Section 4 Additional requirements for the electrical installation
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 3 Functional Unit Types and Special Features - Chapter 4 Accommodation and Support Units - Section 4 Additional requirements for the electrical installation

Section 4 Additional requirements for the electrical installation

Parent topic: Chapter 4 Accommodation and Support Units

4.1 General

4.1.1 In general, electrical installations are to comply with the requirements of Pt 6, Ch 2 Electrical Engineering.

4.1.2 The requirements of this Section are applicable to units with accommodation for more than 50 persons, who are not crew members.

4.2 Emergency source of electrical power

4.2.1 A self-contained emergency source of electrical power is to be provided.

4.2.2 The emergency source of electrical power, associated transforming equipment, if any, transitional source of emergency power, emergency switchboard and emergency lighting switchboard are to be located above the uppermost continuous deck and be readily accessible from the open deck. They are not to be located forward of the collision bulkhead, where fitted on surface type units.

4.2.3 The location of the emergency source of electrical power and associated transforming equipment, if any, the transitional source of emergency power, the emergency switchboard and the emergency lighting switchboard in relation to the main source of electrical power, associated transforming equipment, if any, and the main switchboard is to be such as to ensure that a fire or other casualty in spaces containing the main source of electrical power, associated transforming equipment, if any, and the main switchboard or in any machinery space of Category A (see Pt 7, Ch 3 Fire Safety) will not interfere with the supply, control and distribution of emergency electrical power. The space containing the emergency source of electrical power, associated transforming equipment, if any, the transitional source of emergency electrical power and the emergency switchboard is not to be contiguous to the boundaries of machinery spaces of Category A, see Pt 7, Ch 3 Fire Safety, and those spaces containing the main source of electrical power, associated transforming equipment, if any, or the main switchboard. Where this is not practicable, details of the proposed arrangements are to be submitted.

4.2.4 Provided that suitable measures are taken for safeguarding independent emergency operation under all circumstances, the emergency generator may be used exceptionally, and for short periods, to supply non-emergency circuits.

4.2.5 The electrical power available is to be sufficient to supply all those services that are essential for safety in an emergency, due regard being paid to such services as may have to be operated simultaneously. The emergency source of electrical power is to be capable, having regard to starting currents and the transitory nature of certain loads, of supplying simultaneously at least the following services for the periods specified hereinafter, if they depend upon an electrical source for their operation:

  1. For a period of 36 hours, emergency lighting:
    1. in all service and accommodation alleyways, stairways and exits, personnel lift cars;
    2. in alleyways, stairways and exits, giving access to the muster and embarkation stations;
    3. in the machinery spaces and main generating stations including their control positions;
    4. in all control stations, machinery control rooms, and at each main and emergency switchboard;
    5. at all stowage positions for fireman’s outfits;
    6. at the steering gear;
    7. at the fire pump, the sprinkler pump and the emergency bilge pump and at the starting position of their motors;
    8. at every survival craft, muster and embarkation station;
    9. over the sides to illuminate the area of water into which survival craft are to be launched;
    10. on helicopter decks.
  2. For a period of 36 hours:
    1. the navigation lights, other lights and sound signals required by the International Regulations for the prevention of Collisions at Sea, in force;
    2. the radio communications as required by Amendments to Chapter IV - Radiocommunications as applicable;
    3. the navigational aids as required by Amendments to Regulation 19 - Carriage requirements for shipborne navigational systems and equipmentas applicable;
    4. general alarm and communication systems as required in an emergency;
    5. intermittent operation of the daylight signalling lamp and the unit’s whistle;
    6. the fire and gas detection systems and their alarms;
    7. emergency fire pump; the automatic sprinkler pump, if any; and the emergency bilge pump and all the equipment essential for the operation of electrically powered remote controlled bilge valves;
    8. one of the refrigerated liquid carbon dioxide units intended for fire protection, where both are electrically driven;
    9. on column-stabilised units; ballast valve control system, ballast valve position indicating system, draft level indicating system, tank level indicating system and the largest single ballast pump;
    10. abandonment systems dependent on electric power.
  3. For a period of 24 hours:
    1. permanently installed diving equipment necessary for the safe conduct of diving operations, if dependent upon the unit’s electrical power;
    2. the capability of closing the blow out preventer and of disconnecting the unit from the wellhead arrangements, if electrically controlled, unless it has an independent supply from an accumulator battery suitably located for use in an emergency and sufficient for the period of 24 hours.
  4. The steering gear for the period of time required by Pt 5, Ch 19, 6 Emergency power.
  5. For a period of four days, any signalling lights or sound signals which may be required for marking offshore structures.
  6. For a period of half an hour:
    1. any watertight doors if electrically operated together with their control, indication and alarm circuits;
    2. the emergency arrangements to bring the lift cars to deck level for the escape of persons. The lift cars may be brought to deck level sequentially in an emergency.
4.2.6 The emergency source of electrical power may be either a generator or an accumulator battery, which are to comply with the following:
  1. Where the emergency source of electrical power is a generator, it is to be:
    1. driven by a suitable prime mover with an independent supply of fuel having a flashpoint (closed-cup test) of not less than 43°C;
    2. started automatically upon failure of the electrical supply from the main source of electrical power and is to be automatically connected to the emergency switchboard; those services referred to in Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.5 are then to be transferred automatically to the emergency generating set. The automatic starting system and the characteristics of the prime mover are to be such as to permit the emergency generator to carry its full rated load as quickly as is safe and practicable, subject to a maximum of 45 seconds; and
    3. provided with a transitional source of emergency electrical power according to Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.7.
  2. Where the emergency source of electrical power is an accumulator battery, it is to be capable of:
    1. carrying the emergency electrical power without recharging while maintaining the voltage of the battery throughout the discharge period within 12 per cent above or below its nominal voltage;
    2. automatically connecting to the emergency switchboard in the event of failure of the main source of electrical power; and
    3. immediately supplying at least those services specified in Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.7.
4.2.7 The transitional source of emergency electrical power required by Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.6 is to consist of an accumulator battery suitably located for use in an emergency, which is to operate without recharging while maintaining the voltage of the battery throughout the discharge period within 12 per cent above or below its nominal voltage and be of sufficient capacity and so arranged as to supply automatically in the event of failure of either the main or emergency source of electrical power at least the following services, if they depend upon an electrical source for their operation:
  1. For half an hour:
    1. the lighting required by Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.5.(a) and Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.5.(b).(i);
    2. all services required by Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.5.(b).(iii), Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.5.(b).(iv) and Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.5.(b).(v) unless such services have an independent supply for the period specified from an accumulator battery suitably located for use in an emergency.
  2. Power to operate the watertight doors at least three times, (i.e., closed-open-closed), against an adverse list of 15°, but not necessarily all of them simultaneously, together with their control, indication and alarm circuits as required by Pt 3, Ch 4, 4.2 Emergency source of electrical power 4.2.5.(f).(i).

4.2.8 The emergency switchboard is to be installed as near as is practicable to the emergency source of electrical power.

4.2.9 Where the emergency source of electrical power is a generator, the emergency switchboard is to be located in the same space unless the operation of the emergency switchboard would thereby be impaired.

4.2.10 No accumulator battery except for engine starting, fitted in accordance with this Section, is to be installed in the same space as the emergency switchboard. An indicator is to be mounted in a suitable place on the main switchboard or in the machinery control room to indicate when the batteries constituting either the emergency source of electrical power or the transitional source of emergency electrical power are being discharged.

4.2.11 The emergency switchboard is to be supplied during normal operation from the main switchboard by an interconnector feeder which is to be adequately protected at the main switchboard against overload and short-circuit and which is to be disconnected automatically at the emergency switchboard upon failure of the main source of electrical power. Where the system is arranged for feedback operation, the interconnector feeder is also to be protected at the emergency switchboard at least against short-circuit.

4.2.12 In order to ensure ready availability of the emergency source of electrical power, arrangements are to be made where necessary to disconnect automatically nonemergency circuits from the emergency switchboard to ensure that power will be available to the emergency circuits.

4.2.13 Provision is to be made for the periodic testing of the complete emergency system and is to include the testing of automatic starting arrangements.

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