Niagara Falls 100.000-Hp. Development

Niagara Falls 100,000 Hp. Development [15 FIG. 16—LARGEST PENSTOCK VALVE IN WORLD A Johnson hydraulic valve measuring- 17 ft. x 24 ft. over all is installed at the bottom of each penstock close to the entrance to the wheel casing. The valves are balanced needle-type valves, having- a movable plunger sliding- in an internal cylinder. The plunger is of differential form, providing* two operating chambers which are alternately exhausted to the air to move the plunger, the hydraulic pressure in the penstock furnishing- the sole actuat- ing force. Local or remote control can be used. The valve stroke may be set for any time up to a minimum of thirty seconds for a complete stroke in either direction. The valve can also be set to close automatically in case of a serious break in the wheel casing. cient force upon the flyball mechanism to prevent the flyballs taking up their exact position corresponding to the speed of the unit. It was thought that a turbine of this magnitude should be equipped with a flyball mechanism steady, positive and as near frictionless as possible. The directly connected flyballs embodied in the design of this turbine have met these conditions. The flyball mechanism consists essentially of a fixed collar clamped around the main turbine shaft and a movable collar held in position and away from the shaft by four sets of ball-bearing toggle joints located 90 deg. from each other. Two sets of toggle joints as incorporated in the design act as flyball weights. The outward motion of these sets is resisted by two adjustable springs being- connected through ball bearings to each of the sets. Every toggle is fitted with a type of ball bearing preventing axial motion and consequently each set of toggles prevent endwise motion of the floating ring with respect to that set of toggles and as the two sets of toggles are at 90 deg. the movable collar is rigidly supported and prevented from moving in any direction except axially with respect to the main turbine shaft. It is a unique feature in governor flyball design that the floating collar has no support except through the motion-giving mechanism. This design of flyball, therefore, affords a means of imparting to the pilot valve such motion as is caused in the flyball by the variation in speed of the main turbine shaft and thus is avoided the disturbing motion introduced by belts and gears when the usual type of flyball is used. The motion of the movable collar located around the main shaft is transmitted to the pilot valve by means of levers, reach rods through sliding shoes resting upon an oil-inclosed bearing surface at the upper side of the movable collar. The governor has been adjusted to close the turbine gates from wide open to completely closed in three seconds of time and to open them from closed to wide- open position in four seconds of time. It is expected that the rise of speed with 40,000 hp. suddenly thrown off the unit will not exceed 25 per cent. The regula- tion of the unit and the normal load conditions are remarkably steady and positive. Hydraucone Draft Tube The engineers of the Allis-Chalmers Manufacturing Co. at the time of first putting this unit into opera- tion made a remarkable demonstration to show their confidence in the apparatus. The initial start of the unit was made solely from the station switchboard by closing the switch operating the control motor on the governor which moved the pilot valve causing the main turbine gates to open. This admitted water from the casing to the runner setting the unit in motion. When the unit had attained a speed of 90 r.p.m. the weights of the flyballs came into play and manipulated the pilot valve and regulated the unit perfectly at that speed. Without any adjustment in the governor being made the governor motor was manipulated from the switch- board and the unit brought up to a speed of 150 r.p.m. within ten minutes of the initial starting. The gov- FIG. 17—ALLIS-CHALMERS TURBINE CASING ERECTED IN POWER HOUSE ernor regulated the unit positively, steadily and per- fectly under that speed. One of the greatest losses in hydraulic turbines is in the energy discharged from the runner. Efforts have heretofore been made to utilize this energy by trans- forming the velocity into pressure for maintaining below the runner greater vacuum than would normally result due to the elevation of the runner above tail water level, and thus in effect increasing the effective head on the turbine. The size of the units in water- power development have been increased until the diam- eter of the runner is large compared to the distance from the runner to the tail water level so that in large units it has not been found feasible to design the draft tube on account of the short radius of bend which will most efficiently utilize the energy discharge from the runner with an excavation of tailrace such as the owner is usually willing to make. In Fig. 14 is an illustration of one form of “hydrau- cone regainer.”