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PUMP PERFORMANCE

Brief tests were carried out on an early version of the trolley pump, using a 4 inch barrel, and using rather small valve balls of 38mm diameter. Suction pipe diameter was 2 inch and delivery pipe diameter 1.5 inch. Both pipes were vertical.

Suction head was 1.37 metres and delivery head 1.65 metres. A half-cycle time of 1.5 seconds was used for both the suction and delivery strokes during testing. The empty trolley was pulled by hand using a spring balance. The average force on suction strokes was 23 kg force and 36 kg force on delivery strokes. Discharge was not measured.

From the above figures, pump efficiency was found to be 45%, assuming a pump discharge coefficient of 100%.

Because of this rather low efficiency figure, it was decided to fit larger valve balls, as specified in the accompanying drawings. The use of 55 mm diameter valve balls with a 3 inch valve barrel should give a pump efficiency of 60% or greater, depending on cup washer adjustment.

With a 620mm stroke, a 3 inch barrel, and a 3 second cycle time, the pump flow rate will be 1 litre per second. With 3 metre suction head, 3 metre delivery head and 60% efficiency the average work rate per operator will be 50 watts mechanical power. From the literature review of Human Energy Utilisation, such a work rate is easily sustainable by a reasonably healthy adult for long periods without undue strain.

For a horticultural crop with a peak water requirement of 10mm per day rainfall equivalent, the pump can irrigate an area of 0.25 hectares if used for 7 hours per day (0.25 ha is 2500 metres squared – a rectangular plot 70 x 35 metres or a semi-circular plot of 40 metres radius).

DRIVE MECHANISM COMPARISON..............................................Pump120.htm

PRODUCTION COSTS........................................................................Pump130.htm

OPERATIONAL COSTINGS...............................................................Pump140.htm

SUMMARY AND CONCLUSIONS....................................................Pump150.htm

REFERENCES......................................................................................Pump160.htm

APPENDIX........................................................................................... Pump170.htm

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