3.1 General
Taking into
account, as initial conditions before flooding, the standard loading conditions
required by the relevant provisions of Part B of the IS Code and the damage
assumptions in 3.2, the vessel should comply with the damage stability criteria
as specified in 3.3.
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: 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.
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.