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pump is known as a double acting pump. When the pump has two 

 cylinders it is known as a duplex pump, with three cylinders it is a triplex 

 pump, and in either case may be either double acting or single acting. 



The capacity of the pump will depend on the diameter of the cylinder, 

 the length of the stroke of the piston, and the number of strokes or revolu- 

 tions per minute. The capacities of a few sizes of double acting, single 

 piston pumps, single acting triplex pumps and of double acting duplex 

 pumps are as follows: 



Capacity of Double Acting, Single Piston Pump. 



Capacity of Single Acting, Triplex Piston Pump. 



Capacity of Double Acting, Duplex Pumps. 



The sizes of pumps and the capacities vary with the different manufac- 

 turers. The values stated above show the approximate range of the different 

 sizes. For small capacities the double acting single piston pump may be 

 used. For larger capacities usually the single acting triplex pump and in 

 some cases the double acting duplex pump is used. The triplex pump is 

 generally preferable; it has the advantage that the power is constantly ap- 

 plied because of the strokes overlapping and this gives an even flow with 

 little pulsation. The suction and discharge pipe should be larger than the 

 suction and discharge openings of the pump as for centrifugal pumps. The 

 suction pipe should be as short as possible and the pump placed as near 

 the water surface as possible in order to keep the suction lift low. 



