5.5 Precautions against shock; fire and other hazards of electrical origin
Clasification Society 2024 - Version 9.40
Statutory Documents - IMO Publications and Documents - International Codes - 1979 MODU Code – Code for the Construction and Equipment of Mobile Offshore Drilling Units – Resolution A.414(XI) - Chapter 5 – Electrical Installations for all Types of Units (See also 4.1) - 5.5 Precautions against shock; fire and other hazards of electrical origin

5.5 Precautions against shock; fire and other hazards of electrical origin

  5.5.1

  • .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:

    • .1 they are supplied at a voltage not exceeding 55 volts direct current or 55 volts, root mean square between conductors; autotransformers should not be used for the purpose of achieving this alternating current voltage; or

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

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

  • .2 The Administration may require additional precautions for portable equipment. Particular attention should be paid to the use of such equipment in damp locations having large conductive surfaces.

  • .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.

  • .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.

  5.5.2 Switchboards should be so arranged as to give easy access needed to apparatus and equipment, in order to minimize danger to attendants. 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.

  5.5.3 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 milliamperes under the most unfavourable conditions.

  5.5.4 When a distribution system, whether primary or secondary, for power, heating or lighting, with no connexion 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.

  5.5.5

  • .1 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).

  • .2 All electric cables should be at least of a flame retardant type and should be installed so as not to impair their original flame retarding properties. Administrations may permit the use of special types of cables when necessary for particular applications, such as radio frequency cables, which do not comply with the foregoing.

  • .3 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 possible 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.

  • .4 Wiring should be supported in such a manner as to avoid chafing or other damage.

  • .5 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.

  5.5.6

  • .1 Each separate circuit should be protected against short circuits. Each separate circuit should also be protected against overload, except in accordance with 7.6 or where the Administration may exceptionally otherwise permit.

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

  5.5.7 Lighting fittings should be so arranged as to prevent temperature rises that would be injurious to the wiring, and to prevent surrounding material from becoming excessively hot.

  5.5.8

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

  • .2 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 5.5.10.

  • .3 Accumulator batteries except for batteries of self-contained battery operated lights should not be located in sleeping quarters. Administrations may permit relaxations from this requirement where hermetically sealed batteries are installed.

  5.5.9 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 it 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.

  5.5.10 Electrical apparatus and cables should, where possible, be excluded from any compartment in which explosives are stored. Where lighting is required, it should be achieved 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.

Parent topic: Chapter 5 – Electrical Installations for all Types of Units (See also 4.1)
Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.