Depending on the ship's classification, e.g. ferry, RORO, gas carrier, etc., and tonnage, the SOLAS Convention prescribes minimum requirements for emergency lighting throughout the vessel (Refer to the SOLAS Regulations in Chapter 4).
Emergency light fittings are marked, often with red paint, etc, to indicate their function. The emergency lighting is continually powered from the ship's emergency switchboard at 220V a.c; Chapter 4 elaborates this aspect. A few emergency lights may be supplied from the ship's 24V d.c. battery, e.g., at the communication post in the wheelhouse, and in the machinery space, including the -steering flat (Refer Figures 3.9 and 22.13). Modern emergency lights are generally installed within the normal lighting fixtures and some shipping companies now fit special battery-supported light-fittings along main escape routes in the engine room and accommodation, and at the lifeboat station on the deck. These lights can also be found to be an integral part of the general light-fitting e.g. a fluorescent tube can be designed to house an emergency light that is supplied from an independent emergency source of supply as mentioned in the regulations. Generally, such emergency lights in the accommodation are arranged to produce light immediately upon mains failure; emergency lights at the boat station are switched on when required. Inside the fitting, a maintenance-free battery, usually the nickel-cadmium type is continuously trickle charged from the normal mains supply via a transformer/rectifier circuit. The battery is then available to supply the lamp via a d.c. to a.c. inverter when the main power is absent. Usually the battery will only function for a few hours. Such battery-supported light fittings can be simply tested by switching off the normal mains power supply or, in some cases, by a test switch on the actual fitting. Periodic inspection and testing of all emergency lights is an essential requirement on all ships. This is done once a week or as would be deemed necessary. To conclude, it is important to note that installations on board vary not only between different classes of vessels, but also may be customised.
The relevant circuits and layout diagrams must be referred to in order to obtain adequate information of your ship's lighting system, as it is vital to everyone around you!
