Jacket
water Cooling
The fresh
water enters the diesel engine at the bottom of the cylinder jackets and flows
upwards cooling the cylinder liner covers and exhaust valves before it leaves
at the top of the engine.
The
primary purpose of cooling these components is to :
. Avoid
that high temperatures reduce the strength of the material and cause cracks and
breakdowns.
.Avoid
that high temperatures cause oxidation of the material surface.
.keep the
construction materials at almost constant temperatures to avoid thermal stress.
Normal
working temperature app 80 C maximum temp 90 C.
To
minimize the scale formation, the sea water outlet temperature should never
exceed 50 C.
Sea water
cooling :
Recirculation
of sea water:
In order
to prevent the lubricating oil from thickening in cold climates, a control valve ensures that the cooling water
inlet temperature never is lower than 10 C
Scavenge
air cooler
The
cooling water inlet temperature must be as low as possible.
Central
cooling System
Low
Temperature Fresh Water system (FW LT)
Components
cooled by low temperature fresh water:
>oil
coolers for main and auxiliary engines
>Air
coolers for main and aux engines
>air
compressors
>provisions
and air conditioning cooling systems
>shaft
bearings
>steam
condensers
>fresh
water generator
The FW LT
water Is circulated in a closed system cooling the components. The heat
absorbed is dissipated in the "central cooler" by means of sea water.
Normally
the FW LT temperature is maintained at 36 C.
High
Temperature Fresh water( FW HT)
The FW HT
is circulated in a closed system cooling :
>cylinder
jackets on main and auxiliary engines
The heat
absorbed is dissipated in the "jacket cooler" by means of the FW LT
system.
The sea
water is circulated through the central cooler absorbing the heat from the FW
LT system.
Central
cooling sytem:
Water
flow at sea:
The main
engine jackets are cooled by means of two separate electrical driven pumps
circulating high temperature water through the cylinder jackets and the fresh
water generator.
The
auxiliary engines are equipped with mechanical driven pumps for jacket cooling.
Two
electrical driven central cooling water pumps circulates low temperature fresh
water through all low temperature components.
Central
cooling system at sea:
Temperature
control main engine:
A 3way
control valve is mixing cooled water and hot water to achieve an outlet
temperature from main engine of 80 - 82 C.
Temperature
control auxiliary engine:
A 3way
control valve on the auxiliary engine is mixing HT water and LT water to
achieve an outlet temperature of 80 C.
Central
cooling system:
Water
flow in port >
A port
service pump provides water for the air cooler, the lub oil cooler and the
jacket cooling of the auxiliary engines.
The
auxiliary engine jacket cooling water is circulated by mechanically driven
pumps.
The main
engine is kept pre heated with hot water from the auxiliary engine.
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