Hong Kong Regulations

MERCHANT SHIPPING (INSTRUCTIONS TO SURVEYORS) (PASSENGER SHIPS) REGULATIONS - REGULATION 13

Special rules concerning subdivision

(1) Permissible length of pairs of compartments:

   (a)  A compartment may exceed the permissible length determined by the
        rules of paragraph 12, provided the combined length of each pair of
        adjacent compartments to which the compartment in question is common,
        does not exceed either the floodable length, or twice the permissible
        length, whichever is the less (see also clause (4) of this paragraph).

   (b)  If one of the two adjacent compartments is situated inside the
        machinery space, and the second is situated outside the machinery
        space, and the average permeability of the portion of the ship in
        which the second is situated differs from that of the machinery space,
        the combined length of the two compartments shall be adjusted to the
        mean average permeability of the two portions of the ship in which the
        compartments are situated.

   (c)  Where the lengths of two adjacent compartments are governed by
        different factors of subdivision, the combined length of the two
        compartments shall be determined proportionately.

(2) Additional subdivision at Forward end: In ships 430 feet in length and
upwards, one of the main transverse bulkheads abaft the fore peak shall be
fitted at a distance from the forward perpendicular which is not greater than
the permissible length.

(3) Recesses in Bulkheads: A main transverse bulkhead may be recessed provided
that all parts of the recess lie inboard of vertical surfaces on both sides of
the ship, situated at a distance from the shell plating equal to .20B, and
measured at right angles to the centre-line at the level of the deepest
subdivision loadline. Any part of a recess which lies outside these limits
shall be dealt with as a step in accordance with the following sub-paragraph.

(4) Steps in Bulkheads: A main transverse bulkhead may be stepped provided
that-

   (a)  the combined length of the two compartments, separated by the bulkhead
        in question, does not exceed 90 per cent of the floodable length; or

   (b)  additional subdivision is provided in way of the step to maintain the
        same measure of safety as that secured by a plane bulkhead.

(5) Equivalent plane Bulkheads: Where a main transverse bulkhead is recessed
or stepped, and equivalent plane bulkhead shall be used in determining the
subdivision.

(6) Minimum spacing of Bulkheads: If the distance between two adjacent main
transverse bulkheads, or their equivalent plane bulkheads, or the distance
between the transverse planes passing through the nearest stepped portions of
the bulkheads, is less than .02L+10 feet, only one of these bulkheads shall be
regarded as forming part of the subdivision of the ship in accordance with the
provisions of paragraph 12.

(7) Allowance for Local Subdivision:

   (a)  Where a main transverse watertight compartment contains local
        subdivision and it can be shown to the satisfaction of the Surveyor of
        Ships that, after any assumed side damage extending over a length in
        feet of .02L+10, the whole volume of the main compartment will not be
        flooded, a proportionate allowance may be made in the permissible
        length otherwise required for such compartment. In such a case the
        volume of effective buoyancy assumed on the undamaged side shall not
        be greater than that assumed on the damaged side.

   (b)  The claim for such allowance shall be accompanied by plans showing the
        proposed local subdivision and the volumes of the main and
        sub-compartments concerned. No allowance will be made where the main
        compartment and sub-compartments are liable to be in open
        communication, below the level of the margin line, through air,
        sounding or other pipes, etc.

(8) Longitudinal Subdivision:

   (a)  Where it is proposed to fit watertight decks, inner skins or
        longitudinal bulkheads, watertight or non-watertight, the Surveyor of
        Ships shall be satisfied that the safety of the ship will not be
        diminished in any respect, particularly having in view the possible
        listing effect of flooding in way of such structural arrangements.
        Except as provided in sub-paragraph (7) no relaxation from the
        requirements for transverse subdivision shall be made in respect of
        longitudinal subdivision.

   (b)  The arrangements which fall within the general category of
        longitudinal subdivision are of such a varied character that it is not
        possible to lay down definite rules which would apply equitably to all
        cases that may arise in practice.

   (c)  Calculations of angle of heel or of effect on stability may be
        necessary and plans showing the proposed longitudinal subdivision are
        therefore to be submitted for the Principal Surveyor of Ships for
        consideration and decision as to the calculations to be made and the
        spaces to be assumed flooded. The object of these calculations is to
        show:

        (i)    The angle of heel which might result from flooding due to side
               damage extending over a length in feet not exceeding .02L+10.
               If this angle is more than 7 degrees, the Surveyor of Ships
               will as a rule require such arrangements to be made as will
               enable the list to be expeditiously reduced to an angle not
               exceeding 7 degrees.

        (ii)   The angle of heel which might result from flooding of such
               compartments as may reasonably be assumed vulnerable under
               certain conditions of damage having regard to the arrangements
               under consideration. If this angle is such that the margin line
               would not be submerged the arrangements may be allowed,
               otherwise they will require modification.

        (iii)  The effect on stability of flooding in way of a watertight
               deck. The result of this calculation will be considered on its
               merits.

   (d)  In making these calculations the ship is to be assumed to be in the
        worst anticipated service condition as regards stability, the
        permeabilities of the spaces assumed to be flooded being taken
        consistent with this condition as far as possible.

   (e)  The stability conditions assumed in these calculations are to be
        confirmed after the ship has been inclined (see paragraph 53).