Industrial round-wood damage and operational efficiency losses associated with the maintenance of a single-grip harvester head model: A case study in Russia

Forests 2012, 3, 864-880; doi:10.3390/f3040864 forests ISSN 1999-4907 www.mdpi.com/journal/forests Article Industrial Round-Wood Damage and Operational Efficiency Losses Associated with the Maintenance of a Single-Grip Harvester Head Model: A Case Study in Russia Yuri Gerasimov 1,*, Alexander Seliverstov 2 and Vladimir Syunev 2 1 Joensuu Research Unit, Finnish Forest Research Institute, Yliopistokatu 6, Box 68, Joensuu 80101, Finland 2 Forest Engineering Faculty, Petrozavodsk State University, A. Nevskogo av. 58, Petrozavodsk 185030, Russia; E-Mails: [email protected].ru (A.S.); [email protected] (V.S.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +358-408-015-162; Fax: +358-102-113-251. Received: 5 July 2012; in revised form: 26 August 2012 / Accepted: 20 September 2012 / Published: 27 September 2012 Abstract: A field-based study was performed to broaden our knowledge of operational efficiency losses associated with the neglect of the proper maintenance of the delimbing and feeding mechanisms of a harvester. The post-harvest assessments of industrial round-wood (IRW) processing damage, fuel consumption and productivity were examined in clearcutting operations. Observations were made of seven combinations of wear levels of feed rollers (A—heavy, B—medium, C and C’—without wear) and sharpening states of delimbing knives (1—incorrect, 2—correct), depending on the degree of feed roller wear and matching of angles of knife blades to the technical requirements. The processing defects of IRW were broken down into unprocessed branches, bark stripping, and damage caused by feed roller spikes. The results were then compared with the effective quality requirements, and the IRW losses in terms of the reject rates (RR) were determined in the context of the technical condition. The most frequent damage was by unprocessed branches. The harvester with correctly sharpened knives produced the minimum RR (4% of pine, 6% of spruce and 6% birch logs). The quality of IRW harvested under B1 and C1 resulted in 6%, 6% and 8%. A1 turned out to be the lowest (12%, 10% and 8%). Improvement in the maintenance of delimbing knives can reduce the RR of IRW by 5%. Timely restoration of worn-out rollers can increase productivity by 2% and reduce fuel consumption by 5%. OPEN ACCESS Forests 2012, 3 865 Keywords: cut-to-length; wood damage; fuel consumption; productivity; harvester head 1. Introduction The fully mechanized cut-to-length (CTL) wood harvesting system based on a single-grip harvester is now widely used by the logging industry in temperate and boreal forests, particularly in the Nordic countries. Today almost 100% of logging in Sweden and Finland is carried out by the harvester-forwarder system [1]. In Russia, particularly its northern European part, there has also been a movement towards mechanized CTL [2]. A remarkable growth in Russian forest machine markets is anticipated in the long term, mainly because of the need for renewal of current wood harvesting machines and because of the huge harvest potential of Russian forests [3]. CTL harvesting was introduced in the Russian regions along the Finnish border in the 1990s, mainly because Finnish entrepreneurs and forest machines from Finland operated in this cross-border area. The CTL method has become even more common in the 2000s, along with an increase in the import of harvesters and forwarders. The proportion of harvesting carried out using CTL systems has increased, especially in Northwest Russia, where more than 50% of harvested wood is already logged with the CTL method [4]. The domestic production of harvesters is quite low in Russia, and most of the machines in use (over 300 harvesters per year) are exported to Russia from Finland, Sweden, Canada and the USA [2]. Over 20 years of experience with the operation of CTL harvesting machines has demonstrated their effectiveness for logging companies in Russia; i.e., better labor conditions in terms of ergonomics and safety, less environmental damage, and reliability in combination with convenient operation and maintenance. The productivity of work and quality of industrial round-wood (IRW) with CTL harvesting can be considered acceptable, even though they could still be improved. Previous field studies conducted at a number of large logging enterprises in Russia showed that the companies often could not achieve high output [4] and quality of IRW [5]. Mixed stands with various natural defects in wood and abnormalities in stem shape dominate in Russia, which needs to be taken into account in the design of harvester heads [6]. When buying a whole harvester or a harvester head for the available base machine (the excavator, for instance), the technical features of the equipment should fit operational conditions to avoid unnecessary impairment of its effectiveness. Many developments have been made towards improvement of fully mechanized CTL in the field of harvester productivity and costs [1,7–12], which are dependent upon the silvicultural system, operational phase, ambient temperature, outcome product, stand factors, operator factors and machine factors, terrain and climatic conditions, as well as growing stock per hectare according to a region [13]. The right choice of equipment plays a significant, but not the only, role in achieving effective harvester use. The second factor for success is correct maintenance, which implies the use of oil and technical liquids recommended by the manufacturer and following the sequence and volume of maintenance operations. Special attention should be paid to the maintenance of the saw and delimbing mechanism. In particular, it is necessary to correctly adjust and regulate the delimbing and feeding mechanisms, sharpen delimbing knives, and clean bark and wood remnants from the feed rollers. The overall field-based studies and interviews conducted by Syunev et al. [6] and Seliverstov et al. [14] at Forests 2012, 3 866 15 logging companies in Northwest Russia exposed the fact that most of the harvesters did not meet the requirements of the manuals for sharpening delimbing knives during maintenance. The delimbing knives were sharpened neither regularly nor correctly. The experience of using harvesters in Russia shows that while harvester operators pay proper attention to the sharpening of saw chains, there is a challenge with the maintenance of delimbing mechanisms. As delimbing is done by feeding the stem through the head at high speed (up to 5 m/s), there are high quality demands on the delimbing knives in terms of their durability and ability to retain the optimal geometry of the cutting edge and sides of the knife. Blunting of the cutting edges and changes in the geometry of their shape reduce the capacity of the machines and lower the quality of IRW. The knives wear out faster during the snow-free time, when the branches carry mineral substances and particles of soil during harvesting. Most of the upper movable knives investigated (Figure 1) demonstrated incorrect sharpening of cutting edges for delimbing of thick stems. The reason was that, due to wear, the geometry of the cutting edge changed and was not corrected during subsequent sharpening. Besides the incorrect maintenance of delimbing knives, some cases of failure to observe operational requirements were registered that resulted in mechanical damage to knives. Quite often, when working with a tree, the upper supporting knife is bumped into the machine frame. Such collisions lead to damage to the knife that has to be repaired (Figure 2). Moreover, the incorrect maintenance and operation of the knives and the poor condition of the feed rollers influence both the operational efficiency and the quality of delimbing. According to our observations (Figure 3), damage to the spikes was the most common form of wear on movable feed rollers. Figure 1. Upper movable knife: (a) correct angle for cutting branches from thick stems; (b) incorrect angle for cutting branches from thick stems. Figure 2. Damaged top of supporting knife. Forests 2012, 3 867 Figure 3. Damaged spikes of the movable feed roller. The introduction of the advanced and expensive CTL technology in Russia has shown that serious financial losses can be incurred if the maintenance of a harvester is not done correctly. A survey of John Deere machine failures in the Republic of Karelia in 2003–2006 [15,16] reported that poor operator and technician training systems, inefficient work crew organisation, lack of maintenance support and ubiquitous failure to comply with the operating instructions are problems to solve before CTL can prosper in Russia. According to Salivonik and Shilovsky [16], a harvester head is one of the most weak and critical elements of harvester technical service. Thereby, the necessity to study the effects of the maintenance of the harvester head on its performance is obvious in Russia today. This field-based study was performed to broaden our knowledge of IRW damage and operational efficiency losses associated with the neglect of the proper maintenance of the delimbing and feeding mechanisms of a single-grip harvester. 2. Material and Methods This study was conducted with the overall objective of describing the effects of feed roller wear and sharpening of delimbing knives on (i) fuel consumption; (ii) productivity; and (iii) wood damage. Stem volume groups and tree species have been taken into account as covariates. Many other confounding factors, such as machines and operators, have been avoided through appropriate planning of the experiments. More specifically, the harvester model, the harvester head model, the number and specifications of the logs were the same for all treatments. The feeding pressures of the harvesting head corresponded to their technical requirements. The experiments were carried out in typical working conditions near the town of Vedlozero in the Republic of Karelia in the late winter and summer 2009–2010, and Vyshny Volochek in the Tver region in 2010. A midsized-wheeled John Deere 1270D harvester with an engine output power of 160 kW and operating weight of 17 tons was used on all study sites. All the harvesters studied were equipped with the JD 758 HD harvester head. This model has four feed rollers, one bearing and four sidelong movable delimbing knives. The lower and higher clamping pressures (7.5/16.0 MPa for sidelong movable rollers, 6.0/13.0 MPa for upper knives and 3.0/7.5 MPa for lower knives) were Forests 2012, 3 868 checked and corrected if necessary [17]. Field study data in Karelia were obtained from two single-grip harvesters produced in 2006 and 2008. Both harvesters operated in the same logging company and both operators had the same qualifications and experience (five years). The harvester studied in the Tver field study was produced in 2007. The operator had five years of experience with CTL harvesting, including three years with this harvester. Thus, as far as possible, the well-known and sometimes substantial influence of working environment, machine and operator on the work output in wood harvesting was avoided. Harvested forest stands had not been thinned before the final felling. A typical study stand was of mixed tree age and species. The tree species included spruce [Picea abies (L.) Karst.], pine (Pinus sylvestris L.), birch (Betula pubescens), and aspen (Populus tremula). The average stem volumes of the harvesting sites varied between 0.20 m3 and 0.30 m3 u.b. (under bark). The growing stock of harvested stands varied between 200 m3/ha and 325 m3/ha. Typical soils in the test areas were loam, clay loam, and sandy loam. The basis of stem volumes and tree species distribution by experimental harvesting sites is presented in Table 1. The difference between the average stem volumes from forest inventory data and from the harvester in forest block 45 of the Tver region can be explained by the uneven harvest area structure (i.e., a partial area was harvested). The specification of the harvested IRW is shown in Table 2. The following seven treatments, depending on the degree of wear of feed rollers (A—heavy wear; B—medium wear; C and C’—without wear) and matching of knife blade angles to the technical requirements (1—incorrect and 2—correct sharpening), were each matched to one of the IRW assortments on each harvesting site (Tables 3 and 4): A1—the heavily worn-out feed rollers (wear up to 23%) and the incorrect (prior to the experiment) sharpening of knives (deviation from the requirement of up to 10°); A2—the heavily worn-out feed rollers (23%) and correctly sharpened knives immediately after treatment A1; B1—the medium worn-out feed rollers (13%) and the incorrectly sharpened knives (6°); B2—the medium worn-out feed rollers (13%) and correctly sharpened knives immediately after treatment B1; C’2—the renovated (by welding) feed rollers and the correctly sharpened knives after treatments B1–B2; C1—the brand-new feed rollers and the incorrectly sharpened knives (7°); and C2—the brand-new feed rollers and correctly sharpened knives made immediately after treatment C1. Tables 3 and 4 show the degree of feed roller wear (the damage to the spikes), and the actual (before sharpening) knife-blade angles for the tested harvester heads, compared to the recommendations of the manufacturer. Not all the harvesters tested met the requirements for sharpening delimbing knives in accordance with the JD H758HD harvester head manual [17]. As a result, even if knives were sharpened regularly, it was not always carried out in line with technical requirements. As can be seen, the actual angles differ from the recommended ones by up to 10°. Besides the failure to follow recommendations on sharpening angles, sometimes the geometry of sharpening was faulty. Forests 2012, 3 869 Table 1. Description of harvesting areas. No. Location* Season Average stem volume* (m3) Stock* (m3/ha) Tree species* Treatment Number of observed stems^ Average stem volume^ (m3) Pine Spruce Birch Aspen A Karelia, Vedlozero forest district, block No.32 Winter 0.30 325 50%—pine 30%—spruce 20%—birch A1 75 115 97 58 0.26 A2 81 178 80 84 0.3 B Karelia, Vedlozero forest district, block No.8 Winter 0.26 269 50%—spruce 30%—pine 10%—birch 10%—aspen B1 74 120 84 72 0.34 B2 82 168 158 86 0.34 C’ Karelia, Vedlozero forest district, block No.46 Summer 0.20 292 40%—pine 30%—spruce 20%—birch 10%—aspen C’1 N/A N/A N/A N/A N/A C’2 143 244 113 104 0.22 C Tver region, Esenovichskoye forest district, block No.45 Summer 0.28 200 60%—birch 20%—aspen 20%—spruce C1 N/A 344 226 170 0.37 C2 N/A 325 180 134 0.46 A—the harvester head with the heavy worn-out rollers; B—the medium worn-out rollers; C—the renovated rollers; C’—the brand-new rollers; *—forest inventory data for whole harvesting area; ^—actual data from the harvester. Forests 2012, 3 870 Table 2. Specification of harvested industrial round-wood and quality requirements describing the different types of quality faults. Table 3. Treatments of John Deere H758HD harvester head rollers. No. The average height of elliptical spikes (cm)/roller wear (%) Number of missing spikes, (pcs)/(%) movable fixed on the frame movable fixed on the frame right left right left right left right left A 1.19/21 1.16/23 1.3/13 1.29/14 8/6 29/21 0 3/3 B 1.31/13 1.32/12 1.39/7 1.39/7 4/3 3/2 0 0 C’ 1.50/0 1.50/0 1.39/0 1.39/0 0/0 0/0 0 0 C 1.42/6 1.41/6 1.44/4 1.45/3 10/7 6/4 0 0 Table 4. Treatments of John Deere H758HD harvester delimbing knives. No. State of the cutting edges The angle of sharpening the cutting edges upper movable lower movable stationary a b b a c A 1 40° 50° 45° 30° 30° 2 35° 40° 40° 35° 30° B 1 38° 45° 35° 29° 35° 2 35° 40° 40° 35° 30° C’ 2 35° 40° 40° 35° 30° C 1 40° 47° 40° 35° 37° 2 35° 40° 40° 35° 30° Note: The angles of knives: 1—incorrect sharpening; 2—after correct sharpening (recommended by manufacturer); a—sector for cutting branches from thin stems; b and c—sectors for cutting branches from thick stems. No. IRW Nominal length (m) Diameter over bark (m) Quality faults Min. at the upper end Max. at the lower end (butt) Max. branch length (mm) Bark stripping (%) Damage caused by spikes (mm) A, B, C’, C Spruce sawlogs 6.1 (0, +0.06) 0.170 0.400 10 15 30 A, B, C’ Pine sawlogs 4.0 (0, +0.06) 0.180 0.550 10 15 30 A, B, C’, C Spruce pulpwood 3.6 (±0.15) 0.080 0.400 10 - 30 A, B, C’ Pine pulpwood 6.0 (+0.03, +0.05) 0.060 (under bark) 0.600 (under bark) 10 - 30 A, B, C’, C Birch pulpwood 6.0; 4.0 (+0.03, +0.05) 0.060 (under bark) 0.600 (under bark) 10 - 30 A, B, C’, C Aspen pulpwood 6.0; 4.0 (−0.05, +0.10) 0.075 0.800 10 - 30 Forests 2012, 3 871 2.1. Productivity and Fuel Consumption The performance of each harvester, such as fuel consumption and productivity, was automatically monitored during a single normal operation shift on a harvesting site for each treatment. Altogether, there were about 3595 measured stems or about 1200 m3 u.b., including 455 pines, 1494 spruces, 938 birches and 708 aspens. The detailed data per treatment are presented in Table 1. A new version of the John Deere machine’s performance and condition monitoring system (TimberLink 2.0) was used for collecting data on cutting productivity and follow-up of cutting conditions (tree sizes and species). Performance data were transferred from the harvester to the office with a USB memory stick. The data collection procedure involved gathering preliminary information, such as date, working time, processing time, movement time, stem volume, tree species and number of trees, process productivity, fuel consumption, and some additional information, such as the contractor, machine type, harvester head type, and location. The harvesting operation of the harvesters studied was split into two distinct time elements, which were recorded with the TimberLink system. Time elements were stem selection and stem processing (i.e., delimbing and cross-cutting). The stem selection stage covers everything from driving the machine onto the stand to operating the boom before sawing the stem. The stem processing stage includes the felling, cutting, moving, delimbing and cross-cutting of the stem. TimberLink monitors the time required for the different stages of stem processing when processing differently sized stems. The harvester head measurement system was used to measure sectional diameters and lengths of each tree to determine stem volume. Machine productivity was determined in m3 u.b., both per productive machine hour and per stem processing machine hour (SprocMH). Fuel consumption was determined in litres per m3 u.b., for both productive machine hours (FC) and stem processing machine hours (SprocFC). Productive machine hours represent the time during which the machine performs the harvesting operation excluding breakdowns (i.e., mechanical and non-mechanical delays). It is the time spent by a machine performing its primary task and time spent on support tasks. Short delays that cannot be easily separated from production activities are included in productive time. Stem processing machine hours represent the time during which the machine actually performs felling and stem processing operations (tree felling, delimbing, cross-cutting and harvesting head movement). In addition, stem feeding time (FTstem) in seconds per stem and stem processing fuel consumption (FCstem) in litres per stem were determined. Note the difference between feeding time and processing time. FTstem (seconds per stem) and SprocMH (m3 per hour) are measures for time consumption of stem feeding and productivity of stem processing operations respectively. Therefore they are different in significance within the same treatment effect. 2.2. Post-Harvest Assessments of IRW Damage In order to evaluate the influence of angles of knife sharpening, the quality of IRW was evaluated before and after sharpening of knives on three harvesters working in similar forest stands. The IRW assortments, such as pine saw logs and pulpwood, spruce saw logs and pulpwood, and birch and aspen pulpwood, were collected from three mixed forest stands in Karelia and one in the Tver region (see Table 2). According to the methodology used, the required number of logs to be measured equals 50 for each tree species per treatment; a set of exactly 50 spruces, 50 pines and 50 birches was selected Forests 2012, 3 872 for IRW damage observation during normal harvesting operations within the time gap between harvesters and forwarders. The choice of the number of IRW samples for each treatment was made on the basis of the prior study experiment and by determining the minimum number of measurements to ensure the required accuracy and reliability (p = 0.05 for a 95% confidence interval). The total number of observed logs in all treatments (A–C) was 1300, and the number of observed harvesting sites was four, including two in winter and two in summer (Table 1). All the measurement results were registered on checklists using a data collector. The IRW damage evaluation was based on a number of IRW damage indicators, which are regulated by relevant national standards and forest industry specifications [5]. The forms of processing damage to IRW were broken down into three groups: unprocessed branches (>10 mm), bark stripping, and damage caused by roller spikes. The results were then compared with the effective quality requirements in a given logging company, and the IRW volume loss in terms of the reject rate was determined in the context of the harvesting head’s technical condition. 2.3. Statistical Approach The data obtained in this study were only on a stem level. The number of recorded stems, calculated using a statistical approach, gave reliable data for analyses of IRW damage. The recorded TimberLink data provided accurate data for analyses of productivity, time and fuel consumptions. Therefore, the study results are reliable within the case study. Collected data were analyzed through multivariate analysis of variance and of covariance (MANCOVA) and Fisher’s Least Significant Difference (LSD) tests at 95% confidence level using the SPSS package version 17 [18]. This rather advanced (at least for forest engineering) procedure is concerned with examining the differences between the groups. Treatment effects were tested using MANCOVA with feed roller wear (Roller_wear) and sharpening of knives (Knives_shap) as fixed factors separately for the productivity (FTstem, SprocMH) and fuel consumption (FCstem) factors. A set of covariates, such as tree species, stem volume groups and season, which might be related to our dependent variables, was used in the analysis. In the multivariate analysis with harvesters as an observational unit for FTstem, FCstem, SprocMH dependent variables, tree species and stem volume groups were added as covariates. The seasonal factor was excluded from further MANCOVA analysis because Baranovsky and Nekrasov [19] and Breyter et al. [20] in Russia reported that the season does not have a significant effect on the productivity of the delimbing and feeding mechanisms. In addition, the study by Kuitto et al. [21] in Finland demonstrated that the season does not have a significant effect on harvester productivity and fuel consumption. 3. Results Data obtained in this field study are presented in Tables 5 and 6. Table 5 shows the SprocFC and SprocMH results for the stem volume groups by tree species in the context of treatments. The results for post-harvest assessments of IRW damage, stem processing fuel consumption and feeding time in the context of treatments are shown in Table 6. The results of MANCOVA analysis are shown in Table 7. Forests 2012, 3 879 Acknowledgments The publication was prepared for the projects “Wood Harvesting and Logistics”, financed by the European Union through the Finnish Funding Agency for Technology and Innovation (TEKES), and “Decision support system for the boosting of the rational use of woody biomass”, financed by the Ministry of Education and Science of Russia and within the Strategic development program of Petrozavodsk State University. Conflict of Interest The authors declare no conflict of interest. References 1. Nordfjell, T.; Bjorheden, R.; Thor, M.; Wasterlund, I. 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