Service Contract No 2007 / 147-446 - Swaziland

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5.1.2 S p r i n k l e r p r e s s u r eThe optimal operating pressure (kPa) of the sprinkler should be between 60 and 70 times thenozzle diameter (mm). This is applicable to nozzles of 3 to 7 mm diameter (ARC, 2006).Table 2. Optimal Operating Pressure Vs <strong>No</strong>zzle Diameter for Sprinklers<strong>No</strong>zzle diameterOperating pressure (kPa)Mm inches x 60 x 701,591 / 16 "1,985 / 64 "2,383 / 32 "2,787 / 64 "3,181 / 8 " 191 2223,579 / 64 " 214 2503,975 / 32 " 238 2784,374,765,165,565,956,3511 / 64 " 262 3063 / 16 " 286 33313 / 64 " 310 36115 / 64 " 333 38915 / 64 " 357 4271 / 4 " 381 445Pressure at sprinklers was measured with a pressure gauge, fitted with a pitot tube (Figure17). The point of the pitot tube was held about 2 mm in front of the nozzle opening in the pathof the jet of water to measure the “vena contracta”. Therefore, the velocity pressure, whichindicates the pressure head and is equivalent to the total pressure, was measured.Maphobeni Farmers Association Report - 2009 Page - 35 -
Figure 17. Pressure measurement with a pitot tube end pressure gaugeThe standpipes were three metres high and the pressure of the sprinklers was measured at aheight of one metre above the ground, then 2 m (or 20 kPa) was subtracted from thepressure registered on the pressure gauge, in order to determine the sprinkler pressure atnormal operating height.The choice of the sprinklers at which measurements were to be taken, was influenced by thedifferent pressure zones in a specific irrigation block. In view of the undulating terrain (manyheight differences) in this project the total system was in operation as for normal irrigationbefore the evaluation. According to the ARC (2006) the number of measuring points must berepresentative of the block and the choice depended on the topography of the block, as wellas the distance from the pump station. As per these recommendations completemeasurements were taken at distances 0, L/4, L/2, 3L/4 and L on the lateral and at the samedistance on the sprinkler lines (Figure 18).Maphobeni Farmers Association Report - 2009 Page - 36 -
Page 1 and 2: Restructuring and DiversificationMa
Page 3 and 4: DISCLAIMERThe contents of this repo
Page 5 and 6: 5.2 Delivery tests ................
Page 8 and 9: LIST OF APPENDICESAppendix 1: SEB u
Page 10 and 11: 1 I N T R O D U C T I O NAssociatio
Page 12 and 13: pumps. 2 x Howden 100-400 in the ri
Page 14 and 15: 3.1.2 R e v i e w o f C o n t a c t
Page 16 and 17: 9 SCHEDULE OF BLOCKS THAT IRRIGATE
Page 18 and 19: Maphobeni Farmers Association Repor
Page 24 and 25: Based on equation 1 above the flow
Page 26 and 27: ReducersThe inlet on the pump sucti
Page 28 and 29: d1.5d0.5dd3d 3d 1.5dFigure 9. Spaci
Page 30 and 31: hf6375kQ4d2……………………
Page 32 and 33: Table 1. Pump and motor specificati
Page 34 and 35: Table 2. Irrigation pumps evaluatio
Page 36 and 37: Phase two river pump station‣ Pum
Page 38 and 39: Filters: 3%Capital Recovery Rate (C
Page 40 and 41: 4.3.1 M a i n l i n e s i z eThe So
Page 42 and 43: 5 F I E L D E V A L U A T I O N O F
Page 46 and 47: 0 L/4 L/2 3L/4 LL3L/4LL/2Test block
Page 48 and 49: Phase two booster Pumps running und
Page 50 and 51: The installation of this unit (on t
Page 52 and 53: Old AgePhase one of the irrigation
Page 54 and 55: The effects of different nozzles/em
Page 56 and 57: Interest RatesIt can be argued that
Page 58 and 59: 6 . 2 M a n a g e m e n t P r a c t
Page 60 and 61: 6 . 3 M a i n t e n a n c e S u r v
Page 62 and 63: 7 C O N S T R A I N T S T O E F F I
Page 64 and 65: phase one and two was found to be 1
Page 66 and 67: 8 R E C O M M E N D A T I O N STo e
Page 68 and 69: OVERALL MANAGEMENT AND MAINTENANCEM
Page 70 and 71: 10 L I T E R A T U R E R E F E R E
Page 72 and 73: 11 P R O D U C T I N F O R M A T I
Page 86 and 87: SEB usage for River pump station Ph
Page 88: Appendix 2: capital recovery factor

Service Contract No 2007 / 147-446 - Swaziland

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