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Wood obtained from freshly cut trees has a high moisture content and therefore its mass per volume unit is higher than the mass of dry wood. The natural drying is a simple and effective method of weight (moisture content) reduction, making a better use of the vehicle's payload, and thus reducing costs, including environmental costs. The conclusion is based on simulations and analyzes attempting to evaluate different solutions. As evidenced, the drying process of logs depends on numerous factors, which entails attempts at development of an optimal logging method, especially concerning energy wood, allowing for maximum value growth in as little time as possible. The suggestions cover various forms of logging (of whole trees, long timber), arranging (in piles, bundles), storing (in stands, by the roadside near cutting areas), and protection. Combined methods such as storing under canvas for winter only or storing in cutting areas and later in piles at the exit road also work in practice, but require more funds because their cost is determined by the number of stages composing the whole process. In case of wood, development of an optimal and simultaneously universal method used to prepare the lumber for transport and its delivery with consideration of as little environmental impact as possible is complicated. The numerous variables, some of which cannot be controlled or affected, create a considerable scientific problem as well. The authors covered in the presented literature review often stress the role of specific weather conditions accompanying an experiment or its location, the storage method, or lumber dimensions in the drying process. Storage time is perceived as equally important, but it is a derivative more or less determined by the previous variables. Previous studies of drying at the cutting area have been focused mainly on energy wood and less on industrial wood. They analysed the results of long−term storage and did not stress the potential advantages of short−term drying. Furthermore, we do not have sufficient information on species, including forest trees, which have a lower share in the volume of the logged wood. Advanced research can help establish the minimum mass (moisture content) with considerable impact on supply chain effectiveness improvement or evaluated various storing and drying methods. We reviewed reports explaining the impact of various factors on natural drying of wood, models and storage effects, and analyzing potential economic and environmental benefits.
The aim of this study was to measure the weight of timber obtained from freshly cut trees and compare it with the applicable legal provisions pertaining the capability of transporting heavy loads by hand and also to indicate a problem significant for the occupational safety and health protection of employees working at wood harvesting. In Poland, about 40 million m³ of timber is harvested annually. The logs, with small diameter and length, are prepared for forwarding by arranging them by employees in the so called ‘packages’, which are placed by the route of the machine that collects and transports them to the logging road. Manhandling of the logs is an activity requiring the greatest energy expenditure (over 30 kJ/min) in the process of tree harvesting. Furthermore, it is also one of the key factors, which may lead to the development of musculoskeletal disorders. Regulations existing in the Polish labour law regulate the permitted weight of transported loads depending on the activity duration. For loads transported single−handedly this is 30 kg for a permanent employer, whereas 50 kg for workers doing the job occasionally or temporarily (no more than 4 times per hour and no longer than 4 hours during workday). Logs heavier than 50 kg may be carried only collectively providing the requirements of the minimal length (0,75 m) of the log per one person are met. We produced 2,5 m long logs and weighted them with an accuracy of 0,1 kg. The analysis revealed that approximately 30% of logs weighed between 30 and 50 kg, which introduces limitations in the number of carried logs per one person within a single shift. However, about 10% of the pine, 15% of spruce, 12% of beech and 38% of birch logs were heavier than 50 kg which should prevent carrying them single−handedly. Unfortunately, collective preparation of timber for forwarding is not popular among workers due to reduction in output, and at the same time the lower salary. Even if log for forwarding is prepared by two labourers, they most often work separately. As a result, the limits of the weight carried single-handedly by labourer are notoriously violated and exceeded.
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