This section of the website is under construction and all texts are provisional.
The basic principles of pumping are explained in chapter 2 of the manual on pump selection for affordable low-lift pumping (Van ’t Hof, 2000).
Possible alternative pump types
Essentially there are four types of pumps that can be used for low-lift pumping at static heads of 2-6 meters: (1) Archimedean screws; (2) axial-flow or propeller pumps; (3) bowl-type mixed flow pumps; and (4) volute-type mixed flow pumps. (For images, see Van ’t Hof, 2000).
The first three normally require a pumping station for their installation, thus necessitating additional civil engineering. This makes solutions involving them very costly. The idea of applying them must be discarded, if the aim is to lower pumping costs.
Among these three, there may be an exception: in Asia, mobile axial-flow pumps are not uncommon. In fact, “in east Asia, millions of smaller horsepower (6-15 HP) mobile units powered mostly by single cylinder diesel and petrol engines are used by smaller farmers for crop irrigation, drainage and fisheries.” (Wikipedia, 2012). This could be an interesting option if one’s crop doesn’t totally rely on it (which is often the case in Asia), or if static heads do not exceed 2-3 meters.
However, it is doubtful that they can beat the volute-type mixed-flow pump in terms of reliability and performance when it comes to the full-range of low-lift conditions from 2 to 6 meters (or even a bit more) that prevail along large tracts of the Sahelian rivers. There is one caveat: these volute-type mixed-flow pumps must be operated with suitably dimensioned suction and pressure lines. The cost, and therefore the procurement of these must be taken into account when proposing a solution.
Clearly, an integrated design process is required. PumpSelect enables one to do that for a wide range of engines, pumps, and accessory equipment, such as foot valves and hoses of various costs and dimensions, all the while using the local hydrology (i.e. pumping conditions) as a starting point.
Volute-type mixed-flow pumps
The conclusion can be stated in the following simple terms. There is no need to look for a fundamentally alternative way of pumping along the Niger and Senegal rivers to what has been fairly common practice for decades. Trolley-mounted, diesel-powered, volute-type mixed-flow pumps can continue to be used. Only overall pumping efficiency needs to be optimized for the local pumping conditions by optimizing pump selection and accessory equipment, while at the same time sourcing (most of) the equipment from Asia to slash capital costs. The combined measures have the potential to cut costs by at least 50% as has already been demonstrated with a sub-optimal pumpset from India (Arby & Van ’t Hof, 2000)
Van ’t Hof, Sjon. 2000. Affordable low-lift pumping for small-scale irrigation development : appropriate equipment selection. Ed. François Gadelle. Unpubl. Amersfoort. http://www.scribd.com/doc/106805099/Affordable-Low-lift-Pumping-forSmall-scale-Irrigation-Development-Appropriate-Equipment-Selection.
Arby, Dramane, and Sjon van ’t Hof. 2000. Evaluation d’une motopompe Kirloskar TV-1/NW9ME à Kakondji, Tombouctou, Mali. http://www.scribd.com/doc/77669616/Evaluation-d%E2%80%99une-motopompe-Kirloskar-TV-1-NW9ME-a-Kakondji-Tombouctou-Mali.