Rien Visser

Analyzing and Estimating Delays in Harvester Operations

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.

Determining the shape of the productivity function for mechanized felling and felling-processing

Productivity studies in forest operations are often carried out on new equipment, or on equipment being used in new conditions. Understanding how stand and terrain parameters impact the productivity of harvesting machines is important for determining their optimum use. Such information is normally presented as a productivity or efficiency function; that is, a regression equation that best represents the data. Most studies establish that piece size is the dominant predictor that impacts overall productivity. A common concept known as the “piece-size law” is that productivity increases at a decreasing rate with increasing piece size. What is not well understood is the upper limit to this piece-size law. That is, as the trees get “too” large, we can expect the machine to start to struggle, resulting in a decrease in productivity. Four different data sets—two based in New Zealand and two in Italy—are presented that clearly show an “optimum” piece size for maximum productivity. On average, productivity tended to decrease gradually, not drop off suddenly beyond the optimum. Using more complex statistical functions, it was possible to correctly correlate piece size to productivity.

Cable Corridor Installation Times for European Yarders

Abstract Cable yarding continues to be an efficient and effective harvesting system for the extraction of timber on steep terrain. Modern European silvicultural strategies result in smaller harvest areas, lower extraction volumes and a shift from clear-cut to thinning operations or single tree extraction. Yarder installation time has, especially as a proportion to the extraction time, increased significantly, resulting in higher extraction costs. This study recorded the set-up and take-down time of 79 cable yarder installations. Another 76 installation times were taken from previously published time studies, for a total sample size of 155. The factorial study design differentiated uphill-or downhill yarding, yarder size and whether or not it was the first installation at a landing, or subsequent parallel installation from the same landing area. The covariates recorded were corridor length, terrain slope, number and height of intermediate supports, and number of forest workers. Both a set-up and take-down time models were developed. This will help estimate future cable installation time requirements, and more importantly, provide improved cost estimates for the new silvicultural treatments.

An Applied Hardwood Value Recovery Study in the Appalachian Region of Virginia and West Virginia

Abstract An analysis of log-making (bucking) performance for five logging crews in southern Appalachian mixed-hard- wood stands of Virginia and West Virginia was conducted. Cutting accuracy and value recovery were analyzed and compared to an optimal solution that was determined through the use of the HW-BUCK computer software. In total 148 trees were bucked into 510 logs and only 11 percent were cut accurately. Fifteen percent were under cut and 74 percent were over length. The crew with the best performance in length cutting accuracy also recorded the lowest value recovery loss. An average value loss of 20.7 percent was calculated for all five crews.

Forestry operations in the European mountains: a study of current practices and efficiency gaps

ABSTRACT Timber production is an important ecosystem service of European mountain forests. This paper aimed to assess the current practices in logging operations and to identify the efficiency gaps in timber production. The study was located in 7 case study areas from representative European mountain ranges, where 632 logging operations were analysed. The focus was on road infrastructure, transport systems, harvesting methods and extraction technologies. Often inappropriate technology was used in steep terrain; there was no correlation between the average slope and the selection of harvesting systems (HS). Skidding was the most common extraction method (75%), while cable yarding and forwarding had shares of 15% and 8%. The mean road density was 18.5 m ha−1. The mean extraction distance was 501 m. The mean harvesting and extraction productivity were 9.0 and 10.2 m³ h−1; the mean costs were 11.1 and 11.7 € m−³, respectively. Non-mechanized and obsolete HS reported the lowest efficiency and the highest environmental footprint, while fully mechanized systems reported the highest efficiency, the lowest number of accidents and the lowest stand damage. Cable yarders are the appropriate extraction technology in steep terrain, but they require a well-developed road network. Higher mechanization degree, improved quality of the road networks, knowledge transfer to practice and training of forest workers are some of the necessary measures to overcome the efficiency gaps in timber production in European mountain forests.

Analyses of Parameters Affecting Helicopter Timber Extraction

Abstract In the last 25 years, helicopter extraction of timber has developed as an important harvesting alternative in mountainous areas. Typical helicopter operations include the extraction of valuable timber from stands with inadequate road networks, large areas of difficult to reach wind-throw, and sensitive sites where the negative impact on soil and water must be minimized. An empirical study provides information on the effect of silvicultural treatment and pilot experience on the productivity of the K-Max helicopter. The productivity model is a function of the average stem piece size, the horizontal distance between stump and landing, the silvicultural treatment, and the experience of the pilot. The productivity obtained when harvesting from a clear-cut was greater than from the ‘femel-cut’ (patch-cut) extraction site by 0.20 m3/min, or 21% at an average piece size of 1.5 m3. The inexperienced helicopter pilot had timber extraction experience but just 30 flight hours on the K-Max while the experienced pilot had 22,000 K-Max flight hours. The experienced pilot yielded a 0.37 m3/min increase in productivity, which is a 63% increase at an average piece size of 1.5 m3. This indicates that operator experience on a particular machine may be very important when comparing harvesting systems based on time studies.

The effect of the number of log sorts on mechanized log processing productivity and value recovery

New Zealand’s forestry supply chain handles a wide range of log products to meet domestic and export market demands and to maximize returns to the forest grower. With a strong customer focus in diverse markets, one supply chain implication is the number of grades and sorts that a logging operation is expected to produce. A typical harvesting operation will produce 8–22 log sorts while harvesting one tree species (Pinus radiata). As New Zealand’s log exports have grown strongly over the last 5 years, the prices for major export log grades have risen and converged with structural sawlog grades. This price convergence has reduced the incremental value gains from producing a wide range of log sorts. This paper details a production study at two harvesting operations whereby the mechanized processing component was studied in different market scenarios (5, 9, 12, and 15 log sorts) with respect to both product value and the operational impacts on log processing productivity. The study showed the market scenario with 15 log sorts to decrease processor productivity by around 10%. Cutting nine log sorts was estimated to be the optimum scenario in terms of the value produced per productive machine hour. Expanding on these findings to investigate other parts of the supply chain could result in significant value and productivity improvements through simplification.

Effect of terrain steepness on machine slope when harvesting

Harvesting timber on steep terrain can be both expensive and have higher safety risks. Using ground-based machines on steep terrain has the potential to decrease harvest costs and improve safety through the mechanization of manual forest tasks such as tree felling and choker-setting. To better understand the true range of slopes on which forest machines are operating, a digital accelerometer was attached to 22 forest machines to capture real-time measurements of machine slope. A total of 18 studies were completed in commercial pine plantation operations in New Zealand, and two carried out in Austria and Norway respectively. Site selection deliberately focused on ground-based operations that were working on steep terrain. Machine slope, as measured on the carrier base, was captured using a digital accelerometer at a frequency of 2 Hz, and a GPS unit to capture location data simultaneously. Terrain slope was calculated using two different methods in ArcGIS®; one was based on a triangular irregular network (TIN) file and one was based on a raster file. The evaluated machines were grouped into one of four machine types; felling (n = 4), shovelling (n = 5), skidder (n = 9) or “European” (n = 4). A characterization of the European machines studied was that they were purpose built steep terrain machines, whereas the New Zealand felling and shovelling machines were modified excavators. The machines were analyzed and compared with respect to machine slope (actual) and terrain slope (predicted) based on a digital terrain map and the machines location. All machines studied operated on slopes that exceed the New Zealand Approved Code of Practice guideline of 17 and 22° slope for wheeled and tracked machines respectively. New Zealand-based machines were shown to exceed the guidelines for terrain slope much more frequently, and by a greater margin, than European-based machines. Linear regression showed that the relationship between machine slope and terrain slope was poor for all machines, indicating that terrain slope is a poor predictor for managing machine slope.

Uptake and barriers to the use of geospatial technologies in forest management

BackgroundA survey was conducted to assess the uptake, and barriers to use, of geospatial tools and technologies amongst New Zealand’s plantation forestry sector.MethodsResponses were received from 17 companies representing 63% of New Zealand’s plantation forest by area. A wide range of company sizes were surveyed (net stocked areas ranged from 4,000 – 200,000 hectares), and 7 of the 17 have international operations.ResultsSurvey results suggest that freely available topography, climate, and soil datasets have limited utility, as forest management at the operational level requires higher resolution, remotely sensed data. The most common supplemental data are aerial photography or satellite imagery. High spatial resolution was more highly valued by respondents than spectral diversity (i.e. number of channels); only six companies regularly use imagery containing an infrared band. LiDAR data has been used regularly by only three New Zealand forestry companies, while another six have tried it, suggesting it is an emerging technology in New Zealand. The use of generic GIS software was common amongst all respondents (14 use the ESRI product ArcGIS, three use MapInfo produced by Pitney Bowes). The utility of ArcGIS, in particular, was enhanced by locally developed extensions designed to address specific operational tasks performed regularly by New Zealand’s forestry companies.ConclusionsWhile it is clear that geospatial data and tools are generally adopted by New Zealand’s forest industry, cost-related barriers prevent their widespread adoption. Interestingly, a lack of staff knowledge was also conceded an impediment to uptake, alluding to the importance of tertiary education in the geospatial sciences and continuing education for practitioners.

Automatic GNSS-enabled harvester data collection as a tool to evaluate factors affecting harvester productivity in a Eucalyptus spp. harvesting operation in Uruguay

Uruguay has adopted cut-to-length (CTL) machines in forest harvesting operations, especially in large scale, fast-growing plantations. The majority of modern CTL machines have on-board computers that capture individual tree data and can be coupled with global navigation satellite systems (GNSS). This provides the opportunity to collect data for research purposes and to improve operations. In this study, we retrieved data (StanForD stm and drf files) from a GNSS-enabled harvester working in CTL operations in Eucalyptus spp. plantations in Uruguay. With two thirds of this data we fitted a mixed effects model to evaluate harvester productivity as a function of stem diameter at breast height (DBH), species, shift (day/night), slope, and operator. A slope surface derived from a digital terrain model was overlaid with GNSS stem records. Slope values were assigned to each stem using the Spatial Analyst toolbox in ArcGIS. The reserved third of the data were used to validate the model. DBH was the most influential variable in harvester productivity, showing a positive correlation and a R2 value of 0.73 in the validation model. Operator and species also had significant effects. There was no significant slope effect, whereby the study area only had flat and mildly sloping terrain. Shift did not have a significant effect, indicating there was no drop in night shift productivity. The model developed constitutes the first published harvester productivity model in South America based on data automatically collected by harvesters. In addition, the forestry company may benefit from using the model for operator management.