External Cooling - Volvo D5 series Installation Manual

External cooling

General
When the boat is operating in waters where there is a
lot of sand and sludge, or in ice, it is advisable to fit a
closed cooling system (keel cooling system).
There are several possible cooling system arrange-
ments:
•
skin cooling
•
pipe assemblies (keel cooling)
•
double bottom (skin cooling)
•
external cooling tanks (box cooling)
The principle of an external cooling installation is that
the standard circulation pump of the engine also cir-
culates coolant in the external cooler.
It is important to use the correct materials in the cool-
ers. Use Volvo Penta coolant, a mixture of anti-freeze.
A number of factors must be taken into account when
calculating and designing the external cooling sys-
tem.
• Volvo Penta does not market external cooling sys-
tems or components for such systems.
• Volvo Penta does market engines suitable for
connection to external cooling systems.
Tables in this chapter list the pressures and flows
that must be taken into account when calculating
the system as well as a description of the cooling
system.
• It is essential to choose the correct pipe dimen-
sion and length for pipe coolers, and the correct
tank height and width for double-bottom coolers,
with regard to backpressure, flows and heat to be
dissipated.
• The system must not include any sharp bends or
tanks that end abruptly.
• When calculating pipe length and tank area, fac-
tors to be taken into account are:
. Engine technical data
2. Power and rpm
3. Type of operation
4. Minimum hull speed at full rated power
5. Maximum seawater temperature
6. Cooler dimensions
7. Materials in cooler
8. Thickness of paint on cooler
9. Exhaust system, wet or dry
0. If using power take-off under 0 knot
condition, what are the power and rpm at
which the engine will be loaded?
. The concentration of antifreeze and its
effect on the cooling capacity are stated in
section Coolant.
2. To extend service life, especially on the
D2, it is recommended to install a fresh
water filter between the external circuit and
the engine.
• If the normal expansion tank of the engine is too
small, an extra expansion tank must be installed.
Position the tank at the highest point of the engine
cooling system. The volume of the expansion tank
should be equivalent to about 5% of the total
volume of the keel cooling system. See chapter
Extra expansion tank for further details.
• The extra expansion tank must be connected to
the suction side of the circulation pump of the en-
gine via a static pressure line.
There must be means of venting inbetween the
standard expansion tank and the extra tank, as
well as between the keel cooler and the expan-
sion tank. See chapter Extra expansion tank for
further details.
• Where an intercooled Volvo Penta engine is to
have keel cooling and it proves difficult to keep
the coolant temperature of the engine below the
maximum permitted level, the keel cooling system
can be divided into two circuits. The engine's sea-
water pump is utilised to circulate the coolant of
the intercooler circuit and the circulation pump of
the engine can then be used to circulate the cool-
ant of the engine circuit.
• Where the pressure drop in the cooling system
is too high for the engine circulation pump to
achieve the correct flow, an extra pump can be
connected to the system.
Cooling system
85