Service Contract No 2007 / 147-446 - Swaziland

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7 C O N S T R A I N T S T O E F F I C I E N T S Y S T E MP E R F O R M A N C EThe following constraints were identified to have an effect on productivity once the system isoperated.River pump station:‣ A proper intake structure was not constructed on phase one pump station. The suctioninlets (foot valves) are suspended at the end of the Usuthu River. The foot valves are notprotected in any way and are intermittently in direct contact with the bottom of the channeland debris carried with the river water.‣ Phase two river pump station, on the other hand, has an improperly constructed sump.During operations, the pumps suck debris like mud and sand which affect pumpperformance and the lifetime of the pumps.‣ Suction pipe flow velocity for these pumps through the 200mm suction pipe in PS 1exceeded the 1,5m/sec maximum allowed in norms - causing pump cavitations hencefrequent wearing of impellers and high maintenance cost.‣ Incorrectly sized fittings in suction and delivery manifolds of all pump stations affectsystem performance. The effects of these are severe on the eccentric reducer because itis directly attached to the pump and the sudden restriction in size increases turbulenceoccurrences and cause irregular feeding of the pump hence cavitation. With such aninstallation wearing and maintenance cost of the pump will increase.‣ The evaluation of pumps could not identify whether the pumps are optimally operating ornot because of the absence of flow and on some pressure measuring devices.‣ The water depth above the suction inlet was measure to be less than the acceptedminimum water depth according to suction pipe flow velocities. This reduces pumpefficiency and performance.‣ Based on the duty point of the installed ETA 125-50/2 phase one pump, a smaller andcheaper ETA 100-250 single stage pump could have been used. Pressure measurementsresults reflected that this pump is operating below the design duty point.‣ Pressure requirements from the balancing dam to the critical sprinkler in phase two areestimated at 90m. The impellor diameter of these pumps is 246mm and in order for thesepumps to generate the required pressure a 255mm impellor diameter must be installed inthese pumps.‣ High speed pumps are used in phase two booster pump stationMaphobeni Farmers Association Report - 2009 Page - 53 -
‣ Phase two pump stations are well designed and constructed with ample working spaceand ventilation.‣ The balancing dam is leaking and reduced the conveyance efficiency of the irrigationsystem.‣ There is no mechanism to regulate flow between river pumps and booster pumps.‣ All pumping units in Maphobeni are not serviced but repaired as faults develop.MAIN LINE‣ <strong>No</strong> information was available on mainline pipe sizes, lengths and class and because thereare no pressure measuring points on hydrants, friction loss through the mainline could notbe calculated. An undisputed conclusion, therefore, on whether the supply system wascorrectly designed or not cannot be drawn until details on pipe size, pipe classes, anddistances occupied by the different sizes are obtained.‣ Pipe bursts are one major indicator of under-specification in pipe classes and recurrentpipe breakages were experienced only in phase one mainlines, sub-mains and laterals.‣ The mainline has a leak and this reduces system pressure and flow hence theunacceptable flow and pressure variation.‣ Some Air valves and sections of mainlines are leaking – overall system efficiencycompromised.SPRINKLER INFIELD IRRIGATION‣ The lateral of the irrigation system that was installed by S.I.I. (phase two) are equippedwith mechanically chocked hydraulic valves. Pressure-regulating pilot are not installed.Phase one laterals are equipped with mechanical valves; there are no hydraulic valves inthis phase.‣ This dragline irrigation system is installed with 108m lateral spacing (phase 2) and 216mlateral spacing (phase 1). Emitter spacing is maintained between 17m - 20m.‣ Pressure variation in this irrigation system is at 65.71% for phase one and 50.15% forphase two. The average system operating pressure is 350.1kPa and 299.09kPa for thetwo phases respectively. <strong>No</strong>t only is pressure variation is above the recommendedmaximum of 20%, but phase two average sprinkler operating pressure is below therequired 350kPa sprinkler pressure.‣ Flow variation was above the recommended maximum of 10% averaging a high of45.86% and 51.24% in the two phases respectively. The average sprinkler application forMaphobeni Farmers Association Report - 2009 Page - 54 -
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 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 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
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Service Contract No 2007 / 147-446 - Swaziland

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