GB/T 25444.5-2023 Mobile and fixed offshore units -Electrical installations - Part 5: Mobile units
1 Scope
This document specifies additional characteristics for electrical installations in mobile units.
This document specifies requirements such as those concerning
- environmental conditions,
- limits of inclination for the unit where the equipment is required to operate,
- bilge pumps,
-navigation and obstruction lights,
- steering gear,
- ballast system,
- jacking systems,
and
- anchoring systems.
For electric propulsion, reference is made to IEC 60092-501.
For dynamic positioning systems, reference is made to relevant IMO requirements.
It applies to installations that depend on buoyancy, such as column-stabilized units (semi-submersible units), ship-or barge-type units as well as self-elevating units. It specifies additional characteristics for such units, used during transfer from one location to another and for drilling, production, accommodation, processing, storage and offloading purposes.
It applies to all installations, whether permanent, temporary, transportable or hand-held, to AC installations and DC installations without any limitation on voltage level. Referenced equipment standards may give voltage level limitations.
This document does not apply to
- fixed equipment for medical purposes,
- electrical installations of tankers, and
- control of ignition sources other than those created by electrical equipment.
Note 1: For medical rooms, IEC 60364-7-710 provides specific requirements. Requirements for tankers are given in IEC 60092-502.
Note 2: Guidance on protection of non-electrical equipment can be found in ISO 80079-36, ISO 80079-37 and IMO 2009 MODU Code, 6.7.
Note 3: Attention is drawn to further requirements concerning electrical installations on such mobile offshore units contained in the IMO 2009 MODU Code.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60034-1 Rotating electrical machines - Part 1 : Rating and performance
Note: GB/T 755-2019 Rotating electrical machines - Rating and performance (IEC 60034-1 : 2017, IDT)
IEC 60092-501:2013 Electrical installations in ships - Part 501 : Special features –Electric propulsion plant
Note: GB/T 22190-2008 Electrical installations in ships - Special features - Electric propulsion plant (IEC 60092-501 : 1984,IDT)
IEC 61892-1 Mobile and fixed offshore units -Electrical installations -Part 1 : General requirements and conditions
Note: GB/T 25444.1-2010 Mobile and fixed offshore units - Electrical installations - Part 1 : General requirements and conditions (IEC 61892-1 :2001, IDT)
IEC 61892-2:2019 Mobile and fixed offshore units -Electrical installations -Part 2 : System design
Note: GB/T 25444.2-2010 Mobile and fixed offshore units - Electrical installations - Part 2: System design (IEC 61892-2 :2005, IDT)
IEC 61892-3 Mobile and fixed offshore units - Electrical installations - Part 3 : Equipment
Note: GB/T 25444.3-2023 Mobile and fixed offshore units - Electrical installations - Part 3 : Equipment (IEC 61892-3:2019, IDT)
IEC 61892-6 Mobile and fixed offshore units - Electrical installations - Part 6 : Installation
Note: GB/T 25444.6-2023 Mobile and fixed offshore units - Electrical installations - Part 6 : Installation (IEC 61892-6:2019, IDT)
IALA O-139 Recommendation on the Marking of Man-Made Offshore Structures, 2013
IMO Convention on the International Regulations for Preventing Collisions at Sea (COLREG)
IMO, MSC Circular 645 Guidelines for vessels with dynamic positioning systems, Annex
IMO International Convention for the Safety of Life at Sea (SOLAS), consolidated edition 2014
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61892-1, IEC 61892-2:2019, IEC 61892-3 and IEC 61892-6 apply.
3.1
auxiliary steering gear
equipment, other than any part of the main steering gear, necessary to steer the unit in the event of failure of the main steering gear
Note: not including the tiller, quadrant or components serving the same purpose
3.2
dynamic positioning system
DP system
equipment necessary to provide means of controlling the position and heading of a mobile unit within predetermined limits by means of resultant vectored thrust
3.3
electric steering gear
power operated steering gear where an electric motor applies torque to the rudder stock through mechanical means only
3.4
electrohydraulic steering gear
power operated steering gear where a hydraulic pump, driven by an electric motor, applies torque to the rudder stock through hydraulic and mechanical means
3.5
main steering gear
machinery, rudder actuators, steering gear power units and ancillary equipment and the means of applying torque to the rudder stock necessary for effecting movement of the rudder for the purpose of steering the unit under normal service conditions
Note: for example tiller or quadran
3.6
propulsion machinery
rotating machine normally intended to provide propulsive power
3.7
redundancy
existence, in an item, of more than one means for performing a required function
[Source: IEC 60050-351:2013, 351-42-28, modified]
3.8
steering gear control system
equipment by which orders are transmitted from the navigating bridge to the steering gear power units
Note: Steering gear control systems comprise transmitters, receivers, hydraulic control pumps and their associated motors, motor controllers, piping and cables, etc.
3.9
steering gear power unit
electric motor and its associated electrical and/or hydraulic equipment used to operate the steering gear
4 General requirements
4.1 Environmental conditions
4.1.1 Ambient temperature
Unless otherwise given in the project specification, the values given in Table 1 are applicable.
Where equipment is designed to operate with temperatures higher or lower than those stated in Table 1, permissible temperature rises may be reduced or increased accordingly.
4.1.2 Relative humidity
Electrical equipment shall be designed for a relative humidity up to 95 %.
4.2 Protection against flooding
In every mobile unit, in which electric power is used for the services necessary for the safety of the unit, the generators, switchgear, motors, energy storage devices and associated controlgear for such services shall be so situated or arranged that the intended function of the system is upheld in the event of partial flooding of the unit, within inclination limits referred to in Clause 5.
