Where gutter bars are installed on the weather decks of
tankers in way of cargo manifolds and are extended aft as far as the
after house front for the purpose of containing cargo spills on deck
during loading and discharge operations, the free surface effects
caused by containment of a cargo spill during liquid transfer operations
or of boarding seas while underway require consideration with respect
to the ship's available margin of positive initial stability (GMo).
Where the gutter bars installed are greater than 300 mm
in height, they should be treated as bulwarks according to the Load
Line Convention with freeing ports arranged in accordance with regulation 24 and effective closures provided
for use during loading and discharge operations. Attached closures
should be arranged in such a way that jamming cannot occur while at
sea, ensuring that the freeing ports will remain fully effective.
On ships without deck camber, or where the height of the
installed gutter bars exceeds the camber, and for tankers having cargo
tanks exceeding 60% of the ship's maximum beam at midships regardless
of gutter bar height, gutter bars should not be accepted without an
assessment of the initial stability (GMo) for compliance with the
relevant intact stability requirement taking into account the free
surface effect caused by liquids contained by the gutter bars.