Alternate Hold Loading and the Heavy Cargo Notation
Loading dense cargo in alternate holds: the motive, the doubled hold mass, the unreinforced empty holds, the BC-A service feature and the SOLAS XII/14 bar.
Alternate hold loading is the practice of stowing a high density cargo in alternate cargo holds with the intervening holds left empty. The motive is real: IACS Recommendation No. 46 records that the distribution raises the ship’s centre of gravity and eases the rolling motion, which matters on a cargo dense enough to make a ship uncomfortably stiff. The price is that the weight carried in each loaded hold is approximately double that of a homogeneous distribution, and the holds left empty have not been reinforced for a non-homogeneous distribution.
The practice is permitted only where the ship is approved for it, recorded under the Common Structural Rules as the additional service feature BC-A in the form BC-A with the holds that may be empty named. Recommendation No. 46 is unqualified that ships not approved by their classification society must not adopt the distribution.
Statute can bar it outright. SOLAS regulation XII/14 provides that a single side skin bulk carrier of 150 m and upwards carrying cargoes of density 1,780 kg/m3 and above, which does not meet the standards of regulation XII/5.1 and resolution MSC.168(79), shall not sail with any hold loaded to less than 10 per cent of that hold’s maximum allowable cargo weight in the full load condition after reaching 10 years of age. The full article will cover the notation, the strength basis and the restriction marking under regulation XII/8.