Courtesy, Edson Manufacturing Co. ] =138. Diaphragm Pump.=—The type of pump shown in Fig. 96 is the most common in use for draining small quantities of water from excavations. It is known as the diaphragm pump from the large rubber diaphragm on which the operation depends. The pump is made of a short cast-iron cylinder, divided by the rubber diaphragm or disk to the center of which the handle is connected. The valve is shown at the center of the disk. As the diaphragm is lifted the valve remains closed, creating a partial vacuum in the suction pipe and at the same time discharging the water which passed through the valve on the previous down stroke. When the valve is lowered the foot valve on the suction pipe closes, holding the water in place, and the valve in the pump opens allowing the water to flow out on top of the disk to be discharged on the next up stroke. Table 54 shows the capacities of some diaphragm pumps as rated by the manufacturers. The smaller sizes are the more frequently used and are equipped with a 3–inch suction hose with strainer and foot valve. They are not adapted to suction lifts over 10 to 12 feet. Where greater lifts are necessary one pump may discharge into a tub in which the foot valve of a higher pump is submerged. TABLE 54 CAPACITIES OF DIAPHRAGM PUMPS ─────────────────┬─────────────────┬─────────────────┬───────────────── Diameter of │ Diameter of │Length of Stroke │ Capacity per Cylinder, Inches │ Suction, Inches │ in Inches │ Stroke, Gallons ─────────────────┼─────────────────┼─────────────────┼───────────────── 6│ 3│ 4│ 0.49 8½│ 4│ 6│ 1.47 9[86]│ 2½│ │ 0.75 12½[86]│ 3│ │ 1.25 │ Power driven by 1 horse-power │ 12½[86]│ engine │ 0.58[87] ─────────────────┴───────────────────────────────────┴───────────────── [Illustration: FIG. 97.—McGowan Steam Jet Pump. Courtesy, The John H. McGowan Co. ] =139. Jet Pump.=—The simplicity of the parts of the jet pump is shown in Fig. 97. It has a distinct advantage over pumps containing valves and moving parts in that there are no obstructions offered to the passage of solids as well as liquids through the pump. It is not economical in the use of steam, however. It operates by means of a steam jet entering a pipe at high velocity through a nozzle. This action causes a vacuum which will lift water from 6 to 10 feet. The lower the suction lift, however, the greater the efficiency of the work. The sizes and capacities of jet pumps as manufactured by the J. H. McGowan Co. are shown in Table 55. TABLE 55 CAPACITIES OF JET PUMPS