Dr Brian McIntosh; Donald MacAllister; Erik Harvey
AN ANALYSIS OF SCALE AND TECHNOLOGY IN ROPE-PUMP PISTON MANUFACTURE AND SUPPLY IN SUB-SAHARAN AFRICA
The rope-pump has potential to be a suitable technology option in WaterAids rural water supply programmes in Sub-Saharan Africa. However manufacture and supply of the water lifting component, the pistons, is a bottleneck in the sustainability of the rope-pump. Manufacturing processes are often inefficient or expensive and there is little incentive to produce spare parts.
This study investigated the most appropriate technology for manufacturing pistons finding that manual injection moulding with electrical heating produces good quality pistons at a rate high enough to meet current demand. If production significantly increases then higher capacity technologies should be employed. Break-even costs and production volumes depend on the inputs and complexity of technology. Manual machines used in non-pilot production have low break-even outputs; in Ghana for example production breaks-even at 96 pistons per month, costing a total of $54.
The main constraint on the economic viability of piston production is geographic rope-pump density. There are not enough rope-pumps, in seven out of eight countries, for economically viable manufacture. Spare piston sales and pump density must be increased. A full set of pistons should be replaced as regularly as the rope to generate higher revenue. Developing irrigation and self-supply rope-pump models should increase pump density.