Wood Chippers Research Articles

The Effect of Knife Wear and Sharpening Mode on Chipper Productivity and Delays

The production of wood chips can be achieved using different types of wood chippers whose productivity can be influenced by many factors including proper knife management. Research was conducted to determine the productivity of the new Diamant chipper in chipping air-dried tops stacked at a roadside landing and to compare the efficiency of dry sharpening and wet sharpening in restoring chipper productivity, the time required by dry sharpening with that of knife replacement, and the cost of dry sharpening to knife change in real-life conditions. To clearly define the influence of knife management, a model of the effect of knife wear on chipper productivity was produced. Analysis of variance was used to check the significance of any differences in chipping and total time consumption per cycle. Multiple regression was used to express the relationship between chipping time consumption per cycle and the cumulated mass processed by a set of knives—the latter taken as an indicator of knife wear. The study lasted 10 full workdays, included a total of 136 truckloads or 3560 t of fresh wood chips (or green tons = gt), and resulted in the average productivity of 59.0 gt per productive chipping hour (excluding all delays) or 39.4 gt per machine scheduled hour (including all delays). Delays represented 37% of total worksite time. Knife management (dry sharpening or change) accounted for 30% of the total delay time due to raw material contamination. Dry sharpening took 30% less time than a full knife change. As wear accumulated and knives lost their edge, the chipping time per cycle increased from 25 in the first cycle (full truck load) to 38 min in the third cycle. The presented study offers robust productivity figures, together with a reliable estimate of the productivity losses caused by knife wear, and could help improve knife management in order to increase chipper productivity as well as reduce unnecessary delays.

Pengaruh Variasi Holding Time Pada Proses Heat Treatment (Hardening) Untuk Baja S50c Sebagai Pisau Mesin Pencacah Kayu

S50C Alloy Steel is a widely produced and used medium carbon alloy steel, which serves as a raw material for manufacturing machine components, building structures, tools, and one of them being knife blades for wood chippers. The aim of this research is to determine the hardness value and microstructural changes in S50C steel after the heat treatment of hardening and holding time. The method used in this study is an experimental method, where S50C steel is subjected to heat treatment at a temperature of 850°C, followed by different holding times of 30, 60, and 90 minutes, and then cooled using oil. The research results show that the highest hardness value in S50C steel, treated with rapid cooling using oil, has an average hardness value of 589.29 HV after a 90-minute holding time, compared to the raw material's hardness of 262.67 HV. Microstructural testing reveals that the microstructure of the raw material consists of ferrite and pearlite with balanced crystal shape and size, in accordance with a carbon content of 0.50%. In the group of specimens undergoing rapid cooling with oil in the hardening process, a new microstructure called martensite is obtained, which is the main structure responsible for the increased hardness of the steel.

Impact of Compressed Natural Gas (CNG) Fuel Systems in Small Engine Wood Chippers on Exhaust Emissions and Fuel Consumption

The projected increase in the availability of gaseous fuels by growing popularity of household natural gas (NG) filling stations and the increase in the production of gaseous biogas-derived fuels is conducive to an increase in the use of NG fuel. Currently, natural gas in various forms (compressed natural gas (CNG), liquefied natural gas (LNG)) is popular in maritime, rail and road transport. A new direction of natural gas application may be non-road mobile machines powered by a small spark-ignition engine (SI). The use of these engines in the wood chippers can cause the reduction of machine costs and emissions of harmful exhaust gases. In addition, plant material chippers intended for composting in bio-gas plants can be driven by the gas they are used to produce. The biogas can be purified to bio-methane to meet natural gas quality standards. The article presents the design of the natural gas supply system, which is an upgrade of the Lifan GX 390 combustion engine spark ignition engine (Four-stroke, OHV (over head valve) with a maximum power of 9.56 kW), which is a common representative of small gasoline engines. The engine is mounted in a cylindrical chipper designed for shredding branches with a maximum diameter of up to 100 mm, which is a typical machine used for cleaning work in urban areas. The engine powered by CNG and traditionally gasoline has been tested in real working conditions, when shredding cherry plum (Prunus cerasifera Ehrh. Beitr. Naturk. 4:17. 1789 (Gartenkalender4:189–204. 1784)). Their diameter was ca. 80 mm, 3-metere-long, and humidity content ca. 25%. The systems were tested under the same actual operating conditions, the average power generated by the drives during shredding is about 0.69 kW. Based on the recorded results, it was found that the CNG-fuelled engine was characterized by nitrogen oxides (NOx) emissions higher by 45%. The other effects of CNG were a reduction in carbon dioxide (CO2), carbon monoxide (CO) and hydrocarbon (HC) emissions of about 81%, 26% and 57%, respectively. Additionally, the use of CNG reduced fuel consumption by 31% and hourly estimated machine operating costs resulting from fuel costs by 53% (for average fuel price in Poland: gasoline: 0.99 EUR/L and CNG: 0.71 EUR/m3 on 08 November 2020). The modernization performed by the authors ensured the work of the drive unit during shredding, closer to the value of stoichiometric mixtures. The average (AVG) value of the air fuel ratio (AFR) for CNG was enriched by 1.2% (AVG AFR was 17), while for the gasoline engine the mixture was more enriched by 4.8% (AVG AFR was 14). The operation of spark-ignition (SI) combustion engines is most advantageous when burning stoichiometric mixtures due to the cooperation with exhaust aftertreatment systems (e.g., three-function catalytic converter). A system powered by CNG may be beneficial in systems adapting to operating conditions, used in low-power shredding machines, whose problem is increased HC emissions, and CNG combustion may reduce them. The developed system does not exceed the emission standards applicable in the European Union. For CO emissions expressed in g/kWh, it was about 95% lower than the permissible value, and HC + NOx emissions were 85% lower. This suggests that the use of the fuel in question may contribute to tightening up the permissible emission regulations for non-road machinery.

Trends and Perspectives in the Design of Mobile Wood Chippers

Mobile wood chippers represent a mature technology now available in a wide range of sizes and configurations. Different types exist, but the most widespread are disc and drum chippers. The latter have enjoyed wider popularity in recent years because they are best suited to processing logging residue and other low-quality wood. Drum chippers can be fitted with screens, designed to re-circulate oversize particles. In general, industrial chippers offer high productivity and high fuel efficiency, especially if settings are properly adjusted. Chippers are high-maintenance equipment and require proper care. Maintenance cost increases with machine age and can be predicted quite accurately, and so can chipping productivity and cost. Reliable models exist for estimating both maintenance cost and productivity, based on dedicated user-entered assumptions. All things being equal, there are no substantial productivity and maintenance differences between tractor-powered and independent-engine chippers.

Reduction in Operating Costs and Environmental Impact Consisting in the Modernization of the Low-Power Cylindrical Wood Chipper Power Unit by Using Alternative Fuel

Alternative fuel within the meaning of Directive 2014/94/EU is, among others, LPG (liquefied petroleum gas), characterized by a lower purchase cost and lower emissions of toxic exhaust compounds in comparison to the combustion of classic gasoline. In wood chippers, intended for chopping branches, with low-power internal combustion engines that meet the emission standards in force in 2019 in the European Union, in accordance with Regulation 2016/1628/EU, carburetor fuel supply systems are commonly used. Innovative trends in the development of these drives are: electronic fuel injection, systems supporting the adaptation of the working elements to the conditions of use and the use of alternative fuels. The first two solutions significantly affect the cost of purchasing a power unit or modernizing it. The authors of this article indicate, as a beneficial alternative, a cheap (EUR 105) possibility of modernizing the carburetor fuel supply system. It is based on a modification that will allow for the use of LPG instead of gasoline to drive the working system of the wood chipper. This article presents the results of tests on the fuel consumption of a wood chipper powered with gasoline (3.04 L h−1) and LPG (3.65 L h−1) during continuous chipping. The cost of an hour of chipping related to fuel consumption was determined, which was equal to 3.89 € h−1 while using gasoline, and 2.19 € h−1 when using LPG. The mass flow rate (0.66 t h−1) and volumetric flow rate (3.5 m3 h−1) of a wood chipper powered by a low-power (9.5 kW) internal combustion engine with spark ignition were determined. In addition, we determined the cost of producing 1 m3 of biomass from chipping freshly cut oak branches (Quercus robur L. Sp. Pl. 996 1753) with a maximum diameter of 80 mm and a humidity of 25%. The branches were selected earlier in such a way that their dimensions as as similar as possible. This amounted to EUR 1.11 for a gasoline-powered drive and EUR 0.63 for a LPG powered one. The benefits of using an alternative fuel supply system, the installation of which increases the cost of the machine by 8.4%, have been confirmed.

New drum-chipping technology for a more uniform size distribution of wood chips

AbstractWood chips from a novel type of drum chipper were compared to wood chips from a conventional disc chipper in an evaluation based on demonstration-scale and industrial-scale machinery. The evaluation was performed as the wood chippers were used as production machines in a kraft pulp mill using softwood. The average bulk density of the wood chips from the disc chipper and the drum chipper was similar and within the range of 138–140 kg/m3. The size distribution of the wood chips was investigated using a conventional screening method, and by using an automatized image-analysis system based on laser scanning. The average length was set to be the same, but the wood chips from the drum chipper had a more uniform length. The average thickness was similar, but the drum chipper generated slightly more thinner wood chips. Compared to the disc chipper and using the screening method, the drum chipper generated a similar fraction of oversized and overthick wood chips, 51% more large accept chips, 11% more total accept chips, and 74% less pin chips and fines. Image analysis resulted in similar data. The results indicate that drum chippers warrant further attention as an alternative to conventional industrial-scale disc chippers.

Determining the repair and maintenance cost of wood chippers

Chipping weighs heavily on the total delivered cost of wood fuel, which calls for accurate chipping cost estimates. Chipper repair and maintenance cost is perhaps the most obscure among the figures required for a reliable estimate of chipping cost. To clarify this issue, the authors examined the long-term repair and maintenance records for 51 wood chippers operated by 48 chipping service contractors. Repair and maintenance represented between 1.5% and 29% of total chipping cost, inclusive of fuel and labour (mean = 14%). The ratio between total accumulated repair (TAR) cost and machine price averaged 32% and varied with total use. The relationship between total use and TAR to price ratio was explored through regression analysis, which produced a very strong model (R2 = 0.8). This model predicts a TAR to price ratio of 0.64 at 10000 h, with no significant differences between tractor-driven and independent-engine machines. While the coefficients are different, the structure of this model offers a good match with the repair and maintenance cost models developed for farm tractors and other agricultural machinery. A second model was developed for estimating repair and maintenance cost as a function of fuel consumption. The study also provides reference figures for the contribution of labour cost to total maintenance cost. Farm tractors incur more repairs than preventive maintenance, contrary to the other dedicated components of the chipping operation, where preventive maintenance represents most of maintenance cost. Forestry users should make allowance for the lower structural strength of tractors and select large models.

Occupational fatal injuries associated with mobile hand-fed wood chippers.

Workers are killed every year in wood chipper-related incidents despite the repeated hazard warnings. In-depth, comprehensive, and up-to-date studies are needed to identify causal, risk, and contributing factors and assess the current control measures so that an effective and proactive prevention approach can be developed. Cases were identified from four online databases and manually reviewed to characterize and categorize the fatal events. The study identified 113 wood chipper-related worker deaths (1982-2016). The victims were killed in struck-by (57), caught-in (41), motor vehicle (7), electrical (4), fall (2), and heat stroke (2) incidents while performing chipper-related tasks. Chipper-related worker deaths are preventable. Young and inexperienced workers may be at higher risk for caught-in deaths. The current feed wheel control devices are not effective for workers to self-rescue. Fully automatic feed wheel stop devices are needed to prevent caught-in incidents.

Efficiency of stump chipping of soft and hard broadleaves

Stump removal is a regular measure of terrain preparation during the establishment of poplar plantations. It is implemented in order to increase the efficiency of implementation of regular silvicultural measures, but also the efficiency of comprehensive wood mass utilization. Stump removal in poplar plantations is performed by various facilities, including various types of wood chippers attached to a tractor of certain technical characteristics. The aim of this paper is the evaluation of efficiency of the tractor ?Same Laser 150? with the wood chipper ?Rotor S? attached to it, during the stump chipping of soft and hard broadleaves in various operating conditions. The research was carried out in several sample plots located in an area managed by the public enterprise ?Vojvodina sume?. The differentiation of the operating conditions was based on multiple criteria (distance between stumps, level of forest order establishment, carrying capacity of the ground, percentage share of tree species, etc.). The work effects of stump chipping were established using the work and time study. The duration of stump chipping ranged from 0,82 min/stump to 2,29 min/stump and it depended on stump diameter, root system development, diameter of the auger used for stump chipping, tractor power, etc. In addition to being dependent on some other things, chipping time depends on the number of passes and auger diameter. The time of transition from stump to stump is under the highest impact of ground conditions, which implies the amount of wood residue, the presence of stump shoots, and the occurrence of high weeds. The implemented analysis served as the basis for the ranking of the factors depending on their impact on the work effects of the investigated facility. In addition, it was concluded that greater effects can be achieved by using the command that provides a forward and backward movement of the aggregate without pushing the clutch pedal and pulling the gearshift lever, but also by installing a handle for the change of rpm (revolutions per minute) of the output shaft in the driver?s cabin. This handle is currently located on a differential housing next to the left wheel, so the driver has to leave the cabin to change the rpm of the output shaft. Another problem is that the tractor ?Same Laser 150? has double commands installed in the cabin: the clutch, brake and gas pedal, but when the seat makes a 180 degree turn those pedals are not at the adequate height. In addition to that, the operator does not have enough space for work in the tractor cabin. An increased cabin space and a better position of the above mentioned commands would enhance work efficiency.

Value Retention, Service Life, Use Intensity and Long-Term Productivity of Wood Chippers as Obtained from Contractor Records

Acknowledging the absence of up-to-date empirical data on the value retention, service life and annual use of chipping machinery, in 2017 the authors surveyed the records kept by 50 contractors offering biomass chipping services. The machine fleet and operations in this survey could be taken as representative for most of Europe, where the biomass sector is well established and is facing further expansion. Data collection included the whole chipping unit, comprised of chipper, carrier and loader. Manually-fed units were excluded from the survey. The data pointed at a service life up to and exceeding 10,000 h and 10 years, which relieved any concerns about poor durability. Value retention was good, and may exceed that of other mainstream forestry equipment. Engine power was the main explanatory variable in any models to predict purchase price and productivity. The effect of this variable could explain most of the variability (>80%) in the purchase price and productivity data. Results also pointed at the essential equivalence in price and productivity between PTO-driven (i.e., tractor powered) and independent-engine chippers, once differences in engine power are accounted for. However, the distribution of purchase price between different components of the chipping unit was different between the two unit types, with the chipper accounting for a larger proportion of the total investment in independent-engine units. Machine power was also different, with most PTO-driven units being significantly smaller than independent-engine units, due to the limitations of existing tractors. Furthermore, half of the carriers assigned to a PTO-driven unit were subject to flexible use, i.e., they were not solely used for chipping work.

Safety Improvements on Wood Chippers Currently in Use: A Study on Feasibility in the Italian Context

Following formal opposition by France, the harmonized safety standards regarding manually-loaded wood chippers (EN 13525:2005+A2:2009) which presumed compliance with the Essential Health and Safety Requirements (EHSR) required by the Machine Directive (Directive 2006/42/EC), have recently been withdrawn, and a new draft of the standard is currently under revision. In order to assess the potential impact of the expected future harmonized standards within the Italian context, this study has examined the main issues in implementing EHSRs on wood chippers already being used. Safety issues regarding wood chippers already in use were identified in an analysis of the draft standard, through the observation of a number of case studies, and qualitative analysis of the essential technical interventions. A number of agricultural and forestry operators and companies participated in the study, pointing out the technical and economic obstacle facing the safety features requested by the pending new standard. It emerged that the main safety issues concerned the implementation of the reverse function, the stop bar, and the protective devices, the infeed chute dimension, the emergency stop function, and the designated feeding area. The possibility of adopting such solutions mainly depends on technical feasibility and costs, but an important role is also played by the attitude towards safety and a lack of adequate information regarding safety obligations and procedures among users.

The chipping cost of wood raw material for fuel in Estonian conditions

Abstract In Estonia up to now the producers of wood fuels have not yet adequately analysed the production and transport costs although it is known that the share of these costs form up to half of the final price of wood chips or hog fuel. With this in mind the goal of the case study was defined – to analyse the price formation of comminuted wood fuels in Estonian conditions. Within one year of the survey the initial data was collected from the company SLG Energy. Different types of machines (7 in total) were observed – wood chippers Jenz HEM 561, Jenz HEM 582, Heinola 910ES, and Doppstadt DH 608. All machines were equipped with a GPS tracking device which recorded the route and the fuel consumption and during the observation period all costs and revenues related to the concerned machines were accounted. It was determined that due to frequent repairs the maintenance costs of older machines were higher and productivity lower compared with new machines. The biggest item of expenditure turned out to be the fuel consumption. The second was the cost of repairs in the case of older machines and price in the case of new machines. Also the type of chipper had an impact on the production cost. Under the cumulative effect of various factors the production cost turned out to vary widely from 1.03 to 2.38 €/ml 3.

Exposure to noise in wood chipping operations under the conditions of agro-forestry

An increasing number of agricultural contractors are getting into industrial wood chipping, following the rapid expansion of fiber farms on ex-arable land. Wood chippers are noisy machines and agricultural contractors tend to work long hours, which raises the question about their exposure to noise. The objective of the study was to quantify noise exposure for this occupational group. The Authors selected a representative operation and monitored noise exposure for five full working days, covering the main job types typically encountered in agro-forestry. Noise exposure was highest during chipping time, with 81.8 dB(A). The main source of noise was the powerful diesel engine, followed by the chipper drum: they generated the highest noise levels in the 100–200 Hz and the 20–50 Hz frequency ranges, respectively. Daily noise exposure did not exceed the 80 dB(A) lower action value, and it was similar to the exposure of other workers operating industrial in-wood chippers. However, future optimization measures may lead to increasing the proportion of total time when the machine is under full load, and it generates the highest noise levels. Modeling exposure as a function of efficiency showed that exposure levels may exceed the lower action values, once utilization will increase above 64%. This is a realistic target, which may be achieved in the near future. Fortunately, the problem will materialize only with some specific operation types, which represent a minor component in the wood basket of agro-forestry chipping companies.

Fatal and Nonfatal Occupational Injuries Involving Wood Chippers—United States, 1992-2002

Tree damage from storms and routine tree-trimming operations prompt the need for disposing of branches and brush. Mobile wood chippers shred branches and tree trimmings into mulch. Branches are fed into a chute, in which rotating blades macerate the wood. Mobile chippers pose potential dangers to operators, who can become caught in the feed mechanism and pulled into the rotating chipper knives or struck by the hood of the machine while it is being opened or closed with the knives still rotating. This report summarizes data describing fatal and nonfatal injuries related to occupational wood chipper use, which indicate that those working with mobile wood chippers are at risk for serious injury and death, but that these injuries can be prevented through proper training, machine maintenance, and the use of personal protective equipment.

Injury Associated with Working Near or Operating Wood Chippers

Injury Associated with Working Near or Operating Wood Chippers

Representative noise levels of snow making, slope grooming, and other ski area equipment

In the process of producing the environmental noise assessment for a major expansion of the Mt. Wachusett (MA) ski area, noise data for ski area equipment were collected. Modern ski areas are highly mechanized. Snow making equipment includes large air compressors and snow guns or other air/water dispersal devices. Slopes and trails are groomed by special tractors towing various rollers, plows, scrapers, etc. to provide well‐packed mogul‐free surfaces. Much of the snow making and grooming activities take place at night. By day snowmobiles are used to transport the ski patrol to serious accidents and mechanics to repair stalled lifts. Construction of new ski trails requires additional, typically loud equipment such as chain saws, log skidders, wood chippers, bulldozers, etc. In the rural environment of ski areas these activities can exceed ambient noise at considerable distances. Furthermore, the trend to overnight accommodations for skiers directly on ski hills requires consideration of such equipment noise.

The Application of Synchronous and Induction Motors to Chippers

Wood chippers require motors with special characteristics to operate under exacting conditions involving high peak loads, severe vibration, acceleration of high inertia, and exposure to dirt and moisture. Methods are given to select the most suitable size of chipper, to determine the proper rating and characteristics of a motor to drive it, to choose beetwen synchronous and induction motors, and to select the mechanical arrangement of the drive. The modifications in mechanical construction of the motors to enable them to withstand the severe operating conditions are described and illustrated. Desirable features to be included in the control are given.