490 



HYDRAULICS AND ITS APPLICATIONS 



The register gate, which consists of a rotating cylinder gate, and of 

 which two types are illustrated in Figs. 231 and 232, has the advantage 

 that the travel necessary to cut off the supply is small, and therefore 

 tends to more rapid regulation. On the other hand, it is very liable 

 to get out of order where floating material in the water may jam between 

 gate and guide or wheel vanes, and is less efficient than the plain cylinder 

 gate at part load. In view of these disadvantages, these gates are now 

 practically obsolete. The latter remark also applies to the original form 

 of wicket gate, which, as its name suggests, consisted of a series of plates 



pivoted either at their ends 

 or preferably at their cen- 

 tres, and which throttled 

 the supply by closing the 

 g aide passages as the plates 

 were rotated. As modified 

 by Professor Thomson and 

 by Fink and others, the 

 wicket gate, however, gives 

 very close and efficient 

 regulation under widely 

 varying conditions. It will 

 be considered in further 

 detail in Art. 136. 



Where a draught tube is 

 fitted, regulation may be 

 performed by means of a 

 butterfly valve placed in 



FIG. 233. Francis Turbine with Cylinder Gate Regula- the tube SO as to throttle 

 tion developing 5,500 H.P. at 250 revs, per min. under the discharge. The draw- 

 146 feet head. Penstock 7' C" diam. , , , ,, . . ,, 



back to this system is that 



the valve is large and heavy, possesses considerable inertia, and requires 

 a large force to move it, while part gate efficiency is low. This method 

 of governing has been adopted with success as regards speed regulation 

 in the case of Francis turbines of 6,000 H.P. working under 135 feet head 

 at the Shawinigan Falls. 1 Here the penstocks are of considerable length, 

 and the method promised to give better results than gates on the pressure 

 side of the turbine runner. 



Figs. 233 and 234 illustrate noteworthy examples of Francis turbines 

 with cylinder gate regulation. Fig. 233 shows one of a series of turbines 



1 For a description of the plant see Cassiers Magazine, June, 1904. 



