Rope Pump Modifications to Reach Greater Depths: A Service Project for Clean Water in The Gambia

Abstract

Rope pumps are a locally adaptable and relatively simple technology for water retrieval that are easy to understand and repair and perform well with respect to water quality. Concern Universal - an NGO with offices in Banjul, The Gambia - was introducing the rope pump into The Gambia and needed assistance in designing a rope pump that could lift water from greater depths. Modifications to the rope pump would be needed, which became the basis of an opportunity for a student service-learning project / capstone design experience for students to develop a solution. More specifically, the design criteria were to develop an affordable, easy to use rope pump that could be used to pump water from a depth of 30 m to a storage tank 5 m above ground with a constraint of human power by a single operator. A team of undergraduate students and faculty designed, built and tested a rope pump that was similar to those used in rural Gambian villages. The team’s rope pump design, analyze, build and test process is described in this paper. The design solution began by first modeling the rope pump in a user-defined MATLAB routine to effectively determine the effects of parameters and constraints. A parametric study, where pipe diameter, number of pistons per meter of rope length, well depth and input rotational speeds were varied, was conducted. These results provide a range of conditions for using a rope pump at various depths and provided a basis for designing a pump. Experimental tests were conducted, and the results were compared to theoretical predictions. Experimental results for flow rate were within 3-18% of predicted values. To meet the client’s needs, it was determined that a rope pump with 1.27 cm (0.5 in) diameter piping, two pistons per meter, and a belt drive with gears of ratio of 1.5:1 to increase torque could raise water 35 m using operator under human-power. Additionally, alternative forms of power that would be available to the region are briefly investigated and discussed as potential future work, although further development was beyond the scope of this design project.