5.3 Emergency source of electrical power
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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) - 5.3 Emergency source of electrical power

5.3 Emergency source of electrical power

  5.3.1

  • .1 Every unit should be provided with a self-contained emergency source of electrical power.

  • .2 The emergency source of power, the transitional source of emergency power and the emergency switchboard should be located on or above the uppermost continuous deck or equivalent deck as determined by the Administration and should be readily accessible from an open deck. It should not be forward of the collision bulkhead, if any, except where permitted by the Administration in exceptional circumstances.

  • .3 The location of the emergency source of power, the transitional source of emergency power and emergency switchboard in relation to the main source of electrical power should be such as to ensure to the satisfaction of the Administration that a fire or other casualty in the space containing the main source of electrical power or in any machinery space of Category A will not interfere with the supply or distribution of emergency power. As far as practical, the space containing the emergency sources of power, the transitional source of emergency power and the emergency switchboard should not be contiguous to boundaries of machinery spaces of Category A or of those spaces containing the main sources of electrical power. Where the emergency source of power, the transitional source of emergency power, and the emergency switchboard are contiguous to the boundaries of machinery spaces of Category A or to those spaces containing the main source of electrical power, or to spaces of Zone 1 or Zone 2, the contiguous boundaries should be in compliance with 9.1.

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

  5.3.2 The power available should 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 power should 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 18 hours, emergency lighting:

    • .1 at every embarkation station on deck and over sides:

    • .2 in all service and accommodation alleyways, stairways and exits, personnel lift cars, and personnel lift trunks;

    • .3 in the machinery spaces and main generating stations including their control positions;

    • .4 in all control stations and in all machinery control rooms;

    • .5 in all spaces from which control of the drilling process is performed and where controls of machinery essential for the performance of this process, or devices for emergency switching-off of the power plant are located;

    • .6 at the stowage position(s) for firemen's outfits;

    • .7 at the sprinkler pump if any, at the fire pump referred to in 5.3.2.4, at the emergency bilge pump, if any, and at their starting positions;

    • .8 on helicopter landing decks;

  • .2

    • .1 For a period of 18 hours, the navigation lights, other lights and sound signals, required by the International Regulations for the Prevention of Collisions at Sea, in force;

    • .2 For a period of 4 days:

      – any signalling lights, or
      – sound signals

      which may be required for marking of offshore structures;

  • .3 For a period of 18 hours:

    • .1 all internal communication equipment that is required in an emergency;

    • .2 fire detection and its alarm systems;

    • .3 intermittent operation of the manual fire alarms and all internal signals that are required in an emergency; and

    • .4 the capability of closing the blow-out preventer and of disconnecting the unit from the well head arrangement, if electrically controlled,

    unless they have an independent supply from an accumulator battery suitably located for use in an emergency and sufficient for the period of 18 hours;

  • .4 For a period of 18 hours one of the fire pumps if dependent upon the emergency generator for its source of power;

  • .5 For a period of at least 18 hours permanently installed diving equipment if dependent upon the unit's electrical power.

  5.3.3 The emergency source of power may be either a generator or an accumulator battery.

  • .1 Where the emergency source of power is a generator it should be:

    • .1 driven by a suitable prime mover with an independent supply of fuel, having a flashpoint of not less than 43°C;

    • .2 started automatically upon failure of the normal electrical supply unless a transitional source of emergency power in accordance with 5.3.3.3 is provided; where the emergency generator is automatically started, it should be automatically connected to the emergency switchboard; those services referred to in 5.3.4 should then be connected automatically to the emergency generator; and unless a second independent means of starting the emergency generator is provided, the single source of stored energy should be protected to preclude its complete depletion by the automatic starting system; and

    • .3 provided with a transitional source of emergency power as specified in 5.3.4 unless the emergency generator is capable of supplying the services mentioned in 5.3.4 and of being automatically started and supplying the required load as quickly as is safe and practicable but in not more than 45 seconds.

  • .2 Where the emergency source of power is an accumulator battery it should be capable of:

    • .1 carrying the emergency load without recharging whilst maintaining the voltage of the battery throughout the discharge period within plus or minus 12 per cent of its nominal voltage;

    • .2 automatically connecting to the emergency switchboard in the event of failure of the main power supply; and

    • .3 immediately supplying at least those services specified in 5.3.4.

  5.3.4 The transitional source(s) of emergency power, where required by 5.3.3.1.3, should consist of an accumulator battery suitably located for use in an emergency, which should operate without recharging whilst maintaining the voltage of the battery throughout the discharge period within plus or minus 12 per cent of 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 the emergency source of power, the following services for half an hour at least if they depend upon an electrical source for their operation:

  • .1 the lighting required by 5.3.2.1 and 5.3.2.2. For this transitional phase, the required emergency lighting, in respect of the machinery space and accommodation and service areas, may be provided by permanently fixed, individual accumulator lamps which are automatically charged and operated;

  • .2 all essential internal communication equipment required by 5.3.2.3.1 and 5.3.2.3.2; and

  • .3 intermittent operation of the services referred to in 5.3.2.3.3 and 5.3.2.3.4,

unless in respect of 5.3.4.2 and 5.3.4.3, they have an independent supply from an accumulator battery suitably located for use in an emergency and sufficient for the period specified.

  5.3.5

  • .1 The emergency switchboard should be installed as near as is practicable to the emergency source of power and, where the emergency source of power is a generator, the emergency switchboard should preferably be located in the same space.

  • .2 No accumulator battery fitted in accordance with this requirement for emergency or transitional power supply should be installed in the same space as the emergency switchboard, unless appropriate measures to the satisfaction of the Administration are taken to extract the gases discharged from the said batteries. An indicator should 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 power or the transitional source of power referred to in 5.3.3.2 or 5.3.4 are being discharged.

  • .3 The emergency switchboard should be supplied in normal operation from the main switchboard by an inter-connector feeder which is to be adequately protected at the main switchboard against overload and short circuit. The arrangement at the emergency switchboard should be such that the inter-connector feeder is disconnected automatically at the emergency switchboard upon failure of the main power supply. Where the system is arranged for feedback operation, the inter-connector feeder should also be protected at the emergency switchboard at least against short circuit.

  • .4 In order to ensure ready availability of emergency supplies, arrangements should be made where necessary to disconnect automatically non-emergency circuits from the emergency switchboard to ensure that power is available automatically to the emergency circuits.

  5.3.6 The emergency generator and its prime mover and any emergency accumulator battery should be designed to function at full rated power when it is upright and when inclined up to the maximum angle of heel in the intact and damaged condition as determined in accordance with Chapter 3. In no case need the equipment be designed to operate when inclined more than 221/2 degrees about the longitudinal axis and/or when inclined 10 degrees about the transverse axis.

  5.3.7 Provision should be made for the periodic testing of the complete emergency system and should include the testing of automatic starting arrangements.

Parent topic: Chapter 5 – Electrical Installations for all Types of Units (See also 4.1)
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