A Practical Manual On Sea Water Distillation
With A Description Of The Necessary Machinery For The Process

MULTIPLE DISTILLATION. 2OJ evaporator casing into one common pipe, and led into the discharged circulation water. The brine discharge from each evaporator should be controlled by a suitable valve or cock with an index to work to, and as the pres- sure can be made very steady, the brine cocks or valves are very soon set, and will require very little attention afterwards. A large brine valve is also fitted for emptying out the brine quickly when desired. 7. Coil Drain. 71. The waters discharged from the coil drain of each evaporator are collected in one common pipe leading to the heater, and are utilised in heating the feed-water, as will be explained later on when dealing with the heaters (p. 206). No cock or valve is needed for the coil drain in multiple distillation. 8. Evaporator Casings. 72. As the evaporators in multiple distillation have to work at a pressure more or less great, the casings should be made strong enough to stand a test pressure of at least double the working pressure. Gun-metal casings are the best for wear, and for standing the pressure required. The final evaporator, working at atmospheric pressure or thereabouts, may be made of cast iron, but it should be proved to about 20 to 30 lbs. pressure. (c) THE DISTILLING CONDENSER. 73. What has been already said about the distiller in Chap. vii. regarding an ordinary double distiller condenser on a steam ship applies to the distiller of a multiple dis- tilling apparatus, subject to the following important observations.