Section
4 Side, stern doors and other shell openings
4.1 Symbols
4.1.1 The
symbols used in this Section are defined as follows:
|
d
|
= |
distance
between closing devices, in metres |
|
= |
moment of inertia, in
cm4, of the stiffener or girder, in association with an
effective width of attached plating determined in accordance with Vol 1, Pt 6, Ch 2, 5 Dynamic loading
|
|
σ |
= |
bending stress,
in N/mm2
|
|
σe
|
= |
equivalent
stress, in N/mm2
|
| = |
|
|
σo
|
= |
minimum
yield stress of the bearing material, in N/mm2
|
|
τ |
= |
shear stress,
in N/mm2
|
4.2 General
4.2.1 These
requirements cover service doors in the ship side (abaft the collision
bulkhead) and stern area, below the weather deck and in enclosed superstructures.
4.2.3 Side
and stern doors are to be so fitted as to ensure tightness and structural
integrity commensurate with their location and the surrounding structure, see also
Vol 1, Pt 3, Ch 1, 5 Definitions
4.2.4 In general,
the lower edge of door openings is not to be below a line drawn parallel
to the design draught.
4.2.5 When
the lower edge is below the design draught or doors below the vertical
limit of watertight integrity are to be opened at sea, the arrangements
will be specially considered. In general, the enclosed spaces protected
by the door are to be considered open as well as closed in damage
stability or flooding conditions.
4.2.6 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 lower decks above the waterline.
4.3 Construction and testing
4.3.1 Plans
are to be of sufficient detail for plan approval purposes. Plans showing
the proposed scantlings and arrangements of any side and stern doors
or other shell openings are to be submitted. Side and stern doors
or other shell openings are to be constructed under survey.
4.3.2 Side
and stern doors fitted below the limit of watertight integrity are
to be subject to a pressure test of a prototype to confirm the design
pressure head.
4.4 Scantlings
4.4.1 In general
the strength of side and stern doors is to be equivalent to the strength
of the surrounding structure.
4.4.2 Door
openings in the side shell are to have well rounded corners and adequate
compensation is to be arranged with web frames at sides and stringers
or equivalent above and below, see
Vol 1, Pt 3, Ch 1, 5 Definitions.
4.4.3 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 ship structure.
4.4.4 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.
4.4.5 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 Vol 1, Pt 4, Ch 3, 4.4 Scantlings 4.4.4. Those parts of the stern
door which are not protected by the ramp are to have the thickness
of plating in full compliance with Vol 1, Pt 4, Ch 3, 4.4 Scantlings 4.4.4.
4.4.7 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 ship’s frames and door stiffeners.
4.4.8 Where
necessary, door secondary stiffeners are to be supported by primary
members constituting the main stiffening elements of the door.
4.4.9 The
scantlings of such primary members are to be based on direct strength
calculations. Normally, formulae for simple beam theory may be applied
to determine the bending stress. Members are to be considered to have
simply supported end connections. The design load is the uniformly
distributed external sea pressure, p
e, as
defined in Vol 1, Pt 4, Ch 3, 4.9 Design loads 4.9.1. For minimum
scantlings, p
e is to be taken as 25 kN/m2 and
the permissible stresses are as follows:
4.4.10 The
webs of primary members are to be adequately stiffened, preferably
in a direction perpendicular to the shell plating.
4.4.11 The
stiffness of the edges of the doors and the hull structure in way
are to be sufficient to ensure weathertight integrity. Edge stiffeners/girders
are to be adequately stiffened against rotation and are to have a
moment of inertia not less than:
|
= |
0,8 P
L
d
4 cm4
|
where
|
P
L
|
= |
packing line pressure along edges, not to be taken less than
50 N/cm. |
For edge girders supporting main door girders between
securing devices, the moment of inertia is to be increased in relation
to the additional force.
4.4.12 The
buckling strength of primary members is to be specially considered.
4.4.13 All
load transmitting elements in the design load path from door through
securing and supporting devices into the ship structure, including
welded connections, are to be to the same strength standard as required
for the securing and supporting devices. These elements include pins,
supporting brackets and back-up brackets. Where cut-outs are made
in the supporting structure, the strength and stiffness will be specially
considered.
4.5 Doors serving as ramps
4.5.2 The
design of the hinges for these doors should take into account the
ship angle of trim or heel which may result in uneven loading of the
hinges.
4.6 Closing, securing and supporting of doors
4.6.1 Doors
are to be fitted with adequate means of closing, securing and support
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 generally not to exceed 3 mm.
4.6.2 Devices
are to be simple to operate and easily accessible. They are to be
of an approved type.
4.6.3 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
a proper sequence.
4.6.4 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 of 1,5 kN/m2 acting on the
maximum projected area in the open position.
4.6.5 The
spacing for cleats or closing devices should not exceed 2,5 m and
there should be cleats or closing devices positioned as close to the
corners as practicable. Alternative arrangements for ensuring weathertight
sealing will be specially considered.
4.7 Systems for operation
4.7.1 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 vertical limit
of watertight integrity with a clear opening area greater than 6 m2 are
to be provided with an arrangement for remote control from a position
above the vertical limit of watertight integrity. This remote control
is provided for the:
-
Closing and opening
of the doors.
-
Associated securing
and locking devices.
4.7.2 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.
4.7.3 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 the
ship leaves the berth and that this operation is to be entered in
the ship’s log.
4.7.4 Means
are to be provided to prevent unauthorised operation of the doors.
4.7.5 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.
4.8 Systems for indication and monitoring
4.8.1 The following requirements apply to doors in the boundaries of special
category spaces or vehicle spaces, through which such spaces may be flooded. For ships,
where no part of the door is below the design waterline, doors that are to be opened at
sea are above the vertical limit of watertight integrity, and the area of the door
opening is not greater than 6 m2, then the requirements of this Section need
not be applied.
4.8.2 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.
4.8.3 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.
4.8.4 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
vessel leaves harbour with side shell or stern doors not closed or with any of the
securing devices not in the correct position.
4.8.5 Where not already installed, a Closed circuit television surveillance and a water
leakage detection system, of approved type and suitable for the intended location, shall
be arranged to provide both a visible and an audible indication to the navigation bridge
and to the main machinery control station of any leakage through the side or stern
doors, or any other shell openings which could lead to major flooding.
4.9 Design loads
4.9.1 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:
|
|
|
F
e = Ap
e + F
p kN
|
|
|
Internal force:
|
|
|
F
i = F
o + 10W kN
|
-
Design forces
for securing or supporting devices of doors opening outwards:
|
|
External force:
|
|
|
F
e = Ap
e kN
|
|
|
Internal force:
|
|
|
P
i = P
o + 10W + F
p kN
|
-
Design forces
for primary members:
|
|
External force:
|
|
|
F
e = Ap
e kN
|
|
|
Internal force:
|
|
|
F
i = P
o + 10W kN
|
|
|
whichever is the greater.
|
The symbols used are defined as follows:
|
p
e
|
= |
external sea pressure, in kN/m2, determined at the centre
of gravity of the door opening and is not to be taken less than: |
- for ZG < T 10 (T – ZG ) + 25
kN/m2
- for Z
G ≥ T 25 kN/m2
- For stern doors, p
e is not to be taken less than:
|
p
emin |
= |
|
|
T
|
= |
design draught, in metres |
|
Z
G
|
= |
height of the centre of area of the door, in metres, above the
baseline |
|
L
R
|
= |
length of ship, but need not be taken greater than 200 m |
|
λ |
= |
coefficient
depending on the area where the ship is intended to be operated: |
| = |
1 for sea-going ships with service area notation SA1, SA2 and
SA3
|
| = |
0,5 for ships operated in sheltered waters with service area notation
SA4
|
|
C
H
|
= |
0,0125L
R for L
R <
80 m
|
| = |
1 for L
R ≥ 80 m |
|
A
|
= |
area,
in m2, of the door opening
|
|
W
|
= |
weight
of the door, in tonnes |
|
F
p
|
= |
total packing force, kN. When packing is fitted, the packing
line pressure is to be specified, normally not to be taken less than
5 kN/m2
|
|
F
o
|
= |
the greater of F
c and 5,0A kN
|
|
F
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
items.
|
4.10 Design of securing and supporting devices
4.10.1 Securing
devices and supporting devices are to be designed to withstand the
forces given above using the following permissible stresses:
The terms ‘securing device’ and ‘supporting
device’ are defined in Vol 1, Pt 4, Ch 3, 3 Bow doors
4.10.2 The
arrangement of securing and supporting devices is to be such that
threaded bolts are not to carry support forces. The maximum tensile
stress in way of threads of bolts, not carrying support forces, is
not to exceed:
4.10.3 For
steel to steel bearings in securing and supporting devices, the normal
bearing pressure is not to exceed 0,8σo, see
Vol 1, Pt 4, Ch 3, 4.1 Symbols 4.1.1 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.
4.10.4 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.
4.10.5 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.
4.10.7 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 as defined in Vol 1, Pt 4, Ch 3, 4.10 Design of securing and supporting devices 4.10.1.
4.11 Operating and Maintenance Manual
4.11.1 An
Operating and Maintenance Manual for the doors is to be provided on
board. The manual is to contain the following information:
-
main particulars
and design drawings,
- special safety precautions;
- details of vessel, class and statutory certificates;
- equipment and design loading for ramps;
- key plan of equipment for doors and ramps;
- manufacturers' recommended testing for equipment; and
- a description of the following equipment: side doors; stern doors;
central power pack; bridge panel; ramps leading down from the main
deck; engine control room panel.
-
service conditions:
- limiting heel and trim of the ship for loading/unloading;
- limiting heel and trim for door operations;
- operating instructions for doors and ramps and
- emergency operating instructions for doors and ramps.
-
maintenance:
- schedule and extent of maintenance;
- troubleshooting and acceptable clearances; and
- manufacturers' maintenance procedures.
-
register of inspections,
including inspection of locking, securing and supporting devices,
repairs and renewals.
4.11.2 The
Manual is to be submitted for approval, and is to contain a note recommending
that recorded inspections of the door supporting and securing devices
be carried out by the ship’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.
4.11.3 Documented
operating procedures for closing and securing the doors are to be
kept on board and posted at an appropriate place.
|