Grain Calibrations

When grain cargo is carried in a ship, it must meet the requirements of the "International Code for the Safe Carriage of Grain in Bulk", which is published by the International Maritime organization (IMO) as Chapter VI of the SOLAS Convention 1992.

These rules require heeling curves to be calculated based on an assumed shift of grain. Even for full compartments, the calculations must take account of the settlement of the cargo and the voids, which form between hatch coamings and at the sides of the hatches. As the vessel heels in waves, the grain shifts thus causing a heeling moment.

After taking into account the maximum possible heeling moments due to grain shift, the ship must meet the following criteria at all times:

• the angle of heel due to grain shift shall not exceed 12° or a lesser figure, if required by the Administration,

• the residual dynamic stability up to 40° or the angle of flooding if this is less, shall not be less than 0.075 m-radians, and

• the GM after allowance of liquid free surface effects shall not be less than 0.30 m.

There are three different types of calculation processes that are relevant:

• Grain Calibration, where tables of capacities and heeling moments, are prepared for each grain hold,

• Tables of Allowable Grain Heeling Moments for a range of drafts and vertical centres of gravity (VCG's), and

• Grain Loading Conditions, where different loading scenarios are checked for compliance with the stability criteria, taking into account the heeling moment due to an assumed shift of cargo.

The GRAIN stability criteria set should be selected by you, when setting the main program options.