HYDRAULIC POWER TRANSMISSION 711 



notable examples, private customers are supplied by a system of hydraulic 

 mains, taking water under pressure from the supply station to the service 

 pipes leading into the house or works. The pressure adopted varies from 

 700 to 1,600 Ibs. per square inch, being 750 Ibs. per square inch in the 

 City of London, and 1,120 Ibs. per square inch at Manchester and Glasgow. 

 The arrangement of the Whitworth Street West Station of the Hydraulic 

 Power Supply Department of the Manchester Corporation Waterworks 

 may be taken as typical of such installations. 



Here the motive power is supplied by six inverted cylinder, triple 

 expansion, surface condensing engines, having cylinders 15 inches, 

 22 inches, and 36 inches diameter by 24 inches stroke, and each 

 developing about 200 I.H.P. when working at the normal speed of 

 sixty revolutions per minute, with steam at 120 Ibs. gauge pressure. 



The steam-raising plant consists of five Lancashire boilers, 30 feet by 

 7 feet 6 inches, fitted with Vicars' mechanical stokers, and each capable 

 of evaporating 4,500 Ibs. of water per hour. 



The engine cranks are set at 120, each crosshead being direct coupled 

 to a single-acting plunger pump, 4J inches diameter by 24 inches stroke. 

 The pumps thus have a mean plunger velocity of 240 feet per minute, 

 which may, if necessary, be increased up to 260 feet per minute, 

 the normal delivery of each set being 23Q gallons, and the maximum 

 250 gallons per minute. 



The water supply is taken from the town's mains at a pressure of about 

 40 Ibs. per square inch, and before passing into the storage tanks, from 

 which the pumps derive their supply, is utilized to work a direct-acting 

 intensifying pump, by means of which part is pumped directly into the 

 pressure mains. This pump exhausts into the storage tank, and for each 

 28 gallons which it exhausts, pumps 1 gallon into the pressure mains. 



The water from the storage tanks is circulated through the surface 

 condensers of the engine by means of a special circulating pump, with 

 the result that danger of freezing in winter is largely eliminated. 



Air vessels are fitted on all suction pipes and are charged by portable 

 hand pumps. The volume of each air vessel is approximately 3 cubic feet. 



The main pumps have no delivery air vessels and deliver into a common 

 pipe, this feeding two accumulators, each 18 inches diameter, and having 

 a lift of 23 feet, the dead weight, consisting of iron slag being carried in 

 circular iron cisterns 11 feet 3 inches diameter. The total weight of 

 casing, slag, and ram of each accumulator is approximately 129 tons. 

 One of these is slightly heavier than the other, the heavier one being 

 provided with a tappet gear, by means of which the throttle valves on the 



