PUMPING WATER FROM DOCKS. 333 



The pumping-gear at the Alexandra Dock, Hull, consists of 

 two 39- inch vertical centrifugal-pumps, with 48-inch suction- 

 pipes, driven by a single-cylinder engine to each pump. 



Each pump, driven at 145 revolutions, is capable of throwing 

 31,250 gallons per minute, with a maximum difference of level 

 of 21 feet. 



For ordinary drainage purposes, a small centrifugal-pump, 

 with a 6-inch suction, and worked by an independent vertical 

 engine, is used. 1 



For emptying the dry docks of the Liverpool Northern 

 Extension, Mr. G. F. Lyster, M.I.C.E., adopted a horizontal or 

 turbine type of pump, with a fan 5 feet diameter, driven by 

 gearing from an independent horizontal engine to each pump. 

 The ordinary drainage, which has to be lifted to a great height, 

 is dealt with by chain-pumps of the ordinary pattern. 2 



An example of large reciprocating plunger-pumps is to be 

 found in Portsmouth Dockyard. The plungers of these pumps 

 are 6 feet in diameter, and have a stroke of G feet. 



They are driven by a composite vertical inverted engine, with 

 cylinders 64 and 40 inches in diameter. These pumps lift about 

 18,500 tons of water per hour, with an indicated horse-power 

 of862. 3 



At the Barry Graving-dock, two 40-inch centrifugal-pumps 

 are fixed in an engine-house, 11 feet below high water of spring 

 tides. These pumps can raise 62,000 tons of water in about 

 four hours. 4 



Bute Docks, Cardiff. 5 At these docks, both centrifugal and lift- 

 pumps are used for discharging the water from the graving-dock 

 (Figs. 328 to 330). 



The water from the dock flows through the culvert V, into 

 the lifting-pump well, whence it passes by different culverts, 

 O 0, into the centrifugal-pump wells. The two latter wells are 

 also connected by a culvert closed by a sluice, T. The water from 

 the whole of the pumps flows through the culverts B B and P 

 to the tank C, under the floor of the engine-room, from which 

 it is conveyed away to the outfall by the culvert U (Fig. 328). 



The arrangement of the horizontal centrifugal-pumps, which 



1 M.P.I.C.R, vol. xcii. pp. 155, 179. Ibid. voL c. p. 23. 



* Ibid., vol. Ixiv. p. 145; and Gwynne, "Notes on Centrifugal Pumping- 

 Machinery." 



1 Hid., vol. ci. p. 141. 



* Institute of Mechanical Engineers, 1884, and Engineering, vol. xxxviii. p. 165. 



