Niagara Falls 100.000-Hp. Development

14] Niagara Falls 100,000 Hp. Development the guide vane body is such that the vanes will be in hydraulic balance when about one-third open. They will require considerable force to close the vanes from that point and considerable force to hold them in wide- open position under the high velocity of the water between the vanes, but both forces are minimized. The operating cylinders are 32 in. in diameter and the gov- ernor is designed for a normal operating pressure of 125 lb. so that the two pistons are capable of exerting 150,000 ft.-lb. when moved the full stroke from one end of the cylinder to the other. With a difference between the sides of the pistons equal to an operating pressure of 200 lb. and consequently by the usual method of rating governors, the governor of this unit has a capacity of 240,000 ft.-lb. The operating pressure to the cylinders is controlled by means of a four-ported 12-in. diameter piston valve located in the governor stand. The pipe connecting the ports from the piston valve to the operating cylinders is 6 in. in diameter. This large diameter valve is necessary so that an axial motion of the valve of i in. will at normal pressure afford the area of opening required to pass sufficient water to force the operating pistons from one extreme to the other in two seconds of time. The main piston valve, above described, is moved axially by varying the pressure on each end of its body by means of another four-ported 31-in. diam- eter piston valve and this piston valve in turn is moved axially by varying the pressure on each end of it by a f-in. diameter pilot valve. By means of the smaller piston valve the size of the pilot valve and consequently the force to be exerted by the flyball is materially reduced over what it would have to be were the valve omitted. The edges of the ports and the edges of the piston valves and the pilot valves are so carefully made that under normal operating pressure that is practically no lost motion between the axial motion of the pilot valve and the axial motion of the main piston valve. Under slow motion of the pilot valve the main piston valve will follow with a lag of less than 0.01 in. and under the axial movement of the pilot valve of i in. in 0.01 in a second the maximum lag of the main piston valve would not exceed 0.02 in. By thus reducing the size of the pilot valve the force required to move it has been reduced to such an amount that it does not exert suffi-| FIG. 15—REPRESENTATIVE VIEWS OF HYDRAULIC UNITS BEFORE ASSEMBLY (A) and (B), runner and assembled unit of I. P. Morris construction. (C) Johnson valve for control of water in penstocks, and (D) Allis-Chalmers runner.