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.
