"Water, water everywhere, and nary a drop to drink." Old cargo ships from years back were required to carry large supplies of fresh water to sustain the crew on a long voyage. A ship that had run out of drinking water would be carrying a sad crew indeed. Today, most commercial ships are equipped with a freshwater generator, a type of evaporator that converts sea water into drinkable, fresh water.
The concept of a freshwater generator is simple; sea water is evaporated using a heat source,either by stream from the boiler, main engine jacket cooling water, or by electric coil separating pure water from salt, sediment and other elements. When the ship is underway, the heat from the cooling water of the engine is used. To minimize fuel consumption and maximize the heat generated by the main propulsion engine.
The freshwater generator should include a feature to monitor the salinity of the processed water. If the salinity exceeds a specified level, usually between one and ten parts per million (ppm), the freshwater generator will automatically return the water to the feed line and put it through the cycle again.