Transcript for The Story of Hoover Dam, segment 09 of 12


Turbine pits to hold Hoover Dam's seventeen big hydroelectric units were built into the powerhouse. Generator installations began in nineteen thirty-five. The first generator, Unit N Two, began commercial operation October twenty-sixth, nineteen thirty-six to serve the city of Los Angeles. In ones and twos the generators filled the pits as demand for electrical energy in California, Nevada, and Arizona called them into service. Finally in nineteen fifty-nine, manufacture and installation of the last generator, N Eight, began. For twenty-five years the N Eight pit had lain dormant and silent except for the hum of other Hoover generators. Now as more generating capacity was needed, contracts were awarded for the generator's manufacture and installation. Plants throughout the nation fabricated N Eight's many parts. The design of N Eight followed that of other Hoover generating units. It is a ninety-five thousand kilowatt, sixty cycle, sixteen thousand five hundred volt generator driven by a one hundred fifteen thousand horsepower turbine. Falling water from the reservoir which spins and powers the turbine wheel is controlled by a huge butterfly valve which permits the water to flow to the turbine from the feeder penstock. Weighing two thousand tons, N Eight parts were shipped to Hoover Dam on sixty rail cars.

Arriving at the canyon rim overlooking the dam, the parts were lifted by cableway out over the canyon and down to the powerhouse. Parts descending into the gorge on strands of cable were familiar and almost daily sights reminiscent of previous installations, and the main cableway operator was the same one who had helped install and operate the cableway during the dam's construction in the early nineteen thirties. Others likewise had worked on the project throughout its construction.

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Inside the Nevada wing of the powerhouse, technicians assembled and installed the massive electrical cargo. Crews prepared the N Eight pit to receive the new generating unit. They removed temporary slabs over the turbine and relief valve outlets to the tailrace and river. Liners assembled in these openings were set in concrete. The turbine's scrollcase sections were lowered into the pit. The sections were leveled, bolted together, and aligned. The completed scrollcase was then anchored in concrete. Later the turbine's waterwheel, attached to the bottom end of the shaft, was installed inside the case. The butterfly valve was assembled on the generator floor and later connected between the feeder penstock and the turbine scrollcase.

Meanwhile, the generator's two main parts, the rotor and stator, took form. Steel lamination plates were stacked around the rotor and stator frames. Coils were locked into place, and electrical connections were made. The powerhouse's overhead cranes lifted the completed two hundred fifty-four ton stator from its erection bay and carried it gently to its foundation over the turbine pit where it was lowered and bolted into place. The four hundred sixty-six ton rotor was moved from its erection bay and lowered inside the stator. The rotor was then joined to the turbine water wheel by a thirty-eight inch diameter shaft sixty-three feet long. Guide and thrust bearings and other parts were added to complete the assembly. After test runs, N Eight went on the line December first, nineteen sixty-one, to serve the state of Nevada and to complete the Hoover power plant, raising its capacity to one and one-third million kilowatts, keeping it as one of the world's largest hydroelectric installations.