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This study was conducted using both field experiments and structured questionnaires to investigate the influence of hand transmitted mechanical vibrations and shocks experienced by operators from handles of a single-axle tractor and determine an optimum operator‟s daily exposure limits in field conditions. The field experiments were conducted at Kilimanjaro Agricultural Training Centre (KATC). Four different makes of single-axle tractors were studied, namely: AMEC S 1100A2 (distributed by District Councils), GREAVES GS-15 DIL (supplied by SUMAJKT), KUBOTA K120 and YANMAR TF110ML (supplied by MAFC to Training Institutes) and five experienced single-axle tractor operators were chosen for the field experiments.
The results show that the magnitude of vibration during tillage operation varies between 6.481 m/s2 at 1.54 km/hr to 7.834 m/s2 at 4.51 km/hr for AMEC; 7.908 m/s2 at 1.95 km/hr to 8.442 m/s2 at 5.70 km/hr for GREAVES; 5.350 m/s2 at 1.11 km/hr to 7.856 m/s2 at 2.92 km/hr for KUBOTA; and 6.012 m/s2 at 1.04 km/hr to 10.263 m/s2 at 7.14 km/hr for YANMAR. The magnitude of vibration during rota-puddling operation varies between 5.817 m/s2 at 1.54 km/hr to 6.330 m/s2 at 4.51 km/hr for AMEC; 6.033 m/s2 at 1.95 km/hr to 7.739 m/s2 at 5.70 km/hr for GREAVES; 4.250 m/s2 at 1.11 km/hr to 4.445 m/s2 at 2.92 km/hr for KUBOTA and 5.271 m/s2 at 1.04 km/hr to 5.606 m/s2 at 2.14 km/hr for YANMAR. The magnitude of vibration during transportation operation varies between 10.067 m/s2 at 1.95 km/hr to 10.234 m/s2 at 5.70 km/hr for GREAVES; 6.01
m/s2 at 1.11 km/hr to 6.871 m/s2 at 2.92 km/hr for KUBOTA and 5.622 m/s2 at 1.04 km/hr to 6.903 m/s2 at 2.14 km/hr for YANMAR.
The results further show that, the vibration acceleration total values (ahv) in three operational modes exceed both suggested Exposure Action Value (EAV) and Exposure Limit Value (ELV). The expectation for 10% operators to show symptoms of vibration-induced disorders for single-axle tractor operators working at full load for 8-hours per day in three operational modes are shown as 3 to 4 years for GREAVES operators, 4 to 5 years for AMEC and YANMAR operators and 5 to 7 years for KUBOTA operators.
Structured questionnaires were administered to operators in two irrigation schemes; Lower Moshi in Kilimanjaro Region and Leki Tatu in Arusha Region. During field survey, single-axle tractor operators agree on the physiological or psychological fatigue experienced during operations. The fatigue was due to lack of proper training and skills on the required degree of interface between human-machine systems (coupling); exposure to extreme solar radiation; exposure to high magnitude of vibration through handles; use of extra energy to control the tractor and manoeuvre at headlands. The study results shows the presence of symptoms of vibration-induced disorders in its preliminary stages that if not diagnosed and attended in time, may develop to disorders that may result to impairment of life quality and disability of the affected operator. Therefore, the study demonstrates the susceptibility of operators to the effects of HAVS. The study recommends that further studies are required to be carried out to characterize vibration magnitude of single-axle tractors used in Tanzania so that best practice and guidelines can be established. |
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