DEVELOPMENT OF EVALUATION PROCEDURE FOR IMPROVING PERFORMANCE OF IRRIGATION PUMPING PLANTS FOR SMALL HOLDER FARMS

Abstract

This study was conducted on centrifugal pump-irrigated small private farms in Hasahiesa locality which distributed around the West Bank of the Blue Nile. The ultimate objectives of the study were to evaluate the performance of pumping plants of these farms in terms of pump efficiency, pump adequacy, overall efficiency and the net positive suction head available by each system besides comparing the actual operating conditions of the pumps in particular and the pumping plants in general with the equivalent rated and recommended ones. In addition to development of a computer model to link between the different input and output parameters and hence achieving the calculations associated with such evaluation process besides forming a comprehensive picture of performance that enables the evaluator predicting the effects of the changes in the pumping conditions. The pumping plants were provided with pumps completely of Indian make, powered either by electric motors or diesel-fueled engines and draw water either from the river or shallow wells. These pumping plants were using to irrigate farms with areas ranging between 2 feddans and 40 feddans. 36 units were randomly selected as a sample survey to represent the total population of 806 pumping plants during the growing season 2006-2007. The study relied upon primary data collected via observation and questionnaire besides direct measurements. Then the subsequent relevant calculations were conducted to obtain the ultimate evaluation parameters mentioned above. In addition, a statistical analysis was made upon the obtained data using the SPSS technique. And hence, the results were explained and justified and the impact of the factors affect them were studied. The studied pumps were classified into seven categories according to their mark as follows; Saraf, Cuma, Lusab, Marshal, Atlas, Alfa and Anil. The main actual characteristics of each of these types which included; discharge, total dynamic head, pump speed, No. of v-belts and efficiency were measured and / or calculated and statistically analyzed using t-test to compare them with rated equivalent ones recommended by their manufacturers. Finally, the pumping plants actual operating conditions were measured and / or recorded and / or calculated. These included; the power of the used mover, the net positive suction head imposed by the system, suction XVII pipe size and the overall efficiency. These factors were statistically analyzed using t-test to compare them with the rated equivalent ones recommended by their manufacturers and / or scientifically approved. The analysis results indicated that the pumps were operating at efficiencies ranging between a minimum of 5 % and maximum of 59 %. These values were significantly lower than the approximated value of 50 % considered by Israelsen and Hansen (1962) as average centrifugal pump efficiency. Likewise, they were significantly lower than the rated values. In fact these low values of efficiency were statistically analyzed with the factors that affecting them using t-test and correlation coefficient to show if there is a significant effect for each one individually. As for pump adequacy, there was no significant difference between the actual discharge of these pumps per unit time per unit area and the water need required by the farms they irrigated whereas the potential (rated) capacities of these pumps were found to be significantly higher than the crop water requirements of these farms. Regarding the overall efficiency, the results indicated that the studied pumping plants were operating with overall efficiencies ranging between minimum of 2 % and maximum of 48 %. In fact these values of overall efficiency were statistically analyzed with the factors that affecting them using t-test and correlation coefficient to see if there is a significant effect and / or difference for each one individually. Concerning the NPSHa, the results also revealed that the net positive suction head available by the studied pumping plants were ranging between a minimum of 1.02 m and maximum of 7.08 m. In fact these values of NPSHa were statistically analyzed with the factors that affecting them using t-test and correlation coefficient to see if there is a significant effect for each one. With regard to comparing the actual pump parameters to their equivalent rated ones, the results indicated that all the five actual parameters for the all seven types were found to be significantly lower than the equivalent rated ones except the pump speed parameter where there was no significant difference. As for comparing the pumping plants actual operating conditions with the rated equivalent ones, the results indicated that the values of power of the movers were significantly greater than the values of power required by the pumps they drive. In addition to that, the results also indicated that about 41.7 % of the studied plants have values of NPSHa significantly greater than the values of NPSHr and about 58.3 % have values with no significant XVIII difference. Concerning the suction pipe sizing, the results showed that there was no significant difference between the actual values and the recommended equivalent value (pump intake nozzle size). With regard to the overall efficiency, the results indicate that about 66.67 % of the studied pumping plants were found to be operating with overall efficiency significantly lower than the rated theoretical equivalent values. Regarding the program application, the input data collected from the field was applied to the pumping plant evaluation program the results were found to be extremely close to those manually calculated. Concerning the program verification, the published relevant data of pump efficiency were inadequate. However, these limited data available by the previous similar studies were partially applied and treated by the program. The results reveal that there were significant differences in the model values of pump efficiency and the crosseponding values reached by the former researchers. Such differences were justified. Moreover, the only available data concerning the calculation of overall efficiency was also inadequate but when the program input and output data applied to the formula used by the former researcher, the results were approximately closer to those obtained by the program. Regarding the NPSHa, there were no available data. The sensitivity tests revealed that the program could be used as an effective tool of predicting of the effect of the usually possible changes in the program inputs on the program main output parameters.