a drawing program to lay out the cargo holds.
     
  8. athvas
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    athvas Senior Member

    You can use Autoship (Authohydro) software to perform grain stability calculations........
     
  9. TANSL
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    TANSL Senior Member

    Yes sir, that is to respond to what has been asked. The rest of us have gone through the branches.
     
  10. NavalSArtichoke
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    NavalSArtichoke Senior Member

    You wouldn't know it from the AutoShip website. A horrible place to try to find any detailed information about the capabilities of AutoShip.

    Like I said before in an earlier post, GHS had a grain stability module at one time, but both Autoship and GHS are expensive packages.
     
  11. Dr34m3r
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    Dr34m3r Senior Member

    Any excel or freeware tools available ? or anyone have done it manually ?
     
  12. JosephT
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    JosephT Senior Member

  13. Dr34m3r
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    Dr34m3r Senior Member

    Thanks Joseph, I know about this DelftLoad.

    I have mostly figure it out how to do it manually. But i am stuck with how to get calculate MAXIMUM PERMISSIBLE GRAIN HEELING MOMENTS ? I have added a sample Table from the book (ship stability for masters and mates ).

    Anyone can tell me the theoretical procedures to calculate this AHM ?
     

    Attached Files:

  14. NavalSArtichoke
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    NavalSArtichoke Senior Member

    You've got to take the cross curves of stability for your candidate grain vessel and calculate the maximum allowable grain heeling moment at each combination of intact displacement and vessel VCG such that you meet the intact stability requirements specified in the IMO Grain Code, Section 7. It is quite involved if you don't have a program to search out these values.
     

  15. Dr34m3r
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    Dr34m3r Senior Member

    I have the cross curves of stability result from Delftship. so is it , i calculate the cross curves of stability for 12 degree of inlc, then multiply with volume with GZ value ?
     
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