Section 8 Electric cables, optical fibre cables and busbar trunking systems (busways)

8.1.1 The requirements of Vol 2, Pt 9, Ch 3, 8.1 General apply to all electric and optical fibre cables for fixed wiring unless otherwise exempted. The requirements of Vol 2, Pt 9, Ch 3, 8.17 Busbar trunking systems (bustrunks) apply to busbar trunking systems (busways) where they are used in place of electric cables.

8.1.2 Electric cables for fixed wiring are to be designed, manufactured and tested in accordance with the IEC Standards specified in Table 3.8.1 Electric cables or a specified standard acceptable to the Naval Administration. On application, LR may be able to assess the acceptability of cables in accordance with specified standards other than the relevant IEC Standards, see also Vol 2, Pt 9, Ch 1, 1.2 Application 1.2.4.

8.1.3 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.

8.1.4 Surveys of cables for electric propulsion systems during manufacture and testing, see Vol 2, Pt 9, Ch 1, 1.6 Surveys 1.6.3, are to assess compliance with the applicable International, National or Naval Standards and the application of an acceptable quality management system, see also Vol 2, Pt 9, Ch 1, 1.6 Surveys 1.6.6.

8.1.5 Where increased flexibility is required due to confines of space, cables having Class 5 stranded conductors in accordance with IEC 60228 Conductors of insulated cables may be accepted provided Vol 2, Pt 9, Ch 3, 8.1 General 8.1.2 is otherwise complied with. Provided that the adequate flexibility of the finished cable is assured, conductors of nominal cross-sectional area 2,5 mm² and less need not be stranded.

8.1.6 Electric and optical fibre cables for non-fixed applications are to comply with a relevant National or International Standard.

8.1.7 For the purpose of this Section, pipes, conduits, trunking or any other system for the additional mechanical protection of cables are hereinafter referred to under the generic name ‘protective casings’.

8.1.8 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.

8.2.1 Routine tests, consisting of at least:

1. measurement of electrical resistance of conductors;

2. high voltage test, see also Vol 2, Pt 9, Ch 12, 1.1 Testing 1.1.2;

3. insulation resistance measurement;

4. 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 a relevant National Standard, at the manufacturer’s works prior to despatch.

5. for optical fibres, an attenuation loss (see Vol 2, Pt 9, Ch 12, 1.5 Optical Fibre Communications Systems).

Evidence of successful completion of routine tests is to be provided by the manufacturer, see also Vol 2, Pt 9, Ch 1, 1.6 Surveys 1.6.3.

8.2.2 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 Vol 2, Pt 9, Ch 3, 8.1 General 8.1.2, and a test report issued by the manufacturer.

8.3.1 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.

8.3.2 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.

8.4.1 The maximum rated conductor temperature of the insulating material for normal operation is to be at least 10ºC higher than the maximum ambient temperature liable to be produced in the space where the cable is installed.

8.4.2 The maximum rated conductor temperatures for normal and short circuit operation, for the insulating materials included within the standards referred to in Vol 2, Pt 9, Ch 3, 8.1 General 8.1.2, is not to exceed the values stated in Table 3.8.2 Maximum rated conductor temperature

8.4.3 Electric cables constructed of an insulating material not included in Table 3.8.2 Maximum rated conductor temperature are to be rated in accordance with the National Standard chosen in compliance with Vol 2, Pt 9, Ch 3, 8.1 General 8.1.2.

8.5.1 Electric and optical fibre cables are to be at least of a flame-retardant, low smoke, halogen free type. Compliance with 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 1kW pre-mixed flame, IEC 61034: Measurements of smoke density of electric cables burning under defined conditions, IEC 60754: Tests on gases evolved during combustion of materials from cables will be acceptable. Where cables are installed in bunches, the requirements of Vol 2, Pt 9, Ch 3, 8.8 Installation of electric and optical fibre cables 8.8.13 are to be satisfied. Alternative proposals for equipment cabling that demonstrate satisfactory smoke and toxicity performance under fire conditions for identified areas of a ship may be submitted for consideration.

8.5.2 Exemption from the requirements of Vol 2, Pt 9, Ch 3, 8.5 Construction 8.5.1 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.

8.5.3 Where electric or 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°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, 0kV;;
• 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..

8.5.4 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.

8.5.5 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.

8.5.6 Where it is required that the construction of electric or optical fibre cables includes metallic sheaths, armouring or braids, they are to be provided with an overall impervious sheath or other means to protect the metallic elements against corrosion, see also Vol 2, Pt 9, Ch 3, 8.8 Installation of electric and optical fibre cables 8.8.10 and Vol 2, Pt 9, Ch 3, 8.8 Installation of electric and optical fibre cables 8.8.11.

8.5.7 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.

8.5.8 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.

8.5.9 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.

8.5.10  All high voltage electric cables are to be readily identified by suitable marking.

8.6.1 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 Vol 2, Pt 9, Ch 3, 8.7 Correction factors for cable current rating may be applied as required.

8.6.2 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.

8.6.3 The cable current ratings given in Table 3.8.3 Electric cable current ratings, normal operation, based on ambient 45°C and Table 3.8.4 Electric cable current ratings, r.m.s. short circuit current are based on the maximum rated conductor temperatures given in Table 3.8.2 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 3.8.4 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.

8.6.4 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 Vol 2, Pt 9, Ch 1, 2.1 Quality of power supplies (QPS) be exceeded when the conductors are carrying the maximum current under their normal conditions of service.

8.6.5 The size of earth conductors is to comply with Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding 2.4.7.

8.6.6 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 Vol 2, Pt 9, Ch 3, 8.7 Correction factors for cable current rating 8.7.4.

8.7.1 The correction factors of Vol 2, Pt 9, Ch 3, 8.7 Correction factors for cable current rating 8.7.2 provide a guide for general applications in assessing a current rating. A more precise evaluation based upon experimental and calculated data may be submitted for consideration.

8.7.2  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.

8.7.3  Ambient temperature. The current ratings of Table 3.8.3 Electric cable current ratings, normal operation, based on ambient 45°C are based on an ambient temperature of 45ºC. For other values of ambient temperature the correction factors shown in Table 3.8.5 Correction factors are to be applied.

8.7.4  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

8.7.5  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 Vol 2, Pt 9, Ch 3, 4.6 Diversity factor.

8.8.1 Electric and optical fibre cable runs are to be, as far as practicable, fixed in straight lines and in accessible positions.

8.8.2 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 3.8.6 Minimum internal radii of bends in cables for fixed wiring

8.8.3 The manufacturer’s tensile load limit of the optical fibre is not to be exceeded during installation.

8.8.4 The manufacturer’s minimum bend radii for optical fibres is not to be exceeded during installation.

8.8.5 Pre- and post-installation tests are to be conducted on optical fibre cables as detailed in Vol 2, Pt 9, Ch 12, 1.5 Optical Fibre Communications Systems.

8.8.6 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.

8.8.7 Electric and optical fibre cables for Mobility systems, Ship Type systems, and emergency services are to be arranged, so far as is practicable, to avoid galleys, machinery spaces and other enclosed spaces and areas of high fire risk 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 them being rendered unserviceable by heating of the bulkheads that may be caused by a fire in an adjacent space.

8.8.8 Electric and optical fibre 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.

8.8.9 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.

8.8.10 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.

8.8.11 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.

8.8.12 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.

8.8.13 Where 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, provided that, in addition, there is no shedding of flaming droplets of sheath or insulation material and that they are installed in the same configuration(s) as used in the test(s). If the cables are not so installed, information is to be submitted in satisfactorily demonstrate that suitable measures are taken to ensure that an equivalent limit of fire propagation will be achieved for the configuration(s) used. Particular attention is to be given to cables in 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.

8.8.14  Electric and optical fibre cables are not to be coated or painted with materials which may adversely affect their sheath or their fire performance.

8.8.15 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.

8.8.16 All metal coverings of electric and optical fibre cables are to be earthed in accordance with Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding .

8.8.17 High voltage cables may be installed as follows:

1. 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;

2. contained in earthed metallic protective casings when the cables may be as in (a) 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.

8.8.18 High voltage electric cables are not to be run in the open through accommodation spaces.

8.8.19 High-voltage electric cables are to be segregated from electric cables operating at lower voltages.

8.8.20 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 Vol 2, Pt 9, Ch 3, 8.9 Mechanical protection of cables

8.8.21 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 Vol 2, Pt 9, Ch 3, 8.10 Cable support systems

8.8.22 Electric and optical fibre cables serving any Mobility or Ship Type system, and any glands through which they pass must be able to withstand flooding for a period of 18 hours, based on the water pressure that may occur at the location.

8.8.23 Where electric and optical fibre cables penetrate bulkheads and decks, the requirements of Vol 2, Pt 9, Ch 3, 8.11 Penetration of bulkheads and decks by cables are to be complied with.

8.8.24 Where electric and optical fibre cables are installed in protective casings, the requirements of Vol 2, Pt 9, Ch 3, 8.12 Installation of electric and optical fibre cables in protective casings are to be complied with.

8.8.25 a.c. wiring is to be carried out using multicore cables wherever reasonably practicable. Where it is necessary to install single core electric cables for alternating current circuits in excess of 20 Amps the requirements of Vol 2, Pt 9, Ch 3, 8.14 Single core electric cables for alternating current are to be complied with. See also Vol 2, Pt 9, Ch 3, 8.5 Construction 8.5.8.

8.9.1 Electric or optical fibre 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.

8.9.2 Electric or optical fibre cables installed in spaces where there is exceptional risk of mechanical damage such as hangers, storage spaces, etc. are to be suitably protected by metallic protective casings, even when armoured, unless the ship’s structure affords adequate protection.

8.9.3  Metal protective casings are to be efficiently protected against corrosion, and effectively earthed in accordance with Vol 2, Pt 9, Ch 1, 2.4 Earthing and bonding .

8.10.1 Electric cables are to be effectively supported and secured, without being damaged, to the ships’ structure, either indirectly by a cable support system, or directly by means of clips, saddles or straps to bulkheads etc. see Vol 2, Pt 9, Ch 3, 8.8 Installation of electric and optical fibre cables 8.8.7

8.10.2 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 ships’ 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. In addition, where applicable, military aspects for shock are to be defined as required by Vol 2, Pt 1, Ch 3, 4.8 Astern power

8.10.3 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 3.8.7 Maximum spacing of supports or fixings for securing cables

8.10.4 Where the cables are laid on top of their support system, the spacing of the clips, straps, etc. securing the cables may be increased beyond the spacing given in Table 3.8.7 Maximum spacing of supports or fixings for securing cables, but should take account 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 sea-water impingement.

8.10.5 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.

8.10.6 Cables for emergency alarms and their power sources are to be in accordance with Vol 2, Pt 9, Ch 1, 2.5 Operation under fire conditions.

8.10.7 Electrical equipment and cables for emergency alarms are to be so arranged that the loss of alarms in any one area due to localised fire, collision, flooding or similar damage is minimised, see Vol 2, Pt 9, Ch 1, 2.5 Operation under fire conditions and Vol 2, Pt 9, Ch 1, 2.6 Operation under flooding conditions.

8.11.1 Where electric or 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.

8.11.2 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.

8.11.3 Electric and optical fibre cables passing through decks are to be protected by deck tubes or ducts.

8.11.4 Where cables pass through thermal insulation they are to do so at right angles, in tubes sealed at both ends.

8.12.1 Protective casings are to be mechanically continuous across joints and effectively supported and secured to prevent damage to the electric or optical fibre cables.

8.12.2 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.

8.12.3 The internal radius of bends of protective casings are to be not less than that required for the largest cable installed therein, see Vol 2, Pt 9, Ch 3, 8.8 Installation of electric and optical fibre cables 8.8.2

8.12.4 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.

8.12.5 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.

8.12.6 Expansion joints are to be provided in protective casings where necessary.

8.12.7 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.

8.13.1 Where it is proposed to use non-metallic cable support systems, protective casings or fixings, the additional requirements of this sub-Section apply. Non metallic protective cases are not permitted where Vol 2, Pt 9, Ch 3, 8.8 Installation of electric and optical fibre cables 8.8.17.(b) applies.

8.13.2 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:

1. ambient operating temperatures;

2. safe working load;

3. impact resistance;

4. flame retardancy;

5. smoke and toxicity; and

6. use in explosive gas atmospheres or in the presence of combustible dusts, electrical conductivity;

with satisfactory results.

8.13.3 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.

8.13.4 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.

8.13.5 The load on non-metallic cable support systems or protective casings is not to exceed the tested safe working load.

8.13.6 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.

8.13.7 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.

8.14.1 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.

8.14.2 Cable clips are to include electric cables of all phases of a circuit unless the clips are of non-magnetic material.

8.14.3 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.

8.14.4 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.

8.14.5 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.

8.14.6 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.

8.15.1 Where screw-clamp or spring-clamp type terminations are used in electrical apparatus for external cable connections (see Vol 2, Pt 9, Ch 1, 2.2 Design, construction and location 2.2.14), 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.

8.15.2 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.

8.15.3 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 160ºC.

8.15.4 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.

8.15.5 Electric cables having hygroscopic insulation (e.g. mineral insulated) are to have their ends sealed against ingress of moisture.

8.15.6 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 or corrosion.

8.15.7 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.

8.15.8 Cable terminations are to be suitable for the operating voltages and currents and may be of the screw-clamp or spring-clamp type or plug and socket connectors.

8.16.1 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 or fire-resisting 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.

8.16.2 Tappings (branch circuits) are to be made in suitable boxes of such a design that the conductors remain suitably insulated, protected from atmospheric action and fitted with terminals or busbars of dimensions appropriate to the current rating.

8.16.3 Tappings and splices of optical fibre cables are to be made in accordance with the manufacturers’ recommendations and are 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.

8.16.4 Cables of a fire resistant type (see Vol 2, Pt 9, Ch 3, 8.5 Construction 8.5.3) are to be installed so that they are continuous throughout their length without any joints or tappings.

8.17.1 Where busbar trunking systems are used in place of electric cables, they are to comply with the requirements of Vol 2, Pt 9, Ch 3, 8.17 Busbar trunking systems (bustrunks) 8.17.2, in addition to the applicable requirements in Vol 2, Pt 9, Ch 3, 5 Switchgear and controlgear assemblies

8.17.2 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).

8.17.3 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.

8.17.4 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 Vol 2, Pt 1, Ch 1, 4.4 Installation, integration and test principles. and Vol 2, Pt 1, Ch 1, 4.5 Trials principles for Mobility or Ship Type systems.

8.17.5 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.

8.17.6 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.

8.18.1 To reduce mutual interference, cables with different signal levels are to be grouped in accordance with Table 3.8.8 Cable segregation groups and installed with the separation distances as shown in Table 3.8.9 Separation distances, mm