222 HYDRAULIC EQUIPMENT 



stream-flow or the maximum anticipated load likely to be carried 

 within a certain time limit. The automatic speed regulation is 

 obtained by means of a governor which actuates a deflector, 

 which is placed in front of the nozzle tip and regulates the speed 

 by intercepting or deflecting the stream. It is, therefore, obvious 

 that this system of regulation thus does not permit of any economy 

 in the water consumption, unless the station attendant frequently 

 changes the. needle adjustment by following closely the load 

 curve. It is, therefore, mainly intended for plants that are located 

 on streams where water storage is not feasible, or where other 

 power plants are located on the same stream, making it necessary 

 to allow the full flow of the stream to pass the plant or on those 

 streams where irrigators' or riparian rights have a prime con- 

 trol, thus preventing the storage of water. The above holds also 

 for the second class of control, i.e., deflecting nozzles, as described 

 in the next paragraph and, of course, also, to a certain extent, to 

 water-wasting by-pass relief valves for reaction turbines as pre- 

 viously described. 



The needle-deflecting regulating nozzle, as shown in Fig. 115, 

 consists of an ordinary needle nozzle which is provided with a 

 ball-and-socket joint, permitting it to be raised or lowered so as 

 either to direct the full jet into the buckets of the wheel or to par- 

 tially or entirely direct the jet outside of the path of the buckets 

 of the wheel. 



In both the stationary needle nozzle with the jet deflector and 

 the needle-regulating deflecting nozzle, the needle is usually oper- 

 ated by hand control, the needle being set to utilize to full advan- 

 tage the available supply of water. In plants where either of these 

 types of nozzles is installed and where there are forebay reservoirs, 

 economy in the use of water is secured by setting the needle at 

 different times during the day to carry the maximum load on the 

 plant, the needle being set to follow the general load curve of the 

 plant, while the momentary load changes and speed control are 

 taken care of by the governor either operating the jet deflector or 

 deflecting the nozzle. 



In such plants, where large units are installed, the control of 

 the needle setting may be by means of an electric motor with 

 remote control from the switchboard, so that 'the power plant 

 operator can, from the switchboard, set the position of the needle 

 so as to carry any predetermined load that is desired, the needle 



