Section
8 Scuppers and sanitary discharges
8.1 General
8.1.1 Scuppers
sufficient in number and size to provide effective drainage are to
be fitted in all decks.
8.1.2 Scuppers
draining weather decks and spaces within superstructures or deckhouses
not fitted with efficient weathertight doors are to be led overboard.
8.1.3 Where
the freeboard is such that the deck edge forming the vertical limit
of watertight integrity is immersed when the ship heels 5° or
less, scuppers and discharges which drain spaces below this deck,
or spaces within intact superstructures or deckhouses on this 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 deck
edge forming the vertical limit of watertight integrity 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 Vol 1, Pt 3, Ch 4, 8.2 Closing appliances.
8.1.4 In ships
where an approved fixed pressure water spray fire-extinguishing system
is fitted in vehicle, magazines or hangar spaces, deck scuppers of
not less than 150 mm diameter are to be provided port and starboard,
spaced about 9,0 m apart. Where the design capacity of the drencher
system exceeds an application of water at a rate 5 litres per square
metre of deck area by 10 per cent or more, the scupper area will require
to be increased accordingly. 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.
The mouth of the scupper is to be protected by bars.
8.1.6 The
minimum wall thickness of pipes not indicated in Vol 1, Pt 3, Ch 4, 8.2 Closing appliances 8.2.6 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.
8.1.8 Scuppers
and discharge pipes should not normally pass through fuel oil tanks.
Where scuppers and discharge pipes pass, unavoidably, through fuel
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.
8.1.9 Piping within tanks is to be tested in accordance with Naval Survey
Guidance for Steel Ships, or an otherwise specified and agreed standard.
8.1.10 All
piping is to be adequately supported.
8.2 Closing appliances
8.2.1 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 damage control 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. Spaces with access
only by bolted manholes are not considered accessible.
8.2.2 Where
an approved fire pressure waterspray fire-extinguishing system is
provided in an enclosed vehicle space, magazines or hangar spaces,
the scupper controls are to be operated from a position above the
damage control deck, and outside the space protected by the fire-extinguishing
system, and are to be protected from mechanical damage.
8.2.3 Where
the vertical distance from the design draught to the inboard end of
the discharge pipe exceeds 0,01L
R 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.
8.2.4 Where
the vertical distance from the design waterline to the inboard end
of the discharge pipe exceeds 0,02L
R, a single
automatic non-return valve without positive means of closing may be
fitted, see
Figure 4.8.1 Diagrammatic arrangement of discharge valves
Figure 4.8.1 Diagrammatic arrangement of discharge valves
8.2.5 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, a single screw-down valve operated from the
weather deck is considered to provide sufficient protection.
8.2.6 Scuppers and discharge pipes originating at any level which penetrate the
shell either more than 450 mm below the deck forming the vertical limit of watertight
integrity or less than 600 mm above the design draught waterline, are to be fitted with
an automatic non-return valve at the shell. This valve, unless required by Vol 1, Pt 3, Ch 4, 8.1 General 8.1.3, 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 Vol 1, Pt 3, Ch 4, 8.1 General 8.1.8,
the maximum thickness need not exceed 12,5 mm.
8.2.7 The
outboard valve is to be mounted directly on the shell and secured
in accordance with Vol 2, Pt 7, Ch 1 Piping Design Requirements.
If this is impracticable, a short distance piece of rigid construction
may be introduced between the valve and the shell.
8.2.8 If a
valve is required by Vol 1, Pt 3, Ch 4, 8.1 General 8.1.3,
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 weather
deck, the valve is to be capable of being controlled from an easily
accessible position above the weather 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.
8.3 Rubbish chutes and similar discharges
8.3.1 Rubbish
chutes 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.
8.3.2 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.
8.3.3 Where
the inboard end of the hopper is less than 0,01L
R above the design draught, 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 design
draught. 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.
8.4 Materials for valves, fittings and pipes
8.4.2 All
these items, if made of steel or other approved material with low
corrosion resistance, are to be suitably protected against wastage.
8.4.3 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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