Motion Response Characteristics
55. The motion response characteristics of every floating platform shall be determined by analytical methods or by model tests for the six degrees of freedom for all relevant operational, transit and survival drafts.
Stability of Mobile Platforms
56. (1) For the purpose of this section, “lightship”, in relation to a mobile platform, means a platform with all its permanently installed machinery, equipment and outfit, including permanent ballast, spare parts normally retained on board and liquids in machinery and piping at their normal working levels, but not including liquids in storage or in reserve supply tanks, items of consumable or variable loads, stores and crew and their effects.
(2) Subject to subsection (3), an inclining test shall be carried out to determine the lightship weight and the location of the centre of gravity on every mobile platform.
(3) Detailed weight calculations showing the differences of weight and centres of gravity may be used in lieu of the inclining test required by subsection (2), in respect of a surface or self-elevating mobile platform of a design that is identical with regard to hull form and arrangement to that of a platform for which an inclining test has been carried out, if the accuracy of the calculations is confirmed by a deadweight survey.
(4) Subject to subsection (6), during each five-year survey that is required and carried out by a classification society of a surface or self-elevating mobile platform, a deadweight survey shall be carried out and, where there is a significant discrepancy between the measurement obtained from that survey and the weight change as calculated from weight records,
(a) in the case of a surface platform, an inclining test shall be carried out; and
(b) in the case of a self-elevating platform, the allowable variable load in the elevated condition shall be adjusted in accordance with the deadweight survey and the stability in the floating mode shall be calculated.
(5) Subject to subsection (6), an inclining test shall be carried out during each five-year survey that is required and carried out by a classification society for every column-stabilized mobile platform, except that after the second inclining test, the subsequent tests need only be carried out during every alternate five-year survey if there was no significant discrepancy between the weight records and the results of the second test.
(6) An inclining test is not required pursuant to subsection (4) or (5) where the platform is equipped with instrumentation that is capable of accurately measuring or providing data that permit an accurate calculation of the centre of gravity.
(7) A comprehensive and up-to-date record shall be kept of every change to a mobile platform that involves a change in weight or position of weight.
(8) Where the weight of a mobile platform changes by more than 1 per cent of the lightship weight, a deadweight survey shall be carried out at the earliest opportunity and an up-to-date value of the lightship centre of gravity shall be recorded in the operations manual.
(9) Subject to subsections (10) to (13), the analysis of intact and damage stability of every mobile platform undertaken for the purpose of paragraph 40(1)(e) shall include a verification as to whether the platform complies with Chapter 3 of International Maritime Organization Code for the Construction and Equipment of Mobile Offshore Drilling Units, 1989.
(10) Every mobile platform shall be designed so that, in the intact condition, when subjected to the wind heeling moments described in the Code referred to in subsection (9), it has a static angle of heel of not more than 15 degrees in any direction.
(11) Every column-stabilized mobile platform shall be designed so that, in the intact condition, it has a metacentric height of at least 1 m when it is in the operating and transit draft and a metacentric height of at least 0.3 m in all other draft conditions.
(12) Every surface and self-elevating mobile platform shall be designed so that, in the intact condition, it has a metacentric height of at least 0.5 m.
(13) Every mobile platform shall be designed so that, in the damaged condition or where any compartment is flooded, the final angle of heel does not exceed 15 degrees in any direction and the area under the righting moment curve is at least equal to the area under the heeling moment curve.
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