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

190 SEA WATER DISTILLATION. Margin of Power Advisable. 36. The most satisfactory way to provide for the in- evitable loss of power, owing to the gradual deposit on the heating surfaces, seems to be to treat the production of the apparatus against time as being only about | of its maximum capacity, and the economy stated to be about 4 of what the maximum capacity of the apparatus is. Or, put shortly, the apparatus should be capable of a margin of about 40 to 50 per cent, extra on trial with clean surfaces for a short trial, say of a few hours’ dura- tion, and the economy about 15 to 20 per cent, more at such trial than is specified as the ordinary output of the apparatus. By this means the apparatus may be worked for some considerable time easily and steadily—that is, by beginning with a low boiler pressure, and gradually working up as the heating surfaces get dirty, so that at the end of the run, say three or four weeks (night and day), the apparatus will be found to have made an average output of the specified quantity per day, and an average also of the specified economy. Note.—At the end of a run of this duration, one can tell to a pound the weight of coal that has been consumed by working the apparatus, and to a gallon the quantity of water produced thereby, whilst in short runs and repeated stoppages the ascertainment of the coal con- sumed must be largely guess work. 37. Evaporator makers are always endeavouring to lessen the loss of power due to the formation of deposits on the heating surfaces by making them easier to clean, by adding substances to the sea water, and by other devices. Much has been said for and against all of them,