Abstract
Hand-arm transmitted vibration originating from a 15 horsepower single-axle tractor can be very strong and cause operator fatigue plus various physiological disorders in vascular, neurological, and musculoskeletal systems. The objective of this work was to measure the characteristics of such hand-transmitted vibrations and its effect on the health of the single-axle tractor operator, in a research program conducted at the Melkasa Agricultural Research Center of Ethiopia. During the study, the measurement of anthropometric data and the heart rate of the operators and vibration at the handle of single axle tractor were conducted. From measured data, the requirement of expenditure energy, physical workload, and operators’ daily vibration exposure was calculated. The average measured resting heart rate, working heart rate and heart rate after the operation was 71i‚±7, 162i‚±4 and 126i‚±24 beats/min, respectively. The calculated values of HR reserve (%HRR) or physiological workload and the ratio of working to resting heart rate were 74i‚±10% and 2.3i‚±0.4 (p < 0.0001), respectively. The total energy expenditure of single-axle tractor operators was calculated to be 35i‚±1.2 kJ/min. The daily exposure m/s2A (8) and total exposure points which were calculated indirectly from measured vibrations at the tractor handle and duration of operation were 12.6 m/s2 and 2520 points, respectively. From measurements of operators’ heart rates, it was concluded that the physical workload fell into the category of extremely heavy work, for which the working heart rate more than doubled the resting heart rate (p < 0.0001). Key words: Tractor vibration, hand-transmitted vibration, single-axle tractor, heart rate, physical workload, vibration exposure.
Highlights
IntroductionThe percentage of a country‟s population employed in agriculture has a tendency to decrease with the advancement of national economic development, due to the increase in secondary and tertiary industries
The evaluation of vibration characteristics of hand-arm transmitted vibration originating from a single-axle tractor was conducted at the Melkasa Agricultural Research Center (MARC), located at 117 km East of Addis Ababa
The 3-axis piezoelectric accelerometer vibration sensor was attached at the handle of the single-axle tractor, adjacent to the hand of the operator
Summary
The percentage of a country‟s population employed in agriculture has a tendency to decrease with the advancement of national economic development, due to the increase in secondary and tertiary industries. This progression is supported by increased utilization of large, medium- and small-scale farm machinery that promotes increased agricultural productivity (Sakai, 1990). Single-axle tractors are very important for small-scale farmers in the drive to shift from animalpowered farming to engine-powered farming systems. Whole-body vibration occurs when the human body is supported on a surface which is vibrating, e.g. in most forms of transport and in close proximity to some types of industrial machinery. The human response to vibration depends mainly on the magnitude, frequency, and direction of the vibration signal (Griffin, 1990)
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