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.

1.1.4 For the purpose of this Part, the position of the moulded line for different containment systems is shown in Pt 11, Ch 2, 1.1 General 1.1.4

Figure 2.1.1 Independent prismatic tank, protective distance

Figure 2.1.2 Semi-membrane tank, protective distance

Figure 2.1.3 Membrane tank, protective distance

Figure 2.1.4 Spherical tank, protective distance

Figure 2.1.5 Pressure type tank, protective distance

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 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 Pt 11, Ch 2, 1.3 Damage assumptions 1.3.1.

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 2.4.3	B/15 or 2 m, whichever is less measured from the moulded line of the bottom shell plating at centreline, see 2.4.3

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 Pt 11, Ch 2, 1.3 Damage assumptions 1.3.1 and nowhere less than ‘d’ (see Pt 11, Ch 2, 1.4 Location of cargo tanks 1.4.1 and Pt 11, Ch 2, 1.4 Location of cargo tanks 1.4.1), 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 Figs. Pt 11, Ch 2, 1.1 General 1.1.4 Figure 2.1.1 Independent prismatic 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 Pt 11, Ch 2, 1.3 Damage assumptions in Table Pt 11, Ch 2, 1.3 Damage assumptions 1.3.1 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 Pt 11, Ch 2, 1.5 Flood assumptions 1.5.2

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 Pt 11, Ch 2, 1.7 Survival requirements 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 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

1.6.1 Type 2G ship units shall be capable of surviving the damage indicated in Pt 11, Ch 2, 1.3 Damage assumptions anywhere in its length with the flooding assumptions in Pt 11, Ch 2, 1.5 Flood assumptions.

1.7 Survival requirements

1.7.1 Ship units shall be capable of surviving the assumed damage specified in Pt 11, Ch 2, 1.3 Damage assumptions, to the standard provided in Pt 11, Ch 2, 1.6 Standard of damage, in a condition of stable equilibrium and shall satisfy the following criteria.

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 and other openings capable of being closed weathertight may be permitted; and
the emergency source of power shall be capable of operating.