690 



HYDRAULICS AND ITS APPLICATIONS 



while closing is increased by the provision of a deflector attached to the 

 valve spindle, this deflector also serving as the piston of the air buffer. 

 An auxiliary waste valve F 3 , mounted on the main valve spindle as -shown, 

 opens with the main valve, and allows any gritty material or pebbles to 

 escape. 



If necessary, the hydraulic ram 'may be situated well above the tail 

 water level, the waste valve then discharging into a closed chamber which 

 communicates with the tail water by means of a suction tube. The 

 suction head produced in this discharge pipe then helps to increase the 

 velocity of flow on opening the waste valve. The valve must now, 

 however, be aided by means of a spring so as to be approximately 

 balanced under this suction head. Fig. 333 shows diagrammatically an 



FiG. 334. Hydraulic Ram for pumping clean water by means 

 of a larger supply of dirty water under a lower head. 



arrangement of this type devised by Decoeurs, which has given very good 

 results. 



Fig. 334 shows the hydraulic ram as arranged for utilizing a large 

 supply of impure water for pumping a smaller supply of clean water. 

 Here S and D indicate the clean water suction and delivery pipes. 



In place of the differential plunger pump shown, a flexible diaphragm 

 is sometimes used to divide the waste valve box from the clean water 

 supply and delivery valve box, the vibration of this diaphragm under 

 the action of the ram serving the same purpose as that of the plunger 

 in the previous sketch. As thus constructed, the clean water may be 

 lifted against practically any head though the efficiency is only low. 



A simpler device, but one not so certain in its action, consists in the 

 provision of a pipe leading the clean water under a head about J that ol 

 the supply head into that part of the valve box remote from the supply 

 pipe. A check valve prevents flow out of the valve box along this pipe 

 and a charge of clean water is drawn into the valve box as the pressure 



