Note.—Upon page 212 is represented one of the very earliest types of a turbine pump, an account of which is left by Ewbanks, to whose book on hydraulics credit should be given for the figure. “This pump consists of tubes united in the form of a cross or letter T placed perpendicularly in the water to be raised. The lower end is supported on a pivot; perforations are made to admit the water, and just above them a valve to retain it when the pump is not in motion. The ends of the transverse part are bent downward to discharge the water into a circular trough, over which they revolve. To charge it the orifices may be closed by loosely inserting a cork into each and then filling the pump through an opening at the top which is then closed by a screw-cap. A rapid rotary motion is imparted to the machine by a pulley fixed on the axis and driven by a band, from a drum, &c. The centrifugal force thus communicated to the water in the arms or transverse tube, throws it out; and the atmosphere pushes more water up the perpendicular tube to supply the place of that ejected. These pumps are sometimes made with a single arm like the letter L inverted; at others quite a number radiate from the upright tube. It has also been made of a series of tubes arranged round a vertical shaft in the form of an inverted cone. A valuable improvement was submitted by M. Jorge to the French Academy in 1816. It consists in imparting motion to the arms only, thus saving the power consumed in moving the upright tube, and by which the latter can be inclined as circumstances or locations may require.”
Centrifugal pumps designed to raise clean water alone should not be used for any other purpose, that is to say, pumps for handling more or less solid matter mixed with the water have much more clearance in the case than those for pumping clean water. The fan is also made differently so that it cannot be clogged up by lumps of coal, gravel, and sticks of wood. The accompanying engravings, Figs. [490], [491] and [492], illustrate these ideas, showing the three progressive grades of fans for the kinds of work alluded to.
Fig. [490] shows a fan with hollow arms for clean water only.
Fig. [491] shows the disc type of fan for water containing grit, pulp, etc.
Fig. [492] exhibits a fan used in dredging pumps used for all sorts of stuff that will pass through the connecting pipes.
Fig. 493.
There are two general types of centrifugal pumps, viz., 1, single suction, Fig. [493], in which the suction pipe enters the end of case parallel to, and in line with its center; 2, the double suction, Fig. [494], in which the suction pipe is divided forming a U shape and enters the case at both sides of the center.
The single suction is used for clear water only, while the double suction will pass everything that enters the suction pipe—see engravings.