Principle of comparative time studies in mechanized forest work

Firewood, which is mainly processed by the consumer, is still an important source of energy for heating houses in industrialised countries. Possibilities to compare the mechanization's impact on efficiency of firewood processing are limited, due to variations between working conditions in previous studies. Therefore, the objective was to compare time consumption for two small-scale firewood processing systems with different levels of mechanisation under identical conditions. The systems were tested on two classes of wood: one with a homogeneous and medium-sized diameter of logs and one with a mixture of small and largediameter-logs. Differences in time consumption were analysed for correlations with physical workloads, deviations to routine operations, operator influences and operator perceptions. Twelve operators (60-79 years old) were studied and they showed large variation in time consumption. However, the within-operator time consumption patterns were consistent. In other words, operators all responded similarly to the different combinations of systems and wood classes, but at different absolute levels. The time required to process a unit volume of wood was 25-33% lower when the more highly mechanised system was used, and the time required was 13-22% lower for the homogeneous wood class. Physical work load, deviations and perceptions of the work varied between operators, but were weakly correlated with time consumption. The results' implications for analyses of investments in equipment for firewood-processing for self-sufficiency purposes are discussed.

Section: Operator Influencesmentioning

confidence: 94%

Section: External Validitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effects of increased mechanization on time consumption in small-scale firewood processing

Lindroos¹

2008

“…On the other hand, focusing the study on the actual chipping phase allowed minimizing operator effect, because the machine was totally independent from operator control in this phase. Operator effect is a main source of variability (Purfürst and Erler 2006), and may account for productivity differences up to 77% (Harstela 1988). In fact, it is not certain that using the same operator for different tests or in the same test will categorically exclude operator effect (Lindroos 2010).…”

Section: Discussionmentioning

confidence: 99%

Determining the impact of some wood characteristics on the performance of a mobile chipper

Spinelli¹,

Magagnotti²,

Paletto³

et al. 2011

A study was conducted to determine the effect of some wood characteristics such as species, moisture content and tree part on the performance and product quality offered by a mobile industrial chipper, of the type commonly used for roadside chipping. Two main species, two tree parts and two moisture content levels were combined in a factorial design yielding 8 treatments, each replicated 5 or 6 times. A flow meter was installed on the chipper engine, and all chips produced were weighed and sampled for moisture content and particle size distribution. The results indicated that some wood characteristics such as species and moisture content have a secondary effect on chipper productivity and fuel consumption, which are primarily controlled by piece size. In particular, fuel consumption per unit dry mass seem to be rather constant and in the range of 3.2 l per oven dry ton. Moisture content and tree part may have a significant effect on the particle size distribution of chips. Of course, these results were only verified for the species used in the test and for industrial chippers, and may change if substantially different species or machines are used.

“…The objective of comparative studies is to compare two or several machines, work methods, etc, while the objective of the correlation or relationship study is to describe the relationship between performance and the factors influencing the work (Bergstrand 1991). Time studies can be carried out using continuous time study methods such as continuous or repetitive timing or indirect work sampling (Forest work… 1978, Samset 1990, Harstela 1991. The work sampling technique gives only an approximation of the results obtained by the continuous time study methods, but it has the advantage that longer periods and even multiple processes can be studied at the same time with the same costs (Miyata et al 1981).…”

Section: Introductionmentioning

confidence: 99%

Time consumption analysis of the mechanized cut-to-length harvesting system

Nurminen¹,

Korpunen²,

Uusitalo³

2006

276

300

The time consumption and productivity of harvesting are dependent on stand conditions, the operators' skills, working techniques and the characteristics of the forestry machinery. Even if the basic methods and machine types of the cut-to-length harvesting system have not changed significantly in 10 to 15 years, improvements in the operators' competence, technical solutions in forest machinery and changes in the working environment have undoubtedly taken place. In this study, the objective was to discover the special characteristics in the time consumption of mechanized cutting and forest haulage in Finnish conditions. The empirical time study was conducted with professional operators and medium-sized single-grip harvesters and forwarders in final fellings and thinnings in easy terrain in central Finland. The models for effective time consumption in the work phases and total productivity were formed. Stem size, tree species and bucking affected the cutting, whereas timber density on the strip road, the average driving distance, load capacity, wood assortment and the bunching result of the harvester operator had an effect on the forest haulage performance. The results may be used in simulations, cost calculations and education.