Comparative study on technical and ergonomic performance of lever-operated knapsack sprayers

Farming in tropical countries is labor intensive. Even with the introduction of modern equipment, a significant degree of strenuous labor is always involved with the bulk of work required for farming. Farmers believe that intensive labor is an unavoidable part of farm work. It is for this reason that researchers in the field of ergonomics are trying to find ways by which farm work can be made more comfortable, more productive and safer through simple and practical solutions. Cop spraying is an important part of modern farming. The spraying equipment of used comfortably, efficiently and safely, injury is unlikely to occur. Thus, there must be a balance between ergonomic and technical considerations. This study was conducted to evaluate the technical and ergonomic performance of lever-operated knapsack sprayers. A survey was conducted to document the farmer-respondents utilization of spraying equipment. The sprayer that is widely used by the farmer-respondents, the Tung-Ho sprayer, was compared with the newly-introduced Chinese-made sprayer, the 3WBM-16 model. Recommendations were made to improve both the Tung-Ho and 3WBM-16 sprayers based on technical and ergonomic evaluation results. Results of the technical evaluation revealed that the Tung-Ho sprayer performed better than the 3WBM-16 sprayer in terms of spraying capacity, volumetric efficiency, pressure drop, spray distribution and field capacity and efficiency. The capacity of the 3WBM-16 and Tung-Ho sprayers as determined during a laboratory test was 0.37 ha/hr and 0.41 ha/hr, respectively. Moreover, their volumetric efficiency was respectively recorded at 68.16% and 73.12%. Their field capacity was 0.34 ha/hr and 0.46 ha/hr, and field efficiency was 72.18% and 80.27%, respectively. Ergonomic evaluation showed that the 3WBM-16 sprayer was more preferred by the operators. The us of this sprayer resulted to lesser physical discomfort except on the left arm and wrist. As the time of operation increased, the discomfort rating also increased. Physiological data showed no significant difference on sprayer type with regards to changes in blood pressure and heart rate while respiration rate and body temperature showed significant differences. Physiological responses of the operators were significantly affected by operating time. The causes of discomfort were the weight of the sprayers especially at full tank capacity, actuating the pump lever, long hours of spraying operation, and working condition. The modifications to be made to improve the Tung-Ho sprayer are: reduce the weight by replacing the stainless tank with plastic or by reducing the tank capacity by 4 liters, add rubber fittings on the lid cap thread to minimize spillage; increase lid and strainer diameter for easy refilling; add a waist strap for better support; improve the straps by putting a hook lock; and, pump lever handle be replaced with circular-shaped handle with a diameter ranging from 3.0 to 4.5 cm for better grip. To improve the 3WBM-16 sprayer, the following are recommended: lid cap must be tightened and fittings/connections be improved to avoid leak; the pump also leaks and must be sealed with a better gasket; plastic threads must be replaced with metal to minimize wearing; tank shape must be improved because curved tank is more preferred; nozzle must be replaced with better ones; waist strap must be added; space between straps be increased to at least 9.0 cm to 12.9 cm; lever handle length be increased to at least 9.5 cm for better grip; and, the lance and lever handle diameter be increased to 3.0 to 44.5 cm.