712 



HYDRAULICS AND ITS APPLICATIONS 



main steam pipe are automatically closed as the ram reaches the extreme 

 limit of its upward stroke. The engines under steam are thus brought 

 to a standstill, and remain so until the tappet is released by the descent 

 of the ram. Each accumulator is fitted with an electric bell, which gives 

 warning when the ram is about 10 feet from the bottom of its stroke. 



The pressure water is led into the streets by four 6-inch cast-iron pipes, 

 after which the branch pipes vary in diameter by even inches from 

 6 inches down to 2 inches. 



The joint flanges are oval, the joint consisting of a bevelled spigot and 



faucet union securing af -inch 

 gutta-percha ring by two 

 bolts. Fig. 343 illustrates 

 the type of pipe joint as 

 adopted for a 6-inch pipe, 

 and as invented by Mr. E. B. 

 Ellington, the maximum and 

 minimum diameter of the 

 flange being 19 inches and 

 10J inches respectively. 

 These pipes are laid with the 

 longer axis of the flange hori- 



zontal for facility in getting 



at the bolts. 



The main stop valves are 

 balanced both ways by the 

 insertion of a small valve 

 1J inch in diameter inside 

 the main valve, the effort 

 required to open the latter 

 only being that necefBary to overcome its dead weight. A spring-loaded 

 momentum valve, h wing a ram 1 J inch diameter, is fitted on either 

 side of every stop valve to minimise any shocks that may occur in the 

 main. 



To indicate the condition of the mains and valves, a daily record of th 

 minimum flow during the time the demand is at its lowest (bet wee 

 11 p.m. and 4 a.m.) is kept by means of an automatic electrical recorder 

 Should this show an abnormal increase in the output for several consecu 

 tive nights the mains are tested. For this purpose certain of the sto 

 valves on the trunk mainn are kept closed so that the several circuits ar 

 connected only at the power station. Here they can be separated hit 



Fio. 343.- Joint for 6-in. Pipe, 1,100 Ibs. per square 

 inch. 



