Page 296 - Offshore Electrical Engineering Manual

Communications 283

SECURE POWER SUPPLY SYSTEMS

BATTERIES
Under normal circumstances, batteries will be shipped filled and discharged. Sealed
type batteries will be shipped filled and charged. If batteries are shipped unfilled,
appropriate safe filling facilities will need to be made available offshore.
Battery racking, cell units, connecting conductor links and associated nut, bolt and
washer kits should be inspected for correct type and quantity on arrival. Any damaged
components or shortages will need to be made up before installation can be completed.
Unsealed batteries will require either filling or topping up depending on the con-
dition in which they were supplied.
It is important that batteries are assembled as shown in the drawings supplied.
Incorrect configuration may provide the wrong output voltage and/or discharge dura-
tion and in any case, links will have been provided in the correct numbers and sizes
for a particular configuration. Link and cable lug bolts should be tightened using a
torque limiting tool, particularly with sealed type cells whose terminal posts snap off
at very low torques.
In case of unsealed batteries particularly, all terminals and connections should be
liberally greased with petroleum jelly or a similar substance according to the manu-
facturer’s recommendations.

BATTERY CHARGERS AND INVERTORS

Cubicles should be positioned to ensure that a free flow of cooling air is available and
that the ventilation entries and exits are clear of obstructions. An all-round clearance
space of at least 150 mm is recommended.
Before commissioning, all cabling connections, circuit breakers and fuses should
be checked for correct rating and operation. The manufacturer’s representative
should be present to inspect the equipment to his or her satisfaction before supervis-
ing its commissioning.

COMMUNICATIONS
PUBLIC ADDRESS SYSTEMS
The public address system is vital for communication of hazards and the calling of
staff in the ‘field’, so it is often necessary to commission a part of the system as soon
as it is installed and to minimise disruptions to its operation whilst installation of the
rest of the system continues. This is quite possible provided a powered amplifier rack
is available at an early stage in the proceedings. For reliability, it is a requirement
that in every area, the public address circuits are duplicated. Therefore at least two
circuits of loudspeakers will be required on any installation. In practice, more will be
required because it will be necessary to mute speakers in sleeping areas during nor-
mal operating conditions and on large installations, more than two amplifier circuits