CAUTION
When fluorescent lamps are operated on ac circuits,
the light output creates cyclic pulsations as the current
passes through zero. This reduction in light output
Fluorescent lamps contain mercury, which
produces a flicker that is not usually noticeable at
is extremely toxic! Mercury can be swallowed,
frequencies of 50 and 60 hertz, but may cause
inhaled, or absorbed through the skin. Although
unpleasant stroboscopic effects when moving objects
the amount of mercury contained in each
are viewed. When using a two- or three-lamp fixture,
fluorescent lamp is small, the combined
you can minimize the cyclic flicker by connecting each
numbers of lamps used on board ship could
lamp to a different phase of a three-phase system (fig.
impact on health and marine life if not proper] y
4-9).
discarded. All used fluorescent lamps must be
turned in at the nearest defense property
The fluorescent lamp is inherently a high
disposal office, ship repair facility, or naval
power-factor device, but the ballast required to stabilize
shipyard. If a fluorescent lamp is broken, avoid
the arc is a low power-factor device. The voltage drop
breathing the mercury vapor, and be extremely
across the ballast is usually equal to the drop across the
careful in handling the broken glass to avoid
arc, and the resulting power factor for a single-lamp
cuts. Mercury spillage must be cleaned up
circuit with ballast is about 60 percent.
promptly. Detailed cleanup and disposal
Although the fluorescent lamp is basically an ac
instructions are contained in NSTM, chapter
lamp, it can be operated on dc with the proper auxiliary
330, and, Mercury, Mercury Compounds, and
Components Containing Mercury or Mercury
equipment. The current is controlled by an external
resistance in series with the lamp (fig. 4-8, view D).
Compounds, control of, N A V S E A I N S T
Since there is no voltage peak, starting is more difficult
5100.3B.
and thermal-switch starters are required.
GLOW LAMPS
Because of the power loss in the resistance ballast
box in the dc system, the overall lumens per watt
The glow lamp is a device that produces light by an
efficiency of the dc system is about 60 percent of the ac
ionization process that creates the flow of electrons
system. Also, lamps operated on dc may provide as little
through an inert gas such as neon or argon. This creates
as 80 percent of rated life.
a visible colored glow at the negative electrode.
The majority of the difficulties encountered with
Glow lamps are used as indicator or pilot lights for
fluorescent lights are caused by either worn-out or
various instruments and control panels. These lamps
defective starters, or by damaged or expended lamps.
have a relatively low-light output. They are used to
Lamps are considered defective when the ends are
provide indication of circuit status or to indicate the
noticeably black in color. When observing the abnormal
operation of electrical equipment installed in remote
operation of a fluorescent fixture, you can usually take
locations. The lamp in figure 4-10 energizes when the
care of the problem by replacing either the starter or the
fuse is open to draw the attention of the operator.
lamp or both.
Figure 4-10.--Fuse holder with glow lamp.
Figure 4-9.--Fluorescent fixture three-phase connections.
4-11
