All the principal mains and steam pipes are made in
duplicate, not only for greater security, but in order that each set
of engines and boilers may be connected interchangeably without delay.
The Seine supplies an ample quantity of water, but not in a condition
either for feeding the boilers, for condensation, or for the air
compressors.
[Illustration: THE NEW COMPRESSED AIR STATION AT PARIS. (FIG. 5, 6)]
Special provisions have therefore to be made to filter the water
efficiently before it is used. For this purpose the water is led to a
group of four filters (see L, Fig. 4); from them it passes into the
tanks, JJ, and is pumped into the heaters. The filters can be rapidly
and automatically cleaned by reversing the flow of water through them.
Figs. 5 and 6 show the general form of the type of engine adopted, as
well as the engine house, some of the mains, etc. They are vertical
triple-expansion engines, and are being constructed by MM. Schneider
et Cie, of Creusot, with a guarantee of coal consumption not to exceed
1.54 lb. per horse power per hour, with a penalty of 2,000 francs for
every 100 grammes in excess of this limit. It is evident that with
this restricted fuel consumption, a large margin for economy will
exist at the new works, as compared with the St. Fargeau station,
where the best engines cannot show anything like this result, while
some of the earlier ones are distinctly extravagant, and the whole
installation is handicapped with imperfect means of condensation.
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