FEED HEATERS
As the fuel supply of a vessel cannot easily be replenished on the high seas, economy in coal consumption is very desirable.
If you put a cold spoon into a boiling saucepan ebullition is checked at once, though only for a moment, while the spoon takes in the temperature of the water. Similarly, if cold water be fed into a boiler the steam pressure at once falls. Therefore the hotter the feed water is the better.
The feed heater is the reverse of the condenser. In the latter, cold water is used to cool hot steam; in the former, hot steam to heat cold water. There are many patterns of heaters. One type, largely used, sprays the cold water through a valve into a chamber through which steam is passed from the engines. The spray, falling through the hot vapour, partially condenses it and takes up some of its heat. The surplus steam travels on to the condensers. A float in the lower part of the chamber governs a valve admitting steam to the boiler pumps, so that as soon as a certain amount of water has accumulated the pumps are started, and the hot liquid is forced into the boiler.
Another type, the Hampson feeder, sends steam through pipes of a wavy form surrounded by the feed water, there being no actual contact between liquid and vapour.
An ally of the heater is the