| | PBz shall be calculated as follows: |
|
|
| | PBz = (14.5 – 67 z/DS) (z/DS) |
|
| |
| | PBz = 0.78 + 1.1 (z/DS – 0.1) |
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| |
| | PBz shall not be taken greater than 1. |
|
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| 10 This regulation uses a simplified probabilistic approach where a summation is carried out over the contributions to the mean outflow from each cargo tank. For certain designs such as those characterized by the occurrence of steps/recesses in bulkheads/decks and for sloping bulkheads and/or a pronounced hull curvature, more rigorous calculations may be appropriate. In such cases one of the following calculation procedures may be applied: |
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| .1 | The probabilities referred to in 8 and 9 above may be calculated with more precision through application of hypothetical sub-compartments.* |
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| * *Refer to the Explanatory Notes on matters related to the accidental oil outflow performance, adopted by the Organization by resolution MEPC.122(52). |
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| .2 | The probabilities referred to in 8 and 9 above may be calculated through direct application of the probability density functions contained in the Guidelines referred to in regulation 19.5. |
|
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| .3 | The oil outflow performance may be evaluated in accordance with the method described in the Guidelines referred to in regulation 19.5. |
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| 11 The following provisions regarding piping arrangements shall apply: |
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| .1 | Lines of piping that run through cargo tanks in a position less than 0.30Bs from the ship’s side or less than 0.30Ds from the ship’s bottom shall be fitted with valves or similar closing devices at the point at which they open into any cargo tank. These valves shall be kept closed at sea at any time when the tanks contain cargo oil, except that they may be opened only for cargo transfer needed for essential cargo operations. |
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| .2 | Credit for reducing oil outflow through the use of an emergency rapid cargo transfer system or other system arranged to mitigate oil outflow in the event of an accident may be taken into account only after the effectiveness and safety aspects of the system are approved by the Organization. Submittal for approval shall be made in accordance with the provisions of the Guidelines referred to in regulation 19.5. |
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| 1 For the purpose of calculating hypothetical oil outflow from oil tankers in accordance with regulations 25 and 26, three dimensions of the extent of damage of a parallelepiped on the side and bottom of the ship are assumed as follows. In the case of bottom damages two conditions are set forth to be applied individually to the stated portions of the oil tanker. |
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| 1 | Longitudinal extent(lc): |
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| | 1/3 L2/3 or 14.5 metres, whichever is less. |
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| 2 | Transverse extent (tc) (inboard from the ship’s side at right angles to the centreline at the level corresponding to the assigned summer freeboard): |
|
| | B/5 or 11.5 metres, whichever is less |
|
| | From the base line upwards without limit |
|
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| | For 0.3L from the forward perpendicular of the ship |
| | Any other part of the ship |
|
| 1 | Longitudinal extent (ls): |
|
| | | L/10 or 5 metres, whichever is less |
|
| | B/6 or 10 metres, whichever is less but not less than 5 metres |
| |
| 3 | Vertical extent from the base line (vs): |
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| | B/15 or 6 metres, whichever is less |
| |
| 2 Wherever the symbols given in this regulation appear in this chapter, they have the meaning as defined in this regulation. |
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| Hypothetical outflow of oil |
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| 1 The hypothetical outflow of oil in the case of side damage (Oc) and bottom damage (Os) shall be calculated by the following formulae with respect to compartments breached by damage to all conceivable locations along the length of the ship to the extent as defined in regulation 24 of this Annex. |
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| |
| |
| |
| | Os = 1/3 (∑ ZiWi + ∑ ZiCi) |
|
| |
| | | = | volume of a wing tank in cubic metres assumed to be breached by the damage as specified in regulation 24 of this Annex; Wi for a segregated ballast tank may be taken equal to zero. |
|
|
| | | = | volume of a centre tank in cubic metres assumed to be breached by the damage as specified in regulation 24 of this Annex; Ci for a segregated ballast tank may be taken equal to zero. |
|
|
| | | = | 1 − bi/tc when bi is equal to or greater than tc, Ki shall be taken equal to zero. |
|
|
| | | = | 1 − hi/vs, when hi is equal to or greater than vs, Zi shall be taken equal to zero. |
|
|
| | | = | width of wing tank in metres under consideration measured inboard from the ship’s side at right angles to the centreline at the level corresponding to the assigned summer freeboard. |
|
|
| | | = | minimum depth of the double bottom in metres under consideration; where no double bottom is fitted hi shall be taken equal to zero. |
|
|
| | Whenever symbols given in this paragraph appear in this chapter, they have the meaning as defined in this regulation. |
|
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| 2 If a void space or segregated ballast tank of a length less than lc as defined in regulation 24 of this Annex is located between wing oil tanks, Oc in formula (I) may be calculated on the basis of volume Wi being the actual volume of one such tank (where they are of equal capacity) or the smaller of the two tanks (if they differ in capacity) adjacent to such space, multiplied by Si as defined below and taking for all other wing tanks involved in such collision the value of the actual full volume. |
|
|
| | = | length in metres of void space or segregated ballast tank under consideration. |
|
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| | .1 | Credit shall only be given in respect of double bottom tanks which are either empty or carrying clean water when cargo is carried in the tanks above. |
|
|
| | .2 | Where the double bottom does not extend for the full length and width of the tank involved, the double bottom is considered non-existent and the volume of the tanks above the area of the bottom damage shall be included in formula (II) even if the tank is not considered breached because of the installation of such a partial double bottom. |
|
|
| | .3 | Suction wells may be neglected in the determination of the value hi provided such wells are not excessive in area and extend below the tank for a minimum distance and in no case more than half the height of the double bottom. If the depth of such a well exceeds half the height of the double bottom, hi shall be taken equal to the double bottom height minus the well height. |
|
|
| | | Piping serving such wells if installed within the double bottom shall be fitted with valves or other closing arrangements located at the point of connection to the tank served to prevent oil outflow in the event of damage to the piping. Such piping shall be installed as high from the bottom shell as possible. These valves shall be kept closed at sea at any time when the tank contains oil cargo, except that they may be opened only for cargo transfer needed for the purpose of trimming of the ship. |
|
|
| 4 In these case where bottom damage simultaneously involves four centre tanks, the value of Os may be calculated according to the formula: |
|
| | Os = 1/4 (∑ ZiWi + ∑ ZiCi) |
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| |
| 5 An Administration may credit as reducing oil outflow in case of bottom damage, an installed cargo transfer system having an emergency high suction in each cargo oil tank, capable of transferring from a breached tank or tanks to segregated ballast tanks or to available cargo tankage if it can be assured that such tanks will have sufficient ullage. Credit for such a system would be governed by ability to transfer in two hours of operation oil equal to one half of the largest of the breached tanks involved and by availability of equivalent receiving capacity in ballast or cargo tanks. The credit shall be confined to permitting calculation of Os according to formula (III). The pipes for such suctions shall be installed at least at a height not less than the vertical extent of the bottom damage vs. The Administration shall supply the Organization with the information concerning the arrangements accepted by it, circulation to other Parties to the Convention. |
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| 6 This regulation does not apply to oil tankers delivered on or after 1 January 2010, as defined in regulation 1.28.8. |
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| Limitations of size and arrangement of cargo tanks |
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| 1 Except as provided in paragraph 7 below: |
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| 1. | every oil tanker of 150 gross tonnage and above delivered after 31 December 1979, as defined in regulation 1.28.2; and |
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|
| 2. | every oil tanker of 150 gross tonnage and above delivered on or before 31 December 1979, as defined in regulation 1.28.1, which falls into either of the following categories: |
|
|
| .1 | a tanker, the delivery of which is after 1 January 1977; or |
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| .2 | a tanker to which both the following conditions apply: |
|
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| .1 | delivery is not later than 1 January 1977; and |
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| .2 | the building contract is placed after 1 January 1974, or in cases where no building contract has previously been placed, the keel is laid or the tanker is at a similar stage of construction after 30 June 1974, |
|
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| shall comply with the provisions of this regulation. |
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2 Cargo tanks of oil tankers shall be of such size and arrangements that the hypothetical outflow Oc or Os calculated in accordance with the provisions of regulation 25 of this Annex anywhere in the length of the ship does not exceed 30,000 cubic metres or 400 whichever is the greater, but subject to a maximum of 40,000 cubic metres. |
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| 3 The volume of any one wing cargo oil tank of an oil tanker shall not exceed 75 per cent of the limits of the hypothetical oil outflow referred to in paragraph 2 of this regulation. The volume of any one centre cargo oil tank shall not exceed 50,000 cubic metres. However, in segregated ballast oil tankers as defined in regulation 18 of this Annex, the permitted volume of a wing cargo oil tank situated between two segregated ballast tanks, each exceeding lc in length, may be increased to the maximum limit of hypothetical oil outflow provided that the width of the wing tanks exceeds tc. |
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| 4 The length of each cargo tank shall not exceed 10 m or one of the following values, whichever is the greater: |
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| .1 | where no longitudinal bulkhead is provided inside the cargo tanks: |
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|
| |
| .2 | where a centreline longitudinal bulkhead is provided inside the cargo tanks: |
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|
|
| .3 | where two or more longitudinal bulkheads are provided inside the cargo tanks: |
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|
| .1 | for wing cargo tanks: 0.2L |
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|
| .2 | for centre cargo tanks: |
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|
| .1 | if is equal to or greater than one fifth: 0.2L |
|
|
| .2 | if is less than one fifth: |
|
|
| — | where no centreline longitudinal bulkhead is provided: |
|
|
|
| — | where a centreline longitudinal bulkhead is provided: |
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|
|
| .4 | bi is the minimum distance from the ship’s side to the outer longitudinal bulkhead of the tank in question measured inboard at right angles to the centreline at the level corresponding to the assigned summer freeboard. |
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| 5 In order not to exceed the volume limits established by paragraphs 2, 3 and 4 of this regulation and irrespective of the accepted type of cargo transfer system installed, when such system interconnects two or more cargo tanks, valves or other similar closing devices shall be provided for separating the tanks from each other. These valves or devices shall be closed when the tanker is at sea. |
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| 6 Lines of piping which run through cargo tanks in a position less than tc from the ship’s side or less than vc from the ship’s bottom shall be fitted with valves or similar closing devices at the point at which they open into any cargo tank. These valves shall be kept closed at sea at any time when the tanks contain cargo oil, except that they may be opened only for cargo transfer needed for the purpose of trimming of the ship. |
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| 7 This regulation does not apply to oil tankers delivered on or after 1 January 2010, as defined in regulation 1.28.8. |
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| 1 Every oil tanker of 5,000 tonnes deadweight and above delivered on or after 1 February 2002, as defined in regulation 1.28.7, shall comply with the intact stability criteria specified in paragraphs 1.1 and 1.2 of this regulation, as appropriate, for any operating draught under the worst possible conditions of cargo and ballast loading, consistent with good operational practice, including intermediate stages of liquid transfer operations. Under all conditions the ballast tanks shall be assumed slack. |
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| .1 | In port, the initial metacentric height GMo, corrected for the free surface measured at 0° heel, shall be not less than 0.15 m; |
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|
| .2 | At sea, the following criteria shall be applicable: |
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|
| .1 | the area under the righting lever curve (GZ curve) shall be not less than 0.055 m.rad up to Ɵ = 30° angle of heel and not less than 0.09 m.rad up to Ɵ = 40° or other angle of flooding Ɵf* if this angle is less than 40°. Additionally, the area under the righting lever curve (GZ curve) between the angles of heel of 30° and 40° or between 30° and Ɵf, if this angle is less than 40°, shall be not less than 0.03°m.rad; |
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| * Ɵf is the angle of heel at which openings in the hull superstructures or deckhouses which cannot be closed weather tight, immerse. In applying this criterion, small openings through which progressive flooding cannot take place need not be considered as open. |
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| .2 | the righting lever GZ shall be at least 0.20 m at an angle of heel equal to or greater than 30°; |
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|
| .3 | the maximum righting arm shall occur at an angle of heel preferably exceeding 30° but not less than 25°; and |
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|
| .4 | the initial metacentric height GMo, corrected for free surface measured at 0° heel, shall be not less than 0.15 m. |
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|
| 2 The requirements of paragraph 1 of this regulation shall be met through design measures. For combination carriers simple supplementary operational procedures may be allowed. |
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| 3 Simple supplementary operational procedures for liquid transfer operations referred to in paragraph 2 of this regulation shall mean written procedures made available to the master which: |
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| .1 | are approved by the Administration; |
|
|
| .2 | indicate those cargo and ballast tanks which may, under any specific condition of liquid transfer and possible range of cargo densities, be slack and still allow the stability criteria to be met. The slack tanks may vary during the liquid transfer operations and be of any combination provided they satisfy the criteria; |
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|
| .3 | will be readily understandable to the officer-in-charge of liquid transfer operations; |
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|
| .4 | provide for planned sequences of cargo/ballast transfer operations; |
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|
| .5 | allow comparisons of attained and required stability using stability performance criteria in graphical or tabular form; |
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|
| .6 | require no extensive mathematical calculations by the officer-in-charge; |
|
|
| .7 | 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 |
|
|
| .8 | 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. |
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|
| Subdivision and damage stability |
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| 1 Every oil tanker delivered after 31 December 1979, as defined in regulation 1.28.2, of 150 gross tonnage and above, shall comply with the subdivision and damage stability criteria as specified in paragraph 3 of this regulation, after the assumed side or bottom damage as specified in paragraph 2 of this regulation, for any operating draught reflecting actual partial or full load conditions consistent with trim and strength of the ship as well as relative densities of the cargo. Such damage shall be applied to all conceivable locations along the length of the ship as follows: |
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| .1 | in tankers of more than 225 metres in length, anywhere in the ship’s length; |
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|
| .2 | in tankers of more than 150 metres, but not exceeding 225 metres in length, anywhere in the ship’s length except involving either after or forward bulkhead bounding the machinery space located aft. The machinery space shall be treated as a single floodable compartment; and |
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|
| .3 | in tankers not exceeding 150 metres in length, anywhere in the ship’s length between adjacent transverse bulkheads with the exception of the machinery space. For tankers of 100 metres or less in length where all requirements of paragraph 3 of this regulation cannot be fulfilled without materially impairing the operational qualities of the ship, Administrations may allow relaxations from these requirements. |
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|
| Ballast conditions where the tanker is not carrying oil in cargo tanks, excluding any oil residues, shall not be considered. |
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| 2 The following provisions regarding the extent and the character of the assumed damage shall apply: |
|
|
| or 14.5 metres, whichever is less |
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| 2 | Transverse extent (inboard from the ship’s side at right angles to the centreline at the level of the summer load line): |
|
| or 11.5 metres, whichever is less |
|
| | From the moulded line of the bottom shell plating at centreline, upwards without limit |
|
| |
| | For 0.3L from the forward perpendicular of the ship |
| | Any other part of the ship |
|
| or 14.5 metres, whichever is less |
| or 5 metres, whichever is less |
|
| or 10 metres, whichever is less |
| or 5 metres, whichever is less |
|
| or 6 metres, whichever is less, measured from the moulded line of the bottom shell plating at centreline |
| or 6 metres, whichever is less, measured from the moulded line of the bottom shell plating at centreline |
|
| .3 | If any damage of a lesser extent than the maximum extent of damage specified in subparagraphs 2.1 and 2.2 of this paragraph would result in a more severe condition, such damage shall be considered. |
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|
| .4 | Where the damage involving transverse bulkheads is envisaged as specified in subparagraphs 1.1 and 1.2 of this regulation, transverse watertight bulkheads shall be spaced at least at a distance equal to the longitudinal extent of assumed damage specified in subparagraph 2.1 of this paragraph in order to be considered effective. Where transverse bulkhead are spaced at a lesser distance, one or more of these bulkheads within such extent of damage shall be assumed as non-existent for the purpose of determining flooded compartments. |
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|
| .5 | Where the damage between adjacent transverse watertight bulkheads is envisaged as specified in subparagraph 1.3 of this regulation, no main transverse bulkhead or a transverse bulkhead bounding side tanks or double bottom tanks shall be assumed damaged, unless: |
|
|
| .1 | the spacing of the adjacent bulkheads is less than the longitudinal extent of assumed damage specified in subparagraph 2.1 of this paragraph; or |
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|
| .2 | there is a step or recess in a transverse bulkhead of more than 3.05 metres in length, located within the extent of penetration of assumed damage. The step formed by the after peak bulkhead and after peak top shall not be regarded as a step for the purpose of this regulation. |
|
|
| .6 | If pipes, ducts or tunnels are situated within the assumed extent of damage, arrangements shall be made so that progressive flooding cannot thereby extend to compartments other than those assumed to be floodable for each case of damage. |
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|
| 3 Oil tankers shall be regarded as complying with the damage stability criteria if the following requirements are met: |
|
| .1 | The final waterline, taking into account sinkage, heel and trim, shall be below the lower edge of any opening through which progressive flooding may take place. Such openings shall include air-pipes and those which are closed by means of weathertight doors or hatch covers and may exclude those openings closed by means of watertight manhole covers and flush scuttles, small watertight cargo tank hatch covers which maintain the high integrity of the deck, remotely operated sliding watertight doors, hinged watertight access doors with open/closed indication locally and at the navigation bridge, of the quick-acting or single-action type that are normally closed at sea, hinged watertight doors that are permanently closed at sea, and sidescuttles of the non-opening type. |
|
|
| .2 | In the final stage of flooding, the angle of heel due to unsymmetrical flooding shall not exceed 25°, provided that this angle may be increased up to 30° if no deck edge immersion occurs. |
|
|
| .3 | The stability in the final stage of flooding shall be investigated and may be regarded as sufficient if the righting lever curve has at least a range of 20° beyond the position of equilibrium in association with a maximum residual righting lever of at least 0.1 metre within the 20° range; the area under the curve within this range shall not be less than 0.0175 metre radians. Unprotected openings shall not be immersed within this range unless the space concerned is assumed to be flooded. Within this range, the immersion of any of the openings listed in subparagraph 3.1 of this paragraph and other openings capable of being closed watertight may be permitted. |
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|
| .4 | The Administration shall be satisfied that the stability is sufficient during intermediate stages of flooding. |
|
|
| .5 | Equalization arrangements requiring mechanical aids such as valves or cross-levelling pipes, if fitted, shall not be considered for the purpose of reducing an angle of heel or attaining the minimum range of residual stability to meet the requirements of subparagraphs 3.1, 3.2 and 3.3 of this paragraph and sufficient residual stability shall be maintained during all stages where equalization is used. Spaces which are linked by ducts of a large cross-sectional area may be considered to be common. |
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|
| 4 The requirements of paragraph 1 of this regulation shall be confirmed by calculations which take into consideration the design characteristics of the ship, the arrangements, configuration and contents of the damaged compartments; and the distribution, relative densities and the free surface effect of liquids. The calculations shall be based on the following: |
|
| .1 | Account shall be taken of any empty or partially filled tank, the relative density of cargoes carried, as well as any outflow of liquids from damaged compartments. |
|
|
| .2 | The permeabilities assumed for spaces flooded as a result of damage shall be as follows: |
|
|
| |
| |
| | Occupied by accommodation |
|
| |
| |
| |
| | Intended for consumable liquids |
|
| | * The permeability of partially filled compartments shall be consistent with the amount of liquid carried in the compartment. Whenever damage penetrates a tank containing liquids, it shall be assumed that the contents are completely lost from that compartment and replaced by salt water up to the level of the final plane of equilibrium. |
|
| | Intended for other liquids |
|
| | * The permeability of partially filled compartments shall be consistent with the amount of liquid carried in the compartment. Whenever damage penetrates a tank containing liquids, it shall be assumed that the contents are completely lost from that compartment and replaced by salt water up to the level of the final plane of equilibrium. |
|
| .3 | The buoyancy of any superstructure directly above the side damage shall be disregarded. The unflooded parts of superstructures beyond the extent of damage, however, may be taken into consideration provided that they are separated from the damaged space by watertight bulkheads and the requirements of subparagraph .1 of this regulation in respect of these intact spaces are complied with. Hinged watertight doors may be acceptable in watertight bulkheads in the superstructure. |
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|
| .4 | The free surface effect shall be calculated at an angle of heel of 5° for each individual compartment. The Administration may require or allow the free surface corrections to be calculated at an angle of heel greater than 5° for partially filled tanks. |
|
|
| .5 | In calculating the effect of free surfaces of consumable liquids it shall be assumed that, for each type of liquid at least one transverse pair or a single centreline tank has a free surface and the tank or combination of tanks to be taken into account shall be those where the effect of free surface is the greatest. |
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|
| 5 The master of every oil tanker to which this regulation applies and the person in charge of a non-self-propelled oil tanker, to which this regulation applies shall be supplied in a approved form with: |
|
| .1 | information relative to loading and distribution of cargo necessary to ensure compliance with the provisions of this regulation; and |
|
|
| .2 | data on the ability of the ship to comply with damage stability criteria as determined by this regulation, including the effect of relaxations that may have been allowed under subparagraph 1.3 of this regulation. |
|
|
| 6 All oil tankers shall be fitted with a stability instrument, capable of verifying compliance with intact and damage stability requirements approved by the Administration having regard to the performance standards recommended by the Organization*: |
| * Refer to part B, chapter 4, of the International Code on Intact Stability, 2008 (2008 IS Code), as amended; the Guidelines for the Approval of Stability Instruments (MSC.1/Circ.1229), annex, section 4, as amended; and the technical standards defined in part 1 of the Guidelines for verification of damage stability requirements for tankers (MSC.1/Circ.1461). |
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| .1 | oil tankers constructed before 1 January 2016 shall comply with this regulation at the first scheduled renewal survey of the ship on or after 1 January 2016 but not later than 1 January 2021; |
|
|
| .2 | notwithstanding the requirements of subparagraph .1 a stability instrument fitted on an oil tanker constructed before 1 January 2016 need not be replaced provided it is capable of verifying compliance with intact and damage stability, to the satisfaction of the Administration; and |
|
|
| .3 | for the purposes of control under regulation 11, the Administration shall issue a document of approval for the stability instrument. |
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