Hong Kong Regulations

MERCHANT SHIPPING (PREVENTION OF OIL POLLUTION) REGULATIONS - REGULATION 23A

Prevention of pollution in the event of collision or stranding

(1) This regulation shall apply to oil tankers of 600 tons deadweight and
above-

   (a)  for which the building contract is placed on or after 6 July 1993; or

   (b)  in the absence of a building contract, the keels of which are laid or
        which are at a similar stage of construction on or after 6 January
        1994; or

   (c)  the delivery of which is on or after 6 July 1996; or

   (d)  which have undergone a major conversion-

        (i)    for which the contract is placed after 6 July 1993; or

        (ii)   in the absence of a contract, the construction work of which is
               begun after 6 January 1994; or

        (iii)  which is completed after 6 July 1996.

(2) Every oil tanker of 5000 tons deadweight and above shall-

   (a)  in lieu of regulation 19, as applicable, comply with the requirements
        of paragraph (3) unless it is subject to the provisions of paragraphs
        (4) and (5); and

   (b)  comply, if applicable, with the requirements of paragraph (6).

(3) The entire cargo tank length shall be protected by ballast tanks or spaces
other than cargo and fuel oil tanks as follows-

   (a)  Wing tanks or spaces Wing tanks or spaces shall extend either for the
        full depth of the ship's side or from the top of the double bottom to
        the uppermost deck, disregarding a rounded gunwale where fitted. They
        shall be arranged such that the cargo tanks are located inboard of the
        moulded line of the side shell plating, nowhere less than the distance
        w which, as shown in Figure 1, is measured at any cross-section at
        right angles to the side shell, as specified below-

DW w = 0.5 + _________ (m); or
20000

w = 2.0 m, whichever is the lesser. The minimum value of w = 1.0 m.

   (b)  Double bottom tanks or spaces At any cross-section the depth of each
        double bottom tank or space shall be such that the distance h between
        the bottom of the cargo tanks and the moulded line of the bottom shell
        plating as shown in Figure 1 is not less than specified below-

B h = ___ m); or
15

h = 2.0 m, whichever is the lesser. The minimum value of h = 1.0 m.

   (c)  Turn of the bilge area or at locations without a clearly defined turn
        of the bilge When the distances h and w are different, the distance w
        shall have preference at levels exceeding 1.5 h above the baseline as
        shown in Figure 1.

   (d)  The aggregate capacity of ballast tanks On crude oil tankers of 20000
        tons deadweight and above and product  carriers of 30000 tons
        deadweight and above, the aggregate capacity of wing tanks, double
        bottom tanks, forepeak tanks and afterpeak tanks shall not be less
        than the capacity of segregated ballast tanks necessary to meet the
        requirements of regulation 18. Wing tanks or spaces and double bottom
        tanks used to meet the requirements of regulation 18 shall be located
        as uniformly as practicable along the cargo tank length. Additional
        segregated ballast capacity provided for reducing longitudinal hull
        girder bending stress, trim, etc., may be located anywhere within the
        ship.

   (e)  Suction wells in cargo tanks Suction wells in cargo tanks may protrude
        into the double bottom below the boundary line defined by the distance
        h provided that such wells are as small as practicable and the
        distance between the well bottom and bottom shell plating is not less
        than 0.5 h.

   (f)  Ballast and cargo piping Ballast piping and other piping such as
        sounding and vent piping to ballast tanks shall not pass through cargo
        tanks. Cargo piping and similar piping to cargo tanks shall not pass
        through ballast tanks. Exemptions to this requirement may be granted
        for short lengths of piping, provided that they are completely welded
        or equivalent.

(4) (a) Double bottom tanks or spaces as required by paragraph (3)(b) may be
dispensed with, provided that the design of the tanker is such that the cargo
and vapour pressure exerted on the bottom shell plating forming a single
boundary between the cargo and the sea does not exceed the external
hydrostatic water pressure, as expressed by the following formula- f. hc.Pc.g
+ 100 △p < dn.Ps.g
 where- hc = height of cargo in contact with the bottom shell
plating in metres Pc = maximum cargo density in t/m3 dn = minimum operating
draught under any expected loading condition in metres Ps = density of sea
water in t/m3 △p = maximum set pressure of pressure / vacuum valve provided
for the cargo tank in bars f = safety factor = 1.1 g = standard acceleration
of gravity (9.81 m/s2)

   (b)  Any horizontal partition necessary to fulfil the above requirements
        shall be located at a height of not less than B/6 or 6 metres,
        whichever is the lesser, but not more than 0.6D, above the baseline
        where D is the moulded depth amidships.

   (c)  The location of wing tanks or spaces shall be as defined in paragraph

(3)(a) except that, below a level 1.5 h above the baseline where h is as
defined in paragraph (3)(b), the cargo tank boundary line may be vertical down
to the bottom plating, as shown in Figure 2.

(5) Other methods of design and construction of oil tankers may also be
accepted as alternatives to the requirements prescribed in paragraph (3),
provided that such methods ensure at least the same level of protection
against oil pollution in the event of collision or stranding and are approved
by the Director based on guidelines developed by the Organization.

(6) For oil tankers of 20000 tons deadweight and above the damage assumptions
prescribed in regulation 29(2)(b) shall be supplemented by the following
assumed bottom raking damage-

   (a)  longitudinal extent-

        (i)    ships of 75000 tons deadweight and above - 0.6 L measured from
               the forward perpendicular;

        (ii)   ships of less than 75000 tons deadweight - 0.4 L measured from
               the forward perpendicular;

   (b)  transverse extent - B/3 anywhere in the bottom;

   (c)  vertical extent-breach of the outer hull.

(7) Oil tankers of less than 5000 tons deadweight shall-

   (a)  at least be fitted with double bottom tanks or spaces having such a
        depth that the distance h specified in paragraph (3)(b) complies with
        the following-

B h = ___ (m) with a minimum value of h = 0.76m;
15

in the turn of the bilge area and at locations without a clearly defined turn
of the bilge, the cargo tank boundary line shall run parallel to the line of
the midship flat bottom as shown in Figure 3; and

   (b)  be provided with cargo tanks so arranged that the capacity of each
        cargo tank does not exceed 700 m3 unless wing tanks or spaces are
        arranged in accordance with paragraph (3)(a) complying with the
        following-

2.4 DW w = 0.4 + ______________ (m)
20000

with a minimum value of w = 0.76 m.

(8) Oil shall not be carried in any space extending forward of a collision
bulkhead located in accordance with regulation 3 of the Merchant Shipping
(Safety) (Cargo Ship Construction and Survey) (Ships Built On or After 1
September 1984) Regulations ( Cap 369 sub. leg.). An oil tanker that is not
required to have a collision bulkhead in accordance with that regulation shall
not carry oil in any space extending forward of the transverse plane
perpendicular to the centreline that is located as if it were a collision
bulkhead located in accordance with that regulation.

(9) In approving the design and construction of oil tankers to be built in
accordance with the provisions of this regulation, the Director shall have
regard to the general safety aspects including the need for the maintenance
and inspections of wing and double bottom tanks or spaces.

(Diagram omitted)

Figure 1 Cargo tank boundary lines for the purpose of paragraph (3)

(Diagram omitted)

Figure 2 Cargo tank boundary lines for the purpose of paragraph (4)

(Diagram omitted)

Figure 3 Cargo tank boundary lines for the purpose of paragraph (7)

(L.N. 641 of 1994)