Service Contract No 2007 / 147-446 - Swaziland

4 F I E L D E V A L U A T I O N O F I R R I G A T I O NS Y S T E M4 . 1 P u m p s a n d P u m p S t a t i o n s4.1.1 P u m p S u c t i o n S i d eThe majority of problems occurring with pumps are usually the result of poor suction sidedesign and installation. The installation and designed of the suction side must ensure thatturbulence occurring and collection of air in high places in the suction pipe, is prevented. Inview of the above, the different suction side components are evaluated.4.1.1.1 Suction Pipe Flow RateThe suction pipe flow velocity of river and booster pumps is calculated as follows:353,68 QV m / s2d ………………………………….… (1)Where: V = flow velocity in pipe (m/s)Q = flow rate (m³/h)d = inner diameter of suction pipe (mm).This 151 hectares dragline irrigation system development has three pump stations, two riverpumps and one booster pump station. Pump station one (PS1) supplies 56 ha phase onedevelopment, and phase two of 95ha has a river pump station and a booster pump station.PUMP STATION 1: Phase One Pump StationThis pump station has one KSB ETA 125-50/2 pump driven by a two pole 75kW motor andirrigates a total area of 56ha. The design duty point of this pump is not known. But forpurposes of the evaluation the pump discharge was determined getting a multiple of the totalirrigated area, industry norms of 2.57 sprinklers per hectare (12 positions per sprinkler),1.4m3/hr sprinkler discharge and 10% safety factor for pump discharge. the pump musttherefore generate at least 221.6 m³/hr.Maphobeni Farmers Association Report - 2009 Page - 14 -