MARINE COOLING SYSTEMS
Marine electric plants use heat exchanger and direct type cooling systems.
The only outward
difference between the two systems (new design -
see illustration) is in the type of cap used on the water-
cooled exhaust. manifold.
The heat exchanger system utilizes a pressure cap (with filler neck and over-
* flow tube) while the direct type uses a solid, non-pressure type cap.
To further identify the systems,
the tubes of the heat exchanger can be seen or felt when the cap is removed from the manifold.
TO
drain systems,
turn p?tcock located on lower right front side of crankcase or if this is not provided,
loosen cover plate.
PRESSURE CAP WITH HEAT
EXCHANGER SYSTEM
PRESSURE
f
SOLID CAP WITH DIRECT
rADAQTER
SYSTEM
fWASHER
ncn1 LA
BUNDLE
Uc*T VCHANGER
/
\
COOLED -.N
MANIFOLD
w
I
COOLING
L
nlIT1 Ft
I
TUBE
770’ WITH EXCHANGER SYSTEM 1
138" WITH DIRECT SYSTEM
I
.
FIGURE 6-5 --
WATER COOLED MANIFOLD FOR MARINE COOLING SYSTEMS
Heat Exchanger Systein:
The heat exchanger system is comprised of two circuits--a closed engine
clrcult and the raw or sea water circuit.
In the closed circuit, coolant is circulated by the engine water
pump through the water jacket,
manifold and returned to the pump for recirculation.
Since this is a
closed circuit, antifreeze can be added if required-
the circuit holds 5 to S- l/2 quarts of liquid.
In the
raw water circuit, the belt driven sea water pump picks up sea water and circulates rt through the tube
bundle where it absorbs and carries away heat of the closed circuit which is being circulated around the
tubes.
The heated water is sprayed into and mixed with the exhaust which is in turn ejected through the
wet type silencer and finally is expelled through the exhaust outlet.
Direct Type System:
On the direct system,
the sea water pump introduces sea water directly into the
manrfold where It 1s circulated throughout the engine by the engine water pump.
The heated water is
forced away and injected into the exhaust in the same way as in the heat exchanger system.
Since the
direct system is of the non-pressure type, the solid cap must be used..
This system cannot be protected
with antifreeze since it is an open circuit.
A 138’ therm- is required with the direct system.
63
l
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