Fig. 490.
The centrifugal pump is the converse of the turbine water-wheel. Its development has been analogous to that of the steam turbine in that both were abandoned in favor of reciprocating machines before having been thoroughly exploited; the pump because the principles of its action were not clearly understood, and the steam turbine because of mechanical difficulties in its construction.
Opposite the title page of this book can be seen a representation of a centrifugal wheel of ten thousand horse power; it will repay the careful student to consult also page 133 of part one of this work for the details of this enormous machine; the curious will also be interested in an early form of the centrifugal pump to be seen in Fig. [489] and its description in the Note on page 214.
Fig. 491.
Fig. 492.
Where large quantities of water are to be moved quickly and more especially in cases where the water is impure and contains floating matter, as well as sand, mud, coal and the like, as in wreckage, the centrifugal pump has its peculiar advantages. It is suited particularly for use in tanneries, paper mills, dry docks, corporation work such as building sewers, sand dredging, and with water that contains large quantities of solid matter held in suspension. Pumps used for these purposes have to be primed on starting, and the suction pipe should be as short as possible. Long suction pipes very much impair the efficiency of this type of pump. They will draw water upwards of twenty feet but nothing like the full capacity of the pump can be realized under such circumstances. It is always better to lower the pump as much as possible and force the water instead of trying to suck it.