Service Contract No 2007 / 147-446 - Swaziland

Table 1. Pump and motor specifications and measurements conducted on booster pumpsPUMP SPECIFICATIONS FROM INFORMATION PLATE AND MEASUREMENTSMake / model ETA 125-50/2 Howden 100-400 Howden 100-250Pump identification Phase 1 Phase 2 river Phase 2 boosterNumber of units 1 2 2Pump Duty (estimated) 222m³/hr @ 80m 188m³/hr @ 35m 188m³/hr @ 90mImpeller diameter mm 405/330 385 245Pressure under normal operation (H) m - 30 60MOTOR SPECIFICATIONS FROM INFORMATION PLATE AND MEASUREMENTSModel and type Alstom Dutchi DutchiPower (P motor) kW 75 30 75Power factor (cos ø) 0.87 0.88 0.91Speed rpm 1475 1450 29654.1.1.6.1 Power required on the pump shaftThe power required on the pump shaft is calculated once the total pump head and delivery ismeasured. The pump efficiency is obtained from the pump curve. The following formula wasused to establish whether motors are sized accurately.P g H Q36,000………………………………………. (6)Where: P = power required on the pump shaft (kW)ρ = density of water (1000 kg/m³)g = gravity acceleration (9.81 m²/s)H = pump pressure at service point (m)Q = pump delivery at service point (m³/h)η = pump efficiency at service point (%)Based on the estimated duty point shown in table 1 above the required power on the pumpshaft is a theoretical value of 61.26kW for the phase 1 pumps, 25.08kW for phase two riverpumps and 67.8kW for phase two booster pumps. According the ARC the power output of themotor must be 10-15% greater than the power required on the pump shaft and correspondsto 67.4kW, 27.6kW and 74.6kW respectively. Under this consideration, the 75kW, 30kW andMaphobeni Farmers Association Report - 2009 Page - 23 -