Service Contract No 2007 / 147-446 - Swaziland

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Based on equation 1 above the flow velocity, through the 200mm suction manifold is 2.1m/sand according to the Agricultural Research Council, ARC (<strong>2007</strong>) the ideal suction pipe flowvelocity must be 1.0 m/s, but suction pipe flow velocities up to 1.5 m/s are acceptable. Theexcessively high suction flow velocity in the suction pipe causes turbulence in the pipe, thuscausing irregular feeding of the pump (and eventually causes cavitation). As a result impellorwearing is excessive and thus explains the poor performance by this pump. Maintenancecosts are high as a result.PUMP STATION 2 – Phase Two River Pump StationThis pump station has two Howden 100-400 pumps each driven by low speed 30kW motors.These pumps supply water to a small earth dam irrigating responsible for supplying water to95 hectares. The design duty point of these pumps could not be ascertained but in order formeet sugarcane irrigation requirements these pump must generate at least 376m3/hr totalflow. Each pump therefore has a duty of at least 188m3/hr flow and using equation oneabove, flow velocity through the 250mm suction pipe is 1.11 m/s. this suction pipe is correctlysized and its flow velocity is within recommendations.PUMP STATION 3 – Phase Two Booster Pump StationThese pumps design duty point is also not known but was calculated to be the same as thatof PS 2. The two identical Howden 100-250 high speed pumps in this pump station musttherefore generate at least 188m3/hr each and the flow velocity at this flow through the250mm suction manifold is 1.11 m/s and is within recommended limit.4.1.1.2 Requirements for Fittings90º BendsThe radius (mm) of a 90º bend must be, at least, as shown in Figure 4 belowMaphobeni Farmers Association Report - 2009 Page - 15 -
dFigure 4 Required radius of 90 bends (source: ARC (<strong>2007</strong>))r 2d100mm …………………………………... (2)Where: r = radius of bend (mm)d = inner diameter of suction pipe (mm).All 90° bends measured in the three pump stations had a shorter radius than required.200mm 90° bends in PS 1 are 200mm in radius and PS 2 and 3 250mm 90° bends have aradius of 350mm. According to figure 4 and equation 2 above the required minimum radius is500mm and 600mm for the two sizes respectively. However, there is more than five time thesuction and delivery pipe size diameter pipe further on from these bends; the effects of theincorrect sizes are insignificant.Figure 5. 90° suction bendsMaphobeni Farmers Association Report - 2009 Page - 16 -
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 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 44 and 45: 5.1.2 S p r i n k l e r p r e s s u
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 74 and 75:
Maphobeni Farmers Association Repor
Page 76 and 77:
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
SEB usage for River pump station Ph
Page 88:
Appendix 2: capital recovery factor
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Service Contract No 2007 / 147-446 - Swaziland

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