Levels of Vibration Exposure In Cross-Cutting Operations By Chainsaw: Are They Affected By A Wrong Height of Chain Depth Gauge?

Despite the introduction of high mechanization levels in forest operations, the use of chainsaws is still very common in many countries and many other activities, such as pruning operation, gardening and agriculture are performed using this tool, which is very dangerous. Indeed, chainsaw use exposes workers to many hazards such as noise, exhaust fumes, hand-arm vibrations (HAV), wood dust, cutting wounds, and workload. This research is focused on the vibration exposure and how it is influenced by the quality and efficiency in saw chain maintenance. In fact, while its sharpening must be performed according to the manufacturer instructions, in working conditions it is very common to find important errors in terms of sharpening angle and lowering the depth gauge. These problems could have negative consequences on cutting efficiency and chainsaw lifespan. But the most important, considering workers’ safety, an excessive lowering of the depth gauge often causes a considerable increase in vibration exposure and an increased probability of kickback. Despite the safety recommendations and the increasing efforts to improve the professional level of forest workers, many of them continue operating the bad habit to lower the depth gauge of the chains under the manufacturer recommended level. Why they apply this wrong strategy? Because they are certain to obtain a higher cutting efficiency in this way, not considering the cons of this bad behaviour. For this reason, the aim of this study is to evaluate, during operations with chainsaw, the variations of both the vibrations transmitted to the operator and the cutting efficiency at different levels of depth gauge lowering (correct and excessive levels). The study was performed on European beech and Silver fir squared beams during cross-cutting operations using the same chain type (cutting teeth profile) modified at 3 different level of the depth gauge (0.65 - 1.0 - 1.3 mm). Results showed that for both species the vibration exposure increase was higher moving from 0.65 mm to 1 mm in comparison to the variation recorded moving from 1 to 1.3 mm. This increase was higher in beech than in fir, confirming the higher the basal density of wood, the higher the effects of bad habits in lowering the depth gauge. The measured daily exposures resulted significantly higher than the limits established by Italian Regulation (limit of 5 m/s2 and the daily action value of 2.5 m/s2) when the depth gauge lowering exceed the recommended level of 0.65 mm. On the contrary, applying the recommended level the exposure to vibrations resulted within the law limits for both the wood species considered. Looking at the cutting efficiency, it increased on fir only moving from 0.65 mm 1 mm, while between 1 mm and 1.3 mm no significant improvements were recorded.