8 Stability in damaged conditions (R 8)

Sufficient intact stability shall be provided in all service conditions so as to enable the ship to withstand the final stage of flooding of any one main compartment which is required to be within the floodable length. Where two adjacent main compartments are separated by a bulkhead which is stepped under the conditions of Regulation 7.6.1, the intact stability shall be adequate to withstand the flooding of those two adjacent compartments. Where the required factor of subdivision is 0,50, the intact stability shall be adequate to withstand the flooding of any two adjacent compartments. The requirements of subparagraph .1 shall be determined by calculations which are in accordance with paragraphs .3, .4 and .6 and which take into consideration the proportions and design characteristics of the ship and the arrangement and configuration of the damaged compartments. In making these calculations the ship is to be assumed in the worst anticipated service condition as regards stability. Where it is proposed to fit decks, inner skins or longitudinal bulkheads of sufficient tightness to seriously restrict the flow of water, proper consideration is to be given to such restrictions in the calculations. The stability required in the final condition after damage, and after equalisation where provided, shall be determined as follows: The positive residual righting lever curve shall have a minimum range of 15 ° beyond the angle of equilibrium. This range may be reduced to a minimum of 10 ° in cases where the area under the righting lever curve is that specified in subparagraph .2.3.2 multiplied by the ratio 15/range, where range is expressed in degrees. The area under the righting lever curve shall be at least 0,015 m-rad, measured from the angle of equilibrium to the lesser of: the angle at which progressive flooding occurs; 22 ° (measured from upright) in the case of one-compartment flooding, or 27 ° (measured from the upright) in the case of the simultaneous flooding of two adjacent compartments. A residual righting lever is to be obtained within the range of positive stability, taking into account the greatest of the following heeling moments: the crowding of all passengers towards one side; the launching of all fully loaded davit-launched survival craft on one side; due to wind pressure; as calculated by the formula: GZ(metres) = (heeling moment / displacment) + 0,04 However, in no case is the righting lever to be less than 0,10 metres. For the purpose of calculating the heeling moments in paragraph .2.3.3 the following assumptions shall be made: Moment due to crowding of passengers: four persons per square metre; a mass of 75 kg for each passenger; passengers shall be distributed on available deck areas towards one side of the ship on the decks where assembly stations are located and in such a way that they produce the most adverse heeling moment. Moment due to launching of all fully loaded davit-launched survival craft on one side: all lifeboats and rescue boats fitted on the side to which the ship has heeled after having sustained damage shall be assumed to be swung out fully loaded and ready for lowering; for lifeboats which are arranged to be launched fully loaded from the stowed position, the maximum heeling moment during launching shall be taken; a fully loaded davit-launched life-raft attached to each davit on the side to which the ship has heeled after having sustained damage shall be assumed to be swung out ready for lowering; persons not in the life-saving appliances which are swung out shall not provide either additional heeling or righting moment; life-saving appliances on the side of the ship opposite to the side to which the ship has heeled shall be assumed to be in a stowed position. Moments due to wind pressure: class B: a wind pressure of 120 N/m^(2) to be applied; classes C and D: a wind pressure of 80 N/m^(2) to be applied; the area applicable shall be the projected lateral area of the ship above the waterline corresponding to the intact condition; the moment arm shall be the vertical distance from a point at one half of the mean draught corresponding to the intact condition to the centre of gravity of the lateral area. When major progressive flooding occurs, that is, when it causes a rapid reduction in the righting lever of 0,04 metres or more, the righting lever curve is to be considered as terminated at the angle the progressive flooding occurs and the range and the area referred to in .2.3.1 and .2.3.2 should be measured to that angle. In cases where the progressive flooding is of limited nature that does not continue unabated and causes an acceptably slow reduction in righting lever of less than 0,04 metres, the remainder of the curve shall be partially truncated by assuming that the progressively flooded space is so flooded from the beginning. In intermediate stages of flooding, the maximum righting lever shall be at least 0,05 metres and the range of positive righting levers shall be at least 7. In all cases, only one breach in the hull and only one free surface need be assumed. For the purpose of making damaged stability calculations the volume and surface permeabilities shall be as follows: Whichever results in more severe requirements. Spaces Permeability (%) Appropriated to cargo or stores 60 Occupied by accommodations 95 Occupied by machineries 85 Intended for liquids 0 or 95 Higher surface permeabilities are to be assumed in respect of spaces which, in the vicinity of the damaged waterplane, contain no substantial quantity of accommodation or machinery and spaces which are not generally occupied by any substantial quantity of cargo or stores. Assumed extent of damage shall be as follows: longitudinal extent: 3,0 metres plus 3 % of the length of the ship, or 11,0 metres or 10 % of the length of the ship, whichever is less; transverse extent (measured inboard from the ship's side, at right angles to the centreline at the level of the deepest subdivision load line): a distance of one fifth of the breadth of the ship; and vertical extent: from the base line upwards without limit; if any damage of lesser extent than that indicated in .4.1, .4.2 or .4.3 would result in a more severe condition regarding heel or loss of metacentric height, such damage shall be assumed in the calculations. Unsymmetrical flooding is to be kept to a minimum consistent with efficient arrangements. Where it is necessary to correct large angles of heel, the means adopted shall, where practicable, be self-acting, but in any case where controls to cross-flooding fittings are provided they shall be operable from above the bulkhead deck. For new class B, C and D ships the maximum angle of heel after flooding but before equalisation shall not exceed 15 °. Where cross-flooding fittings are required the time for equalisation shall not exceed 15 minutes. Suitable information concerning the use of cross-flooding fittings shall be supplied to the master of the ship. The final conditions of the ship after damage and, in the case of unsymmetrical flooding, after equalisation measures have been taken shall be as follows: in the case of symmetrical flooding there shall be a positive residual metacentric height of at least 50 mm as calculated by the constant displacement method; unless provided otherwise in paragraph .6.2b, in the case of unsymmetrical flooding the angle of heel for one-compartment flooding shall not exceed 7 ° for class B ships (new and existing) and 12 ° for classes C and D ships (new). For the simultaneous flooding of two adjacent compartments, a heel of 12 ° may be permitted for existing and new class B ships, provided that the factor of subdivision is nowhere greater than 0,50 in that part of the ship that is flooded; for existing class B non ro-ro passenger ships, constructed before 29 April 1990, in the case of unsymmetrical flooding, the angle shall not exceed 7 °, except that in exceptional cases the Administration may allow additional heel due to the unsymmetrical moment, but in no case shall the final heel exceed 15; in no case shall the margin line be submerged in the final stage of flooding. If it is considered that the margin line may become submerged during an intermediate stage of flooding, the Administration of the flag State may require such investigations and arrangements as it considers necessary for the safety of the ship. The master of the ship shall be supplied with the data necessary to maintain sufficient intact stability under service conditions to enable the ship to withstand the critical damage. In the case of ships requiring cross-flooding, the master of the ship shall be informed of the conditions of stability on which the calculations of heel are based and shall be warned that excessive heeling might result should the ship sustain damage when in a less favourable condition. The data referred to in paragraph .7 to enable the master to maintain sufficient intact stability shall include information which indicates the maximum permissible height of the ship's centre of gravity above keel (KG), or alternatively the minimum permissible metacentric height (GM), for a range of draughts or displacements sufficient to include all service conditions. The information shall show the influence of various trims taking into account the operational limits. Each ship shall have scales of draughts marked clearly at the bow and stern. In the case where the draught marks are not located where they are easily readable, or operational constraints for a particular trade make it difficult to read the draught marks, then the ship shall also be fitted with a reliable draught indicating system by which the bow and stern draughts can be determined. On completion of loading of the ship and prior to its departure, the master shall determine the ship's trim and stability and also ascertain and record that the ship is in compliance with stability criteria in the relevant regulations. The determination of the ship's stability shall always be made by calculation. An electronic loading and stability computer or equivalent means may be used for this purpose. No relaxation from the requirements for damage stability may be considered by the Administration of the flag State unless it is shown that the intact metacentric height in any service condition necessary to meet these requirements is excessive for the service intended. Relaxations from the requirements for damage stability shall be permitted only in exceptional cases and subject to the condition that the Administration of the flag State is to be satisfied that the proportions, arrangements and other characteristics of the ship are the most favourable to stability after damage which can practically and reasonably be adopted in the particular circumstances.

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Source: EUR-Lex (Cellar) · retrieved 2026-11-10 · Text as adopted (Official Journal); later amendments are not incorporated in this text.