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<br />1,.....'1""1 <br />iuil <br />50 MF.TI!OPOLIT.~N WATEIl DISTHICT <br /> <br />The purpose of the tests was to determine whether the pumps com- <br />ply with all of the requirements of the specifications. <br />The most important characteristics are capacity and efficiency; <br />that is. thc ability of the pumps to rleliver the required amount of <br />water and their economy in the use of electric power. The pump <br />manufacturers were required by the District to guarantee that <br />each pump would deliver not less than 200 cubic feet per second of <br />water with an efficiency of 88 per cent, and were offered a bonus <br />if the pump efficiency exceeded that percentage. The efficiency is <br />the ratio between the useful work performed by the pump in lifting <br />the water the required height and the actual amount of energy <br />delivered to the pump by the driving motor. <br />In making the pump tests it was necessary to make accurate <br />measurements of capacity, head, power, and the speed of rotation <br />of the pump. <br />Capacity is the quantity of water delivered by the pump expressed <br />in cubic feet per second. Head is the net pressure developed by the <br />pump, including the lift through which the water is raised, and the <br />pressure necessary to overcome the friction of the water in the <br />pipe lines. From the measured head and capacity, the useful work <br />done by the pump is calculated. <br />The power is measured in kilowatts of electrical energy put iuto <br />the driving motor. Each of the motors was completely tested at <br />the factory and the motor losses determined. When the power input <br />to the motor was measured in the field the known motor losses were <br />deducted to give the net power delivered to the pump shaft. The <br />motor losses are less than 3 per cent, which means that more than <br />97 per cent of the power delivered to the motors by the transmission <br />line from the Boulder power plant is used in driving the pumps. <br />For measuring the power input, a special set of test meters was <br />used. These meters were carefully matched agaiust standard in- <br />struments of known accuracy both before and after the tests at <br />each plant in order that any variation which might have taken <br />place during the tests could be detected. The precise measurement <br />of electric power requires that the meters be kept at a constant <br />temperature rluring calibration and while in use in the field tests. <br />This was accomplished by placing the meters in an insulated box <br />in which constant temperature was maintained by electric heating <br />elements. <br />Measurements of speed were made with a cathode ray oscillo- <br />scope. This instrument compares visually the electrical speed of <br />