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

86 SEA WATER DISTILLATION. evaporator, and in 1889 and 1890 (under the Naval Defence Act) a very large number of cruisers and battle- ships of H.M. Navy were fitted with these evaporators, Fig. 6a. working in combination with the “ Normandy ” distilling condenser. Messrs. Weir have, however, since then in- troduced a different type of evaporator, with vertical cylinder fitted with horizontal tubes or coils. 44. The advantage of having an easily removable coil for cleaning purposes was soon appreciated, and very soon further improvements were made in this direction. The most approved type of evaporator which succeeded the “ Weir ” original evaporator appears to have been the evaporator introduced by Caird & Rayner, the novelty of which was in having the coils in the form of a volute, placed horizontally in the casing, and fitted to the door, so that by opening the door the coils came out all of a piece therewith, and were then detachable for the purposes of cleaning. 45. Perhaps the most important feature of the Caird & Rayner invention was that the pressure inside the coil was utilised as a means of cracking off the scale deposited on the outer surface. The pressure had a tendency to slightly straighten the coil, and thus effected the cracking off of the scale. Fig. 7 shows the original type of the Caird & Rayner evaporator, introduced about 1891 or 1892, and a great many ships of H.M. Navy and the mercantile marine were fitted with this type of evaporator. Fig. 8 shows an improvement on this. The coils being