Question 1

Since the IMSBC Code's 2022 edition, ammonium nitrate based fertiliser cargoes are now split into which two schedules?

Accepted Answer

Ammonium Nitrate Based Fertilizer (MHB) — Group B, and Ammonium Nitrate Based Fertilizer — Group C The old single "Non-Hazardous" schedule was replaced with two more specific ones: Group B (materials hazardous only in bulk, MHB) and Group C (not subject to IMSBC's special chemical-hazard precautions) — reflecting that a single blanket classification had allowed cargo with real decomposition risk to be shipped as if it carried none.

Question 2

The yacht is loading additional stores and fuel before a long passage, raising the displacement significantly. What effect does this have on stability that you, as OOW, should be aware of?

Accepted Answer

Increased displacement generally raises the centre of gravity if weight is added high up, and free surface effects in partially-filled tanks can reduce the effective metacentric height (GM) Adding weight changes the vessel's centre of gravity depending on where it is stowed, and partially-filled tanks create free surface effects that reduce GM. OOWs should understand these basic stability principles even on smaller vessels without a dedicated loading computer.

Question 3

During a survey, watertight door seals in a transverse bulkhead below the waterline are found to be perished and not closing properly. As Master, what is the significance of this for the vessel's damage stability?

Accepted Answer

Significant — a failed watertight closure compromises the subdivision the vessel's damage stability calculations rely on, potentially allowing progressive flooding between compartments in the event of damage Damage stability calculations assume watertight subdivision functions as designed. A bulkhead door that cannot seal properly defeats that subdivision, allowing flooding to spread beyond the single compartment the design assumed — this must be rectified before further operation.