3.2 Damage assumptions
3.2.1 Damage should be assumed to occur anywhere in the vessel.s length between transverse watertight bulkheads.
3.2.2 The assumed extent of damage should be as follows:
- longitudinal extent:
- for a vessel the keel of which is laid or which is at a similar stage of construction1* before 22 November 2012:
with length (L) not greater than 43 m: 10% of L; and with length (L) greater than 43 m: 3 m plus 3% of L;
- for a vessel the keel of which is laid or which is at a similar stage of construction on or after 22 November 2012:
with length (L) not greater than 43 m: 10% of L;
with length (L) greater than 43 m and less than 80 m:
3 m plus 3% of L; and
with length (L) from 80 m to 100 m: 1/3L2/3;
- transverse extent:
- for a vessel the keel of which is laid or which is at a similar stage of construction before 22 November 2012:
760 mm measured inboard from the side of the vessel perpendicularly to the centreline at the level of the summer load waterline;
- for a vessel the keel of which is laid or which is at a similar stage of construction on or after 22 November 2012:
with length (L) less than 80 m: 760 mm; and
with length (L) from 80 m to 100 m: B/20, but not less than 760 mm;
The transverse extent should be measured inboard from the side of the vessel perpendicularly to the centreline at the level of the summer load waterline; and
- vertical extent:
from the underside of the cargo deck, or the continuation thereof, for the full depth of the vessel.
3.2.3 For a vessel the keel of which is laid or which is at a similar stage of construction:
- before 22 November 2012:
A transverse watertight bulkhead extending from the vessel's side to a distance inboard of 760 mm or more at the level of the summer load line joining longitudinal watertight bulkheads may be considered as a transverse watertight bulkhead for the purpose of the damage calculations.
- on or after 22 November 2012:
For a vessel with length (L) less than 80 m, a transverse watertight bulkhead extending from the vessel's side to a distance inboard of 760 mm or more at the level of the summer load line joining longitudinal watertight bulkheads may be considered as a transverse watertight bulkhead for the purpose of the damage calculations. For a vessel with length (L) from 80 m to 100 m, a transverse watertight bulkhead extending from the vessel's side to a distance inboard of B/20 or more (but not less than 760 mm) at the level of the summer load line joining longitudinal watertight bulkheads may be considered as a transverse watertight bulkhead for the purpose of the damage calculations.
3.2.2 The assumed extent of damage should be as follows:
longitudinal extent: vessels with the length (L) greater than 43 m, 3 m plus 3% of the vessel.s length. For those with length (L) not greater than 43 m, 10% of the vessel.s length,
transverse extent: transverse extent of damage should be assumed as 760 mm, measured inboard from the side of the vessel perpendicularly to the centreline at the level of the summer load waterline,
vertical extent: from the underside of the cargo deck, or the continuation thereof, for the full depth of the vessel.
3.2.3 A transverse watertight bulkhead extending from the vessel's side to a distance inboard of 760 mm or more at the level of the summer load line joining longitudinal watertight bulkheads may be considered as a transverse watertight bulkhead for the purpose of the damage calculations.
3.2.4 If pipes, ducts or tunnels are situated within the assumed extent of damage, arrangements should be made to ensure that progressive flooding cannot thereby extend to compartments other than those assumed to be floodable for each case of damage.
3.2.5 If damage of a lesser extent than that specified in 3.2.2 results in a more severe condition, such lesser extent should be assumed.
3.2.6 Where a transverse watertight bulkhead is located within the transverse extent of assumed damage and is stepped in way of a double bottom or side tank by more than 3.05 m, the double bottom or side tanks adjacent to the stepped portion of the transverse watertight bulkhead should be considered as flooded simultaneously.
3.2.7 If the distance between adjacent transverse watertight bulkheads or the distance between the transverse planes passing through the nearest stepped portions of the bulkheads is less than the longitudinal extent of damage given in 3.2.2.1, only one of these bulkheads should be regarded as effective for the purpose of 3.2.1.
1 A similar stage of construction means the stage at which:
- construction identifiable with a specific ship begins; and
- assembly of that ship has commenced comprising at least 50 tonnes or one per cent of the estimated mass of all structural material, whichever is less.
3.3 Damage stability criteria
3.3.1 The final waterline, taking into account
sinkage, heel and trim, should be below the lower edge of any opening through
which progressive flooding may take place. Such openings should include air
pipes and those which are capable of being 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 watertight
sliding doors and sidescuttles of the non-opening type.
3.3.2 In the final stage of flooding, the
angle of heel due to unsymmetrical flooding should not exceed 15°. This angle
may be increased up to 17° if no deck immersion occurs.
3.3.3 The stability in the final stage of
flooding should 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
100 mm within this range. Unprotected openings should not become immersed at
an angle of heel within the prescribed minimum range of residual stability
unless the space in question has been included as a floodable space in
calculations for damage stability. Within this range, immersion of any of the
openings referred to in 3.3.1 and any other openings capable of being closed
weathertight may be authorized.
3.3.4 The Administration should be satisfied
that the stability is sufficient during intermediate stages of
flooding.
3.4 Assumptions for calculating damage stability
3.4.1 Compliance with 3.3 should be confirmed by calculations which take into consideration the design characteristics of the vessel, the arrangements, configuration and permeability of the damaged compartments and the distribution, specific gravities and the free surface effect of liquids. MSC 82/24/Add.2
3.4.2 The permeability of compartments assumed to be damaged should be as follows:
Spaces | Permeability |
Appropriated to stores | 60 |
Occupied by accommodation | 95 |
Occupied by machinery | 85 |
Void spaces | 95 |
Intended for dry cargo | 95 |
The permeability of tanks should be consistent with the amount of liquid carried, as shown in the loading conditions specified in 3.1. The permeability of empty tanks should be assumed to be not less than 95.
3.4.3 The free surface effect should be calculated at an angle of heel of 5° for each individual compartment, or the effect of free liquid in a tank should be calculated over the range of positive residual righting arm, by assessing the shift of liquids by moment of transference calculations.
3.4.4 Free surface for each type of consumable liquid should be assumed for at least one transverse pair of tanks or a single centreline tank. The tank or tanks to be taken into account should be those where the effect of free surface is the greatest.
3.4.5 Alternatively, the actual free surface effect may be used provided the methods of calculation are acceptable to the Administration.
3.5 Subdivision
3.5.1 The machinery spaces and other working
and living spaces in the hull should be separated by watertight
bulkheads.
3.5.2 Arrangements made to maintain the
watertight integrity of openings in watertight subdivisions should comply with
the relevant provisions for cargo ships contained in chapter II-1 of the
Convention.
3.5.3 A collision bulkhead should be fitted
that complies with relevant provisions for cargo ships of chapter II-1 of the
Convention.
3.5.4 An afterpeak bulkhead should be fitted
and made watertight up to the freeboard deck. The afterpeak bulkhead may,
however, be stepped below the freeboard deck, provided the degree of safety of
the vessel as regards subdivision is not thereby diminished.