File:Holyoke Testing Flume arranged for testing horizontal turbines.jpg

The testing flume consists of an iron penstock, A, about nine feet in diameter, through which the water flows from the head race into a chamber, B, from which it is admitted through two head gates, G,G, into the chamber, C, and from thence through trash racks into the wheel pit, D. Passing through the wheel to be tested, it flows into the tail-race, E, where it is measured as it flows over a weir, at O. The object of the chamber, B, is to afford opportunity for the use of the two head gates, G,G, to control the admission of water, and consequently the head acting on the wheel. There is also a head gate at the point where the penstock, A, takes in water from the first level canal. A small penstock, F, about 3 feet in diameter takes water from the chamber, B, independently of the gates and leads to a turbine wheel, H, set in an iron casing, in the chamber, C, in order that this wheel can run when C and the wheel pit, D, are empty. The wheel, H, discharges through the floor at the bottom of C, and through the arch, I, and the supplementary tail-race, K, into the second level canal. This wheel is used to operate the repair shops; also to operate the gates, G. The chamber, C, is bounded on one side by a tier of stop-planks, L, and, on another side by a tier of stop-planks, M. The object of stop-planks, L, is to afford a waste-way out of the chamber, C. This is of especial use in regulating the height of the water when testing under low heads. The water thus passed over the planks, L, falls directly into the tail-race, K. and passes into the second level. The stop-planks, M, are used when scroll or cased wheels are tested. In such cases D is empty of water and the wheel case in question is attached by a short pipe or penstock from an opening cut in the planks, M. Flume wheels are set in the center of the foor of D, and D is filled with water. They discharge through the floor of D and out of the three culverts, N,N,N, into the tail-race, E. Horizontal wheels are set in the pit, D, with their shafting projecting through a stuffing-box in the side of the pit. At the down-stream end of the tail-race is the measuring weir, O (Fig 227). The crest of the weir is formed of a strip of planed iron plate twenty feet in length. The depth of water on the weir is measured in a cylinder, P, set in a recess, Q, fashioned in the sides of the tail-race. These recesses are water-tight, and the observer is thus enabled to stand with the water-level at convenient height for accurate observation. The cylinder, P, is connected with a pipe that crosses the tail-race or weir box about ten feet back of the weir crest. The pipe is placed about one foot above the floor and is perforated in the bottom with 1/8 inch holes. A platform, R, surrounds the tail-race, and is suspended from the iron beams that carry the roof. Above the tail-race is the street, over which the wheels to be tested arrive on wagons from which they are lifted by a traveling crane that runs on a frame-work over the street, and by means of which the wheels are carried into the building and are lowered into the wheel pit, D. Spiral stairs lead into a passageway that leads in turn to the platform, R. In the well-hole of these stairs are set up the glass tubes which measure the head of water upon the wheel. These gauge tubes are connected with the pit, D, and the chamber, C, by means of pipes, one of which enters the wheel pit through a cast iron pipe, T, built into the masonry dam which forms the down stream end of the wheel pit, D. The other pipe passes back under the wheel pit, D, and crosses the tail-race at the extreme back line and close under the pit floor. This pipe is perforated throughout its length across the race in a manner similar to the pipe used for determining the head on the weir. To enable observers at the brake wheel, head gauge, and measuring weir to take simultaneous observations, an electric clock rings three bells, simultaneously at intervals of one minute.