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Analyzing and Estimating Delays in Harvester Operations Raffaele Spinelli Rien Visser ABSTRACT Time and motion studies have been and still are frequently used to describe, understand, and improve forest operations. Delays are recognized as being one of the major factors that limit productivity in most operations and are, therefore, an in- tegral part of most time studies. But, delay events are erratic in both occurrence and magnitude and are, therefore, difficult to precisely quantify within the relatively short observation period of a typical time and motion study. Thus, delay information from individual studies have limited transferability. This paper analyzes the delay component of 34 harvester time study data sets that were recorded between 1998 and 2006. All of the stud- ies were designed and carried out with the same principal inves- tigator.The data sets were all based on harvesters either harvest- ing and or processing. Three delays categories were used: me- chanical, operator, and other. Delays averaged 28.9 percent of the total scheduled time for all 34 studies, comprising of 7.1 percent mechanical, 4.7 percent operator, and 17.1 percent other delays.Delay averages were compared within category de- scriptions assigned to each data set for statistical significance. Example results include: total delays were higher for operations working on hot decks versus cold decks and operations working in mixed stands had more than twice the overall delays com- pared to operations in plantations. Considering only mechani- cal delays, machines that both felled and processed, compared to just processing, had higher mechanical delays. Interestingly, dedicated harvesting machines versus harvesting heads mounted on an excavator base had on average higher operator delays. Keywords: time study, logging, harvester, machine delays, forestry Introduction Time and motion studies have been and still are frequently used to describe, understand, and improve forest operations. Research on the productivity of forest operations is obtained by measuring the time consumed and the quantity produced and then carrying out a statistical evaluation to relate the two quan- tities (Steinlin 1955). Performance studies can be comparative or correlation studies (Samset 1990). The aim of correlation studies is to find the relationship between the performance of the machine and the various influencing factors, such as tree size, extraction distance, terrain slope, etc. (Appelroth 1985, LeDoux and Huyler 2000). Correlation studies should only be carried out on machines and methods which are generally used in practical forest operations (Bergstrand 1991). For most forest operations productivity studies,the data col- lection procedure consists of a set of detailed time and motion studies conducted at the cycle level. In general, detailed time studies are more discriminating than shift-level studies and can detect smaller differences between treatments (Olsen et al.
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  • Winter '17
  • Delay, Time and motion study, delay factor, International Journal of Forest Engineering

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