troubleshooting procedures are discussed in the
following paragraph.
Since thermocouples monitor temperature, you
must allow them to cool before you begin
troubleshooting. Thermocouples on GTEs can be cooled
by motoring the engine. You can check the
thermocouple and its leads by using a multimeter to take
resistance readings. Take resistance readings between
each pin and each pinto ground. Check the technical
manual to determine if the readings are within the
m i n i m u m acceptable limits. If the thermocouple
resistance system measurements are within limits,
troubleshoot the ship's instrumentation. As mentioned
earlier in this chapter, always refer to the manufacturer's
technical manual when you test, troubleshoot, and repair
any electrical equipment.
LEVEL CONTROL DEVICES
In the engineering plant on a gas turbine-powered
ship, operating personnel must know the levels of the
various liquids in different locations in the ship. The
level in the ship's freshwater tanks is an example of a
Figure 6-10.--Liquid-level float switch.
liquid level that must always be known. There are other
liquid levels that are also important. These include the
levels in the fuel oil service tanks, fuel oil stowage tanks,
liquid level reaches a preset point, the float switch
lubricating oil sumps, and drain tanks.
completes the circuit to the pump, signaling the pump
A wide variety of devices, some of them simple and
to start to remove the liquid from the tank. When the
s o m e complex, are available for measuring and
level drops to the preset point, the pump secures.
controlling liquid levels. Without level control devices,
engineering and operating personnel could not plan for
MAGNETIC FLOAT DEVICES
their supply needs. GSEs are responsible for the repair,
maintenance, and installation of these devices. Level
Each tank level indicator (TLI) system is made up
control devices used aboard gas turbine-powered ships
of equipment and accessories that are necessary for the
include liquid-level float switches and magnetic float
specific installation. The TLI system components can be
devices.
divided into four general groups: (1) the liquid-level
detection devices (transmitter), (2) the receiver devices
LIQUID-LEVEL FLOAT SWITCHES
(receiver panel or module), (3) the remote alarm or
liquid-level indicating devices (alarm and gauges), and
A relatively new development in indicating alarm
( 4 ) the accessories (tubing and so forth). These
and control functions is the liquid-level float switch. A
components are shown in figure 6-11.
liquid-level float switch is shown in figure 6-10. This
The purpose of the liquid-level detection devices
type of switch is usually found in tank- and bilge-level
installed in tanks is to convert the liquid level into an
alarm circuits.
electrical signal. The two types of detection devices
The liquid-level float switch has a
available are the transmitters and the level links.
doughnut-shaped, floatable magnetic core operating
Transmitters provide a continuous level measurement,
over an encapsulated reed switch. The entire assembly
w h i l e level links provide a point or incremental
is mounted at a predetermined level. The switch can be
measurement.
made normally open or closed by reversal of the core.
Study the transmitter shown in figure 6-12. The
Level conditions are shown as normal, above normal, or
transmitter consists of a network of voltage divider
below normal. The switch can also be used to start and
resistors and magnetic reed switches contained in silicon
stop pumps, such as in a drain tank system. When the
6-10
