Testing and analysis of the Bangladeshi Treadle pump

The Treadle pump was invented in 1980 by development workers to provide low cost, low technology and locally manufacturable irrigation for farmers in northern Bangladesh. The twin cylinder steel-bodied suction pump, called the Treadle pump, operated by a walking motion upon two centrally pivoted levers, is well suited to the high water tables of much of Bangladesh. The increased popularity of the pump, resulting from extensive marketing efforts, with annual sales of over 50,000 units in 1987/88, has prompted suggestions for design alterations, specifically pump material changes to decrease costs and increase sales. A technical field and laboratory study supported by calculations from hydraulic theory was required as a basis upon which to start design alterations. In laboratory tests, different pump body configurations were found to have negligible impact on overall pump performance characteristics. These findings were supported by results obtained from calculations of friction and turbulent loss. Any worthwhile alterations must rather be justified by cost and manufacturing benefits. The combination of computer-aided instrumentation and high speed data collection in laboratory testing, theoretical analysis, and field testing in Bangladesh revealed that the losses in pump performance are a result of poor valve sealing, valve opening and closing delays and leakage past the piston seal, resulting in lower discharges than had been previously assumed. The reduced discharge for irrigation and the operator power input limit, measured at the pump, of 55 watts results in a four meter maximum depth of water table to which the standard 89 mm (3.5 inch) pump can be used, with some variation due to irrigation requirements and operator strengths. Improvements to piston valve and foot valve design to reduce leakage and valve-delay times and the use of a smaller 77 mm (3 inch) cylinder diameter, are achievable and are recommended. These improvements combine to permit operation of the pump to nearly six meters without exceeding the limit of input power or reducing the discharge below the crop irrigation requirements.Applied Science, Faculty ofCivil Engineering, Department ofGraduat