Tankers

Intact Stability

The MSC approved an interpretation to the draft MARPOL Regulation I/25A which requires oil tankers built after 1 January 1998 to meet:

1.an initial GMo > 0.15m, during loading and unloading; and

2.a minimum righting arm curve having adequate magnitude, area and range, under all conditions at sea, with the ship loaded in “the worst possible condition of cargo and ballast loading, consistent with good operational practice”.

To assess compliance, the vessel is to be loaded with all cargo tanks filled to a level corresponding to the maximum combined vertical moment of the cargo plus free surface inertia moment at 0o heel for each tank. Cargo density should be based on a cargo deadweight (with full departure consumable and 1% total ballast water capacity) determined at the displacement at which the transverse metacentre (KMT) reaches a minimum. When calculating the initial transverse metacentric height (GMo), the maximum free surface at 0o heel for each ballast tank may be used.