Niagara Falls 100.000-Hp. Development

 18] Niagara Falls 100,000 Hp. Development Units NS 17 & 18 Unit N° 16 Section A" A (Racks Removed) FIG. 23—CROSS-SECTION OF NEW STATION WITH THREE 37,500-HP. TURBINES AND STATION RATING OF 100,000 HP. of cast steel and steel plate and is 17 ft. inside diame- ter through the body of the valve and tapers to 10 ft. 6 in. diameter at the outlet end. The entrance end to the valve housing is made of steel plate forming a flar- ing extension of the 15-ft. 6-in. penstock. The length of the valve is about 24 ft. Throughout the total length, approximately 24 ft., the area of the water passage is reduced without abrupt changes or sharp curves and the stream-line shape of the valve parts renders the hydraulic losses practically negligible. Trash Racks and Stone Catcher The trash racks which run the entire length of the forebay are composed of 4 x i in. flat steel bars spaced by cast-iron spreaders 4 in. centers. These racks are supported by a framework of steel designed with the assumption that the racks might become clogged and carry the entire hydrostatic pressure. The steel sup- ports are designed to carry the entire head with a work- FIG. 24—-REINFORCEMENT OF SETTING FOR ALLIS-CHALMERS UNIT FIG. 25—FOUNDATION SLAB FOR TURBINE SETTING ing stress of 100 per cent greater than the usual work- ing stress called for in the ordinary design. In the bottom of the forebay and in front of the racks is a long groove running the entire length of the fore- bay, being 5 ft. deep. It is placed there to act as a stone catcher. As excavation will be carried on in the canal for some time after the completion of the station, loose rocks will be carried down the stream by the swift current and brought into the forebay. As the water in the forebay moves at a velocity of about 1J ft. per sec. they will drop into this groove and not be carried down the penstock. When this stone catcher becomes filled the loose rocks will be removed by a grab bucket oper- ated from the electric crane in the forebay house. Ice Skimmer and Run To prevent ice coming into the forebay an ice skim- mer was built in front of the inlets. This consists of removable steel plate sections which extend 9 ft. below the water surface and are hung from the roadway slab above and braced laterally by steel framing to the con- crete inlet piers. They will receive considerable press-