NAVIGATION AIDS

Navigation aids consist of the following equipment:

1. Flashing marker lights.
2. Fog horns.
3. Platform nameplates.
4. Aircraft hazard lights.
5. Helideck landing facilities.
6. Radio communications and beacons.
7. Radar.
8. Echo-sounding and sonar.

1) FLASHING MARKER LIGHTS

A typical requirement is that recommended by the British Department of Trade document ‘Standard Making Schedule for Offshore Installations’,

1. White and red lights flashing the Morse letters ‘U’ every 15 seconds as follows:

Eclipse 1.00 s

Flash 1.00 s

Eclipse 1.00 s

Flash 3.00 s

Eclipse 8.00 s

Total Period 15.00 s

2. Fog signals sounding the ‘U’ every 30 seconds as follows:

Blast 0.75 s

Silent 1.00 s

Blast 0.75 s

Silent 1.00 s

Blast 2.50 s

Silent 24.00 s

Total Period 30.00 s

3. Illuminated identification panels.
4. Navigation buoys.

2) WHITE AND RED FLASHING LIGHTS

The ‘normal’ range and ‘apparent intensity’ of these flashing lights should be in accordance with the local requirements, e.g. for UK waters, IALA publication ‘Recommendations for the Notation of Luminous Intensity and Range of Lights’.

a) MAIN LIGHTS

The main white lights should have a ‘nominal’ range of 15 miles and be visible in every direction of approach; there should normally be a minimum of two and a maximum of four main white lights.

b) SUBSIDIARY LIGHTS

Subsidiary red lights of 3 miles ‘nominal’ range should be positioned to mark the horizontal extremities of the structure, in positions not occupied by white lights, to indicate any irregular projections of the complex.

c) SECONDARY LIGHTS

Secondary white lights of 10 miles ‘nominal’ range and visible in every direction of approach should automatically come into operation in the event of failure of the 15 mile main white lights; these are normally mounted in similar location to the main white lights.

d) OPERATION AND CONTROL OF LIGHTING SYSTEMS

Navigation lighting systems can be fitted with a device to automatically switch on 15 minutes before sunset until sunrise or whenever the visibility is less than 2 sea miles. There can also be a manual override device to enable the navigation aids to be switched on during unusual conditions or for maintenance and testing etc.

Failure of any of the navigation lights can be indicated in the central control room and in the radio room.

In the event of failure of the main white lights control equipment, control should automatically be transferred to the secondary system, which would cause the secondary and the main lights to flash in synchronism, and generate an alarm in the central control room and the radio room.

All subsidiary lights should operate in synchronism.

The secondary and subsidiary lights can be equipped with an automatic lamp changer or multiple filament bulbs. This provides a minimum of one standby lamp or filament which will be automatically activated in the event of a filament failure. Filament failure should produce an alarm in the central control room and the radio room until a defective bulb is replaced.

On long narrow structures or structures linked by bridges where lights may otherwise be several hundred metres apart, intermediary 3 mile red lights should be mounted in positions to deter vessel from colliding with the central sections of the structure of bridges.

The secondary and subsidiary lights should be capable of operating for 96 hours from a battery power source which is independent of the main supply. The equipment would normally operate on the main AC supply, with automatic switching to an alternative AC supply in the event of main supply failure, and automatic switching to battery supplies when no AC supply is available.

3) NAVIGATION BUOYS

Navigation marker buoys can be wave or solar powered or alternatively fitted with batteries. They would be retained in a position to facilitate quick manual launching, and provision should be made for ready inspection and maintenance of batteries.

4) IDENTIFICATION PANELS

The structure identification panels usually consist of black letter and figures one metre high on a yellow background with illumination or be on a retro-reflective background.

5) AIRCRAFT HAZARD LIGHTING

Hazard lighting should be provided on all projections from the structure which could present a danger to helicopters approaching the platform. Positions where it would be impractical to fit red lights due to the possibility of damage or difficulty of maintenance caused by high temperature, such as flare towers and exhaust stacks, would be flood lit from convenient locations.

In the event of main supply failure the hazard lighting would be supplied from an emergency generator or battery supply.

No form of lighting on the structure should be capable of creating a hazard to helicopters by night-blinding the pilot due to dazzle or glare.

6) HELICOPTER LANDING FACILITIES

Helideck markings and illumination should be in accordance with appropriate standards.

A high frequency radio beacon with a minimum range of 30 miles can be provided for the guidance of approaching helicopters, and VHF/AM radio would be provided for communication with pilots to comply with the appropriate standards, for the location.

The structure would also be equipped with suitable devices for ascertaining the wind speed and direction, air temperature, barometric pressure, visibility and cloud cover.

7) RADAR

Radar is not used on all offshore platforms. Its use is determined by the nature of the platform and the frequency and type of local sea traffic. When surveillance radar is installed precautions should be adopted to ensure the minimum of danger to personnel from high energy radiation and dangers associated with rotating aerial scanners, interference with electronic instruments and communication, and the elimination of ignition in hazardous atmosphere in accordance with the standards e.g. BS3192 and 4992.

All of the equipment and interconnecting cables should be located in a safe area. The transmitters and aerials should not be located near telecommunication equipment, electronic instruments and similar equipment which could suffer interference or damage due to high energy radio frequency radiation. The aerials must be positioned to prevent the creation of high energy radio frequency fields in hazardous areas where they could cause ignition.

The aerials should be installed in such a manner and location as to allow reasonable safe access for at least two people for servicing and maintenance, whilst preventing access to un-authorized personnel.

Emergency stop switches could be provided in a safe position, adjacent to the aerials, to switch off the scanners and transmitters.

8) RADIO DIRECTION-FINDER

Platforms that are permanently manned would require equipment for obtained bearings on radio navigation beacons and survival craft transmitting on international distress frequencies. If the equipment is of a type approved by the British Department of Trade (or similar national standard) in accordance with SOLAS (1974) Regulation 12, then the SOLAS requirements could also be supplemented as follows:

• The equipment should be located in the radio room.
• The aerials and feeder cables should be located in a safe area as close as possible to the radio room.
• An emergency power supply should provide a minimum of 6 hours duration, and minimum of 3 hours of this supply should be from batteries. The batteries, charger and supply cables should be in a safe area as close as possible to the radio room.

9) SONAR DEVICES

If echo-sounding equipment is required then it should be of a type approved by the Department of Trade, or similar national authority appropriate to the location, in accordance with SOLAS (1974). The installation of sonar devices should be in accordance with appropriate standards, and particular regard should be directed towards the dangers that high-powered underwater sonar transmissions may present during diving operations.