Section
4 Side and stern doors and other shell openings
4.1 General
4.1.1 These requirements
cover cargo and service doors in the craft side (abaft the collision
bulkhead) and stern area, below the freeboard deck and in enclosed
superstructures.
4.1.4 In general,
the lower edge of door openings are not to be below a line drawn parallel
to the freeboard deck at side, which is at its lowest point at least
230 mm above the upper edge of the uppermost Load Line.
4.1.5 When the
lower edge is below the uppermost Load Line, the arrangement will
be specially considered. Special consideration is to be given to preventing
the spread of leakage water over the deck. The reference to the uppermost
Load Line is to be taken as the tropical fresh water line.
4.1.6 Doors are
generally to be arranged to open outwards, however inward opening
doors will be considered provided strongbacks are fitted when the
doors are situated in the first two 'tween decks above the waterline.
4.1.7 For passenger
craft the following is also applicable:
-
Gangway, cargo and
service ports fitted below the margin line, see
Pt 3, Ch 4, 1.2 Downflooding 1.2.2, are to satisfy the strength
requirements given for side doors in this Section. They are to be
effectively closed and secured watertight before the craft leaves
port, and are to be kept closed during navigation. Such ports are
not to have their lowest point below the deepest subdivision Load
Line.
-
Where the inboard
end of a rubbish chute is below the margin line in a passenger craft,
the inboard end cover is to be watertight and, in addition to the
discharge flap interlock, a screwdown automatic non-return valve is
to be fitted in an easily accessible position above the deepest subdivision.
The valve is to be controlled from a position above the bulkhead deck
and provided with an open/shut indicator, and kept closed when not
in use. A suitable notice is to be displayed at the valve position.
4.1.8 Where doors
and platforms are fitted in the shell, the structural and watertight
integrity of the hull is to be maintained. Such doors and platforms
are not to lead directly into the craft and an internal watertight
compartment is to be provided in way of the shell openings. The doors
and platforms are to be arranged to open outwards. The sill height
of the access hull opening is not to be less than 230 mm above the
upper edge of the uppermost Load Line and the sill height of the internal
access is to be not less than 300 mm higher than the hull sill. Alternative
arrangements will be specially considered.
4.1.9 Doors may
be of steel, aluminium alloy or FRP construction and are to be efficiently
connected to the adjoining structure and of equivalent strength and
are to have adequate securing and sealing arrangements. It is recommended
that doors are hinged about their forward edges and open outwards.
Details are to be submitted for approval. Other materials will be
specially considered.
4.1.10 For craft
complying with the requirements of this Section, the securing, supporting
and locking devices are defined as follows:
-
A securing device
is used to keep the door closed by preventing it from rotating about
its hinges or other pivoted attachments to the craft.
-
A supporting device
is used to transmit external and internal loads from the door to a
securing device and from the securing device to the craft's structure,
or a device other than a securing device, such as a hinge, stopper
or other fixed device, that transmits loads from the door to the craft's
structure.
-
A locking device
locks a securing device in the closed position.
4.2 Symbols
4.2.1 The symbols
used in this Section are defined as follows:
|
σ |
= |
bending
stress, in N/mm2
|
|
σe
|
= |
equivalent
stress, in N/mm2
|
|
|
= |
|
|
τ |
= |
shear stress,
in N/mm2
|
σo is defined in Pt 3, Ch 3, 1.2 General.
4.3 Scantlings
4.3.1 In general
the strength of side and stern doors is to be equivalent to the strength
of the surrounding structure.
4.3.3 Doors are
to be adequately stiffened, and means are to be provided to prevent
movement of the doors when closed. Adequate strength is to be provided
in the connections of the lifting/manoeuvring arms and hinges to the
door structure and to the craft structure.
4.3.4 The thickness
of the door plating is to be not less than the shell plating calculated
with the door stiffener spacing, and in no case to be less than the
minimum adjacent shell thickness.
4.3.5 Where stern
doors are protected against direct wave impact by a permanent external
ramp, the thickness of the stern door plating may be reduced by 20
per cent relative to the requirements of Pt 3, Ch 4, 4.3 Scantlings 4.3.4. Those parts of the stern door which are not protected by
the ramp are to have the thickness of plating in full compliance with Pt 3, Ch 4, 4.3 Scantlings 4.3.4.
4.3.6 The section
modulus of horizontal or vertical stiffeners is to be not less than
required for the adjacent shell framing using the actual stiffener
spacing. Consideration is to be given, where necessary, to differences
in fixity between shell frames and door stiffeners.
4.3.7 Where necessary,
door secondary stiffeners are to be supported by primary members constituting
the main stiffening elements of the door.
4.3.8 The webs
of primary members are to be adequately stiffened, preferably in a
direction perpendicular to the shell plating.
4.3.9 The buckling
strength of primary members is to be specially considered.
4.3.10 All load
transmitting elements in the design load path from door through securing
and supporting devices into the craft structure, including welded
connections, are to be to the same strength standard as required for
the securing and supporting devices.
4.4 Doors serving as ramps
4.5 Closing, securing and supporting of doors
4.5.1 Doors are
to be fitted with adequate means of closing, securing and supporting
so as to be commensurate with the strength and stiffness of the surrounding
structure. The hull supporting structure in way of the doors is to
be suitable for the same design loads and design stresses as the securing
and supporting devices. Where packing is required, the packing material
is to be of comparatively soft type, and the supporting forces are
to be carried by the steel structure only. Other types of packing
may be considered. Maximum design clearance between securing and supporting
devices is not generally to exceed 3 mm.
4.5.2 Securing
devices are to be simple to operate and easily accessible. They are
to be of an approved type.
4.5.3 Securing
devices are to be equipped with mechanical locking arrangements (self
locking or separate arrangements), or are to be of gravity type. The
opening and closing systems as well as securing and locking devices
are to be interlocked in such a way that they can only operate in
the proper sequence.
4.5.4 Means are to be provided to enable the doors to be mechanically fixed in the
open position taking into account the self weight of the door and a minimum wind
pressure. The following minimum wind pressure and direction need to be considered:
- 1,5 kN/m2 (0,153 tonne-f/m2) acting on the maximum
projected area in the open position. Maximum projected area is to be determined by
the projected area of the open door onto the ship’s vertical plane, thereby
considering static heel angles of the vessel of up to 15 degrees; and
- 150 N/m2 acting on the maximum projected area of the open door onto a
horizontal plane .
4.5.5 The spacing
for cleats or closing devices is not to exceed 2,5 m and cleats or
closing devices are to be positioned as close to the corners as practicable.
Alternative arrangements for ensuring weathertight sealing will be
specially considered. Where special consideration is made, the maximum
deflection of the door edge between the cleats under the pressure
loading (internal/external for outside/inside opening doors respectively)
is to be limited to 1/1000 of the cleats distance, applying the load
specified in Pt 3, Ch 4, 4.5 Closing, securing and supporting of doors 4.5.11 acting to
push the door open.
4.5.6 Doors with
a clear opening area of 12 m2 or greater are to be provided
with closing devices operable from a remote control position. Doors
which are located partly or totally below the freeboard deck with
a clear opening area greater than 6m2 are to be provided
with an arrangement for remote control from a position above the freeboard
deck. This remote control is provided for the:
-
Closing and opening
of the doors.
-
Associated securing
and locking devices.
4.5.7 The location
of the remote control panel is to be such that the opening/closing
operation can be easily observed by the operator or by other suitable
means such as closed circuit television.
4.5.8 A notice
is to be displayed at the operating panel stating that the door is
to be fully closed and secured preferably before, or immediately prior
to, the craft leaving the berth and that this operation is to be entered
in the craft's log. This notice is to be supplemented by warning indicator
lights indicating if any door is not fully closed, secured and locked.
4.5.9 Means are
to be provided to prevent unauthorised operation of the doors.
4.5.10 Where
hydraulic securing devices are applied, the system is to be mechanically
lockable in the closed position so that in the event of hydraulic
system failure, the securing devices will remain locked. The hydraulic
system for securing and locking devices is to be isolated from other
hydraulic circuits when in the closed position.
4.5.11 The design
force considered for the scantlings of primary members, securing and
supporting devices of side shell doors and stern doors are to be taken
not less than:
-
Design forces for
securing or supporting devices of doors opening inwards:
External force:
Internal force:
-
Design forces for
securing or supporting devices of doors opening outwards:
External force:
Internal force:
-
Design forces for
primary members:
External force:
Internal force:
whichever is the greater.
The symbols used are defined
as follows:
|
p
e
|
= |
external sea pressure, not to be taken less than 25 kN/m2
|
|
A
|
= |
total
area of door opening, in m2 to be determined on the basis
of the load area taking account of the direction of pressure
|
|
W
|
= |
weight
of the door, in tonnes |
|
F
p
|
= |
total packing force, kN. When packing is fitted, the packing
force per unit length is to be specified, normally not to be taken
less than: 5 kN/m |
|
P
o
|
= |
the greater of P
c and 5A kN
|
|
P
c
|
= |
accidental force, in kN, due to loose cargo, etc. to be uniformly
distributed over the area A and not to be taken less
than 300 kN. For small doors such as bunker doors and pilot doors,
the value of P
c may be taken as zero, provided
an additional structure such as an inner ramp is fitted, which is
capable of protecting the door from accidental force due to loose
cargoes.
|
4.6 Systems for indication and monitoring
4.6.1 The following
requirements apply to doors in the boundaries of special category
spaces or ro-ro spaces, as defined in the SOLAS Convention, through
which such spaces may be flooded. For cargo craft, where no part of
the door is below the uppermost waterline and the area of the door
opening is not greater than 6 m2, then the requirements
of this Section need not be applied.
4.6.2 Separate
indicator lights and audible alarms are to be provided on the navigation
bridge and on each operating panel to indicate that the doors are
closed and that their securing and locking devices are properly positioned.
The indication panel is to be provided with a lamp test function.
It is not to be possible to turn off the indicator light.
4.6.3 The indicator
system is to be designed on the fail safe principle and is to indicate
by visual alarms if the door is not fully closed and not fully locked,
and by audible alarms if securing devices become open or locking devices
become unsecured. The power supply for the indicator system is to
be independent of the power supply for operating and closing the doors
and is to be provided with a back-up power supply. The sensors of
the indicator system are to be protected from water, ice formation
and mechanical damages.
4.6.4 The indication
panel on the navigation bridge is to be equipped with a mode selection
function `harbour/sea voyage', so arranged that audible alarm is given
if the craft leaves harbour with side shell or stern doors not closed
or with any of the securing devices not in the correct position.
4.6.5 For passenger
craft, a water leakage detection system with audible alarm and television
surveillance are to be arranged to provide an indication to the navigation
bridge and to the engine control room of any leakage through the doors.
For cargo craft, a water leakage detection system with audible alarm
is to be arranged to provide an indication to the navigation bridge.
4.7 Design of securing and supporting devices
4.7.3 For steel
to steel bearings in securing and supporting devices, the normal bearing
pressure is not to exceed 0,8σo. For other bearing
materials, the permissible bearing pressure is to be determined according
to the manufacturer's specification. The normal bearing pressure is
to be calculated by dividing the design force by the projected bearing
area.
4.7.4 The distribution
of the reaction forces acting on the securing and supporting devices
may require to be supported by direct calculations taking into account
the flexibility of the hull structure and the actual position and
stiffness of the supports. Small and/or flexible devices, such as
cleats, intended to provide load compression of the packing material
are not generally to be included in these calculations.
4.7.5 Only the
active supporting and securing devices having an effective stiffness
in the relevant direction are to be considered in the calculation
of the reaction forces acting on the devices.
4.7.6 The number
of securing and supporting devices is generally to be the minimum
practicable whilst complying with Pt 3, Ch 4, 4.5 Closing, securing and supporting of doors 4.5.3 and
taking account of the available space in the hull for adequate support.
Table 4.4.1 Permissible stress for bolts,
closing and supporting devices
| Material
|
Closing and supporting devices
|
Thread of bolts
|
| Direct stress
|
Shear stress
|
Equivalent
stress
|
Direct stress
|
| N/mm2
|
N/mm2
|
N/mm2
|
N/mm2
|
| Steel
|
|
|
|
|
| Aluminium
|
|
|
|
|
|
|
4.7.7 The arrangement
of securing devices and supporting devices in way of these securing
devices is to be designed with redundancy so that in the event of
failure of any single securing or supporting device the remaining
devices are capable of withstanding the reaction forces, without exceeding,
by more than 20 per cent, the permissible stresses referred to in Pt 3, Ch 4, 4.7 Design of securing and supporting devices 4.7.1.
4.8 Operating and Maintenance Manual
4.8.1 An Operating
and Maintenance Manual for the doors is to be provided on board and
is to contain necessary information on:
-
main particulars
and design drawings;
-
service conditions,
(e.g. service area restrictions, acceptable clearances for supports);
-
maintenance and function
testing;
-
register of inspections
and repairs.
This Manual is to be submitted to LR for review, and is to contain
a note recommending that recorded inspections of the door supporting
and securing devices be carried out by the craft's staff at monthly
intervals or following incidents that could result in damage, including
heavy weather or contact in the region of the doors. Any damages recorded
during such inspections are to be reported to LR.
4.8.2 Documented
operating procedures for closing and securing the doors are to be
kept on board and posted at an appropriate place.
4.9 Engine removal arrangements
4.9.1 Where portable
plates are required for unshipping machinery, or for other similar
reasons, they may be accepted provided they are of equivalent strength
to the unpierced structure and are secured by gaskets and close spaced
bolts. The pitch spacing of the bolts will be specially considered
depending on the hatch stiffening and support arrangements but should
not exceed ten diameters.
4.10 Testing on completion
|