Section
1 Ship Survival Capability And Location Of Cargo Tanks
1.1 General
1.1.1 The requirements of this Chapter, except for requirement Pt 11, Ch 2, 1.1 General 1.1.3on ship unit type
description, are not classification requirements. However, in cases where LR is
requested to do so by an Owner, Operator or Duty Holder, the requirements of this
Chapter will be applied, together with any amendments or interpretations adopted by
the appropriate National Authority.
Reference should be made to the Guidelines for Uniform Application of
the Survival Requirements of the Bulk Chemical Code and the Gas Carrier
Code.
1.1.2 Ship units shall survive the hydrostatic effects of flooding following
assumed hull damage caused by some external force. In addition, to safeguard the
ship unit and the environment, the cargo tanks shall be protected from penetration
in the case of minor damage to the ship unit resulting, for example, from contact
with a shuttle tanker, offshore support vessel or tug, by locating them at specified
minimum distances inboard from the shell plating of the ship unit. Both the damage
to be assumed and the proximity of the tanks to the shell of the ship unit should be
dependent upon the degree of hazard presented by the product to be carried. In
addition, the proximity of the cargo tanks to the shell of the ship unit shall be
dependent upon the volume of the cargo tank.
1.1.3 Ship units subject to this Part shall be designed to Type
2G standard. Type 2G is defined as a ship unit intended for the storage of
liquefied hydrocarbon gases as indicated in Pt 11, Ch 19 Summary of Minimum Requirements, that require significant preventive measures to
preclude their escape.
1.2 Freeboard and stability
1.2.1 Ship units subject to this Part may be assigned the minimum freeboard
permitted by the International Convention on Load Lines in force. However, the
draught associated with the assignment shall not be greater than the maximum draught
otherwise permitted by these Rules.
1.2.2 The stability of the ship unit, in all sea-going conditions including
inspection/maintenance, ballasting and during loading and unloading cargo, shall
comply with the requirements of the International Code on Intact Stability.
1.2.3 When calculating the effect of free surfaces of consumable liquids for
loading conditions, it shall be assumed that, for each type of liquid, at least one
transverse pair or a single centre tank has a free surface. The tank or combination
of tanks to be taken into account shall be those where the effect of free surfaces
is the greatest. The free surface effect in undamaged compartments shall be
calculated by a method according to the International Code on Intact
Stability
1.2.4 Solid ballast should not normally be used in double bottom spaces in the
cargo area. Where, however, because of stability considerations, the fitting of
solid ballast in such spaces becomes unavoidable, its disposition shall be governed
by the need to enable access for inspection and to ensure that the impact loads
resulting from bottom damage are not directly transmitted to the cargo tank
structure.
1.2.5 The Operator of the ship unit shall be supplied with a loading and
stability information booklet. This booklet shall contain details of typical service
and inspection/maintenance conditions, loading, unloading and ballasting operations,
provisions for evaluating other conditions of loading and a summary of the survival
capabilities of the ship unit.
In addition, the booklet shall contain sufficient information to enable
the Operator to load and operate the ship unit in a safe and seaworthy manner.
See also
Pt 1, Ch 2 Classification Regulations
List of abbreviations and Pt 10, Ch 3, 1.2 Loading guidance .
In addition, the Operator is to be given an approved stability
instrument to assess the intact stability and the damage stability condition
according to the standard damage cases and the actual damage condition of the ship
unit. The stability instrument input data and output results have to be approved by
the Administration.
1.2.6 Damage survival capability shall be investigated on the basis of loading
information submitted to the Administration for all anticipated conditions of
loading and variations in draught and trim. This shall include ballast and, where
applicable, cargo heel.
1.3 Damage assumptions
1.3.1 The assumed maximum extent of damage shall be as shown in Table 2.1.1 Assumed maximum extent of
damage.
Table 2.1.1 Assumed maximum extent of
damage
| Location of damage
|
Assumed maximum extent of
damage
|
| 1. Side damage
|
To any part of the ship unit
|
| 1.1 Longitudinal
extent
|
1/3L
2/3 or 14,5 m, whichever is less
|
| 1.2 Transverse extent
measured inboard from the moulded line of the outer shell at
right angles to the centreline at the level of the summer load
line
|
B/5 or 11,5 m, whichever is less
|
| 1.3 Vertical extent from
the moulded line of the outer shell at right angles to the
centreline at the level of the summer load line
|
Upwards, without limit
|
| 2. Bottom damage
|
For 0,3L from the
forward perpendicular of the ship unit
|
To any other part of the
ship unit
|
| 2.1 Longitudinal
extent
|
1/3L
2/3 or 14,5 m, whichever is less
|
1/3L
2/3 or 14,5 m, whichever is less
|
| 2.2 Transverse
extent
|
B/6 or 10 m, whichever is less
|
B/6 or 5 m, whichever is less
|
| 2.3 Vertical
extent
|
B/15 or 2 m, whichever is less measured from the moulded
line of the bottom shell plating at centreline, see
Pt 11, Ch 2, 1.4 Location of cargo tanks 1.4.3
|
B/15 or 2 m, whichever is less measured from the moulded
line of the bottom shell plating at centreline, see
Pt 11, Ch 2, 1.4 Location of cargo tanks 1.4.3
|
1.4 Location of cargo tanks
1.4.1 Cargo tanks shall be located at the following distances inboard:
Type 2G ship unit: from the moulded line of the bottom shell at
centreline not less than the vertical extent of damage specified in Pt 11, Ch 2, 1.3 Damage assumptions in Table 2.1.1 Assumed maximum extent of
damage and nowhere
less than ‘ d’ ( see
Figure 2.1.6 Cargo tank location
requirements, centreline profile, Type 2G ship units and Figure 2.1.7 Cargo tank location
requirements, transverse sections, Type 2G ship units), where ‘ d’ is as
follows:
- for V
c below or equal to 1000 m3, d = 0,80 m
- for 1000 m3 < V
c < 5000 m3,
d = 0,75 +
V
c × 0,20/4000
- for 5000 m3 ≤ V
c < 30 000 m3,
d = 0,8 +
V
c/25 000
- for V
c ≥ 30 000 m3, d = 2 m,
where
V
c corresponds to 100 per cent of the gross design volume of
the individual cargo tank at 20°C, including domes and appendages. For
the purpose of cargo tank protective distances, the cargo tank volume is
the aggregate volume of all the parts of tank that have a common
bulkhead(s).
NOTE
‘d’ is
measured at any cross-section at a right angle from the moulded line of
outer shell.
Figure 2.1.6 Cargo tank location
requirements, centreline profile, Type 2G ship units
Figure 2.1.7 Cargo tank location
requirements, transverse sections, Type 2G ship units
1.4.2 For the purpose of tank location, the vertical extent of bottom damage
shall be measured to the inner bottom when membrane or semi membrane tanks are used,
otherwise to the bottom of the cargo tanks. The transverse extent of side damage
shall be measured to the longitudinal bulkhead when membrane or semi membrane tanks
are used, otherwise to the side of the cargo tanks. The distances indicated in Pt 11, Ch 2, 1.3 Damage assumptions and Pt 11, Ch 2, 1.4 Location of cargo tanks shall be applied as in Figure 2.1.1 Independent prismatic tank,
protective distance to
Figure 2.1.5 Pressure type tank, protective
distance. These
distances shall be measured plate to plate, from the moulded line to the moulded
line, excluding insulation.
1.4.3 Suction wells installed in cargo tanks may protrude into the vertical
extent of bottom damage specified in Table 2.1.2 Permeability of spaces
assumed to be provided that such wells are as
small as practicable and the protrusion below the inner bottom plating does not
exceed 25 per cent of the depth of the double bottom or 350 mm, whichever is less.
Where there is no double bottom, the protrusion below the upper limit of bottom
damage shall not exceed 350 mm. Suction wells installed in accordance with this
paragraph may be ignored when determining the compartments affected by damage.
1.4.4 Cargo tanks shall not be located forward of the collision bulkhead.
1.4.5 When more than one independent tank is fitted in a space, sufficient
clearance is to be left between the tanks for inspection or repairs.
1.5 Flood assumptions
1.5.1 The requirements of Pt 11, Ch 2, 1.7 Survival requirements shall be confirmed by calculations that take into consideration
the design characteristics of the ship unit, the arrangements, configuration and
contents of the damaged compartments, the distribution, relative densities and the
free surface effects of liquids and the draught and trim for all conditions of
loading.
1.5.2 The permeability of spaces assumed to be damaged shall be as given in
Table 2.1.2 Permeability of spaces
assumed to be
Table 2.1.2 Permeability of spaces
assumed to be
| Space
|
Permeability
|
| Stores
|
0,6
|
| Accommodation
|
0,95
|
| Machinery
|
0,85
|
| Voids
|
0,95
|
| Hold spaces
|
0,95
see Note 1
|
| Consumable liquids
|
0 to 0,95
see Note 2
|
| Other liquids
|
0 to 0,95
see Note 2
|
Note
1. Other values of
permeability can be considered based on detailed
calculations; refer to MSC/Circ.651 Interpretations
of part B-1 of SOLAS Chapter II-1.
Note
2. The permeability of
partially filled compartments shall be consistent with
the amount of liquid carried in the compartment.
|
1.5.3 Wherever damage penetrates a tank containing liquids, it shall be
assumed that the contents are completely lost from that compartment and replaced by
saltwater up to the level of the final plane of equilibrium.
1.5.4 The ship unit shall be designed to keep unsymmetrical flooding to the
minimum consistent with efficient arrangements.
1.5.5 Equalisation 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 Survival requirements Pt 11, Ch 2, 1.7 Survival requirements 1.7.2 and
sufficient residual stability shall be maintained during all stages where
equalisation is used. Spaces linked by ducts of large cross-sectional area may be
considered to be common.
1.5.6 If pipes, ducts, trunks or tunnels are situated within the assumed
extent of damage penetration, as defined in Pt 11, Ch 2, 1.3 Damage assumptions, arrangements shall be such that progressive flooding cannot
thereby extend to compartments other than those assumed to be flooded for each case
of damage.
1.5.7 The buoyancy of any superstructure directly above the side damage shall
be disregarded. However, the unflooded parts of superstructures beyond the extent of
damage may be taken into consideration provided that:
- they are separated from the damaged space by watertight
divisions and the requirements of Pt 11, Ch 2, 1.7 Survival requirements 1.7.2.(a) in
respect of these intact spaces are complied with; and
- openings in such divisions are capable of being closed by
remotely operated sliding watertight doors and unprotected openings are not
immersed within the minimum range of residual stability required in Pt 11, Ch 2, 1.7 Survival requirements 1.7.3. However, the
immersion of any other openings capable of being closed weathertight may be
permitted.
1.6 Standard of damage
1.7 Survival requirements
1.7.2 In any stage of flooding:
- the waterline, taking into account sinkage,
heel and trim, shall be below the lower edge of any opening through which
progressive flooding or downflooding may take place. Such openings shall
include air pipes and openings that are closed by means of weathertight
doors or hatch covers and may exclude those openings closed by means of
watertight manhole covers and watertight flush scuttles, small watertight
cargo tank hatch covers that maintain the high integrity of the deck,
remotely operated watertight sliding doors and sidescuttles of the non
opening type;
- the maximum angle of heel due to unsymmetrical flooding shall
not exceed 25°, except that this angle may be increased to 30° if no deck
immersion occurs; and
- the residual stability during intermediate stages of flooding
shall not be significantly less than that required by Pt 11, Ch 2, 1.7 Survival requirements 1.7.3.
1.7.3 At final equilibrium after flooding:
- the righting lever curve shall have a minimum
range of 20° beyond the position of equilibrium in association with a maximum
residual righting lever of at least 0,1 m within the 20° range; the area under
the curve within this range shall not be less than 0,0175 m radians. The 20°
range may be measured from any angle commencing between the position of
equilibrium and the angle of 25° (or 30° if no deck immersion occurs).
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 Pt 11, Ch 2, 1.7 Survival requirements 1.7.2.(a)
and other openings capable of being closed weathertight may be permitted;
and
- the emergency source of power shall be capable of operating.
|