1 Member Governments are advised that the intact
stability of double hull tankers and other tanker designs, which are subject
to significant free surface effect during liquid transfer operations
including lightering operations and tank cleaning operations, require
special consideration.
2
Mandatory requirements to address such difficulties for new ships are being
considered by the Committees. Such requirements are unlikely to become
mandatory before the year 1998.
3
It is recommended that owners and operators should:
.1 ensure
that an oil tanker:
.1 in port, has the
initial metacentric height GMo, corrected for free surface measured at 0
degrees heel, not less than 0.15 m; and
.2 at sea, complies with the requirements specified in
paragraphs 3.1.2.1 to 3.1.2.4 of the Intact Stability Code (resolution
A.749(18)), the initial metacentric height GMo being corrected for free
surface measured at 0 degrees heel; and
.2 adopt
appropriate operational methods, where necessary, for the oil tanker to
comply with the above requirements.
4 Where operating methods are
necessary, simple operating instructions which supplement existing stability
information should be prepared for the master, including:
.1 the
number of tanks which may be slack under all conditions of liquid transfer;
and
.2 the tanks (cargo and
ballast) which may be slack under any specific condition of liquid transfer,
including possible ranges of cargo densities. The slack tanks may vary
during the liquid transfer operations and be of any combination which
satisfies the criteria.
5 In the context of this recommendation,
simple operating instructions to the ship's operating personnel mean
instructions which:
.1 are understandable to the
officer-in-charge of transfer operations;
.2 provide for planned sequences of cargo/ballast transfer
operations;
.3 allow comparisons
of attained and required stability using stability performance criteria in
graphical or tabular form;
.4
require no extensive mathematical calculations by the officer-in-charge;
.5 provide for corrective actions
to be taken by the officer-in-charge in case of departure from recommended
values and in case of emergency situations; and
.6 are prominently displayed in the approved trim
and stability booklet and at the cargo/ballast transfer control station and
in any computer software by which stability calculations are performed.