Service Contract No 2007 / 147-446 - Swaziland

Table 3. Pressure and nozzle size measurements resultsMeasuring point Type of sprinkler/nozzle Measured nozzlediameterMeasurednozzle pressurePhase one RC 140 11/64" nozzle 4.4 440Phase one Rain bird BH30 11/64" nozzle 4.4 220Phase one Rain bird 14070 11/64" nozzle 5 220Phase one Rain bird 14070 11/64" nozzle 4.4 420Phase one Rain bird 14070 11/64" nozzle 4.4 450Phase two VYRSA 35 11/64" nozzle 4.4 340Phase two VYRSA 70 11/64" nozzle 4.5 330Phase two – block I RC 130 11/64" nozzle 4 250Phase two – block I VYRSA 70 11/64" nozzle 4.5 240Phase two – block I VYRSA 70 11/64" nozzle 4.5 230Phase two RC 130 11/64" nozzle 4 350Phase two – block I VYRSA 70 11/64" nozzle 4.5 210Phase two VYRSA 70 11/64" nozzle 5 290Phase two VYRSA 70 11/64" nozzle 5 360Phase two VYRSA 70 11/64" nozzle 5 330Phase two VYRSA 70 11/64" nozzle 5 360Average Pressure (kPa) 350.5 299.09Minimum Pressure (kPa) 220 210Maximum Pressure (kPa) 450 360Pressure Variation (kPa) 65.71 50.15According to the SABI norms, pressures in the infields may not vary more than 20% from theaverage pressure. Pressure measurement results as indicated by the above table reflect anunacceptable pressure variation of 65.71% for phase one and 50.15% for phase two. Theaverage system operating pressure is 350.1kPa and 299.09kPa for the two phasesrespectively. Phase one average sprinkler operating pressure is above the recommendedsprinkler operating pressure of 350kPa. Phase two average sprinkler operating pressure, onthe other hand is lower that the recommended 350kPa.The least amount of pressure was recommended on blocks I. this block is on top of a smallhill at the highest elevation and all hydromatics in the lateral were connected to sprinklers.Each lateral had up to 23 operating sprinkler connected to it.The following is an outline some of the factors affecting the above pressure reading;Maphobeni Farmers Association Report - 2009 Page - 38 -