(1)
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(a) Discharges led through the shell either from
spaces below the freeboard deck or from within superstructures and
deckhouses on the freeboard deck fitted with doors complying with
the requirements of regulation 12 shall, except as provided in paragraph
(2), be fitted with efficient and accessible means for preventing
water from passing inboard. Normally each separate discharge shall
have one automatic non-return valve with a positive means of closing
it from a position above the freeboard deck. Where the inboard end
of the discharge pipe is located at least 0.01L above the Summer Load
Line, the discharge may have two automatic non-return valves without
positive means of closing. Where that vertical distance exceeds 0.02L,
a single automatic non-return valve without positive means of closing
may be accepted. The means for operating the positive action valve
shall be readily accessible and provided with an indicator showing
whether the valve is open or closed.
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(b) One automatic non-return valve and one sluice
valve controlled from above the freeboard deck instead of one automatic
non-return valve with a positive means of closing from a position
above the freeboard deck, is acceptable.
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(c) Where two automatic non-return valves are
required, the inboard valve shall always be accessible for examination
under service conditions (i.e., the inboard valve shall be above the
level of the Tropical Load Line). If this is not practicable, the
inboard valve need not be located above the Tropical Load Line, provided
that a locally controlled sluice valve is fitted between the two automatic
non-return valves.
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(d) Where sanitary discharges and scuppers lead
overboard through the shell in way of machinery spaces, a locally
operated positive closing valve at the shell, together with a non-return
valve inboard, is acceptable. The controls of the valves shall be
in an easily accessible position.
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(e) The position of the inboard end of discharges
shall be related to the Summer Timber Load Line when a timber freeboard
is assigned.
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(f) The requirements for non-return valves are
applicable only to those discharges which remain open during the normal
operation of a ship. For discharges which are to be kept closed at
sea, a single screw down valve operated from the deck is acceptable.
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(g) Table 22.1 provides
the acceptable arrangements of scuppers, inlets and discharges.
Table 22.1
(2) Scuppers led through the shell from enclosed
superstructures used for the carriage of cargo shall be permitted
only where the edge of the freeboard deck is not immersed when the
ship heels 5° either way. In other cases the drainage shall be
led inboard in accordance with the requirements of the International
Convention for the Safety of Life at Sea in force.
(3) In manned machinery spaces, main and auxiliary
sea inlets and discharges in connection with the operation of machinery
may be controlled locally. The controls shall be readily accessible
and shall be provided with indicators showing whether the valves are
open or closed.
(4) Scuppers and discharge pipes originating at
any level and penetrating the shell either more than 450 mm below
the freeboard deck or less than 600 mm above the Summer Load Line
shall be provided with a non-return valve at the shell. This valve,
unless required by paragraph (1), may be omitted if the piping is
of substantial thickness (see paragraph (7) below).
(5) Scuppers leading from superstructures or deckhouses
not fitted with doors complying with the requirements of regulation 12 shall be led overboard.
(6) All shell fittings and the valves required
by this regulation shall be of steel, bronze or other approved ductile
material. Valves of ordinary cast iron or similar material are not
acceptable. All pipes to which this regulation refers shall be of
steel or other equivalent material to the satisfaction of the Administration.
(7) Scupper and discharge pipes:
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(a) For scupper and discharge pipes, where substantial
thickness is not required:
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(i) for pipes having an external diameter equal
to or less than 155 mm, the thickness shall not be less than 4.5 mm;
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(ii) for pipes having an external diameter equal
to or more than 230 mm, the thickness shall not be less than 6 mm.
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Intermediate sizes shall be determined by linear interpolation.
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(b) For scupper and discharge pipes, where substantial
thickness is required:
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(i) for pipes having an external diameter equal
to or less than 80 mm, the thickness shall not be less than 7 mm;
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(ii) for pipes having an external diameter of
180 mm, the thickness shall not be less than 10 mm;
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(iii) for pipes having an external diameter equal
to or more than 220 mm, the thickness shall not be less than 12.5
mm.
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Intermediate sizes shall be determined by linear interpolation.