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GRAIN RULES

Any bulk cargo having angle of repose less than 36* known as grain. After completion of loading it has to be secured before commencement of voyage. If it is not effectively secured grain become very dangerous become it liable to shift transversely as v/l rolls. Grain does not act like a liquid due to friction so simple reduction of GM is not sufficient. If the v/l rolls heavily to a large angle grain will shift to one side but with the return roll it may not all shift back?

PRINCIPLES:   The IMO grain rules is based on the fact that the void spaces in filled compartments are bound to occur. This happens because of the difficulty in trimming of cargo and also because of the cargo settling during the voyage. Therefore during calculation an allowance is made for grain shift. So the resulting “TOTAL GRAIN HEELING” is used to determine the reduction in righting levers. The loss of righting arm is called  “HEELING ARM”. The basis of the rules is that after taking into account the grain shift the v/l have sufficient residual stability she will be allowed to load grain.

INTACT STABILITY REQUIREMENT:

Ø  The angle of heel due to grain shift shall not exceed 12 or Q de whichever least.

Ø  The net or residual area between the heeling arm curve and the righting arm curve upto the angle of maximum difference between tow curves, or 40 or the angle of flooding (Of) whichever is least shall not less than 0.075 meter-radius.

Ø  The initial GM, after correction for free surface effect, shall not less than 0.30m.

POINTS TO REMEMBER

Ø  Heeling arm take care of the transverse shift of grain.

Ø  Vertical component allowed for either by the following, (a) If KG of cargo is taking into account then multiply grain heeling moment by 1.06 for full compartment and by 1.12 for partially filled compartment.

Ø  When calculating grain-heeling moments, assume that the grain will shift through 15 in full compartment and 25 in partially full compartments.

Ø  All full compartments should be trimmed, if they are not trimmed, a grain shift of 30 is assumed

IMPROVING CONDITION

 After loading if vessel fails to confirm with the requirement of grain rules. The situation can be handled by either improving vessel’s stability or reducing grain shift.

STABILITY MEASURES:  

Ø  Reducing free surface effect by pressing up employing tanks. This results in increase in fluid GM.

Ø  Increase the solid GM by lowering weights or by adding weight low down (e.g. filling a double bottom tank).

CARGO MEASURES.

The shift can be reduced in full compartment by:

Ø  Fitting of temporary longitudinal subdivision (shifting boards).

Ø  Use of bugged cargo in a saucer.

Ø  Bundling in bulk.

  The shift can be eliminated in partially filled compartment by building a dunnage platform on top level of grain and then:

Ø  Over stowing with other cargo.

Ø  Over stowing with bagged cargo.

Ø  Stropping and lashing using steel strops and bottle screw.

DOCUMENTS OF AUTHORISATION:

This document is issued to any ship intending to carry grain by ship’s national administration. It is the evidence that the ship is capable of carrying grain as per grain regulations. This document should be kept onboard along with ship’s “GRAIN LOADING STABILITY BOOKLET” as guidance for Master to load grain.        

GRAIN LOADING STABILITY BOOKLET:

Grain loading stability booklet includes the following information.

Details of required stability criteria as given by IMO.

General arrangement plan and stability for the vessel.

Curve or table of grain heeling moment for every compartment, filled or partially filled. Effect of temporary filling such as shifting boards.

Tables of maximum permissible heeling moments.

Details of shifting board, saucer and bundling in bulk and overstowing arrangements.

Typical loaded departure and arrival calculation.

Worked example for grain stowing at 1.25, 1.53 and 1.81m/t.

Instruction for maintaining adequate stability throughout the voyage.

Other information supplied under ship’s particular.

            WT HEELING MOMENT=  VOL. HEELING MOMENT

                                                                  STOWAGE FACTOR

            APPROX. ANGLE OF HEEL =  TOTAL HEELING MOMENT          X 12