Page 192 - Offshore Electrical Engineering Manual

Redundancy, Diversity and Safety Issues 179

4. All lifeboats (TEMPSCs) are also to be equipped with the statutory telecom-
munications fit

A typical package would consist of the following:

1. A dual multichannel VHF (FM) transceiver operating in the International Maritime
Mobile Band, is provided for communication with supply vessels, standby vessels
and shuttle tanker. Private channels are also used for communications with the
shuttle tanker, supply vessels, crane cabs and hand portables. Each crane is equipped
for VHF communication.
2. Lifeboats are equipped with a VHF radio telephone, working on channel
16 and at least one other channel, complete with suitably certified battery
chargers. They also carry an EPIRB (Emergency Position-Indicating Radio-
Beacon station) and SART (Search and Rescue Transponder) to satisfy SOLAS
requirements.
3. A duplicated (main/standby) VHF (AM) aeronautical transceiver with control
electronics and a number of aeronautical hand portable radios are available to
communicate with aircraft.
4. A radio beacon also provides for navigation of helicopters on approach to the
platform.
5. All normal communications to shore are usually through dual (K-band) satellite
communication systems.
1
6. The INMARSAT unit provides emergency communication direct to shore.
The system provides two-way communications as a backup to the installation’s
multichannel communication links, fax and SOLAS facilities.

REDUNDANCY, DIVERSITY AND SAFETY ISSUES
1. The external communications must all be provided with secure battery-backed
supplies to ensure that they will work if the main power systems have been
disabled. The two UPS supply batteries should be located in geographically
separate rooms.
2. Cables for alternative telecom systems and their electrical supplies should
be routed separately in order to minimise the possibility of common
mode-failures.
3. Unless it is isolated on a confirm gas alarm, all external communication equipment
requires to be suitable for operation in at least zone 2 hazardous areas, so that the
risk of igniting uncontrolled gas releases is minimised.
4. Care must be taken to avoid inadvertent ignition of flammable gases due
to microwave radiation from radar antennae or radio navigation beacons
(Reference 6).

1 International Marine/Maritime Satellite (organization).