the THERMOSTATIC POSITION. Turn the
adjusting wheel until the pointer is opposite 2 on
the scale plate. Loosen the locknut and unscrew
the valve stem until it is free of the thermostatic
stem. Then turn the adjusting wheel until the
pointer is opposite 8 on the scale plate. (Note: The
preceding steps should be performed with the ther-
mostatic bulb removed from the ships piping and
when the bulb temperature is below 100°F.)
Again rotate the manual crankpin until the
lower end of the seating sleeve is flush with the
lower end of the thermostatic stem. With the
seating sleeve and the indicator pointer in this
position, loosen the screws in the indicator plate
and slide the plate up or down as needed to align
the THERMOSTATIC mark in the center of the
plate with the indicator pointer. Then retighten
the screws. (The marks COOLER CLOSED and
COOLER BY-PASS on the indicator plate are
only approximate.) Screw the valve stem into the
thermostatic stem and turn it until the cooler pop-
pet valve seats firmly. Turn the adjusting wheel
until the pointer is opposite 2 on the scale plate.
Turn the valve stem one full turn into the ther-
mostatic stem and retighten the locknut.
With the manual control on the THER-
MOSTATIC position, turn the adjusting wheel
in a direction to bring the pointer to number 9
on the scale plate. Run the engine at warmup
speed until the temperature of the fluid, as
indicated by the thermometer in the line with the
thermostatic bulb, rises to the desired
temperature. (The desired temperature must be
determined in advance from applicable
instructions.)
With the engine running at warmup speed and
the temperature at the thermostatic bulb at the
desired value, turn the adjusting wheel until the
cooler poppet just begins to leave its seat. This
action is shown by the movement of the mark on
the valve stem downward from the COOLER
CLOSED mark on the valve position indicator.
Valves adjusted in accordance with this procedure
will normally maintain the temperature of the
fluid at the thermostatic bulb between the desired
value and a temperature approximately 20°
higher, under any conditions of engine load or
injection temperature. This 20° difference is the
temperature rise required to cause the poppet
valve to move through the necessary travel.
HEATING EXCHANGER
DEFINITIONS
Problems with the cooling system of an engine
may prevent the cooling system from keeping the
engine parts and working fluids at safe operating
temperatures. Failure of the system may lead to
several of the troubles and casualties that have
been discussed earlier.
In marine installations, lubricating oil and
most of the engine parts are cooled by the circula-
tion of seawater, freshwater, or both. When the
cooling of an engine part is mostly by oil spray
or oil circulation, the oil is cooled by circulation
through an oil cooler. Figure 3-11 illustrates a
cooling system in which both freshwater and
seawater serve as coolants.
When maintaining engine cooling water
temperatures within specified limits, the principal
difficulties you may encounter are in maintain-
ing circulating pumps in operating condition;
preventing corrosion; reducing the cause of scale
formation in water jackets and heat exchangers;
cleaning jackets and heat exchangers according
to proper procedures; and in preventing leaks in
the various parts of the system.
The coolers (or heat exchangers) which remove
the heat from the cooling water of an engine may
vary considerably in design. Those used in cool-
ing systems may be classified basically as the
radiator type and the tubular type. The radiator
is sometimes referred to as the strut or the Har-
rison type, while the tubular is identified as the
Ross or shell-and-tube type. A heat exchanger of
both types is shown in figure 3-12. The heat ex-
changer on the top of the picture is a radiator type
heat exchanger; the one on the bottom is a
tubular-type heat exchanger. In heat exchangers
of the radiator type, the freshwater passes through
the tubes and the seawater passes around them.
In the tubular type, the freshwater surrounds the
tubes and the seawater passes through them.
CASUALTIES
Although heat exchangers vary in design, they
are all subject to similar casualties. The principal
difficulties which may prevent heat exchangers
from functioning properly are excessive scale
deposits on the cooler element, clogged cooler
elements, or cooler leakage.
Chapter 3ENGINE MAINTENANCE
3-11