Productivity analysis and costs of wheel cable skidder during salvage logging in European beech stand

Salvage logging is increasing in Central Europe because of the growth of severe meteorological events, and timber harvesting in these conditions is challenging in terms of both productivity performances and safety of the operations. In recent years, with the increase of natural calamities, several researchers studied machinery productivity performances regarding salvage logging carried out by ground-based systems. In fact, a common post-disturbance management approach is salvage logging which consists of the widespread removal of damaged trees. In this research, system productivity and the cost of salvage logging are analysed in European beech stands affected by wet snow. The accretion of heavy wet snow poses the greatest risk to forests in the Northern Hemisphere. This type of snow attaches more effectively to tree crowns and branches when temperatures are close to freezing at the time of precipitation. As a result, trees may break or bend and may be uprooted when the soil is unfrozen. This study has been implemented to evaluate the productivity and cost-effectiveness of extraction in salvage logging deployed with a skidder in beech stands affected by two different types of wet snow damage. The results show that the productivity of the four-wheel-drive cable skidder, despite operating in salvage cutting with a removal intensity of 10%, is 14.73 m3·SMH–1, similar to skidder performances in ‘ordinary’ cuttings. Skidder’s productive time was 86% of the scheduled time, whereas the delays were due to organisational reasons, mechanical delays, and adverse weather conditions. The mean travel speed of the cable skidder obtained in this study is close to the results obtained from other studies on similar machines. The costs per unit are lower than effective cost consumptions for the other cable skidders and agricultural tractors, adapted for skidding operated in hardwood salvage logging. Therefore, under the given conditions, the operation of the fourwheel-drive cable skidder is viable from a silvicultural, technical, and economic point of view in the salvage operation logging

Improvement of wheel skidder tractive performance by tire inflation pressure and tire chains

The motion resistance ratio, gross traction ratio and net traction ratio of a wheel cable skidder were determined and mathematical models derived for three tire inflation pressure values with or without tire chains on forest road in mountainous conditions. The motion resistance ratio increases with the increase of tire inflation pressure. On the contrary, the gross traction ratio increases with the decrease of tire inflation pressure. However, when the tires are equipped with tire chains the skidder motion resistance is higher. The motion resistance ratio with tire chains also increases with the decrease of tire inflation pressure due to windage between the tires and chains, which results in lower tractive performance of tire chains. Therefore, by using tire chains, an increase of gross tractive ratio could be achieved, as well as the increase of motion resistance ratio compared to tires without chains. The results of the study show that it is strongly recommended to use tire chains as tightly as possible

Improvement of wheel skidder tractive performance by tire inflation pressure and tire chains

The motion resistance ratio, gross traction ratio and net traction ratio of a wheel cable skidder were determined and mathematical models derived for three tire inflation pressure values with or without tire chains on forest road in mountainous conditions. The motion resistance ratio increases with the increase of tire inflation pressure. On the contrary, the gross traction ratio increases with the decrease of tire inflation pressure. However, when the tires are equipped with tire chains the skidder motion resistance is higher. The motion resistance ratio with tire chains also increases with the decrease of tire inflation pressure due to windage between the tires and chains, which results in lower tractive performance of tire chains. Therefore, by using tire chains, an increase of gross tractive ratio could be achieved, as well as the increase of motion resistance ratio compared to tires without chains. The results of the study show that it is strongly recommended to use tire chains as tightly as possible

Improvement of wheel skidder tractive performance by tire inflation pressure and tire chains

The motion resistance ratio, gross traction ratio and net traction ratio of a wheel cable skidder were determined and mathematical models derived for three tire inflation pressure values with or without tire chains on forest road in mountainous conditions. The motion resistance ratio increases with the increase of tire inflation pressure. On the contrary, the gross traction ratio increases with the decrease of tire inflation pressure. However, when the tires are equipped with tire chains the skidder motion resistance is higher. The motion resistance ratio with tire chains also increases with the decrease of tire inflation pressure due to windage between the tires and chains, which results in lower tractive performance of tire chains. Therefore, by using tire chains, an increase of gross tractive ratio could be achieved, as well as the increase of motion resistance ratio compared to tires without chains. The results of the study show that it is strongly recommended to use tire chains as tightly as possible

Evaluation of Salvage Logging Productivity and Costs in the Sensitive Forests of Bulgaria

Steep terrain harvesting can only be implemented by a limited set of operational alternatives; therefore, it is important to be efficient in such conditions, in order to avoid incurring high costs. Harvesting abiotically-disturbed forests (salvage harvests caused by wet snow), which is becoming common these days, can significantly impact the operational efficiency of extraction operations. This study was implemented in order to evaluate the performance of truck-mounted uphill cable yarding operations in salvage logging deployed in coniferous stands. A time study was used to estimate the productivity and yarding costs, and predictive models were developed in order to relate the time consumption and productivity to the relevant operational factors, including the degree of wood damage. The average operational conditions were characterized by an extraction distance of 101 m and a lateral yarding distance of 18 m, resulting in a productivity rate of 20.1 m3 h−1. In response to different kind of delays, the productivity rate decreased to 12.8 m3 h−1. Under the prevailing conditions, lateral yarding accounted for 32% of the gross work cycle time, and for 50% of the delay-free work cycle time of the machine. Decreasing the lateral yarding distance and increasing the payload volume to the maximum capacity of the machine would eventually lead to a yarding productivity of close to 30 m3 per SMH (scheduled machine hour). The calculation of the gross costs of uphill yarding showed that the labor costs (35.7%) were slightly higher than the fixed costs (32.9%), and twice as high compared to the variable costs (17.7%). The remote control of the carriage, mechanical slack-pulling mechanisms, and radio-controlled chokers are just some of the improvements that would have led to increments in operational efficiency

Work accidents during cable yarding operations in Central Europe 2006 – 2014

Aim of study: This study is focused on detailed analysis of accidents in yarding during the years 2006–2014. There is still not enough information about such accidents in Central Europe in the literature available.Area of study: We collected the data on occupational accidents recorded in timber yarding from the databases of the Slovak state forest enterprise. Material and Methods: The data on occupational accidents were recorded according to actual European Regulation, the form of the record meets the requirements of the ESAW (European Statistics on Accidents at Work) methodology. To analyze the data, we used the multiple regression and correlation analysis, contingency tables, and a χ2 –test.Main results: Almost half of the accidents were the foot injuries and the most frequent type of injury was fracture of a bone. The most hazardous operation was yarding. Most of the accidents occurred between 1301-1400 h (22 %). The most frequent agent causing accidents were Particles, dust, splinters, fragments, etc. (14.05 by ESAW). Research highlights: This study informs about the most important risk factors in timber yarding, the most hazardous parts of shift, as well as the days when the most accidents occur during the week, and as such contributes to better understanding of how the accidents happen in timber yarding. The information can be subsequently used in knowledge-based improvement of safety trainings in forest enterprises

Modeling Productivity and Estimating Costs of Processor Tower Yarder in Shelterwood Cutting of Pine Stand

Cable-based yarding technology has had a long tradition on steep slopes in Europe, and the new implementation of yarding functions in recent decades favored operational efficiency and lower extraction costs. The main goal of this study was to evaluate the performance of the Syncrofalke 3t truck-mounted Processor Tower Yarder (PTY) on steep terrain, in coniferous forests managed with the shelterwood system. In particular, the aim was to determine PTY productivity and costs, with attention to parameters that could increase PTY effectiveness. The study was carried out in the Sredna Gora Mountains, Central Bulgaria, in pure Scots pine stand, with trees of average DBH = 34 cm and height = 22 m. The study was carried out in six corridors with 120 work cycles of tree extraction up the hill, 28° (53%). The mean productivity of PTY was 15.20 m3 per productive machine hour (PMH) and 12.29 m3 per scheduled machine hour (SMH) and was mainly influenced by the productivity of the yarder unit. Under the given conditions, the performance of PTY significantly increased if more than one tree (at least two trees) were attached and extracted per yarder cycle, since the productivity of the processor was approximately twice that of the yarder. The gross costs of the studied PTY were calculated at 297.48 EUR PMH−1 and 16.17 EUR m−3. The variable costs (75%) predominate in the net costs distribution, followed by the fixed costs (15%) and the labor costs (10%). The time, productivity and cost results obtained showed the high efficiency and level of integration of PTY operations in order to achieve economic efficiency of logging in montane pine forest managed in a shelterwood system