Cargo Operations and Stowage
What the cargo paper tests
Bulk and general cargo safety: hold preparation, stability and stress effects, dangerous goods segregation, ventilation decisions, and the codes that regulate practice, principally IMSBC, IMDG, CSS and the grain code.
Core rules
- Hogging and sagging come from unequal distribution of weight along the hull; check shear force and bending moment against the loading manual before any multi-hold sequence.
- IMSBC Code groups: A cargoes that may liquefy, B cargoes with chemical hazards, C other bulk cargoes with no special hazard. Group A cargoes must stay below their transportable moisture limit.
- Ventilation: for hygroscopic cargoes such as grain and timber, ventilate only when the dew point of the outside air is lower than the dew point of the hold air. For cargo that can sweat, surface ventilation only may be appropriate.
- IMDG segregation: keep incompatible classes apart by distance, compartment or hold according to the segregation table; class 1 requires the most care.
- SOLAS VGM: the shipper must provide a verified gross mass for every packed container before loading.
- Draught survey: use six draughts, apply corrections for trim and density, deduct lightship and constants, and compare deadweight with the manifest.
Worked example
Hold air 28 degrees C, dew point 22 degrees C. Outside air 24 degrees C, dew point 24 degrees C. Outside dew point is higher than hold dew point, so ventilating would bring moisture in and cause cargo sweat. Keep the hatches closed and monitor the hold dew point, ventilating only when the outside dew point falls below the hold value.
Traps that cost marks
- Ventilating for temperature rather than dew point.
- Loading a Group A cargo without checking moisture content against the TML.
- Ignoring shear force when trimming a heavy cargo into one hold.
- Accepting a container without a verified gross mass, or with the wrong declared tolerance.