Answer
High-Density Bulk Cargo Operations (IMSBC Code)
Under the International Maritime Solid Bulk Cargoes (IMSBC) Code,
High-density solid bulk cargo means a solid bulk cargo having a stowage factor of 0.56 m³/t or less.
SF≤0.56m3/t
Since, Density≈1/ SF
a stowage factor of 0.56 m³/t corresponds approximately to: 1/ 0.56 = 1.786 t/m3
So a useful memory figure is roughly:1,780kg/m3
while certain SOLAS XII structural provisions use cargo-density thresholds such as 1,000 kg/m³ and 1,780 kg/m³ for bulk carriers. Do not mix these definition
- Key Hazards & Examination Focus Points:
- Tanktop Structural Overloading: High mass concentrated over small areas can collapse inner bottom plating and floors. Always verify maximum allowable tanktop load (tonnes/m2) from the vessel’s Stability Booklet.
- Cargo Liquefaction (Group A Cargoes): Fine-grained moist cargoes can shift into a dynamic fluid state if moisture content exceeds the Transportable Moisture Limit (TML). Master must verify Shipper’s Moisture Declaration (sampling within 7 days) and conduct "Can Tests" on board prior to/during loading.
- "Stiff Ship" Condition & Excessive GM: Concentrating heavy cargo low in lower holds drops KG, resulting in an excessively high metacentric height (GM). This causes violent, short rolling periods, exerting extreme dynamic stresses on the ship’s structure.
- Alternate Hold / Block Loading: To raise G and avoid excessive GM, high-density cargo is often loaded in alternate holds (e.g., Holds 1, 3, 5) if authorized by the vessel's approved Loading Manual.
- High Loading Rates & Shear Stresses: Modern high-capacity shore loaders (>10,000 tonnes/hr) can quickly induce unacceptable Shear Forces (SF) and Bending Moments (BM). The Loading/Unloading Plan (SOLAS VI/7) must be monitored continually using the Onboard Loading Computer.
- Bilge Well Protection: Bilge strainers must be wrapped with burlap/filter fabric to prevent fine cargo dust from clogging cargo hold drainage systems.