Service Contract No 2007 / 147-446 - Swaziland

75kW motors that drive these respective pumps are correctly specification. Phase twobooster pumps are driven by high speed motors, these are not recommended.4.1.1.6.2 Pump OperationPump curves of all the pumps are used to evaluate whether these pumps function asindicated by the pump curve. Measurements of the operational pressure and discharge fromthese pumps were used for this exercise but because no flow meter was installed in thisproject this could not be carried out. Pressure measurements however revealed that allpumps are operating below their recommended duties. For example, at closed valve pressurethe Howden 100-400 pump generated 400kPa. The operating curves indicate that, at no flowthese pumps should be able to deliver at least 500kPa (at 385mm impellor diameter).4.1.1.6.3 Output PowerThe required powerPrequiredof the pump, calculated above, is then compared with the outputpower (Pu) of the electric motor obtained from measurements of voltage and current. Theoutput power of the motor is calculated using equation 7 below3IV cosP u……………………………………….. (7)1000Where: Pu = output power of the motor (input power of the pump) (kW)I = average measured current (A)V = average measured voltage (V)η = motor efficiency (fraction)cos ø = power factor (factor).The output power of motors that were in operation during the evaluation is indicated in table 2below. One of phase one pump was not running because it had a faulty foot valve. The builtinnon-return valve could not stop backflow of water and the pump could not be primed.Maphobeni Farmers Association Report - 2009 Page - 24 -