Centrifugal Pumps. 97 



1 85 1 the Appold pump with curved arms of the form shown in 

 Fig. 5, Plate 4, gave a maximum duty of o*68, while the same 

 pump with the arms made straight and inclined at an angle 

 of 45 degrees to the radius gave a duty of only 0-463, and 

 when the vanes were made straight and radial this duty was 

 further reduced to 0*243. This pump had a 12-inch fan with 

 internal width of 3 inches in two divisions of 1 1- inch each. The 

 central opening for the admission of the water on each side of 

 the fan was 6 inches in diameter. The quantity of water dis- 

 charged was 2100 gallons (9*37 tons) per minute at a height 

 of 8*20 feet, and 681 gallons (3* 04 tons) at a height of 27*60 

 feet, the fan making 828 revolutions in the former case, and 

 876 in the latter. 



The pumps having horizontal spindles, from the ease with 

 which they can be fixed, are eminently adapted for temporary 

 purposes or for drainage in places where it is not considered 

 desirable to cut through a river bank. For small drainage 

 areas pumps of this type are preferable to those which are 

 submerged, owing to the greater facility of access to the 

 fan should it become choked with weeds, ropes, or other 

 matter liable to be twisted I'ound the blades. Substances 

 escaping through the protecting gratings, which will readily 

 pass through the openings in large pumps, frequently get 

 wrapped round the fans and spindles of the smaller pumps ; 

 and if not actually bringing the pump to a standstill, seriously 

 affect the efficiency and throw a greater strain on the engine. 

 The action of a small centrifugal pump has been known to be 

 completely stopped by eels, which had become twisted round 

 the spindle. To remove these impediments without taking 

 the case to pieces a hand-hole is frequently left in the cover, 

 and so fixed on with screws as to be readily removable. 



Pumps should be so fixed that all the parts can be readily 

 accessible, and the suction pipe provided with means for 

 slinging it with a rope or chain when required to detach it 

 from the pump. The side plates are put together with bolts 



