ACCUMULATORS 



719 



Storage capacity = 1,120x8177 23 foot Ibs. 

 = 6,554,000 foot Ibs. 



6,554,000 

 = 33QOQ x 60 ~ horse power hours. 



The accumulator is therefore capable of giving out energy at the rate of 

 3-31 H.P. for one hour, or 39'7 H.P. for five minutes. 



From this example it is evident that the storage capacity is not large 

 and that the main function of an accumulator is not so much to store 

 energy, in the sense that an electric accumulator stores it, as to permit of 

 momentary fluctuations in the rates of 

 supply and demand, or in other words, 

 to act as a flywheel does to a steam or 

 gas engine. It also serves to regulate 

 the delivery pressure, and is usually 

 made to control the motive power auto- 

 matically. Its efficiency is high, up to 

 98 per cent, of the energy expended 

 in charging being returned during 

 delivery. 



In its most common form, the ac- 

 cumulator consists of a vertical cylinder, 

 fitted with a ram carrying a platform 

 which is weighted with some heavy 

 material, usually pig iron or iron slag. 1 

 Fig. 344 shows this type, the weight 

 here being carried in a wrought iron 

 cistern suspended from the ram platform. 



Inlet and outlet passages are provided 



in the base of the cylinder, and an air valve is fitted in the top of the 

 cylinder for convenience in first filling. The ram is guided in its travel 

 by a framework not shown in the figure. If the pumps are delivering 



1 The following table shows the approximate volume occupied per ton of weighting 

 material : 



Motors 



From 

 Pumps 



FIG. 344. Accumulator. 



Substance. 



Pig iron or wrought iron scrap 

 Broken stone 

 Clay or earth . 

 Bricks 



Cubic Feet per Ton . 



6-25 

 17-2 

 18-5 

 22-2 



