Ergonomic evaluation of manual coconut dehuskers

Abstract

The different models of coconut husking devices presently available have not been evaluated in the context of operator discomfort and ease of operation. The KAU coconut husking tool (Keramithra) is the most popular dehusker and it is the widely accepted one. In this study, two coconut husking devices were selected, viz., the Keramithra, and a variant of the design, available in the local market. Through this study, work load, energy cost and subjective rating aspects of the selected models of the coconut huskers could be assessed. Four male and four female subjects were selected for this study in the age group twenty five to thirty five years, medically fit and experienced in operating the manual coconut husking tools. The anthropometric dimensions of these subjects, particularly the functionally relevant components, with respect to operation of the coconut huskers, were measured with instruments such as Integrated Composite Anthropometer, electronic push pull dynamometer, back-legs-chest dynamometer, digital hand dynamometer, finger goniometer and grip diameter cone. The selected eight subjects were calibrated in the laboratory by indirect assessment of oxygen uptake. The relationship between the heart rate and oxygen consumption of the subjects was found to be linear for all the subjects. Then, energy cost of operation of the selected coconut de-husking devices were computed by multiplying the oxygen consumed by the subject during the trial period with the calorific value of oxygen as 20.88 kJlit -1 . Energy cost of operating model 1 was in the range of 18 kJmin -1 to 26 kJmin -1 while model 2 had a range of 15 kJmin -1 to 24 kJmin -1 . Energy cost is comparatively less for the locally available model as compared to that of the Keramithra, indicating that design modifications are required in Keramithra to reduce the energy cost. The overall discomfort rate was higher for model 1, for both male and female subjects, when compared to model 2. Provisions for adjustment of the height of the husker can be provided to reduce the energy expenditure for model 1. Energy cost of operation was higher for female subjects compared to males. This is due to the anthropometric, physiological and strength differences of females from males. The mean heart rate, during the operation of the coconut de-husker, for male subjects (177.5 beatsmin -1 ) was less than that of female subjects (179.25 beatsmin -1 ), while the aerobic capacity of male subjects (1.71 Lmin -1 ) was more than that of female subjects (1.76 Lmin -1 ). Acceptable workload for this operation was much higher than that of the AWL limits of 35 per cent, indicating that dehusking of coconut using these huskers could not be done continuously for 8 hours, without frequent rest-pauses. De-husking with model 2 was found to be easier than using model 1, as indicated from the overall ease of rate calculation. The subjects operating model 2 experience lesser discomfort on neck, shoulders, and low and mid back regions in comparison to model 1. In the case of discomfort in the operating arm, however, operators experience lesser discomfort while working with model 1. Through this study, it was found that model 2 was easier and more comfortable to the operators, due to its height. However, the lower discomfort in operating arm, which indicates a lesser strain and hence a possibly longer duration of operation, while using the model 1, show that model 1 would reduce discomfort when its design is modified, with provisions for an adjustment of height of tool. Studies on force analysis may be conducted to optimise the shape of blades and hence reduce the force required for husking operation.