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

132 SEA WATER DISTILLATION. at (BB), for use when desired. (K) is an air knob to pre- vent syphoning action. (6) Boiling under Pressure. 147. This automatic arrangement is, of course, possible only with a pressure in the steam-room about equal to that of the atmosphere. If the evaporator is working with either a pressure much above the atmosphere, or considerably below it, other arrangements have to be made for the brine discharge. Thus, if there is a pressure in the casing above that of the atmosphere, the brine can be got rid of by letting the pressure blow it away, but if the pressure inside the casing is less than that of the atmosphere, the boiling brine has to be drawn out by a pump. 148. Some makers combine the feed pump and brine pump in due proportion to their respective requirements. This is useful when the evaporation is steady, but if the evaporation exceeds or is less than two-thirds of the feed, the speed of the pump would require altering, or some other arrangement adopted to make all three—that is to say, the feed, evaporation, and brine—proportionate. (7) Brine Dilution—(a) Method of Diluting. 149. Formerly, it used to be the custom for the brine to be allowed to run into the bilge, or into a tank at the bottom of the ship, with which the ship’s brine pump was connected and always at work. The brine was got rid of in this way. The hot brine, however, was considered objectionable, and a brine pump was required to be part of the distilling apparatus. 150. Cooling and diluting the brine after its discharge