Transcript Ancillary Electrical Services - Pomorski fakultet u Splitu

ANCILLARY ELECTRICAL SERVICES:
SHIP’S LIGHTING AND
MAINTENANCE OF LIGHTING
FITTINGS
(Adapted from:D.T. Hall:Practical Marine Electrical Knowledge)
 To ensure a safe working environment, together with
off duty comfort in the accommodation quarters on
board your ship, a considerable proportion of the
generated electric power is absorbed in the ancillary
services.
 Lighting of the ship's deck areas, engine room and
accommodation to meet specified levels of illumination
is provided by various light fittings (luminaires) designed
to work safely in their particular locations.
 The hotel services for food storage, preparation and
cooking, together with accommodation air-conditioning
and laundry services, are essential for the general
maintenance of the mariner.
 Historically, the original application of electricity
in ships was for lighting. Oil lanterns were a
definite fire risk and the ship's lamp trimmer had
great difficulty in maintaining his navigation
lights in stormy weather.
 To meet the safety and comfort levels of
illumination required throughout your ship a
wide range of lighting fittings (luminaires) are
used. The power ratings of the lamps used will
vary from a few watts for alarm indicator lamps
to a few kW for deck floodlights and searchlights
(e.g. a Suez Canal Projector Light).
 Group replacement of lamps is often considered by
shipping companies to be more economic and
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convenient than individual replacement following
lamp failure. Cleaning of the fittings can also be
carried out during group lamp replacement so
maintaining a high luminous efficiency.
Lamp end caps are many and various but the most
common types are screw and bayonet fittings.
Broadly, the luminaires employ one of two general
lamp types classified as:
Incandescent
Discharge
Incandescent Lamps
 The most common lamp used for general lighting is
the simple filament type. A current is passed
through the thin tungsten wire filament which
raises its temperature to around 3000 °C when it
becomes incandescent (it glows).
 The glass bulb is filled with an inert gas such as
nitrogen or argon which helps to reduce filament
evaporation to allow an operating life expectancy of
about 1000 hours. Lamp power ratings are available
from 15 W to 1000 W.

Discharge Lamps
 The light output from a discharge lamp is
generated by the flow of current in an electric
arc between two electrodes through a gas and
metal vapour inside a sealed glass bulb or tube.
 The most common metal vapours employed in
discharge lamps are:
1. Mercury (as used in a fluorescent tube) and
2. Sodium
Voltage Effects on Lighting
 Naturally, all lamps are designed to produce their
rated luminous output at their rated voltage. An
overvoltage on an incandescent lamp produces a
brighter and whiter light because the filament
temperature is increased. Its operating life is,
however, drastically reduced. A 5% increase over its
rated voltage will reduce the lamp life by 50%.
 Conversely, a supply voltage reduction will increase
the operating life of a GLS lamp but it produces a
duller, reddish light. Lamps rated at 240 V are often
used in a ship's lighting system operating at 220 V.
This under-running should more than double the
lamp life.
 Similar effects on light output and operating life
apply to discharge lamps but if the supply
voltage is drastically reduced (below 50%) the
arc discharge ceases and will not re-strike until
the voltage is raised to nearly its normal value. A
fluorescent tube will begin to flicker noticeably
as the voltage is reduced below its rated value.
Navigation and Signal Lights
 The number, position and visible range of
navigation lights aboard ships are prescribed by
the International Maritime Organization (IMO) in
their "International Regulations for Preventing
Collisions at Sea".
 By far the most common arrangement is to have
five specially designed navigation running lights
referred to as Foremast, Mainmast (or Aftmast),
Port, Starboard and Stern.
 Two anchor lights, fitted forward and aft, may
also be switched from the Navigation Light
Panel on the bridge. The side lights are red for
Port and green for Starboard while the other
lights are white. For vessels length more than 50
metres, the masthead light(s) must be visible
from a range of six nautical miles and the other
navigation lights from three nautical miles.
 To achieve such visibility, special incandescent
filament lamps are used each with a typical
power rating of 65 W but 60 W and 40 W ratings
are also permitted in some cases.
 Due to the essential safety requirement ( for
navigation lights it is common practice to have
two fittings at each position, or two lamps and
lampholders within a special dual fitting.
 Each light is separately supplied, switched, fused
and monitored from a Navigation Light Panel in
the wheelhouse. The electric power is provided
usually at 220 V a.c. with a main supply fed from
the essential services section of the main
switchboard.
 An alternative or standby power supply is fed
from the emergency switchboard.
 A changeover switch on the Navigation Light
Panel selects the main or standby power supply.
 The Navigation Light Panel has indicator lamps
and an audible alarm to warn of any lamp or
lamp-circuit failure. Each lamp circuit has an
alarm relay which monitors the lamp current.
The relay may be electromagnetic or electronic.
 Various signal lights with red, green, white and blue
colours are arranged on the signal mast. These
lights are switched to give particular combinations
to signal states relating to various international and
national regulations.
 Pilotage requirements, health, dangerous cargo
conditions, etc., are signalled with these lights.
White Morse-Code flashing lights may also be fitted
on the signal mast.
 The NUC (Not Under Command) state is signalled
using two all-round red lights vertically mounted at
least 2 m apart. Such important lights are fed from
the 24 V d.c. emergency supply but some ships may
also have an additional NUC light-pair fed from the
220 V a.c. emergency power supply.
Emergency Lighting
 Depending on the ship's classification, e.g. ferry, roro, gas carrier, etc., and tonnage the Safety of Life
at Sea (SOLAS) Convention prescribes minimum
requirements for emergency lighting throughout
the vessel.
 Emergency light fittings are specially identified,
often with a red disc, to indicate their function. Most
of the emergency lighting is continually powered
from the ship's emergency switchboard at 220 V a.c.
 A few emergency lights may be supplied from the
ship's 24 V d.c. battery, e.g. at the radio-telephone
position in the wheelhouse, the main machinery
spaces and the steering flat.
 Some shipping companies now fit special battery-supported
lighting fittings along main escape routes in the engine
room, accommodation and at the lifeboat positions on deck.
Generally, such emergency lights in the accommodation are
arranged to produce light immediately on mains failure.
 Boat station emergency lights are switched on when
required. Inside the fitting a maintenance-free battery,
usually nickel-cadmium, is continually 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. This power supply
arrangement is called an uniterruptible power supply or UPS.
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.
 A visible, illuminated escape route reduces uncertainty and assists
orderly evacuation.
 Passenger ships carrying more than 36 passengers are required by
IMO resolution A752(18) to be fitted with Low Location Lighting (LLL)
to identify escape routes where normal emergency lighting is less
effective due to the presence of smoke. An LLL system must function
for at least 60 minutes after activation and it should indicate a line
along the corridors of an escape route.
 The installation of LLL should be on at least one side of the corridor,
either on the bulkhead within 300 mm of the deck or on the deck
within 150 mm of the bulkhead. In corridors more than 2m wide, it
should be installed on both sides.
 The LLL light sources may be low power LED's, incandescent lamps
or a photoluminescent material containing a chemical that stores
energy when illuminated by visible light. Of these sources, the LED
and incandescent lamp are the most effective. For hazardous areas
such as car decks on a ferry, an intrinsically safe (Exia) version can be
installed.
Maintenance of Lighting Fittings
 The performance of electric lamps will deteriorate with time.
Eventually they fail and the lamps must be replaced. Simple
lamp replacement becomes the most obvious maintenance
task. When a luminaire fails to light-up when switched on, it is
natural to suspect lamp failure. If this does not solve the
problem, checks on the lamp control equipment and power
supply must follow.
 An incandescent lamp may be checked (out of circuit) for low-
ohm continuity using a multimeter. If the lamp appears intact
then the fault must lie in the supply or its connections. Voltage
and continuity checks of the supply, fuse/ MCB and ballast
circuit must be applied. Remember that a single earth fault on
an insulated two-wire lighting supply will not blow a fuse.
However, a similar earth fault on an earthed supply system (as
used for a 110V transformer supply to deck sockets for portable
tools and handlamps) will blow a fuse.
A maintenance check list:
 Remember that it is good practice to replace both
fuses after clearing a fault which has ruptured only
one of them.
 When replacing a lamp, ensure that the circuit is
dead and isolated while removing the old lamp and
inserting the new one. The glass bulb or tube of an
old and corroded fitting may break loose from its
end-cap while attempting to remove the lamp. If
the supply is still connected, it is relatively easy to
cause an accidental short- circuit during the removal
process and the corresponding arc flash may cause
blindness, burns and fire.
 Always replace a lamp with the correct size,
voltage and power rating for the fitting it is
housed in. Overheating and fire can easily result
by using a higher powered incandescent lamp
than the fitting was designed for. Check the
lampholder wire connections behind the
lampholder for signs of overheating (hard,
brittle insulation on the wires) and replace if
necessary.
 Take care when disposing of lamps, particularly
discharge tubes, which should be broken
(outdoors) into a container (e.g. a strong plastic
bag) to avoid handling the debris.
 Remember that in a fluorescent lamp circuit the
capacitor may remain charged for a while after
switch off unless fitted with a discharge resistor.
Play safe, discharge the capacitor with a screwdriver
blade before touching its terminals.
 Cleaning of the lamp glass and reflectors is essential
for safety and necessary to maintain the luminous
efficiency of the luminaire.
 Particular care should be paid to the maintenance of
the watertight integrity of exposed luminaires (e.g.
for navigation, signal and deck lighting) at their
flanged joints and cable gland entry. Similarly, a
regular inspection of all portable handlamps and
portable cargo light fittings, together with their
flexible cables and supply plugs, should be
undertaken.