Particularly in the modern days the layout of cooling systems is full integration into separate engine components and the practical absence of external connectors. The cooling system for medium and high-speed four-stroke diesel engines consists of high temperature (HT) and low-temperature circuits (LT). In HT there is always fresh, chemically treated water, in LT there can be fresh or seawater in use. In the high-temperature circuit at the engine output, temperatures from 75 ° C to 90 ° C and pressures of 2.0-4.0 bar are maintained in the running engine.When engine is on preheating mode CFW temperatures are often lower. Heating the engine (approx. 60 ° C) is necessary to avoid condensation in the combustion chamber and to prevent low-temperature corrosion.
Maintaining a certain temperature is important to ensure complete combustion of fuel, especially at low loads. Heating of charge air at low loads or at engine start-up is carried out by supplying hot water to the second stage of the air cooler to ensure good ignition and complete combustion of fuel and, what is very important, for reducing hydrocarbon emissions into the atmosphere.
HT and LT cooling is performed in plate or tube water coolers pumped by seawater. Often in engines, the HT and LT circuits are mixed with the aid of thermostats, i.e. one expansion tank is provided. Pumps can be suspended or stand-alone.
Particular attention should be paid to the chemical treatment of cooling water. The manufacturer’s instructions always indicate the required parameters.