Section
4 Scuppers and sanitary discharges
4.1 General
4.1.1 Scuppers
sufficient in number and size to provide effective drainage are to
be fitted in all decks.
4.1.2 Scuppers
draining weather decks and spaces within superstructures or deckhouses
not fitted with efficient weathertight doors are to be led overboard.
4.1.3 Where
the freeboard is such that the freeboard deck edge is immersed when
the ship heels 5° or less, scuppers and discharges which drain
spaces below the freeboard deck, or spaces within intact superstructures
or deckhouses on the freeboard deck fitted with efficient weathertight
doors, are to be led to the bilges in the case of scuppers or to suitable
sanitary tanks in the case of sanitary discharges. Where the freeboard
is such that the freeboard deck edge is immersed when the ship heels
greater than 5° then they may be led overboard and fitted with
means of preventing water from passing inboard in accordance with Pt 3, Ch 12, 4.2 Closing appliances.
4.1.4 In
ships where an approved fixed pressure water spray fire−extinguishing
system is fitted in vehicle or cargo spaces, deck scuppers of not
less than 150 mm diameter are to be provided port and starboard, spaced
about 9,0 m apart. The scupper area will require to be increased if
the design capacity of the drencher system exceeds the Rule required
capacity by 10 per cent or more. After installation, the two adjacent
sections with the greatest aggregate drencher capacity are to be tested
in operation to ensure that there is no build up of water on the deck, see also
Pt 4, Ch 2, 10.2 Openings in main vehicle deck 10.2.2.
The mouth of the scupper is to be protected by bars.
4.1.5 Where
a sewage system is fitted, the shipside valves on the discharge pipe
from the effluent tank(s) and the by-pass system are to comply with Pt 3, Ch 12, 4.2 Closing appliances.
4.1.6 The
minimum wall thickness of pipes not indicated in Pt 3, Ch 12, 4.2 Closing appliances 4.2.6 is to be:
- 4,5 mm for pipes of 155 mm external diameter or smaller.
- 6,0 mm for pipes of 230 mm external diameter or greater.
Intermediate minimum thicknesses are to be determined by linear
interpolation.
4.1.8 Scuppers
and discharge pipes should not normally pass through fuel oil or cargo
oil tanks. Where scuppers and discharge pipes pass, unavoidably, through
fuel oil or cargo oil tanks, and are led through the shell within
the tanks, the thickness of the piping should be at least the same
thickness as Rule shell plating in way, derived from the appropriate
Chapters, but need not exceed 19 mm.
4.1.10 All
piping is to be adequately supported.
4.2 Closing appliances
4.2.1 In
general, each separate overboard discharge is to be fitted with a
screw-down non-return valve capable of being operated from a position
always accessible and above the freeboard deck. An indicator is to
be fitted at the control position showing whether the valve is open
or closed. A machinery space, whether manned or unattended (i.e. with UMS notation), is considered accessible. Cargo holds or spaces
with access only by hatches or bolted manholes are not considered
accessible.
4.2.2 Where
a drencher fire-extinguishing system is provided in an enclosed vehicle
space of a ferry, the scupper controls are to be operated from a position
above the bulkhead deck, and outside the vehicle space protected by
the drencher system, and are to be protected from mechanical damage.
4.2.3 Where
the vertical distance from the summer load waterline to the inboard
end of the discharge pipe exceeds 0,01L
L the
discharge may be fitted with two automatic non-return valves without
positive means of closing, instead of the screw-down non-return valve,
provided that the inboard valve is always accessible for examination
under service conditions.
4.2.4 Where
the vertical distance from the summer load waterline to the inboard
end of the discharge pipe exceeds 0,02L
L,
a single automatic non-return valve without positive means of closing
may be fitted, see
Figure 12.4.1 Diagrammatic arrangement of discharge valves.
Figure 12.4.1 Diagrammatic arrangement of discharge valves
4.2.5 The
requirements for non-return valves are applicable only to those discharges
which remain open during the normal operation of the ship. For discharges
which are closed at sea, such as gravity drains from topside ballast
tanks, a single screw down valve operated from the freeboard deck
is considered to provide sufficient protection.
4.2.6 Scuppers
and discharge pipes originating at any level which penetrate the shell
either more than 450 mm below the freeboard deck or less than 600
mm above the summer load waterline, are to be fitted with an automatic
non-return valve at the shell. This valve, unless required by Pt 3, Ch 12, 4.1 General 4.1.3, may be omitted provided
the piping has a minimum wall thickness of:
- 7,0 mm for pipes of 80 mm external diameter or smaller;
- 10,0 mm for pipes of 180 mm external diameter;
- 12,5 mm for pipes of 220 mm external diameter or greater.
Intermediate minimum thicknesses are to be determined by linear
interpolation. Unless required by Pt 3, Ch 12, 4.1 General 4.1.8, the maximum thickness need not exceed 12,5 mm.
4.2.8 If
a valve is required by Pt 3, Ch 12, 4.1 General 4.1.3,
this valve should preferably be fitted as close as possible to the
point of entry of the pipe into the tank. If fitted below the freeboard
deck, the valve is to be capable of being controlled from an easily
accessible position above the freeboard deck. Local control is also
to be arranged, unless the valve is inaccessible. An indicator is
to be fitted at the control position showing whether the valve is
open or closed.
4.2.9 In
a ship to which timber freeboards are assigned, the summer load waterline
is to be regarded as that corresponding to the timber summer freeboard.
4.3 Rubbish chutes, offal and similar discharges
4.3.1 Rubbish
chutes, offal and similar discharges should be constructed of mild
steel piping or plating of shell thickness. Other materials will be
specially considered. Openings are to be kept clear of the sheerstrake
and areas of high stress concentration.
4.3.2 Rubbish
chute hoppers are to be provided with a hinged weathertight cover
at the inboard end with an interlock so that the discharge flap and
hopper cover cannot be open at the same time. The hopper cover is
to be secured closed when not in use, and a suitable notice displayed
at the control position.
4.3.3 Where
the inboard end of the hopper is less than 0,01L
L above
the summer load waterline, a suitable valve with positive means for
closing is to be provided in addition to the cover and flap in an
easily accessible position above the deepest seasonal waterline. The
valve is to be controlled from a position adjacent to the hopper and
provided with an open/shut indicator. The valve is to be kept closed
when not in use, and a suitable notice displayed at the valve operating
position.
4.3.4 Where
damage stability requirements apply and the inboard end of the chute
is below the equilibrium waterlines, or in passenger ships, where
the inboard end of a rubbish chute is below the margin line; see
Pt 3, Ch 11, 8.2 General 8.2.8.(b).
4.3.5 In
trawlers or fish factory ships, offal discharges in the fish working
spaces are to be provided with either a non-return flap, preferably
fitted at the shell which can be positively secured weathertight,
or a separate positively controlled valve kept closed when not in
use. A suitable notice is to be displayed at the flap or valve operating
position.
4.4 Materials for valves, fittings and pipes
4.4.2 All
these items, if made of steel or other approved material with low
corrosion resistance, are to be suitably protected against wastage.
4.4.3 The
lengths of pipe attached to the shell fittings, elbow pieces or valves
are to be of galvanised steel or other equivalent approved material.
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