Circulating system of a ship.
The older system of cooling would use sea water to cool lubricating oil , piston cooling, jacket water, charge air, turbocharger oil (if the turbocharger is provided with sleeve type bearing), fuel valve cooling, compressors and evaporators. Other auxillary machinary may also be provided with cooling directly from sea water as well.
Two sea water pumps are provided as main and standby units. There can also be a single sea water circulating pump and another pump which is used for other services like ballast pump.
Ship side suction valve can be such that high or low sea chest can be used.
(High sunction is used for shallow water so that sediments from the sea/river can be avoided. Low suction is used during sea voyages so that chances of getting air into the system due to rolling can be eliminated.
Ship side valves are made of specialised metal such as steel or other ductile metal as normal cast iron holds risk of falling if had a direct impact.
Fresh water ciculating system which comprises of jacket water circulating pump, fresh water cooler, cylinder jackets, cylinder head ,exhaust valve(if fitted as in main engine), turbo blower is always under positive pressure head, and thus its a closed system with a header tank.
The engine systemm temperature is kept as high as practicable. The system has salt water bypass valves on oil and water coolers for temperature control. These valves are controlled by thermo pneumatic controller. All system are provided with heating systen for jacket water for starting engine.
Sea water pipelines are prone to internal wastage from corrosion and errosion.
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