150 



WATER] CONDUCTORS AND ACCESSORIES 1 



trouble. This is evident by considering that some large valves 

 would require hours to close by hand. When sluice gates are 

 installed in gatehouses a traveling crane is often provided for 

 lifting them. Their closing is then done through their own 



weight, and brakes are installed 

 for regulating the same (Fig. 75). 

 Whatever method of operation 

 is chosen it should be simple and 

 positive in its action. 



There are numerous hand- 

 operated lifting devices such as 

 rack-and-pinion with an operating 

 lever, windlass, floorstands with 

 threaded gate stems and operating 

 wheels, etc. Gear trains should 

 always be provided where there is 

 considerable pressure on the gate, 

 or, otherwise, it may be impos- 

 sible for the operator to start the 

 gates especially when they have 

 been closed for some time. 

 Arrangements are, however, gen- 

 erally made for shifting the hand- 

 wheel directly to the stem after 



Ar ^ e g a t e nas b een opened slightly, 



flr J * n or< ^ er ^at the opening may be 



accomplished more rapidly. Roll- 



"' ers and ball bearings are also 



sometimes provided, either with 

 the discs or the lifting devices so 

 as to reduce the friction. 



Gate valves may also be 

 operated by hydraulic cylinders. 



The regulating valve consists of a flat valve which is operated 

 by a piston, this in turn being moved by releasing the pressure 

 on either side by means of small poppet valves which may be 

 operated by hand or electrically from any convenient point. A 

 valve of the latter type is shown in Fig. 76, and the electrical con- 

 nections in Fig. 77. 



A double-throw control switch and an alarm bell are mounted 



FIG. 76. Ludlow Hydraulic 

 Operated Cylinder Valve with 

 Electric Control. 



