Analyzing and Estimating Delays in Harvester Operations
Authors
Raffaele Spinelli
CNR (National Research Council), Italy
Rien Visser
Virginia Tech
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 integral 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 studies were designed and carried out with the same principal investigator. The data sets were all based on harvesters either harvesting and or processing. Three delays categories were used: mechanical, 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 descriptions 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 compared to operations in plantations. Considering only mechanical 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.
