Efficiency and Ergonomic Benefits of Using Radio Controlled Chokers in Cable Yarding
نویسندگان
چکیده
Nacrtak Chokers are wire rope slings used to secure the felled trees to the rigging during cable yarder extracting. Standard chokers are set manually by the choker-setters along the corridor, and then unhooked manually by the yarder operator at the landing. Radio-controlled chokers are also set manually but have the advantage that they can be released remotely at the landing. In addition to possible safety improvement at the landing, the advantage is that it reduces the unhook phase of the operation and thereby potentially improve productivity. However, the additional weight of the radio controlled chokers may also increase the work load of the choker-setters on the slope. A standard manual choker bell weighs 0.34 kg, whereas the radio-controlled choker bell weighs 1.6 kg. To assess the possible efficiency and ergonomic benefits of radio-controlled chokers a study was carried out on a Wanderfalke yarder. The study site was in the eastern Austrian Alps, working in Norway Spruce with a piece size ranging from 0.4 to 0.86 m3, on slopes between 50 and 60%, and in corridors of 90 to 200 m long. It included both a time and motion study in a full factorial layout as well as measuring the choker-setter workload through continuous monitoring of the heart-rate. Results showed that there was a 9% productivity gain using the radio-controlled chokers at the average piece size. However the workload of the choker-setter also increased; the percent heart rate reserve, a measurement of worker strain, increased from 40 to 44%. So although this study showed that productivity improvements are possible with radio-controlled chokers, it was at the expense of increased worked load of the choker-setter.
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