Penstocks and Scroll Cases for Niagara Power Project

The twenty-five penstocks and scroll cases for the two Niagara Power Plants combine into a record size welded steel plate construction project. The Power Authority of the State of New York channeled water from the Niagara River above the falls to twenty-five generating units at Lewiston, New York. With a total installed capacity of 2, 190,000 kw, this is now the largest hydro-electric development in the Free World. Accelerated construction schedules required completion of steel plate erection, welding and x-ray inspection on unprecedented minimum time schedules. Erection of the thirteen 24 ft 0 in. to 28 ft 6 in. increasing elbows at top of cliff by means of pin-joint bar anchors is considered unique in unconventional design and erection. Special welding procedures to produce highest feasible quality results on plates as thick as 1.812 in. had to be developed to insure minimum delays for cut-outs and repairs of welds after the x-ray inspection on all butt-welded joints.

A 50% overload strength test and complete visual examination for possible leakage was required prior to concrete encasement. A five stage construction procedure permitted rapid completion and saved approximately 2,000 tons of steel plates. Test heads were removed and rewelded to the ends of successive stage sections. Great numbers of test heads were necessary to avoid delays in testing and encasement. Each stage unit after test and inspection remained pressurized to hold roundness tolerances during concrete encasement. Construction of the 13 penstocks in rock trenches on the 48° slope at full speed under adverse winter weather conditions presented hazardous and difficult problems. This was further complicated by the close correlation demanded by the general contractor's wide spread rock excavation and concrete placement operations carried on day and night throughout all months of the year. As a result the combined penstock and scroll case construction project was more difficult than most previous large size welded steel plate construction undertakings.