System
Introduction
Although there is an abundance of free sea water available, marine diesel engines do not use it directly to keep the hottest parts of the engine cool.
This is because of the corrosion which would be caused in the cooling water spaces, and the salts which would be deposited on the cooling surfaces interfering with the heat flow.
Instead, the water circulated around the engine is fresh water which is then itself cooled using sea water. This fresh water is treated with chemicals to keep it slightly alkaline ( to prevent corrosion) and to prevent scale formation. Of course, if distilled water, which some ships can make from sea water using evaporators, is used then there is a reduced risk of scale formation. Fresh Water Cooling System
Diagram
Fresh Water Generator
The concept of a freshwater generator is simple; sea water is evaporated using a heat source, separating pure water from salt, sediment and other elements.
Freshwater
generators often use the diesel engine jacket as a heat source, although steam can also be used as a heat source. Because freshwater generators often use existing heat to run, the cost of operation is low.
A water cooling system is divided into two separate systems: one for cooling the cylinder jackets, cylinder heads and turbo-blowers; the other for piston cooling.
Jacket Cooling System
The cylinder jacket cooling water after leaving the engine passes to a sea-water-circulated cooler and then into the jacket-water circulating pumps.
It is then pumped around the cylinder jackets, cylinder heads and turboblowers.
The jacket cooling system is a closed circuit.
Water passing from the engine returns through a cooler to the circulating pump and then to the engine. A header or expansion tank is placed at a sufficient height to allow the venting and water make-up in the system. This has connection from the engine discharge and to the pump suction line. A heater is included with by-pass to warm the