1 A double bottom shall be fitted extending from
the collision bulkhead to the afterpeak bulkhead, as far as this is
practicable and compatible with the design and proper working of the
ship.
2 Where a double bottom is required to be fitted,
the inner bottom shall be continued out to the ship's sides in such
a manner as to protect the bottom to the turn of the bilge. Such protection
will be deemed satisfactory if the inner bottom is not lower at any
part than a plane parallel with the keel line and which is located
not less than a vertical distance h measured from the
keel line, as calculated by the formula:
h = B/20
However, in no
case is the value of h to be less than 760 mm, and need
not be taken as more than 2,000 mm.
3.1 Small wells constructed in the double
bottom in connection with drainage arrangements shall not extend downward more than
necessary. The vertical distance from the bottom of such a well to a plane coinciding
with the keel line shall not be less than h/2 or 500 mm, whichever is greater, or
compliance with paragraph 8 of this regulation shall be shown for that part of the
ship.
3.2 Other wells (e.g. for lubricating oil
under main engines) may be permitted by the Administration if satisfied that the
arrangements give protection equivalent to that afforded by a double bottom complying
with this regulation.
3.2.1 For a cargo ship of 80 m in length and
upwards or for a passenger ship, proof of equivalent protection is to be shown by
demonstrating that the ship is capable of withstanding bottom damages as specified in
paragraph 8. Alternatively, wells for lubricating oil below main engines may protrude
into the double bottom below the boundary line defined by the distance h provided that
the vertical distance between the well bottom and a plane coinciding with the keel line
is not less than h/2 or 500 mm, whichever is greater.
3.2.2 For cargo ships of less than 80 m in
length the arrangements shall provide a level of safety to the satisfaction of the
Administration.
4 A double bottom need not be fitted in way of
watertight tanks, including dry tanks of moderate size, provided the
safety of the ship is not impaired in the event of bottom or side
damage.
5 In the case of passenger ships to which the
provisions of regulation 1.5 apply
and which are engaged on regular service within the limits of a short
international voyage as defined in regulation
III/3.22, the Administration may permit a double bottom to
be dispensed with if satisfied that the fitting of a double bottom
in that part would not be compatible with the design and proper working
of the ship.
6 Any part of a cargo ship of 80 m in length and upwards or
of a passenger ship that is not fitted with a double bottom in accordance with
paragraphs 1, 4 or 5, as specified in paragraph 2, shall be capable of withstanding
bottom damages, as specified in paragraph 8, in that part of the ship. For cargo ships
of less than 80 m in length the alternative arrangements shall provide a level of safety
to the satisfaction of the Administration.
7 In the case of unusual bottom arrangements in a cargo
ship of 80 m in length and upwards or a passenger ship, it shall be demonstrated that
the ship is capable of withstanding bottom damages as specified in paragraph 8. For
cargo ships of less than 80 m in length the alternative arrangements shall provide a
level of safety to the satisfaction of the Administration.
8 Compliance with paragraphs 3.1, 3.2.1, 6 or 7 is to be
achieved by demonstrating that si, when calculated in accordance with
regulation
7-2, is not less than 1 for all service conditions when subject to bottom
damage with an extent specified in subparagraph .2 below for any position in the
affected part of the ship:
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.1 Flooding of such spaces shall not render emergency power and
lighting, internal communication, signals or other emergency devices inoperable in
other parts of the ship.
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.2 Assumed extent of damage shall be as follows:
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|
|
For 0.3 L from the forward perpendicular of the
ship
|
Any
other part of the ship
|
| Longitudinal extent
|
1/3 L2/3 or 14.5 m, whichever is less
|
1/3 L2/3 or 14.5 m, whichever is less
|
| Transverse extent
|
B/6 or 10 m, whichever is less
|
B/6 or 5 m, whichever is less
|
| Vertical extent, measured from the keel line
|
B/20, to be taken not less than 0.76 m and not more than
2 m
|
B/20, to be taken not less than 0.76 m and not more than
2 m
|
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.3 If any damage of a lesser extent than the maximum damage specified
in .2 would result in a more severe condition, such damage should be
considered.
9 In case of large lower holds in passenger ships,
the Administration may require an increased double bottom height of
not more than B/10 or 3 m, whichever is less, measured
from the keel line. Alternatively, bottom damages may be calculated
for these areas, in accordance with paragraph 8, but assuming an increased
vertical extent.