278 HYDRAULICS AND ITS APPLICATIONS 



maximum discharge, while the true pressure in the pipe is now measured 

 by the vertical distance between A" C" and the pipe line. 



Where a regulating valve is to be used on a syphon, this should always 

 be placed on the outlet leg. 



ART. 83. INVERTED SYPHON. 



Where the pipes connecting two reservoirs cross a deep valley it is 

 usual to use an inverted syphon (Fig. 125). The main pipe line is led 

 into a storage tank at A , and out of a second tank at (7, the connection 

 between A and C being made by means of the inverted syphon. This 

 has the advantage of reducing the maximum pressure which may be 



FIG. 125. 



= / ^L 



V(i+^ 



brought to bear on the pipe line by the sudden closing of a valve, since 

 the pressure at A cannot now exceed that of the atmosphere. 



Here, as in the case of the ordinary syphon, the velocity of flow is 

 given by 



or if Z A Z c = H 



With an inverted syphon, an automatic valve should always be placed 

 at the entrance, so that if, due to the bursting of a pipe, the velocity 

 of flow attains more than its normal value, water may be automatically 

 cut off from the pipe line. 



ART. 84. FLOW THROUGH NOZZLE AT END op PIPE LINE. 



Where a supply of water moving with a high velocity is required, as 

 for fire extinguishing, or for the jets of an impulse turbine or Pelton 

 wheel, a converging nozzle is fitted to the delivery end of the supply 

 pipe. (See also Art. 126.) 



