Section
11 Electric cables, optical fibre cables and busbar trunking systems
(busways)
11.1 General
11.1.2 Electric
cables for fixed wiring are to be designed, manufactured and tested
in accordance with the relevant IEC Standard stated in Table 2.11.1 Electric cables or an adequate and
relevant National Standard.
11.1.3 Details
of optical fibre cables for fixed installation are to be submitted
to assess compliance with applicable international or National Standards.
These are to include:
- Flame retardancy;
- Fire resistance (if applicable);
- Smoke density;
- Halogen content;
- Mechanical properties;
Suitability for use in the marine environment.
11.1.4 Electric cables for electric propulsion systems are to be Type Approved in
accordance with LR’s Type Approval System Test Specification Number 3 or,
alternatively, surveyed by the Surveyors during manufacture and testing to assess
compliance with the applicable International or National Standards and application of an
acceptable quality management system, see also
Pt 6, Ch 2, 1.4 Surveys 1.4.6.
11.1.5 Provided
that adequate flexibility of the finished cable is assured, conductors
of nominal cross-section area 2,5 mm2 and less need not
be stranded.
11.1.6 Electric
and optical fibre cables for non-fixed applications are to comply
with a relevant national or international Standard.
11.1.7 For
the purpose of this Section, pipes, conduits, trunking or any other
system for the additional mechanical protection of cables are hereafter
referred to under the generic name 'protective casings'.
11.1.8 Electrical
cables for telecommunications and data transfer are, whenever practicable,
to be selected in accordance with the recommendations of IEC TR 60092-370: Guidance on the selection of cables for telecommunication and data
transfer including radio-frequency cables.
Table 2.11.1 Electric cables
Application
|
IEC Standard
|
Title
|
General constructional and testing
requirements
|
60092–350
|
Electrical installations in ships – Part 350:
General construction and test methods of power, control and instrumentation
cables for shipboard and offshore applications
|
Fixed power and control
circuits
|
60092–353
|
Electrical installations in ships – Part 353:
Power cables for rated voltages 1 kV and 3 kV
|
Fixed power circuits
|
60092–354
|
Electrical installations in ships – Part 354:
Single- and three-core power cables with extruded solid insulation for rated
voltages 6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)
|
Instrumentation, control
and communication circuits up to 60 V
|
60092-370
|
Electrical installations in ships –
Part 370: Guidance on the selection of cables for telecommunication and data
transfer including radio-frequency cables
|
Control circuits and instrumentation
up to 250 V
|
60092–376
|
Electrical installations in ships – Part 376:
Cables for control and instrumentation circuits 150/250 V (300 V)
|
Mineral insulated
|
60702 (all parts)
|
Mineral insulated cables and their terminations with a
rated voltage not exceeding 750 V
|
11.2 Testing
11.2.1 Routine
tests, consisting of at least:
-
measurement of
electrical resistance of conductors;
-
high voltage
test, see also
Pt 6, Ch 2, 21 Testing and trials;
-
insulation resistance
measurement;
-
for high voltage cables, partial discharge tests are to be made in
accordance with the requirements of IEC 60885-2: Electrical test methods for
electric cables – Part 2: Partial discharge tests, or an acceptable and
relevant National Standard, at the manufacturer's works prior to despatch; and
-
for optical fibres, an attenuation loss (see
Pt 6, Ch 2, 21.6 Optical Fibre Communications Systems).
Evidence of successful completion of routine tests is to be
provided by the manufacturer, see also Pt 6, Ch 2, 11.1 General 11.1.4.
11.2.2 Particular,
special and type tests are to be made, when required, in accordance
with the requirements of the relevant publication or National Standard
referred to in Pt 6, Ch 2, 11.1 General 11.1.2 and
a test report issued by the manufacturer.
11.3 Voltage rating
11.3.1 The
rated voltage of any electric cable is to be not lower than the nominal
voltage of the circuit for which it is used. The maximum sustained
voltage of the circuit is not to exceed the maximum voltage for which
the cable has been designed.
11.3.2 Electric
cables used in unearthed systems are to be suitably rated to withstand
the additional stresses imposed on the insulation due to an earth
fault.
11.4 Operating temperature
11.4.1 The
maximum rated conductor temperature of the insulating material for
normal operation is to be at least 10°C higher than the maximum
ambient temperature liable to be produced in the space where the cable
is installed.
11.4.2 The
maximum rated conductor temperatures for normal and short-circuit
operation, for the insulating materials included within the standards
referred to in Pt 6, Ch 2, 11.1 General 11.1.2 is
not to exceed the values stated in Table 2.11.2 Maximum rated conductor
temperature.
Table 2.11.2 Maximum rated conductor
temperature
Type of insulating compound
|
Maximum rated conductor temperature, °C
|
Abbreviated
designation
|
Normal operation
|
Short-circuit
|
Elastomeric or thermosetting, based upon:
|
|
|
|
Ethylene-propylene rubber or similar
(EPM or EPDM)
|
EPR
|
90
|
250
|
High modulus or hard
grade ethylene propylene rubber
|
HEPR
|
90
|
250
|
Cross-linked
polyethylene
|
XLPE
|
90
|
250
|
Cross-linked polyolefin material for halogen-free cables
|
HF90
|
90
|
250
|
Silicone
rubber
|
S95
|
95
|
350
|
11.5 Construction
11.5.1 Electric
and optical fibre cables are to be at least of a flame-retardant type.
IEC 60332-1-2: Tests on electric and optical fibre cables under
fire conditions – Part 1-2: Test for vertical flame propagation
for a single insulated wire or cable – Procedure for 1 kW pre-mixed
flame, will be acceptable.
11.5.2 Exemption
from the requirements of Pt 6, Ch 2, 11.5 Construction 11.5.1 for
applications such as radio frequency or digital communication systems,
which require the use of particular types of cable, will be subject
to special consideration.
11.5.3 Where
electric and optical fibre cables are required to be of a `fire resistant
type', they are in addition to be easily distinguishable and comply
with the performance requirements of the appropriate part of IEC 60331: Tests for electric cables under fire conditions – Circuit integrity,when tested with a minimum flame application time of 90 minutes,
as follows:
- IEC 60331-1:Tests for electric cables under fire conditions – Circuit
integrity – Part 1: Test method for fire with shock at a temperature of at least
830 degrees C for cables of rated voltage up to and including 0,6/1,0 kV and with
an overall diameter exceeding 20 mm;
- IEC 60331-2: Tests for electric cables under fire conditions – Circuit integrity
– Part 2: Test method for fire with shock at a temperature of at least 830 Degrees
C for cables of rated voltage up to and including 0,6/1,0 kV and with an overall
diameter not exceeding 20 mm;
- IEC 60331-21: Tests for electric cables under fire conditions – Circuit integrity
– Part 21: Procedures and requirements – Cables of rated voltage up to and
including 0,6/1,0 kV;
- IEC 60331-23: Tests for electric cables under fire conditions
– Circuit integrity – Part 23: Procedures and requirements
– Electric data cables; or
- IEC 60331-25: Tests for electric cables under fire conditions
– Circuit integrity – Part 25: Procedures and requirements
– Optical fibre cables.
11.5.4 Where
electric or optical fibre cables are installed in locations exposed
to the weather, in damp and in wet situations, in machinery compartments,
refrigerated spaces or exposed to harmful vapours including oil vapour
they are to have the conductor insulating materials or optical fibres
enclosed in an impervious sheath of material appropriate to the expected
ambient conditions.
11.5.5 Where
electric or optical fibre cables are installed in locations which
are totally submerged for extended periods of time, they are to have
the conductor insulating materials or fibres enclosed in an impervious
sheath of material appropriate to the expected submerged conditions
and duration.
11.5.7 Where
cables are installed in an area where contamination by oil is likely
to occur, the oversheath is to be of an enhanced oil resistance grade.
11.5.8 Where
single core electric cables are used in circuits rated in excess of
20 Amps and are armoured the armour is to be of a non-magnetic material.
11.5.9 Electric
cables are to be constructed such that they are capable of withstanding
the mechanical and thermal effects of the maximum short-circuit current
which can flow in any part of the circuit in which they are installed,
taking into consideration not only the time/current characteristics
of the circuit protective device but also the peak value of the prospective
short-circuit current. Where electric cables are to be used in circuits
with a maximum short-circuit current in excess of 70 kA, evidence
is to be submitted for consideration when required demonstrating that
the cable construction can withstand the effects of the short-circuit
current.
11.5.10 All
high voltage electric cables are to be readily identified by suitable
marking.
11.6 Conductor size
11.6.1 The
maximum continuous load carried by a cable is not to exceed its continuous
current rating. It is to be chosen such that the maximum rated conductor
temperature for normal operation for the insulation is not exceeded.
In assessing the current rating the correction factors in Pt 6, Ch 2, 11.7 Correction factors for cable current rating may be applied as required.
11.6.2 The
cross-sectional area of the conductors is to be sufficient to ensure
that, under short-circuit conditions, the maximum rated conductor
temperature for short-circuit operation is not exceeded, taking into
consideration the time current characteristics of the circuit protective
device and the peak value of the prospective short-circuit current.
11.6.3 The
cable current ratings given in Table 2.11.3 Electric cable current ratings,
normal operation, based on ambient 45°C and Table 2.11.4 Electric cable current ratings,
r.m.s. short-circuit current are
based on the maximum rated conductor temperatures given in Table 2.11.2 Maximum rated conductor
temperature. When cable sizes
are selected on the basis of precise evaluation of current rating
based upon experimental and calculated data, details are to be submitted
for consideration. Alternative short-circuit temperature limits, other
than those given in Table 2.11.4 Electric cable current ratings,
r.m.s. short-circuit current,
may be applied using the data provided in:
- IEC 60724: Short-circuit temperature limits of electric
cables with rated voltages of 1kV (Um=1,2kV) and 3kV (Um=3,6kV); or
- IEC 60986: Short-circuit temperature limits of electric
cables with rated voltages from 6kV (Um=7,2kV) and up to 30kV (Um=36kV).
Alternative short-circuit temperature limits provided in an
acceptable and relevant National Standard may also be considered.
11.6.4 The
cross-sectional area of the conductors is to be sufficient to ensure
that at no point in the installation will the voltage variations stated
in Pt 6, Ch 2, 1.8 Quality of power supplies be exceeded when the
conductors are carrying the maximum current under their normal conditions
of service.
11.6.5 The
size of earth conductors is to comply with Pt 6, Ch 2, 1.12 Earthing of non-current carrying parts 1.12.8.
Table 2.11.3 Electric cable current ratings,
normal operation, based on ambient 45°C
Nominal
cross-section (mm2)
|
Continuous r.m.s. current rating, in amperes
|
Elastomeric (90°C)
|
Elastomeric or thermosetting, based on silicon rubber (95°C)
|
Single Core
|
2 core
|
3 or 4 core
|
Single Core
|
2 core
|
3 or 4 core
|
0,75
|
15
|
13
|
11
|
17
|
14
|
12
|
1
|
18
|
15
|
13
|
20
|
17
|
14
|
1,25
|
21
|
18
|
14
|
23
|
20
|
16
|
1,5
|
23
|
20
|
16
|
26
|
22
|
18
|
2
|
28
|
24
|
19
|
31
|
26
|
22
|
2,5
|
30
|
26
|
21
|
32
|
27
|
22
|
3,5
|
37
|
32
|
26
|
39
|
33
|
28
|
4
|
40
|
34
|
28
|
43
|
37
|
30
|
5,5
|
49
|
42
|
35
|
52
|
44
|
37
|
6
|
52
|
44
|
36
|
55
|
47
|
39
|
8
|
62
|
53
|
44
|
66
|
56
|
46
|
10
|
72
|
61
|
50
|
76
|
65
|
53
|
14
|
88
|
75
|
62
|
94
|
80
|
66
|
16
|
96
|
82
|
67
|
102
|
87
|
71
|
22
|
117
|
100
|
82
|
124
|
106
|
87
|
25
|
127
|
108
|
89
|
135
|
115
|
95
|
30
|
142
|
121
|
100
|
151
|
128
|
106
|
35
|
157
|
133
|
110
|
166
|
141
|
116
|
38
|
165
|
140
|
116
|
175
|
149
|
122
|
50
|
196
|
167
|
137
|
208
|
177
|
146
|
60
|
220
|
187
|
154
|
233
|
198
|
163
|
70
|
242
|
206
|
169
|
256
|
218
|
179
|
80
|
263
|
224
|
184
|
278
|
237
|
195
|
95
|
293
|
249
|
205
|
310
|
264
|
217
|
100
|
302
|
257
|
212
|
320
|
272
|
224
|
120
|
339
|
288
|
237
|
359
|
305
|
251
|
125
|
348
|
295
|
243
|
368
|
313
|
258
|
150
|
389
|
331
|
272
|
412
|
350
|
288
|
185
|
444
|
377
|
311
|
470
|
400
|
329
|
200
|
466
|
396
|
326
|
494
|
420
|
346
|
240
|
522
|
444
|
365
|
553
|
470
|
387
|
300
|
601
|
511
|
421
|
636
|
541
|
445
|
Table 2.11.4 Electric cable current ratings,
r.m.s. short-circuit current
Nominal cross-section
(mm2)
|
Fault
current (kA) at 250°C
|
Fault current (kA) at 350°C
|
1 s duration
|
0,5 s duration
|
0,1 s duration
|
1 s duration
|
0,5 s duration
|
0,1 s duration
|
0,75
|
0,1
|
0,2
|
0,3
|
0,1
|
0,2
|
0,4
|
1
|
0,1
|
0,2
|
0,5
|
0,2
|
0,2
|
0,5
|
1,25
|
0,2
|
0,3
|
0,6
|
0,2
|
0,3
|
0,7
|
1,5
|
0,2
|
0,3
|
0,7
|
0,3
|
0,4
|
0,8
|
2
|
0,3
|
0,4
|
0,9
|
0,3
|
0,5
|
1,1
|
2,5
|
0,4
|
0,5
|
1,1
|
0,4
|
0,6
|
1,4
|
3,5
|
0,5
|
0,7
|
1,6
|
0,6
|
0,8
|
1,9
|
4
|
0,6
|
0,8
|
1,8
|
0,7
|
1,0
|
2,2
|
5,5
|
0,8
|
1,1
|
2,5
|
0,9
|
1,3
|
3,0
|
6
|
0,9
|
1,2
|
2,7
|
1,0
|
1,5
|
3,2
|
8
|
1,1
|
1,6
|
3,6
|
1,4
|
1,9
|
4,3
|
10
|
1,4
|
2,0
|
4,5
|
1,7
|
2,4
|
5,4
|
14
|
2,0
|
2,8
|
6,3
|
2,4
|
3,4
|
7,6
|
16
|
2,3
|
3,2
|
7,2
|
2,7
|
3,9
|
8,7
|
22
|
3,1
|
4,5
|
10,0
|
3,8
|
5,3
|
11,9
|
25
|
3,6
|
5,1
|
11,3
|
4,3
|
6,0
|
13,5
|
30
|
4,3
|
6,1
|
13,6
|
5,1
|
7,3
|
16,2
|
35
|
5,0
|
7,1
|
15,8
|
6,0
|
8,5
|
18,9
|
38
|
5,4
|
7,7
|
17,2
|
6,5
|
9,2
|
20,6
|
50
|
7,2
|
10,1
|
22,6
|
8,6
|
12,1
|
27,1
|
60
|
8,6
|
12,1
|
27,1
|
10,3
|
14,5
|
32,5
|
70
|
10,0
|
14,2
|
31,7
|
12,0
|
16,9
|
37,9
|
80
|
11,4
|
16,2
|
36,2
|
13,7
|
19,4
|
43,3
|
95
|
13,6
|
19,2
|
43,0
|
16,3
|
23,0
|
51,4
|
100
|
14,3
|
20,2
|
45,2
|
17,1
|
24,2
|
54,1
|
120
|
17,2
|
24,3
|
54,3
|
20,5
|
29,0
|
64,9
|
125
|
17,9
|
25,3
|
56,6
|
21,4
|
30,2
|
67,6
|
150
|
21,5
|
30,4
|
67,9
|
25,7
|
36,3
|
81,2
|
185
|
26,5
|
37,4
|
83,7
|
31,7
|
44,8
|
100,1
|
200
|
28,6
|
40,5
|
90,5
|
34,2
|
48,4
|
108,2
|
240
|
34,3
|
48,6
|
108,6
|
41,1
|
58,1
|
129,9
|
300
|
42,9
|
60,7
|
135,7
|
51,3
|
72,6
|
162,3
|
11.6.6 The
cross-sectional area of conductors used in circuits supplying cyclic
or non-continuous loads is to be sufficient to ensure that the cables
maximum rated conductor temperature for normal operation is not exceeded
when the conductors are operating under their normal conditions of
service, see
Pt 6, Ch 2, 11.7 Correction factors for cable current rating 11.7.4.
11.7 Correction factors for cable current rating
11.7.2
Bunching
of cables. Where more than six electric cables, which may be
expected to operate simultaneously at their full rated capacity, are
laid close together in a cable bunch in such a way that there is an
absence of free air circulation around them, a correction factor of
0,85 is to be applied. Signal cables may be exempted from this requirement.
11.7.3
Ambient temperature. The current ratings of Table 2.11.3 Electric cable current ratings,
normal operation, based on ambient 45°C are based on an ambient temperature of 45°C.
For other values of ambient temperature the correction factors shown in Pt 6, Ch 2, 11.7 Correction factors for cable current rating 11.7.3 are to be applied.
Table 2.11.5 Correction factors
Insulation material
|
Correction factor for ambient air temperature of °C
|
35
|
40
|
45
|
50
|
55
|
60
|
65
|
70
|
75
|
80
|
85
|
Elastomeric or thermosetting (90°C)
|
1,10
|
1,05
|
1,00
|
0,94
|
0,88
|
0,82
|
0,74
|
0,67
|
0,58
|
0,47
|
—
|
Elastomeric or thermosetting, based on silicone
rubber (95°C)
|
1,10
|
1,05
|
1,00
|
0,95
|
0,89
|
0,84
|
0,77
|
0,71
|
0,63
|
0,55
|
0,45
|
11.7.4
Short
time duty. When the load is not continuous, i.e. operates for
periods of half an hour or one hour and the periods of no load are
longer than three times the cable's time constant, T in
minutes, the cable's continuous rating may be increased by a duty
factor, calculated in accordance with:
When the load is not continuous, is repetitive and
has periods of no-load less than three times the cable's time constant,
so that the cable has insufficient time to cool down between the applications
of load, the cable's continuous rating may be increased by an intermittent
factor, calculated in accordance with:
where
t
p
|
= |
the intermittent period, in minutes, i.e. the total period of
load and no-load before the cycle is repeated |
T
|
= |
0,245d
1,35 where d is the overall diameter
of the cable, in mm
|
t
s
|
= |
the service time of the load current in minutes |
11.7.5
Diversity. Where cables are used to supply two or more final sub-circuits
account may be taken of any diversity factors which may apply, see
Pt 6, Ch 2, 5.6 Diversity factor.
11.8 Installation of electric and optical fibre
cables
11.8.1 Electric
and optical fibre cable runs are to be as far as practicable fixed
in straight lines and in accessible positions.
11.8.2 Bends
in fixed electric and optical fibre cable runs are to be in accordance
with the cable manufacturer’s recommendations. The minimum internal
radius of bend for the installation of fixed electric cables is to
be chosen according to the construction and size of the cable and
is not to be less than the values given in Table 2.11.6 Minimum internal radii of bends in
cables for fixed wiring.
11.8.3 The manufacturer’s tensile load limit of the optical fibre is not to be exceeded during
installation.
11.8.4 The manufacturer’s minimum bend radii for optical fibres is not to be exceeded during
installation.
11.8.6 The
installation of electric and optical fibre cables across expansion
joints in any structure is to be avoided. Where this is not practicable,
a loop of electric cable of length sufficient to accommodate the expansion
of the joint is to be provided. For electric cables, the internal
radius of the loop is to be at least 12 times the external diameter
of the cable. For optical fibre cables, the internal radius of the
loop is to meet the manufacturers’ minimum recommendations.
11.8.7 Electric
and optical fibre cables for essential and emergency services are
to be arranged, so far as is practicable, to avoid galleys, machinery
spaces and other enclosed spaces and high fire risk areas except as
is necessary for the service being supplied. Such cables are also,
so far as reasonably practicable, to be routed clear of bulkheads
to preclude their being rendered unserviceable by heating of the bulkheads
that may be caused by a fire in an adjacent space.
11.8.8 Electric
cables having insulating materials with different maximum rated conductor
temperatures are to be so installed that the maximum rated conductor
temperature for normal operation of each cable is not exceeded.
11.8.9 Electric
and optical fibre cables having a protective covering which may damage
the covering of other cables are not to be bunched with those other
cables.
Table 2.11.6 Minimum internal radii of bends in
cables for fixed wiring
Cable construction
|
Overall diameter of
cable
|
Minimum internal
radius of bend (times overall diameter of cable)
|
Insulation
|
Outer
covering
|
Elastomeric 600/1000 V and below
|
Metal
sheathed Armoured and braided
|
Any
|
6D
|
Other
finishes
|
≤ 25 mm > 25
mm
|
4D
6D
|
Mineral
|
Hard metal sheathed
|
Any
|
6D
|
Elastomeric above 600/1000 V
|
Any
|
Any
|
12D
|
– single core
|
– multicore
|
Any
|
Any
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9D
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11.8.10 Cables
having an exposed metallic screen, braid or armour are to be installed
in such a manner that galvanic corrosion by contact with other metals
is prevented. Sufficient measures are also to be taken to prevent
damage to exposed galvanised coatings during installation.
11.8.11 Protection
is to be provided for cable oversheaths in areas where cables are
likely to be exposed to damaging substances under normal circumstances
or areas where the spillage or release of harmful substances is likely.
11.8.12 Electric
and optical fibre cables are to be as far as practicable installed
remote from sources of heat. Where installation of cables near sources
of heat cannot be avoided and where there is consequently a risk of
damage to the cables by heat, suitable shields, insulation or other
precautions are to be installed between the cables and the heat source.
The free air circulation around the cables is not to be impaired.
11.8.13 Where
electric and optical fibre cables are installed in bunches, provision
is to be made to limit the propagation of fire. This requirement is
considered satisfied when cables of the bunch have been tested in
accordance with the requirements of IEC 60332-3-22: Tests on
electric and optical fibre cables under fire conditions – Part
3-22: Test for vertical flame spread of vertically-mounted bunched
wires or cables – Category A, and are installed in the
same configuration(s) as are used for the test(s). If the cables are
not so installed, information is to be submitted to demonstrate satisfactorily
that suitable measures have been taken to ensure that an equivalent
limit of fire propagation will be achieved for the configurations
to be used. Particular attention is to be given to cables in:
- atria or equivalent spaces; and
- vertical runs in trunks and other restricted spaces.
In addition, cables that comply with the requirements of IEC
60332-3-22 are also required to meet the requirements of IEC 60332-1-2: Tests on electric and optical fibre cables under fire conditions –
Part 1-2: Test for vertical flame propagation for a single insulated
wire or cable – Procedure for 1 kW pre-mixed flame.
11.8.14 Electric
and optical fibre cables are not to be coated or painted with materials
which may adversely affect their sheath or their fire performance.
11.8.15 Where
electric and optical fibre cables are installed in refrigerated spaces
they are not to be covered with thermal insulation but may be placed
directly on the face of the refrigeration chamber, provided that precautions
are taken to prevent the electric cables being used as casual means
of suspension.
11.8.17 High
voltage cables may be installed as follows:
-
in the open,
(e.g. on carrier plating), when they are to be provided with a continuous
metallic sheath or armour which is effectively bonded to earth to
reduce danger to personnel. The metallic sheath or armour may be omitted
provided that the cable sheathing material has a longitudinal electric
resistance high enough to prevent sheath currents which may be hazardous
to personnel;
-
contained in
earthed metallic protective casings when the cables may be as in Pt 6, Ch 2, 11.8 Installation of electric and optical fibre cables 11.8.17 or the armour or metal sheath
may be omitted. In the latter case care is to be taken to ensure that
protective casings are electrically continuous and that short lengths
of cable are not left unprotected.
11.8.18 High
voltage electric cables are not to be run in the open through accommodation
spaces.
11.8.19 High-voltage
electric cables are to be segregated from electric cables operating
at lower voltages.
11.8.20 Electric
and optical fibre cables are to be, so far as reasonably practicable,
installed remote from sources of mechanical damage. Where necessary
the cables are to be protected in accordance with the requirements
of Pt 6, Ch 2, 11.9 Mechanical protection of cables.
11.8.21 Electric
and optical fibre cables with the exception of those for portable
appliances and those installed in protective casings are to be fixed
securely in accordance with the requirements of Pt 6, Ch 2, 11.10 Cable support systems.
11.8.22 Electric
and optical fibre cables serving any essential services and any glands
through which they pass must be able to withstand flooding for a period
of 36 hours, based on the water pressure that may occur at the location.
11.9 Mechanical protection of cables
11.9.1 Electric
cables exposed to risk of mechanical damage are to be protected by
suitable protective casings unless the protective covering (e.g. armour
or sheath) is sufficient to withstand the possible cause of damage.
11.9.2 Electric
cables installed in spaces where there is exceptional risk of mechanical
damage such as holds, storage spaces, cargo spaces, etc. are to be
suitably protected by metallic protective casings, even when armoured,
unless the ship's structure affords adequate protection.
11.10 Cable support systems
11.10.2 Cable
support systems, which may be in the form of trays or plates, separate
support brackets, hangers or ladder racks, together with their fixings
and accessories, are to be robust and are to be of corrosion-resistant
material or suitably corrosion inhibited before erection. The cable
support system is to be effectively secured to the ship's structure,
the spacing of the fixings taking account of the probability of vibration
and any heavy external forces, e.g. where located in areas subject
to impact by sea-water.
11.10.3 The
distances between the points at which the cable is supported (e.g.
distances between ladder rungs, support brackets, hangers, etc.) are
to be chosen according to the construction of cable (i.e. size and
rigidity) and the probability of vibration and are to be generally
in accordance with those given in Table 2.11.7 Maximum spacing for supports or
fixings for securing cables.
Table 2.11.7 Maximum spacing for supports or
fixings for securing cables
External diameter of cable
|
Non-armoured
cables
|
Armoured cables
|
exceeding
|
not
exceeding
|
mm
|
mm
|
mm
|
mm
|
–
|
8
|
200
|
250
|
8
|
13
|
250
|
300
|
13
|
20
|
300
|
350
|
20
|
30
|
350
|
400
|
30
|
-
|
400
|
450
|
11.10.4 Where
the cables are laid on top of their support system, the spacings of
fixings may be increased beyond those given in Table 2.11.7 Maximum spacing for supports or
fixings for securing cables, but should take account
of the probability of movement and vibration and in general is not
to exceed 900 mm. This relaxation is not to be applied where cables
can be subjected to heavy external forces, e.g. where they are run
on, or above, open deck or in areas subject to impact by sea-water.
11.10.5 Single
core electric cables are to be firmly fixed, using supports of strength
adequate to withstand forces corresponding to the values of the peak
prospective short-circuit current.
11.11 Penetration of bulkheads and decks by cables
11.11.1 Where
electric and optical fibre cables pass through watertight, fire insulated
or gastight bulkheads or decks separating hazardous zones or spaces
from non-hazardous zones or spaces, the arrangements are to be such
as to ensure the integrity of the bulkhead or deck is not impaired.
The arrangements chosen are to ensure that the cables are not adversely
affected.
11.11.2 Where
cables pass through non-watertight bulkheads or structural steel,
the holes are to be bushed with suitable material. If the steel is
at least 6 mm thick, adequately rounded edges may be accepted as the
equivalent of bushing.
11.11.3 Electric
and optical fibre cables passing through decks are to be protected
by deck tubes or ducts.
11.11.4 Where
cables pass through thermal insulation they are to do so at right
angles, in tubes sealed at both ends.
11.11.5 A schedule of watertight cable penetrations is to be prepared by the shipbuilder in
either hard copy or digitised media. The schedule is to record for each type of
penetration installed the following details:
- the marking or identification system used;
- the manufacturer’s installation drawings and manual(s);
- the Type Approval certification;
- the as built condition of the penetration after the final inspection in the
shipyard; and
- any inspection, modification, repair, and maintenance activities conducted.
11.12 Installation of electric and optical fibre cables in protective
casings
11.12.1 Protective
casings are to be mechanically continuous across joints and effectively
supported and secured to prevent damage to the electric or optical
fibre cables.
11.12.2 Protective
casings are to be suitably smooth on the interior and have their ends
shaped or bushed in such a manner as not to damage the cables.
11.12.4 The
space factor (ratio of the sum of the cross sectional areas corresponding
to the external diameters of the cables to the internal cross-sectional
area of the protective casings) is not to exceed 0,4.
11.12.5 Where
necessary, ventilation openings are to be provided at the highest
and lowest points of protective casings to permit air circulation
and to prevent accumulation of water.
11.12.6 Expansion
joints are to be provided in protective casings where necessary.
11.12.7 Protective
casings containing high voltage electric cables are not to contain
other electric or optical fibre cables and are to be clearly identified,
defining their function and voltage.
11.13 Non-metallic cable support systems, protective casings and fixings
11.13.2 Non-metallic
cable support systems and protective casings are to be installed in
accordance with the manufacturer’s recommendations. The support
systems and protective casings are to have been tested in accordance
with an acceptable test procedure for:
-
ambient operating
temperatures;
-
safe working
load;
-
impact resistance;
-
flame retardancy;
-
smoke and toxicity;
and
-
use in explosive
gas atmospheres or in the presence of combustible dusts, electrical
conductivity;
with satisfactory results.
11.13.3 Non-metallic
cable support systems, protective casings and fixings installed on
the open deck are to be protected from degradation caused by exposure
to solar radiation.
11.13.4 Where
the cable support system, protective casing or fixings are manufactured
from a material other than metal, suitable supplementary metallic
fixings or straps spaced at regular distances are to be provided such
that, in the event of a fire or failure, the cable support system,
protective casing and the affixed cables are prevented from falling
and causing an injury to personnel and/or an obstruction to any escape
route. Alternatively, the cables may be routed away from such areas.
11.13.5 The
load on non-metallic cable support systems or protective casings is
not to exceed the tested safe working load.
11.13.6 When
a cable support system or protective casing is secured by means of
clips or straps manufactured from a material other than metal the
fixings are to be supplemented by suitable metal clips or straps spaced
at regular distances each not exceeding 2 m and, for non-metallic
cable support systems or protective casings, that used during safe
working load testing.
11.13.7 Non-metallic
fixings are to be flame retardant in accordance with the requirements
of IEC 60092-101: Electrical installations in ships –
Part 101: Definitions and general requirements, or an alternative
relevant National or International Standard.
11.14 Single-core electric cables for alternating current
11.14.1 When
installed in protective casings, electric cables belonging to the
same circuit are to be installed in the same casing, unless the casing
is of non-magnetic material.
11.14.2 Cable
clips are to include electric cables of all phases of a circuit unless
the clips are of non-magnetic material.
11.14.3 Single-core
cables of the same circuit are to be in contact with one another,
as far as possible. In any event the distance between adjacent electric
cables is not to be greater than one cable diameter.
11.14.4 If
single-core cables of current rating greater than 250 A are installed
near a steel bulkhead, the clearance between the cables and the bulkhead
is to be at least 50 mm unless the cables belonging to the same a.c.
circuit are installed in trefoil formation.
11.14.5 Magnetic
material is not to be used between single core cables of a group.
Where cables pass through steel plates, all the conductors of the
same circuit are to pass through a plate or gland, so made that there
is no magnetic material between the cables, and the clearance between
the cables and the magnetic material is not to be less than 75 mm,
unless the cables belonging to the same a.c. circuit are installed
in trefoil formation.
11.14.6 Electric
cables are to be installed such that the induced voltages, and any
circulating currents, in the sheath or armour are limited to safe
values.
11.15 Electric cable ends
11.15.1 Where
screw-clamp or spring-clamp type terminations are used in electrical
apparatus for external cable connections, see
Pt 6, Ch 2, 1.11 Location and construction 1.11.9, cable conductors of the
solid or stranded type may be inserted directly into the terminals.
Where flexible conductors are used, a suitable termination is to be
fitted to the cable conductor to prevent 'whiskering' of the strands.
11.15.2 If
compression type conductor terminations are used on the cable ends,
they are to be of a size to match the conductor and to be made with
a compression type tool with the dies selected to suit the termination
and conductor sizes and having a ratchet action to ensure completion
of the compression action.
11.15.3 Soldered
sockets may be used in conjunction with non corrosive fluxes provided
that the maximum conductor temperature at the joint, under short-circuit
conditions, does not exceed 160°C.
11.15.4 High
voltage cables of the radial field type (i.e. having a conducting
layer to control the electric field within the insulation) are to
have terminations which provide electrical stress control.
11.15.5 Electric
cables having hygroscopic insulation (e.g. mineral insulated) are
to have their ends sealed against ingress of moisture.
11.15.6 Cable
terminations are to be of such a design and dimensions that the maximum
current likely to flow through them will not result in degradation
of the contacts or damage to insulation as the result of overheating.
11.15.7 The
fixing of conductors in terminals at joints and at tappings is to
be capable of withstanding the thermal and mechanical effects of short-circuit
currents.
11.16 Joints and branch circuits in cable systems
11.16.1 If
a joint is necessary it is to be carried out so that all conductors
or fibres are adequately secured, insulated and protected from atmospheric
action. The flame retardant properties of the cable are to be retained,
the continuity of metallic sheath, braid or armour is to be maintained
and the current carrying capacity or transmission of data through
the cable is not to be impaired.
11.16.2 Tappings
(branch circuits) are to be made in suitable boxes of such a design
that the conductors and fibres remain suitably insulated, protected
from atmospheric action and fitted with terminals or busbars of dimensions
appropriate to the current rating.
11.16.3 Tappings
and splices of optical fibre cables are to be made in accordance with
the manufacturers’ recommendations and to be provided with appropriate
fittings. In addition they are to be located within suitably designed
enclosures to ensure that the protection of the optical fibres is
maintained.
11.16.4 Cables
of a fire resistant type, see
Pt 6, Ch 2, 11.5 Construction 11.5.3 are to be installed so that
they are continuous throughout their length without any joints or
tappings.
11.17 Busbar trunking systems (bustrunks)
11.17.2 The
busbar trunking, or enclosure system, is to have a minimum ingress
protection of IP54, according to IEC60529: Degrees of protection
provided by enclosures (IP Code).
11.17.3 The
internal and external arrangements of the busbar trunking, or enclosure
system, are to ensure that the fire and/or watertight integrity of
any structure through which it passes is not impaired.
11.17.4 Where
the busbar trunking system is employed for circuits on and below the
bulkhead deck, arrangements are to be made to ensure that circuits
on other decks are not affected in the event of partial flooding under
the normal angles of inclination given in Pt 6, Ch 2, 1.10 Inclination of ship for essential electrical equipment.
11.17.5 Supports
and accessories are to be robust and are to be of corrosion-resistant
material or suitably corrosion inhibited before erection. The support
system is to effectively secure the busbar trunking system to the
ship's structure.
11.17.6 When
accessories are fixed to the busbar system by means of clips or straps
manufactured from a material other than metal, the fixings are to
be supplemented by suitable metal clips or straps, such that, in the
event of a fire or failure, the accessories are prevented from falling
and causing injury to personnel and/or an obstruction to any escape
route. Alternatively, the busbar system may be routed away from such
areas.
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