Hong Kong Regulations

MERCHANT SHIPPING (PREVENTION OF OIL POLLUTION) REGULATIONS - REGULATION 29

Subdivision and stability

(1) Every new oil tanker shall comply with the subdivision and damage
stability criteria as specified in paragraph (3) of this regulation, after the
assumed side or bottom damage as specified in paragraph (2) of this
regulation, for any operating draught reflecting actual partial or full load
conditions consistent with the trim and strength of the ship as well as the
specific gravities of the cargo. Such damage shall be assumed to have occurred
at all conceivable locations along the length of the ship as follows-

   (a)  in tankers of more than 225 metres in length, anywhere in the ship's
        length;

   (b)  in tankers of more than 150 metres, but not exceeding 225 metres in
        length, anywhere in the ship's length except locations involving
        either after or forward bulkheads bounding the machinery space located
        aft. This machinery space shall be treated as a single floodable
        compartment;

   (c)  in tankers not exceeding 150 metres in length, anywhere in the ship's
        length between adjacent transverse bulkheads with the exception of the
        machinery space. Any tanker of 100 metres or less in length which
        cannot fulfil all the requirements of paragraph (3) of this regulation
        without materially impairing the operational qualities of the ship
        shall comply with such lesser requirements as the Director may impose.
        Ballast conditions where the tanker is not carrying oil in cargo tanks
        excluding any oil residues, shall not be taken into account.

(2) The following provisions regarding the extent and the character of the
assumed damage shall apply-

   (a)  Side damage

        (i)    Longitudinal extent (1c): 1/3L2/3 or 14.5 metres, whichever is
               less

        (ii)   Transverse extent (inboard from the ship's side at right angle
               to the centreline at the level of the summer load line) B/5 or
               11.5 metres, whichever is less

        (iii)  Vertical extent From the moulded line of the bottom shell
               plating at centre line, upwards without limit

   (b)  Bottom damage Position of Damage
For 0.3 L from the forward of perpendicular of the ship Any other part the
ship

        (i)    Longitudinal extent 1/3L2/3 or 14.5 metres, whichever is less
               1/3L2/3 or 5 metres, whichever is less

        (ii)   Transverse extent B/6 or 10 metres, whichever is less B/6 or 5
               metres, whichever is less

        (iii)  Vertical extent B/15 or 6 metres,whichever is less measured
               from the moulded line of the bottom shell plating at centre
               line B/15 or 6 metres,whichever is less measured from the
               moulded line of the bottom shell plating at centre line

   (c)  If any damage of a lesser extent than the maximum extent of damage
        specified in sub-paragraphs (a) and (b) of this paragraph would result
        in a more severe condition in relation to the ship's stability, such
        damage shall be assumed.

   (d)  Where the damage envisaged in sub-paragraph (1)(a) or (b) of this
        regulation would involve transverse watertight bulkheads, such
        bulkheads shall not be considered effective unless they are spaced at
        a distance at least equal to the longitudinal extent of the assumed
        damage specified in sub-paragraphs (a) and (b) of this paragraph.
        Where such bulkheads are spaced at a lesser distance, one or more of
        these bulkheads within such extent of damage shall be assumed to be
        non-existent for the purpose of determining which compartments are
        flooded.

   (e)  Where the damage envisaged in sub-paragraph (1)(c) of this regulation
        occurs between adjacent transverse watertight bulkheads no main
        transverse bulkhead or transverse bulkhead bounding side tanks or
        double bottom tanks shall be assumed damaged unless-

        (i)    the spacing between the adjacent bulkheads is less than the
               longitudinal extent of the assumed damage specified in
               sub-paragraphs (a) and (b) of this paragraph; or

        (ii)   there is a step or recess in the transverse bulkhead of more
               than 3.05 metres in length, located within the extent of
               penetration of the assumed damage. The step formed by the after
               peak bulkhead and after peak tank top shall not be regarded as
               a step for the purpose of this regulation.

   (f)  If pipes, ducts or tunnels are situated within the assumed extent of
        damage, arrangements shall be made so that progressive flooding cannot
        thereby extend to compartments other than those assumed to be
        floodable for each case of damage.

(3) Oil tankers shall be regarded as complying with the damage stability
criteria if the following requirements are met-

   (a)  The final waterline, taking into account sinkage, heel and trim, shall
        be below the lower edge of any opening through which progressive
        flooding may take place. Such openings shall include air pipes and
        those openings which are closed by means of weathertight doors or
        hatch covers, but may exclude those openings which are 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 side scuttles of the
        non-opening type.

   (b)  In the final stages of flooding, the angle of heel due to
        unsymmetrical flooding shall not exceed 25 degrees, provided that this
        angle may be increased up to 30 degrees if no deck edge immersion
        occurs as a result of such increase.

   (c)  The stability in the final stage of flooding shall be investigated and
        may be regarded as sufficient if the righting lever curve has a range
        of at least 20 degrees beyond the condition of equilibrium in
        association with a maximum residual righting lever of at least 0.1
        metre within the 20 degree range; the area under the curve within this
        range shall not be less than 0.0175 metre radian. 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 sub-paragraph (a) of this paragraph and other
        openings capable of being closed weathertight may be permitted.

   (d)  Equalization arrangements requiring mechanical aids such as valves or
        cross-levelling pipes, if fitted, shall not be taken into account for
        the purpose of reducing an angle of heel or attaining the minimum
        range of residual stability to meet the requirements of sub-paragraphs
        (a), (b) and

   (c)  of this paragraph and sufficient residual stability shall be
        maintained during all stages where equalization is used. Spaces which
        are linked by ducts of large cross-sectional area may be considered to
        be as one.

   (e)  A Certifying Authority, before approving the stability for the ship,
        shall be satisfied that the stability is sufficient during
        intermediate stages of flooding.

(4) The requirements of paragraph (1) of this regulation shall be deemed not
to have been complied with unless compliance is confirmed by calculations
which take into consideration the design characteristics of the ship, the
arrangements, configuration and contents of the damaged compartments; and the
distribution, specific gravities and free surface effect of liquids. The
calculations shall be based on the following-

   (a)  Account shall be taken of any empty or partially filled tank, the
        specific gravity of the cargo carried, and any outflow of liquids from
        damaged compartments.

   (b)  The permeabilities assumed for spaces flooded as a result of damage
        shall be as follows- Spaces Permeability Appropriate to stores 0.60
        Occupied as crew accommodation 0.95 Occupied by machinery 0.85 Voids
        0.95 Intended for consumable liquids 0 to 0.95* Intended for other
        liquids 0 to 0.95*

* The permeability of partially filled compartments shall be consistent with
the amount of liquid carried in the compartment. Whenever damage penetrates a
tank containing liquid, it shall be assumed that the contents are completely
lost from that compartment and replaced by salt water up to the level of the
final plane of equilibrium.

   (c)  The buoyancy of any superstructure directly above the side damage
        shall not be taken into account. The unflooded parts of superstructure
        beyond the extent of damage may be taken into account provided that
        they are separated from the damaged space by watertight bulkheads and
        that the requirements of sub-paragraph (3)(a) of this regulation in
        respect of these intact spaces are complied with. Hinged watertight
        doors may be fitted in watertight bulkheads in the superstructure.

   (d)  The free surface effect shall be calculated at an angle of heel of 5
        degrees for each individual compartment. The Director may require, or
        allow, the free surface corrections to be calculated at any angle of
        heel greater than 5 degrees for partially filled tanks.

   (e)  In calculating the effect of free surfaces of consumable liquids it
        shall be assumed that, for each type of liquid at least one transverse
        pair of tanks or a centreline tank has a free surface and the tank, or
        combination of tanks, to be taken into account shall be those where
        the effect of the free surface is the greatest.

(5) The master of every new oil tanker and the person in charge of a new
non-self-propelled oil tanker to which these Regulations apply shall be
supplied by the owner with- (L.N. 177 of 1991)

   (a)  information relative to loading and distribution of cargo necessary to
        ensure compliance with the provision of this regulation; and

   (b)  data on the ability of the ship to comply with the damage stability
        criteria prescribed by this regulation, including the effect of any
        lesser requirements that may have been imposed under sub-paragraph
        (1)(c) of this regulation. Such information and data shall be supplied
        in a form approved by the Director.