Figs. 404, 405, 406 and 407.
Suction or hydrant connection may be made at either side of the engine; and, in operation, the central core of the pump body is practically a continuation of the suction hose, and serves to establish a direct communication with the receiving pump valves, arranged on opposite sides of the chamber. This chamber, as shown in the sectional view, Fig. [408], thus becomes the distributing center, from which the incoming water flows to the suction valves. The current from the suction is not required to change its general direction, and but little friction is encountered by the water in its diversion through the pump valves.
The position of the suction or receiving valves, in relation to the water cylinders, may be understood by reference to Fig. [408], which shows the same arranged in a cluster around the open ends of the barrels. The suction valve area is large, and the proportions adopted contribute largely to the smooth running of the pump, under conditions of speed seldom attempted in ordinary practice.
Fig. 408.
The valves in this pump are controlled by improved springs, the tension of which is at all times the same; and which are made of phosphor bronze; the force chambers in opposite ends of the pumps are practically equal, and, owing to the close proximity of the valves, the clearance is reduced to a minimum The discharging outlets are elevated above the highest point of the valve chambers, and the communicating passages are designed to prevent conflicting currents, and also to permit the pump to free itself promptly of air. The pistons are of a frictionless type, and in accordance with the usual practice of working double pumps in unison, the cranks controlling the movements of the pistons are placed at 90 degrees.
Fig. 409.
A convenient and effective arrangement of suction strainers is shown in Fig. [409]. Perforated cages are introduced into the suction chambers through the inlets on opposite sides of the pump. The ends of these cages are open, and a short sleeve, which is permanently secured within the pump, serves to support and also to establish communication from one cage to the other.