Service Contract No 2007 / 147-446 - Swaziland

hf6375kQ4d2………………………………….. (4)A summation of friction loss across the river pumps foot valves, the suction pipe, and theeccentric reducer gave a total hf of 0.72m, 0.2m and 0.5m for PS1, PS 2 and PS 3respectively. Friction in the suction pipe has a direct effect on maximum suction height andconsequently the available net positive suction head (NPSH) and is discussed below.Where: hf = secondary friction loss in fitting (m)k = friction loss factor (annexure 1)Q = flow rate in the fitting (m³/h)d = inner diameter of the fitting (mm).4.1.1.5 Suction heightThe essence of this evaluation was to determine the actual static suction head of the installedpumps and then compare it to the designers suction height assumption. The maximumsuction height is calculated using equation 5 below;hs(max) hdhfhvp NPSHrequired ………………. (5)Where: hs (max) = maximum suction height (m)hdhfhvp= atmospheric pressure on terrain (m)= suction side losses (friction losses, as well as secondary losses in fittings, m= vapour pressure of water (m)NPSH required = net positive suction head from the pump curve (m)Maphobeni Farmers Association Report - 2009 Page - 21 -