5.6 Precautions against shock, fire and other hazards of electrical origin
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - International Codes - 2009 MODU Code - Code for the Construction and Equipment of Mobile Offshore Drilling Units, 2009 – Resolution A.1023(26) - Chapter 5 - Electrical Installations for All Types of Units - 5.6 Precautions against shock, fire and other hazards of electrical origin

5.6 Precautions against shock, fire and other hazards of electrical origin

  5.6.1 Exposed metal parts of electrical machines or equipment which are not intended to be live but which are liable under fault conditions to become live should be earthed (grounded) unless the machines or equipment are:

  • .1 supplied at a voltage not exceeding 55 V direct current or 55 V, root mean square between conductors; auto-transformers should not be used for the purpose of achieving this voltage; or

  • .2 supplied at a voltage not exceeding 250 V by safety isolating transformers supplying only one consuming device; or

  • .3 constructed in accordance with the principle of double insulation.

  5.6.2 The Administration may require additional precautions for portable electrical equipment for use in confined or exceptionally damp spaces where particular risks due to conductivity may exist.

  5.6.3 All electrical apparatus should be so constructed and so installed that it does not cause injury when handled or touched in the normal manner.

  5.6.4 Where not obtained through normal construction, arrangements should be provided to effectively earth (ground) all permanently installed machinery, metal structures of derricks, masts and helicopter decks.

  5.6.5 Switchboards should be so arranged as to give easy access, where needed, to apparatus and equipment, in order to minimize danger to personnel. The sides and backs and, where necessary, the fronts of switchboards should be suitably guarded. Exposed live parts having voltages to earth (ground) exceeding a voltage to be specified by the Administration should not be installed on the front of such switchboards. There should be non-conducting mats or gratings at the front and rear, where necessary.

  5.6.6 Distribution systems with hull return should not be installed, but this does not preclude, under conditions approved by the Administration, the installation of:

  • .1 impressed current cathodic protective systems;

  • .2 limited and locally earthed systems (e.g., engine starting systems);

  • .3 limited and locally earthed welding systems; where the Administration is satisfied that the equipotential of the structure is assured in a satisfactory manner, welding systems with hull return may be installed without this restriction; and

  • .4 insulation level monitoring devices provided the circulation current does not exceed 30 mA under the most unfavourable conditions.

  5.6.7 When a distribution system, whether primary or secondary, for power, heating or lighting, with no connection to earth is used, a device capable of continuously monitoring the insulation level to earth and of giving an audible or visual indication of abnormally low insulation values should be provided.

  5.6.8 Except as permitted by the Administration in exceptional circumstances, all metal sheaths and armour of cables should be electrically continuous and should be earthed (grounded).

  5.6.9 All electric cables and wiring external to equipment should be at least of a flame-retardant type and should be so installed as not to impair their original flame-retarding properties.footnote Where necessary for particular applications, the Administration may permit the use of special types of cables such as radio frequency cables, which do not comply with the foregoing.

  5.6.10 Cables and wiring serving essential or emergency power, lighting, internal communications or signals should, so far as practicable, be routed clear of galleys, machinery spaces of category A and their casings and other high fire risk areas. Cables connecting fire pumps to the emergency switchboard should be of a fire-resistant type where they pass through high fire risk areas. Where practicable all such cables should be run in such a manner as to preclude their being rendered unserviceable by heating of the bulkheads that may be caused by a fire in an adjacent space.footnote

  5.6.11 Cables and wiring should be installed and supported in such a manner as to avoid chafing or other damage.

  5.6.12 Terminations and joints in all conductors should be so made that they retain the original electrical, mechanical, flame-retarding and, where necessary, fire-resisting properties of the cable.

  5.6.13 Each separate circuit should be protected against short circuit and against overload, except as permitted in section 7.6, or where the Administration may exceptionally otherwise permit.

  5.6.14 The rating or appropriate setting of the overload protection device for each circuit should be permanently indicated at the location of the protection device.

  5.6.15 Lighting fittings should be so arranged as to prevent temperature rises which could damage the cables and wiring, and to prevent surrounding material from becoming excessively hot.

  5.6.16 Accumulator batteries should be suitably housed, and compartments used primarily for their accommodation should be properly constructed and efficiently ventilated.

  5.6.17 Electrical or other equipment which may constitute a source of ignition of flammable vapours should not be permitted in these compartments except as permitted in paragraph 5.6.19.

  5.6.18 Accumulator batteries, except for batteries of self-contained battery-operated lights, should not be located in sleeping quarters. Administrations may grant exemptions from or equivalencies to this provision where hermetically sealed batteries are installed.

  5.6.19 In paint lockers, acetylene stores, and similar spaces where flammable mixtures are liable to collect as well as any compartment assigned principally to accumulator batteries, no electrical equipment should be installed unless the Administration is satisfied that such equipment is:

  • .1 essential for operational purposes;

  • .2 of a type which will not ignite the mixture concerned;

  • .3 appropriate to the space concerned; and

  • .4 appropriately certified for safe usage in the vapours or gases likely to be encountered.

  5.6.20 Electrical apparatus and cables should, where practicable, be excluded from any compartment in which explosives are stored. Where lighting is required, the light should come from outside, through the boundaries of the compartment. If electrical equipment cannot be excluded from such a compartment it should be so designed and used as to minimize the risk of fire or explosion.

  5.6.21 Where spilling or impingement of liquids could occur upon any electrical control or alarm console, or similar electrical enclosure essential to the safety of the unit, such equipment should have suitable protection against the ingress of liquids.footnote

Parent topic: Chapter 5 - Electrical Installations for All Types of Units
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