Productivity and Time Consumption of Timber Extraction with a Grapple Skidder in Selected Pine Stands

This paper presents the results of the study on work time and productivity of the John Deere 548G-III grapple skidder operating in pine stands on flat terrain. The research covered three types of treatment: late thinning, removal cutting in openings and clear cutting in openings. The average skidding distance was between 120 and 250 m. In the clear-cut stands, a mean duration of a skidding cycle accounted for 12 minutes, while in the thinned ones it was longer, lasting ca. 16 minutes. The investigators performed an estimate of parameters of multiple regression models, which revealed dependences between: Þ duration of skidding cycles and stand conditions, number of logs per load and skidding distance, and Þ productivity achieved in specific skidding cycles and the above-mentioned variables, as well as wood volume per load. The highest productivity within the productive work time of a skidder was recorded in the stand where removal cutting in openings was performed; it exceeded 14 m3×h-1. In other stands, the efficiency was lower, not greater than 9 m3×h-1. However, differences between the productivity achieved within the productive work time and that recorded for the work place time did not exceed 20%, which indicated that skidding operations in the stands under scrutiny were organised properly

Productivity and Working Time Structure of Timber Forwarding in Flatland Thinned Pine Stand with the Use of Farm Tractors

Farm tractors are very popular in Poland and other European countries. When coupled with trailers equipped with a crane with a grapple, they are also used, especially in easily accessible, flat terrain, for timber forwarding in the CTL (Cut-to-Length) method. A comparative analysis of working time and productivity was performed on two forwarding units, consisting of a farm tractor Ursus and a Farma trailer with the load capacity of 6 tons, as well as a farm tractor Valtra Valmet and a Palms trailer with the capacity of 9 tons, which forwarded wood in a mature pine stand. An analysis was done for 64 work cycles with an average load volume of 2.1 m3 for the former unit, and 36 cycles with an average load volume of 7.9 m3 for the latter. The working time structure of both units was similar. During work, tractor operators spent most time, i.e. over 35%, loading the timber, then travelling with the load and unloading. The lowest share in the work cycle, around 5%, belonged to travelling without a load and forwarding. The average forwarding time for the Farma unit amounted to 33 minutes and was about twice shorter than that for the Palms unit, amounting to 64 minutes. The distance covered during loaded travel was the only factor that had a significant influence on the duration of forwarding cycles. The coefficients of correlation between these variables were 0.56–0.76. The net productivity obtained in the operating time of the Palms unit was 7.5 m3×PMH-1 and was almost twice as high as that of the Farma unit, i.e. 3.8 m3×PMH-1. For both units multiple regression models were developed, in which forwarding cycles productivity is calculated based on the volume of the transported load and the distance of loaded travel

Analysis of Accuracy of Evaluating the Structure of a Harvester Operator’s Workday by Work Sampling

The study covered an analysis of the accuracy level of measuring time within a working shift using the method of regular snapshot observation at a harvester operator’s worksite in Scots pine stands. A conformance level of the analyzed methods was evaluated through assessing the accuracy of rectilinear fitting of time structures, established using the photography of work day method and snapshot observations. The accuracy of snapshot measurements performed in 3-minute intervals was determined as high, exceeding 95%. Increasing the time interval between observations to 10 or 15 minutes resulted in higher estimation error in snapshot observation time, ranging between 5 and 10% for late thinned and clear-cut stands. The accuracy of evaluating proportions of specific work times within a working shift, in regular snapshot observations, was correlated with work cyclicality. The strongest work cycle in thinned stands consisted of 43 activities, with total duration of 13 minutes, whereas in clearcut stands it comprised 45 activities, with total duration of 15 minutes. One of the advantages of the described method, apart from its lower labour intensity as compared to working day photography, was the possibility to assess labour time and breaks as well as estimate the share of downtime

Workload analysis in logging technology employing a processor aggregated with a farm tractor

Aim of study: The aim of this research was to analyze the workload of the operators while logging at the motor-manual level in coniferous stands undergoing two tending treatments (early and late thinning). The technologies under the investigation employed a power chainsaw, tractor equipped with a cable winch as well as delimbing and cross-cutting Hypro 450W processor.Area of study, materials and methods: The research areas were located in lowlands and in a mountain range of the Western Carpathians. In the analysis it was assumed that the heart rate at work, expressed in beats per minute, would be an indicator of the workload affecting the human organism. Based on the heart rate, three indicators were calculated: relative heart rate at work (%HRR), 50% level of heart rate reserve, ratio of working heart rate to resting heart rate.Main results: The lowest average workload (typical for light work, %HRR40%) was for the chainsaw operator in early thinning, working with a processor. Cumulative distribution function of the workload at the work station of the skidder operator was characterized by bimodality – an occurrence of two extreme, high and low, workload values.Research highlights: The workload in early thinning was higher by about 7% than in late thinning at the work station of both, the processor operator as well as the chainsaw operator working with a processor.Keywords: logging; tractor processor; heart rate; workload; cardiovascular strain.

Efficiency of timber harvesting using harvester in thinned young pine stands as a function of working technique

In Poland, more and more timber is harvested with the use of harvesters of different types. These machines can also be used in cooperation with chainsaw operators, e.g. in stands damaged by violent winds, in the removal of windthrows, or in stands of younger age classes in the technological variant with the so-called „midfield”. The aim of the study was to characterise the working time structure and to estimate the efficiency of timber harvesting with a harvester in two technological variants. In the first variant, the felling of trees was carried out by a chainsaw operator and the processing was performed by a harvester operator. In the second variant all operations were carried out by a harvester operator. In both variants, the machine worked on the skid trails, but in the second variant, the operator descended from the skid trails a short distance into the stand. Harvesting was conducted in two pine stands that were approximately the same age and differed in site conditions. The structure of the harvester operator's work time was clearly dominated by the moving of felled trees to the skid trails in both variants. Of all the activities studied, the observed differences between their durations in both variants were insignificant only in the case of delimbing and bucking (processing). In the case of cooperation between harvester operator and chainsaw operator, a higher work efficiency was achieved than in the case of timber harvesting with a harvester alone. At the same time, significantly lower work time consumption was observed. However, when considering the efficiency of the entire technologies, thinning with two workers was 30-60% more time consuming. Significant relationships were found between the amount of merchantable timber of harvested trees and the efficiency of the harvester operator

Estimation of Productivity and Costs of Using a Track Mini-Harvester with a Stroke Head for the First Commercial Thinning of a Scots Pine Stand

The aim of the present work was to estimate the productivity and costs of timber harvesting and forwarding during the first commercial thinning of a Scots pine stand. Three harvesting models were introduced and compared: narrow trail, wide access trail, and schematic extraction. The analyzed harvesting equipment consisted of a track mini-excavator (34 kW) with a stroke harvester head (gripping range 4–30 cm), and a farm tractor coupled to a logging trailer with a hydraulic crane. Merchantable timber (roundwood with a minimum diameter of 5 cm inside bark) was harvested from a 25-year-old planted Scots pine stand growing on a grid of 1.4 m × 1.8 m. The study showed the productivity of the mini-harvester ranged from 3.09 to 3.47 m3/PMH15 (productive machine hours plus 15 min), and that of the forwarding equipment to be 4.07 m3/PMH15. The analyzed model of productivity as a function of tree volume and thinning intensity was statistically significant, but the intensity parameter was significant only on plots located along wide access trails (3.7 m) and insignificant on plots located along narrow access trails (2.5 m). The distance between trees was not found to be significant. The calculated net machine costs for the forwarding equipment and track mini-harvester were EUR 36.12 and 52.47 per PMH, respectively. An increase in the usage rate of the harvesting equipment to 80% would reduce the harvesting and forwarding costs to EUR 22.07/m3

Effectiveness and Injury Risk during Timber Forwarding with a Quad Bike in Early Thinning

Within the majority of forest areas where timber is harvested for industrial and energy purposes, working technologies using highly efficient multi-operational machinery and equipment are employed. The situation is different in fragmented, privately owned forests. In such forests, timber harvesting is mainly based on motor-manual technologies with a high proportion of manual labor, both at the stage of felling and timber processing and at the stage of its transport. The study aimed to characterize the work time structure of the ATV unit driver and his helper, to determine the productivity of this team, and to estimate the risk of injury during manual loading and unloading. Based on the data collected during the field research, the theoretical work time structure, work productivity and costs, and injury risk were estimated as a result of using a professional small trailer equipped with a hydraulic crane for timber forwarding, designed for aggregation with the ATV. The average, calculated productivity of timber forwarding (over an average distance of about 500 m) with manual loading and unloading was almost twice as low as the estimated average productivity of forwarding with mechanical loading and unloading using a hydraulic crane. The total unit costs (including labor costs) of forwarding with manual loading and unloading were almost threefold higher than those of forwarding using a trailer with a hydraulic crane. The use of small forest trailers equipped with a hydraulic crane not only ensures higher productivity and cost effectiveness but also allows reducing (even by several percent) the inconvenience of manual timber handling and the risk of strain of the musculoskeletal system

Effectiveness and Injury Risk during Timber Forwarding with a Quad Bike in Early Thinning

Within the majority of forest areas where timber is harvested for industrial and energy purposes, working technologies using highly efficient multi-operational machinery and equipment are employed. The situation is different in fragmented, privately owned forests. In such forests, timber harvesting is mainly based on motor-manual technologies with a high proportion of manual labor, both at the stage of felling and timber processing and at the stage of its transport. The study aimed to characterize the work time structure of the ATV unit driver and his helper, to determine the productivity of this team, and to estimate the risk of injury during manual loading and unloading. Based on the data collected during the field research, the theoretical work time structure, work productivity and costs, and injury risk were estimated as a result of using a professional small trailer equipped with a hydraulic crane for timber forwarding, designed for aggregation with the ATV. The average, calculated productivity of timber forwarding (over an average distance of about 500 m) with manual loading and unloading was almost twice as low as the estimated average productivity of forwarding with mechanical loading and unloading using a hydraulic crane. The total unit costs (including labor costs) of forwarding with manual loading and unloading were almost threefold higher than those of forwarding using a trailer with a hydraulic crane. The use of small forest trailers equipped with a hydraulic crane not only ensures higher productivity and cost effectiveness but also allows reducing (even by several percent) the inconvenience of manual timber handling and the risk of strain of the musculoskeletal system