1.2.1 Coamings and hatchway covers to exposed
hatchways situated above the second superstructure tier or its equivalent,
or above the third tier or its equivalent, in the forward quarter
of the ships length, may be regarded as being situated above the superstructure
deck, for the purpose of giving effect to regulation 14(2) of the 1966 LL Convention. Partially weathertight hatch
covers fitted to hatchways situated in such locations may be accepted
subject to the following conditions.
1.2.2 Coamings and hatchway covers may be fitted
to hatchways located on exposed decks situated at least two standard
superstructure heights above the actual freeboard deck or an assumed
freeboard deck, on the basis of which a calculation of the freeboard
may be made corresponding to the draught, which should be not less
than that which would correspond to the freeboard actually assigned
to the ship. If any part of the hatchway is forward of a point located
a quarter of a ship's length (0.25L) from the forward perpendicular,
this hatchway should be located on an exposed deck which is situated
at least three standard superstructure heights above the actual or
assumed freeboard. It should be noted that use is made of a notional
freeboard deck solely for the purpose of measuring the height of the
deck on which hatchways are located; it may consist of an imaginary
or a virtual deck which, under such circumstances, is not used for
the actual assignment of the freeboard. The freeboard of the ship
should be assigned on the basis of an actual deck, referred to as
the freeboard deck, which should be determined in accordance
with the provisions of the 1966 LL Convention and
of IACS Unified Interpretation LL39, as contained in LL.3/Circ.77.
1.2.3 The height of the hatchway coamings should
not be less than 600 mm.
1.2.4 Non-weathertight gaps between the hatchway
covers should be regarded as unprotected openings with respect to
the requirements relating to intact stability and damage stability
calculations. The gaps should also be as small as possible and proportional
to the capacity of the bilge pumping system and the estimated amount
of water penetration, as well as to the capacity and the operational
efficiency of the fire-extinguishing system, and in any case should
be not more than 50 mm.
1.2.5 Labyrinths, gutters or other equivalent
means should be fitted close to the edges of each hatch cover at right
angles with the openings in order to reduce to a minimum the quantity
of water that might penetrate into the hold from the upper surface
of each cover. Figures 1.2.5-1 and 1.2.5-2 are examples of labyrinth
and gutter arrangements.
Figure 1.2.5-1 Interface between Port and Starboard Hatch Covers (Looking
Aft)
Figure 1.2.5-2 Hatch Cover Interface with Hatch Coaming Labyrinth Bar (Looking
Inboard)
1.2.6 Scantlings for hatchway covers and the components
of clamping devices used to secure the covers to the structure supporting
them and the coamings, should be at the very least equivalent to those
applying to weathertight hatchway covers and be in accordance with
the relevant provisions of a recognized organizationfootnote or with the appropriate national standards
established by the Administration and which provide for an equivalent
level of safety.