Thus the pressure upon the bottom layer of air 10 in the figure is due to all the layers of water in the pipe (17.35 pounds), and the pressure upon the uppermost layer of air 1 is due to the single layer of water, 1, at the moment of its discharges beginning—viz., 1.74 pounds per square inch. As this discharge progresses this is lessened, until at the completion of the discharge of the water layer the air layer is of the same tension as the normal atmosphere.
The air pipe is connected with an air receiver on the surface, which is at or near the engine room, in which there is an air compressor. This air pipe is provided with a valve on the surface. Before turning on the air the conditions in the well show water at the same level on the outside and inside of the eduction-pipe. At the first operation there must be sufficient air pressure to discharge the column of water which stands in the eduction-pipe.
This goes out en masse, after which the pump assumes a normal condition, the air pressure being lowered and standing at such a point as corresponds with the normal conditions in the well. This is determined by the volume of water which the well will yield in a certain time and the elevation to which the water is discharged.
Note.—This extended description of the principles upon which an air lift operates—with its illustrations—is drawn almost word for word from the original patent claims of Dr. Pohle. The occupation of the space in the work is justified by the increasing importance of this system of water supply and its practical applications in the industrial world.
Year by year the world’s visible supply of coal—so long stored and hidden away in the earth’s crust awaiting the advent of man—is diminishing, next will dawn the age of air and water with electric transmission.
After the standing water column has been thrown off by the pressure the air rises through the water reduces its weight, with the result that the water is expelled as fast as the well supplies it, the water outside the pipe, acting as a head, flows into the discharge pipe by the force of gravity.
The machinery necessary for a system of pumping comprises, 1, an air compressor; 2, a receiver to store and equalize the pressure; 3, the head piece and foot piece for the well; and, 4, the necessary piping for the air supply and water discharge.
Fig. 383.