BS IEC 61892-5:2000 pdf free download – Mobile and fixed offshore units – Electrical installations
4.1 In every mobile unit in which electric power is used for the services necessary for the safety of the unit, the generators, switchgear, motors and associated controlgear for such services, with the exception of machinery in the platform of semi-submersibles, shall be so situated or arranged that they continue to operate satisfactorily in the event of partial flooding by bilge water above the tank top in the space in which they are situated. The design criterion for partial flooding shall be assumed to be a depth of water 1 /1 2 th beam but not exceeding a depth of 1 ,5 m except where this requirement is impracticable for horizontally mounted propulsion generators and motors. In such circumstances the machine enclosures shall, at least, be watertight to the underside of the shaft.
4.2 Rotating machines shall be installed to minimise the effects of motion. The design of bearings of all machines and the arrangement for their lubrication shall be adequate to withstand the motions encountered in heavy weather and operation for prolonged periods at the list and trim specified in clause 5 without the spillage of oil.
4.3 Conductors and equipment shall be placed at such a distance from each magnetic compass or shall be so disposed that the interfering external magnetic field is negligible; that is, the total singular deviation shall not exceed 30 minutes when any combination of circuits is switched on and off.
4.4 Where the total installed electrical power of the main generators exceeds 3 MW the busbars of the main switchboard shall be subdivided into at least two parts. The subdivision may be effected by removable links, circuit-breakers or other suitable means so that the main generators and any supplies to duplicated services which are directly connected to the busbars are, as far as is practicable, equally divided between the sections.
7.5 The following electrical arrangements relate only to the navigation lights referred to in 7.3 and 7.4.
– Each light shall be connected by a separate cable to a distribution board reserved solely for navigation lights, fitted in an accessible place under the control of watchkeeping personnel.
– There shall be two separate power supply systems to the distribution board, one being from the main switchboard and one from the emergency switchboard. Where a transitional source of emergency power is required by the Safety of Life at Sea (SOLAS) Convention, the arrangements shall enable the lights to be supplied from this source in addition to the emergency switchboard.
– So far as is practicable, the arrangements should be such that a fire, a fault or mechanical damage at any one point will not render both systems inoperative. It is, however, accepted that the systems must come together at some point where the changeover can be effected. This should, preferably, be at or near to the distribution board.
– Each light shall be controlled and protected in each insulated pole by a switch and fuse or by a circuit-breaker mounted in the distribution board.
– Each light shall be provided with an automatic indicator to give an acoustic and/or optical alarm in the event of a lamp failure. If an optical signal is used, which is connected in series with the steaming light, means to prevent failure of the indicator extinguishing the steaming light shall be provided. If an acoustic device alone is used it shall be connected to an independent source of supply, for example a battery, and provision shall be made for
testing this supply.