54 THOMAS COMMERFORD MARTIN 



employed in electric pumpinfi; operatioiie are of noteworthy 

 size, developing as much as 650 to 750 horsepower. 



For electric pumping the pump itself need embody no 

 special features. Both reciprocatmg and rotary pumps 

 are used; they may be either horizontal or vertical, and re- 

 ciprocating pumps may be of either piston or plunger type, 

 according to the circumstances of the installation. Wliere 

 a reciprocating engine is employed, however, it is generally 

 considered advisable to use a double acting pump, either 

 duplex or triplex. A triplex double acting pump does not 

 require so large a motor as does a simplex acting pump doing 

 the same duty. To raise a great quantity of water against 

 a certain head takes just so much power, but if the work be 

 divided among two or three acting cylinders there will nec- 

 essarily be a more uniform flow of water, and hence the strain 

 on the motor and the pump will be reduced. 



On account of its rotary motion and its high speed, ap- 

 proximating the speed of a motor, the centrifugal pump also 

 is peculiarly suited for electrical operation, the pump and 

 motor being usually direct connected. This pump has been 

 found of special utility in working against low heads and for 

 handling muddy water. 



The use of rotary pumps coupled direct to small motoi-s 

 running at high speed in place of reciprocating ram or plunger 

 pumps has met with general approval. These rotary pumps 

 are made with several chambers placed in tandem and are 

 of a type between an ordinary centrifugal pump and a form 

 of reverse turbine. 



Another type of electric pump is the sinking pump. The 

 electric sinking pump can be lowered from one location to 

 another in much less time than a steam or compressed air 

 pump, and as it can be completely submerged it does not have 

 to be relocated as often as a steam pump. The question 

 of what would happen to an electric motor in a mine if pumps 

 and motors get flooded has often come up. From tests made 

 recently at the University of Liege, Belgium, it appears that 

 a suitably designed polyphase alternating current motor will 

 suffer very little damage. A 3-phase mining motor of a 

 type largely used on the continent of Europe was completely 



