TEMPERATURE CONTROL DEVICES
these checks prove satisfactory, check your ship's
Temperature, like pressure, is one of the basic
troubleshooting procedures, refer to the manufacturer's
engineering measurements that must be monitored aboard
ship. Like pressure readings, temperature readings also
provide you with an indication of the operating condition
When you must replace a transducer, read all
of the equipment. Temperature control devices operate
applicable instructions, class advisories, and bulletins
from changes in the temperature that take place in an
before removing the unit. All pressure transducers are
enclosure or in the air surrounding the temperature-sensing
removed and installed in the same manner. Differential
element. Temperature control devices are used with
pressure transducers, however, have two pressure lines.
h i g h - t e m p e r a t u r e alarm systems, generator air
(See the detail block in fig. 6-6.) Refer to figure 6-7 as
temperature control circuits, and fire detection alarm
you read the description of the transducer removal
systems. They are also used to stop and start ventilation
procedures. The numbers in parentheses refer to the
motors and to control the heating of fuel and lube oil.
Common temperature control devices include temperature
associated numbered parts in the figure.
switches and thermocouples.
To remove a transducer, first shut off the
transducer. Secure and tag out the electrical power to the
transducer and remove the electrical lead (4) from the
A temperature switch opens or closes a set of contacts
unit. Next, remove the nut, washer, and bonding strap
at a preset temperature Temperature switches provide
(6) from the transducer stud (5). Disconnect the pressure
alarm indications or stop a piece of equipment if a high
lines (1) from the transducer. Next, remove the bolts and
temperature condition develops. A temperature switch
with two types of sensing elements is shown in figure 6-8.
washers that secure the transducer to the mounting plate.
The main function of a temperature switch is to convert
Remove the transducer. Finally, remove the pressure
thermal energy into electrical energy. Although the shapes,
line unions (2). Remove and discard the O-rings (3)
configuration, and sizes of temperature switches may
from the unions.
differ, their primary function is the same.
The following paragraph describes the procedures
you should use to properly replace a pressure transducer.
Again, follow along in figure 6-7 as you study this
Temperature-operated switches are usually
single-pole, single-throw, quick-acting, normally open
First, install new O-rings (3) on the unions (2). Next,
install the unions into the transducer and torque the
unions to 135 to 150 inch pounds (in. lb). Place the
transducer on the mounting plate so it is flat when the
locator pin is inserted into the transducer flange. Next,
install the bolts and washers to secure the transducer to
the mounting plate. Torque these bolts to 40 to 60 in. lb.
Connect the pressure lines (1) to the transducer and
torque the fittings to 135 to 150 in. lb. Next, attach the
bonding strap (6) to the stud (5) on the transducer with
the washer and nut. Torque this nut to 70 to 110 in. lb.
Make sure the seal is in the electrical lead (4) connector
and attach the lead to the transducer. Finally, remove the
tag and restore electrical power to the transducer.
Calibrate the pressure transducer according to the
applicable MRC. Follow the basic troubleshooting
p r o c e d u r e s and all applicable electrical safety
p r e c a u t i o n s whenever you calibrate, remove, and
Figure 6-8.--Temperature switch with two types of sensing
elements. A. Bulb unit. B. Helix unit.
replace pressure transducers.