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

2 14 SEA WATER DISTILLATION. requirements, and the same may be said with regard to the capacity of the other pumps—i.e., for the fresh water and the feed-pumps. It is always well to have plenty of margin as to capacity, so as not to necessitate driving the pump at an excessive speed. The steam cylinder of the pump should be made amply large so that the net working pressure may be kept low. Its Lubrication. 100. As the exhaust steam from the pump is utilised by being re-converted into water, and its latent heat not wasted, the water thus produced, and included in the general output of drinking water, should not be greasy or oily. It is well, therefore, to avoid greasy lubrication as far as possible. There is a natural desire of all engineers in charge of machinery to oil the steam cylinder and the plungers, in fact, all parts where there is any friction. Now, to put oil or grease inside the steam cylinders would at once manifest itself in the exhaust steam, and then in the water condensed from it. If a steam pump is well made, the cylinder may be so constructed that oil and grease are unnecessary, and, by leaving the cylinder unlagged, the slight condensation of the steam inside the cylinder acts as a lubricant. Pumps made on this system have been known to work well for many years. The piston-rod may be lubricated with oil, as the small quantity of oil getting into the cylinder is not sufficient to taint the exhaust steam, but the plungers should not be oiled ; a well constructed and suitable pump has water channels round the plungers for water to replace oil as a lubricant.