Question 1

How does the International Code on Intact Stability (IS Code 2008) address ice accretion for vessels operating in areas where icing is a recognised risk?

Accepted Answer

The IS Code includes specific guidance/criteria for accounting for the weight and effect of ice accretion in stability calculations for vessels intended to operate in areas where icing is a recognised risk, requiring the additional ice weight and its effect on the vertical centre of gravity to be incorporated into the vessel's approved stability information, rather than treating icing purely as an unplanned operational hazard with no design-stage consideration This connects the operational hazard back to the regulatory/design framework — a vessel genuinely intended for icing-prone service should have this risk reflected in its approved stability information from the design stage, not left purely to operational judgement after the fact, which is exactly the kind of design-stage risk consideration mirrored in the DP FMEA principle discussed elsewhere in this content.

Question 2

Why does ice accretion present a disproportionately greater capsize risk to smaller vessels (such as fishing vessels) compared to large merchant ships, even in the same icing conditions?

Accepted Answer

A given mass of accreted ice represents a much larger percentage of a small vessel's total displacement and a proportionally greater rise in centre of gravity relative to its (generally smaller) margin of stability, compared to the same ice mass on a much larger vessel — small vessels with high topside structure (masts, rigging, gear) relative to their hull size are especially vulnerable This explains the documented pattern of small fishing vessel losses attributed to icing — the same weather conditions that are a manageable nuisance for a large ship can be genuinely capsize-inducing for a small vessel with high gear/rigging and a comparatively small stability margin, which is why icing guidance places particular emphasis on smaller vessel operations.

Question 3

What combination of conditions creates the most rapid and severe superstructure icing?

Accepted Answer

Low air temperature (well below freezing) combined with strong wind generating significant sea spray, particularly when the vessel is heading into or across the weather such that spray is regularly thrown over the bow/sides onto exposed structure — the combination of cold air and wind-driven spray icing rate is far more severe than either factor alone This is the practical forecasting knowledge an OOW needs — icing risk is a function of combined air temperature and spray generation, not either alone, and recognising this combination developing (forecast cold air plus building sea state/wind) allows proactive route or heading adjustment before icing becomes severe, rather than reacting only once visible ice has already built up.