In cross section the pump somewhat resembles a box girder. This peculiarity of the pump’s combined form furnishes a rigid base for the entire structure, simplifies the driving mechanism and enables it to endure extraordinary strains without vibration.
It will be seen by reference to the cuts that any of the valves can be easily and quickly examined, and, if necessary, replaced, by simply removing the caps and heads.
The pump barrels are provided with removable linings, which can readily be replaced with new ones in case the same should become worn after years of service. These, as well as the valve seats, are made of gun metal, no cast iron or other material subject to corrosion by water being used in any part of the pumps.
Both the suction and discharge valves are supplied with improved valve springs, the tension of which is, at all times, the same; and being made of phosphor bronze, the springs retain their elasticity and will not corrode.
The steam cylinders used in connection with this pump are of the ordinary slide-valve type, with which most mechanics are familiar, and are thus easily repaired when necessary. The cylinders and pumps are detached from the boiler, and are separated therefrom sufficiently to allow every facility for getting at each and every part. All connections, both steam and water, are made outside of the boiler.
The La France steam fire engine pump is shown in outline in Fig. [433], which consists of a double plain slide-valve engine, operating a double pump.
The steam piston rod of each side connects with its pump rod, by means of square bars, two of which are on each side of the crank shaft. The crank is operated by the cross-head through a connecting rod; the arrangement of these parts can be seen in Fig. [433]. The cross-head guide is entirely done away with, as the stiffness of the connection between the two piston rods takes the thrust of the connecting rod.
The pump barrel is enclosed by an outer casing. The space between barrel and casing is always kept filled with water which is supplied through the suction pipe.
