Merchant Shipping Act, 1951 (Act No. 57 of 1951)

Schedules

Second Schedule

Protocol of 1978 Relating to the International Convention for the Safety of Life at Sea, 1974

Annex

Chapter II–1 : Construction — Subdivision and Stability, Machinery and Electrical Installations

Part B — Subdivision and Stability

Regulation 7 : Stability of ships in damaged condition
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(a)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 subparagraph (e) (i) of Regulation 6 of this Chapter the intact stability shall be adequate to withstand the flooding of those two adjacent main compartments.

 

Where the required factor of subdivision is 0,50 or less but more than 0,33 intact stability shall be adequate to withstand the flooding of any two adjacent main compartments.

Where the required factor of subdivision is 0,33 or less the intact stability shall be adequate to withstand the flooding of any three adjacent main compartments.

 

(b)        

(i)The requirements of paragraph (a) of this Regulation shall be determined by calculations which are in accordance with paragraphs (c), (d) and ( f ) of this Regulation 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.
(ii)Where it is proposed to fit decks, inner skins or longitudinal bulkheads of sufficient tightness to seriously restrict the flow of water, the Administration shall be satisfied that proper consideration is given to such restrictions in the calculations.
(iii)In cases where the Administration considers the range of stability in the damaged condition to be doubtful, it may require investigation thereof.

 

(c)For the purpose of making damage stability calculations the volume and surface permeabilities shall be in general as follows:

 

Spaces                                                Permeability

 

Appropriated to Cargo, Coal or Stores                60

Occupied by Accommodation                        95

Occupied by Machinery                        85

Intended for Liquids                                0 or 95

 

Higher surface permeabilities are to be assumed in respect of spaces which, in the vicinity of the damage waterplane, contain no substantial quantity of accommodation or machinery and spaces which are not generally occupied by any substantial quantity of cargo or stores.

 

(d)Assumed extent of damage shall be as follows:
(i)Longitudinal extent: 3,05 metres (10 feet) plus 3 per cent of the length of the ship, or 10,67 metres (35 feet) whichever is the less. Where the required factor of subdivision is 0,33 or less the assumed longitudinal extent of damage shall be increased as necessary so as to include any two consecutive main transverse watertight bulkheads;
(ii)transverse extent (measured inboard from the ship’s side, at right angles to the centre line at the level of the deepest subdivision load line): a distance of one-fifth of the breadth of the ship, as defined in Regulation 2 of this Chapter; and
(iii)vertical extent: from the base line upwards without limit.
(iv)If any damage of lesser extent than that indicated in subparagraphs (i), (ii) and (iii) of this paragraph would result in a more severe condition regarding heel or loss of metacentric height, such damage shall be assumed in the calculations.

 

(e)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 sel-facting, but in any case where controls to cross-flooding fittings are provided they shall be operable from above the bulkhead deck. These fittings together with their controls as well as the maximum heel before equalization shall be acceptable to the Administration. Where crossflooding fittings are required the time for equalization shall not exceed 15 minutes. Suitable information concerning the use of cross-flooding fittings shall be supplied to the master of the ship.

 

(f)The final conditions of the ship after damage and in the case of unsymmetrical flooding, after equalization measures have been taken shall be as follows:
(i)In the case of symmetrical flooding there shall be a positive residual metacentric height of at least 50 millimetres (2 inches) as calculated by the constant displacement method;
(ii)in the case of unsymmetrical flooding the total heel shall not exceed seven degrees, except that, in special cases, the Administration may allow additional heel due to the unsymmetrical moment, but in no case shall the final heel exceed fifteen degrees;
(iii)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 may require such investigations and arrangements as it considers necessary for the safety of the ship.

 

(g)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 be warned that excessive heeling might result should the ship sustain damage when in a less favourable condition.

 

(h)
(i)No relaxation from the requirements for damage stability may be considered by the Administration unless it is shown that the intact metacentric height in any service condition necessary to meet these requirements is excessive for the service intended.
(ii)Relaxations from the requirements for damage stability shall be permitted only in exceptional cases and subject to the condition that the Administration 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.