Twin Turbines for Pacific Coast Power Company
Two 20,400-horsepower hydraulic turbines are being built for the White River hydro-electric plant of the Pacific Coast Power Co. This development is being carried on about 20 miles east of Tacoma, Wash. The White river, from which the water is diverted, is fed by the glaciers of Mt. Ranier. The water is to be diverted into a settling pond in which the silt may be deposited.
The main storage reservoir is designed to hold sufficient water for three or four months continuous operation, without receiving water from the White river. This storage reservoir is made up ct several existing lakes which are to be interconnected and dammed, and whose banks are to be strengthened. From the storage reservoir the water is to be carried through a 300-foot tunnel and through 2.200-feet steel pipe lines. The power house will be approximately 373 feet long and 70 feet wide. About 46 feet of the width is to be used for six generating units, which are to 1H“ placed with their shafts in line. The other side of the building, 26 feet wide, will be used for exciter units, transformer rooms, etc. At first, only two generating units will be installed, room being left for four. Each turbine will develop the rated capacity of 20,400 horsepower under a head of 480 feet. Each unit will be direct connected to a 60-cycle, three-phase, 6,600-volt generator driving it at 360 r. p. m. The turbine runner is to be a high-pressure Francis type with horizontal shaft. A cast-steel runner will receive the water from a spiral casting, divide it into two lines of flow, and the discharge from the wheel will be by tvvo quarter turns to separate draft tubes. The flow of water to the turbine will be controlled by cast-steel butterfly valves. These valves will be something over seven feet in diameter, and are said to be the largest of this type ever designed. The governors for these turbines will be of a standard, oil-pressure type, designed for close regulating. Separate governors will lie supplied for each unit, but there will be a central oilpressure system. This plant will have to regulate me supply of energy to the whole system of this company so that proper regulation of each turbine becomes of added importance. There is also a necessity of conserving the storage supply of water so far as possible. To this end, pressure regulators will be installed on each turbine. The Stone & Webster Engineering Corporation is acting as consulting engineers for the Pacific Coast Power Co.