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:
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.1 ensure that an oil tanker:
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.1 in port, has the initial metacentric height
GMo, corrected for free surface measured at 0° heel, not less
than 0.15 m; and
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.2 at sea, complies with the requirements specified
in paragraphs 3.1.2.1 to 3.1.2. of the Intact Stability Code (resolution
A.749(18)), the initial metacentric height GMo being corrected for
free surface measured at 0° heel; and
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.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:
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.1 the number of tanks which may be slack under
all conditions of liquid transfer; and
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.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:
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.1 are understandable to the officer-in-charge
of transfer operations;
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.2 provide for planned sequences of cargo/ballast
transfer operations;
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.3 allow comparisons of attained and required
stability performance criteria in graphical or tabular form;
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.4 required no extensive mathematical calculations
by the officer-in-charge;
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.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
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.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.