PART IIAnalysis and Design (continued)
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.
Ballast and Bilge Systems
(2) Every floating platform shall have a ballast system so arranged that any ballast tank can be filled or emptied by any one of at least two ballast pumps or by controlled free flow.
(3) Each lower hull on a floating platform with two lower hulls shall be provided with at least two ballast pumps each with the capacity to fill or empty any ballast tank in that hull.
(4) The ballast system for a column-stabilized mobile platform shall be designed to prevent uncontrolled transfer of water between tanks or through sea-connected inlets or discharges in any one of the following situations:
(5) Ballast piping in a ballast system for a floating platform that leads from a pump to more than one tank shall be led from readily accessible manifolds.
(6) All power-operated sea inlets, discharge valves and ballast tank isolating valves on a floating platform shall be designed to close automatically on loss of control power and remain closed when power is re-established until specific action is taken to open them.
(7) Where crude oil is to be stored in a floating platform, the platform shall have enough ballast capacity, segregated from the crude storage, to be able to float at minimum operating draft with no crude oil on board.
(8) Every floating platform shall be provided with a main ballast control station equipped with
(a) an effective means of communication with other spaces that contain equipment relating to the operation of the ballast system;
(b) a ballast pump control and status system;
(c) a ballast valve control and status system;
(d) a tank level indicating system;
(e) a draft indicating system;
(f) emergency lighting;
(g) heel and trim indicators;
(h) bilge and flood alarms; and
(i) remote control indicators for watertight closing appliances.
(9) Every column-stabilized mobile platform shall be equipped with a secondary ballast control station equipped with
(b) a ballast pump control and status system;
(c) a ballast valve control and status system;
(d) a tank level indicating system;
(e) emergency lighting;
(f) heel and trim indicators; and
(g) a permanently mounted ballast schematic diagram.
(10) The main and secondary ballast control stations required by subsections (8) and (9) shall be located above the waterline in the final condition of equilibrium after flooding when the platform is in a damaged condition.
(11) Every column-stabilized mobile platform shall have a ballast system that is capable, with any ballast pump out of operation,
(a) of providing safe handling and operation of the platform under normal operating and transit conditions;
(b) of restoring the platform to a normal operating or transit draft and level trim from an inclination of 15 degrees in any direction; and
(c) of raising the platform from the deepest operating draft to severe storm draft within three hours.
(12) Every floating platform shall be equipped with a bilge system that has at least two bilge pumps connected to the bilge main and that is capable, under all conditions from upright to 15 degrees in any direction, of pumping or draining any watertight compartment except for those spaces permanently designated for the storage of fresh water, water ballast, fuel oil or liquid cargo and for which other effective means of pumping are provided.
(13) No floating platform shall be considered to comply with this section until the ballast and bilge system has been assessed through a failure modes and effects analysis.
Watertight Integrity of Floating Platforms
58 (1) The boundaries of watertight compartments in a floating platform shall contain no more openings than necessary for the operation of the platform and, where penetration of those boundaries is necessary for access, ventilation, piping and cables or any other similar purpose, arrangements shall be made to maintain the strength and watertight integrity of the boundaries.
(2) Every watertight boundary and associated closing appliance on a floating platform shall be of sufficient strength and tightness of closure to withstand without failure the pressure and other loads likely to occur in service.
(3) All watertight doors and hatches on a floating platform shall be operable locally from both sides of the associated bulkhead or deck.
(4) Side scuttles and windows on a floating platform shall be of the non-opening type, fitted with internal hinged deadlight covers.
(5) All pipes and ducts on a floating platform shall, where possible, be routed clear of those compartments that are vulnerable to penetration damage or, where such routing is not possible, positive means of closure of those pipes and ducts shall be provided for each watertight boundary.
(6) Every valve required at a watertight boundary on a floating platform shall be remotely operable from the ballast control station or by a mechanical means from another readily accessible position that is above the waterline in the final condition of equilibrium that could result when the platform is in a damaged condition.
(7) Every inlet or discharge port on a floating platform that is submerged at maximum operating draught shall be fitted with a valve that is remotely controlled from the ballast control station, and each such valve shall close automatically when the source of power fails, unless safety considerations require that it remain open.
(8) Every discharge port on a floating platform that penetrates a boundary to a compartment intended to be watertight shall be fitted with an automatic non-return valve and with a second such valve or with a device whereby the port may be closed from a position outside and above the compartment.
(9) Every door or hatch on a floating platform used to ensure the watertight integrity of internal access openings during the operation of the platform shall, while the platform is afloat, be equipped with an indicator at the ballast control station to indicate whether the door or hatch is open or closed.
(10) Every door or hatch on a floating platform that is normally closed while the platform is afloat shall be equipped
(11) All external openings on a floating platform, except manholes that are fitted with close-bolted watertight covers and that are kept permanently closed while the platform is afloat, shall, in the intact condition or in a damaged condition, be completely above any waterline associated with the platform being heeled because of wind forces.
(12) Every external opening on a floating platform that becomes wholly or partially submerged when the platform is at the maximum angle of heel that could occur while the platform meets the area ratio requirement for intact and damage stability set out in the Code referred to in subsection 56(9) or that may become intermittently submerged because of wave action when the platform is in a damaged condition shall
(a) be designed and constructed to withstand any sea condition without penetration;
(b) in the case of an opening that may become intermittently submerged when the platform is in a damaged condition,
(c) in the case of an external opening that cannot be quickly closed,
(d) in the case of a door or hatch that may be used during operation of the platform, be equipped with closing appliances that are operable locally from both sides of the bulkhead or deck;
(e) in the case of a door or hatch that may become intermittently submerged when the platform is in a damaged condition,
(i) be equipped with an indication system to show in the ballast control station the status of the closing appliances,
(ii) be self-closing on being submerged, or readily and quickly closable, and
(iii) bear a notice to the effect that the door or hatch is not to be left open during operation of the platform;
(f) in the case of a ventilator or ventilation intake or outlet that may be used during operation of the platform,
(g) in the case of a closing appliance that is not to be opened during operation of the platform, bear a notice to that effect;
(h) in the case of air pipes to a ballast tank, be equipped with an anti-flooding device; and
(i) in the case of a chain locker opening on a column-stabilized platform, except where the chain locker is kept full of water or is designed to be free-flooding, be fitted with a device that will prevent significant ingress of water in the event of submergence and with a suitable means for pumping out, both of which are remotely operable from a ballast control station.
(13) All of the closing appliances required by subsection (12) shall be able to withstand without failure any wave impact load to which they may be subjected.
(14) Every compartment on a floating platform required to remain watertight to comply with the intact and damage stability criteria described in section 56 shall incorporate a device suitably positioned to detect flooding and, where flooding occurs, trigger an alarm in a ballast control station.
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