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OPERATIONAL COSTINGS

The following table compares the initial cost of the pump with that of some commercially-available pumps:

Now if we assume the following:

Operational life of motorised centrifugal pump = 2500 hours

Total pumping head = 6 metres

Pump efficiency = 25%

Petrol Engine efficiency = 20%

Petrol Calorific Value = 11 kW-hour/litre

Petrol Cost = US$ 0.40/litre

Interest Rate: 0%

Then we find that:

Unit fuel cost = US$ 0.015 / metre cubed of water raised

Unit Capital Cost = US$ 0.040 / metre cubed of water raised

This can be compared with paid or self-employed labor supplying water in 20 litre buckets lifted through 6 metres head at a rate of 25 buckets per man-hour for 6 hours per day, and being paid US$ 2 per day. The resultant net work rate is only 10 watts but gross work rate is probably 100 watts. Cost is US$ 0.670 / metre cubed of water raised.

Now consider the trolley pump with the US$ 332 cost amortised over 7 years at average utilisation of 500 hours per year. Take labor cost as US$ 0.25/hour per person and output as 1 litre/second for 2 operators.

Thus unit capital cost = US$ 0.030 / metre cubed raised

And unit labor cost = US$ 0.150 / metre cubed raised

The above unit cost figures for the trolley pump compare well with using direct labor with buckets, and not too badly with the motorised pump, when one considers the following:

• streams and dams may not have enough capacity to utilise a pump passing 4 litres per second
• a quoted operational lifetime of 2,500 hours may be wildly optimistic under prevailing conditions of maintenance and repair
• in most 3^rd world countries, the import content of the motorised pump would be much higher than the trolley pump – and the use of shadow price factors for imports would greatly decrease the unit cost advantage of the motorised pump
• applying an interest rate of 5% through 50% per annum would also greatly change the numbers on trolley pump vs. Motorised pump

Finally, the average value of horticultural produce from a 0.25 hectare plot, asuming yields of 10 tonnes/hectare per 120 day growing season and a saleable crop value of US$ 0.75 per kg will be US$ 1750 per season. That compares well with the pump + piping cost of US$ 332 and a pump operator labour cost of well under US$ 480 per season.

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

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

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

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