Fuel consumption of forest machinery and vehicles depends mainly on terrain conditions, working methods, drivers’ skills, engine load under working conditions, engine speed, type and technical characteristics of the machine. In timber harvesting operations, fuel consumption is significant for both, economic (costs), and environmental issues (80-95% of exhaust emissions and soot particles are associated with fuel consumption). The objective of this study was to compare fuel consumption in two different forwarders and to analyse two different measuring devices for fuel consumption. Fuel consumption was measured on a 6-wheeled Valmet 840.2 forwarder and an 8-wheeled Valmet 860.4 during roundwood and energy wood extraction in winter period. A differential fuel flow meter and a fuel measuring probe were used for measuring fuel consumption as well as a Fleet Management System (FMS) for transmitting measured data. Fuel consumption was expressed in six different ways depending on the stage of the working cycle, time, travelled distance, load volume and load mass. Finally, both the advantages and disadvantages of the used fuel measuring devices were gained. The results indicated higher fuel consumption of the smaller Valmet 840.2 forwarder due to lower soil bearing capacity and longer extraction distances. For both forwarders, higher fuel consumption (expressed in l t-1 km-1) was observed while extracting energy wood due to its lower overall mass.
Fuel consumption in timber harvesting operations is of economic and ecological importance. It may vary depending on ground and operating conditions, drivers’ skills, engine load under different operating conditions, engine speed, type and technical characteristics of the vehicle. Determining the influence of certain factors is difficult due to an interaction of individual factors (
The rational organisation of timber extraction consists of a series of factors that can affect the reduction of fuel consumption thus affecting the other costs of timber harvesting operations. Main factors influencing the reduction of fuel consumption are: (i) the selection of a vehicle, which is based on its technical characteristics and working conditions in the stand; (ii) the regular maintenance of the vehicle; (iii) the application of the appropriate technology with a good organisation of work, a motivation of the driver and his/her professional training.
Fuel consumption of machinery is often expressed as energy consumption per unit of extracted timber (MJ m-3), fuel consumption per unit of extracted timber (l m-3) or per unit of time (l h-1). However, as the fuel consumption of timber extraction is directly dependent on the extraction distance, the most accurate way of expressing fuel consumption is per mass of extracted timber along with the extraction distance (l t-1 km-1) in both long-distance truck transportation or short-distance timber transportation from the stand to the landing site.
The simplest way to measure fuel consumption of machinery and vehicles is the volumetric method of refilling the tank with fuel at the end of the working operations or at the end of the working day. The filling up of the tank is carried out by using a measuring gauge or by using a measuring gun for accurate measurements (
where Q is the fuel consumption (L m-3), V is the load volume (m3), and L is the average extraction distance (m).
Beneficial effect of the CTI system on fuel consumption and soil damage was already given by
Forwarder with an electric-hybrid transmission, compared to the standard hydrostatic-mechanical transmission has a lower fuel consumption up from 20% to 50% and a lower mass because of a simpler transmission system without a bogie axle. Its mass is 9,500 kg, while its carrying capacity is 12,000 kg (
It is known that in the near future substantial reductions in greenhouse gas emissions from transportation will be required. This study aims to compare the fuel consumption in two different forwarder models during extraction of roundwood and energy wood in the lowland stands of pedunculate oak in order to assess the impact of changes in different vehicles, loads and stand conditions on transportation energy consumption.
The study was conducted in the compartments 143a (45° 03′ 52.2″ N, 18° 53′ 35.4″ E) and 64f (44° 57′ 11.6″ N, 19° 02′ 56.2″ E), Forest Administration Vinkovci, lowland part of Croatia. The research was carried out during seed and final cut in the stands of pedunculate oak and narrow-leafed ash. Age of the stand in the sub-compartment 143a was 134 years, and a total of 249 trees were marked for the seed cut comprising to the volume of 537 m3. Average length of the assortments was 3.71 m with average volume of 0.47 m3. Age of the stand in the sub-compartment 64f was 140 years, and a total of 203 trees were marked for the final cut comprising to the volume of 1221 m3. Average length of the assortments was 3.43 m with average volume of 0.80 m3. Terrain was flat with an altitude between 79-81 m. In the investigated departments, felling and processing were made with a chainsaw. Forest residues were transported by forwarders, which means that the transport of energy wood took place after the transportation of the roundwood. Felling and extracting were time-separated. The timber was processed by a buck-to-quality method according to the current standards, while the crowns were cut as needed for easier loading and transportation of energy wood. During the extraction of roundwood by Valmet 840.2 forwarder, the ground was covered with a 10 cm thick snow cover that was melting on a daily basis. The snow has completely melted until the last day of the extraction of energy wood (measured soil cone index -
The objects of research were a 6-wheel Valmet 840.2® forwarder (
For measuring fuel consumption of Valmet 860.4® forwarder a LLS 20160® fuel measuring probe (Omnicomm, Moscow, Russia) was used in the second part of the research. The measuring probe detects a sudden drop in fuel levels and uses a Fleet Management System (FMS) with wireless data transmission to the machine owner.
The FMS’s role is to record specific parameters on the vehicle and wireless data transfer
The biggest advantage of the mobile unit is that it can be connected to different measuring transducers that can be used to monitor the operation of the vehicle. The measuring transducers that were connected to the mobile unit in this study were a flow meter device for measuring fuel consumption and a tachometer for measuring the speed of the propulsion engine. The mobile unit was also connected to forwarders’ computer and to one of the solenoid valves of the hydraulic installation through which the hydraulic crane is operated.
In the data obtained from the control centre system (FMS), containing the fuel consumption along with the coordinates of the forwarders’ position, detection of hydraulic crane operation and the engine speed is shown in dependency of time. All recorded parameters were compared in the program package ArcGIS® ver. 10.1 (ESRI, Redlands, CA, USA) and fixed (transition) points were determined. Fixed points represent the shift between the individual stages of the working cycle. Each working cycle was divided into four basic stages: (i) driving unloaded; (ii) loading; (iii) driving loaded; and (iv) unloading. Based on the transition points, fuel consumption was calculated for each of the individual stage and finally for the total fuel consumption of each working cycle (l cycle-1).
With the help of the transition points and with calculation, a time duration of each stage of the working cycle was obtained, which provided data for the calculation of the total period of each working cycle and hourly fuel consumption (l h-1).
Using ArcGIS based on the recorded coordinates of the position of the forwarder, the length of the travelled distance was obtained, and the fuel consumption was expressed by consumed fuel per 100 m of travelled distance (l 100m-1).
During the extraction of the logs, the data of identification plates (containing tree species, volume, assortment type, etc.) of the assortments were gathered on the landing site. Identification plates were placed on the front of every log in the forest stand after processing and before extraction. Based on these numbers a gross volume (over bark) of each piece of roundwood in each working cycle of forwarders was obtained. The length of the logs was measured with a measuring tape, and a calliper was used for measuring mid-diameter of each log. The fuel consumption in each working cycle of forwarders was related to the total gross volume of logs, and based on that fuel consumption per cubic meter of extracted timber (l m-3) was calculated.
On the landing site, a portable measuring platform described by
Finally it was decided that the most accurate way to express fuel consumption is the ratio of consumed fuel to travelled distance and the mass of the extracted timber (l t-1 km-1).
Statistical analysis was carried out using the software package STATISTICA® ver. 8 (StatSoft Inc., Tulsa, OK, USA). To examine significant differences between two independent data sets, Student’s
In the case of fuel consumption per working cycle, higher consumption was observed during extraction of roundwood (15.61 l cycle-1) than while extracting energy wood (14.81 l cycle-1), but according to the
The reason for the higher fuel consumption during extracting of roundwood can be attributed to the higher mass loadable due to a higher bulk density of the load, which averaged in 12.317 kg and which is statistically different from the average mass of energy wood (8,468 kg). Though, the extraction differences in distances for roundwood (2,272 m) and energy wood (2,335 m) were not statistically significant.
The fuel consumption per metric tons of transported load was higher when extracting energy wood (1.74 l t-1) and significantly differed from fuel consumption when extracting roundwood (1.29 l t-1). The reason for the higher fuel consumption during extraction of energy wood expressed in this way was the lower average mass of energy wood load compared to loads of roundwood.
The fuel consumption per gross volume of the load when extracting roundwood was 1.18 l m-3. According to the fuel consumption expressed in l t-1 km-1, the value of 0.56 l t-1 km-1 while extracting roundwood was achieved, while the fuel consumption during extraction of energy wood was 0.78 l t-1 km-1. The difference between these two values was statistically significant.
The increasing trend is the same while extracting both roundwood and energy wood, but the amount of fuel consumption is higher when it comes to energy wood extraction because of the reduced load mass (
The biggest share in forwarders’ fuel consumption was while driving unloaded (
In the case of a loading stage, the share of fuel consumption while loading energy wood (27.2%) was higher than while loading roundwood (17.2%). While loading energy wood, timeshare was also higher (42.3%) compared to time used for loading roundwood (29%). The reason for the higher fuel consumption and the amount of time during loading energy wood was the higher number of solenoid valve engagements for the displacement of the hydraulic crane (163) and the higher workload of the hydraulic crane compared to loading roundwood where on average 99 engagements were detected (the crane was controlled
Higher fuel consumption per working cycle was recorded during extraction of energy wood (7.09 l cycle-1) compared to extraction of roundwood (6.22 l cycle-1 -
Fuel consumption expressed in tons of extracted timber was lower during roundwood extraction (0.44 l t-1) compared to fuel consumption during energy wood extraction (0.9 l t-1) with a statistically significant difference. The reason for this is almost 50% lower mass of average load of energy wood (7,996 kg) compared to the average mass of roundwood load (14,689 kg).
A similar situation was also observed in fuel consumption expressed in l t-1 km-1, where the fuel consumption while extracting roundwood was almost halved (0.45 l t-1 km-1) compared to the fuel consumption during energy wood extraction (0.83 l t-1 km-1) with a statistically significant difference.
The largest share of fuel consumption refers to the loading stage of both loads together with the highest timeshares (
The share of travelled distance (driving unloaded, driving loaded) during extraction of energy wood differed significantly from the share of travelled distance during extraction of roundwood. The reason for this was the further landing site position for energy wood. It is interesting to note that despite a bigger share of travelled distances while extracting energy wood (driving loaded), the percentage of fuel consumption was lower compared to driving loaded during extracting roundwood, which indicates that fuel consumption is directly affected by load mass.
Significant differences existed in the share of fuel consumption while loading and unloading. A higher share of fuel consumption was recorded while loading energy wood. This was due the large and curved branches of old oak crowns that were difficult to load in order to maximise the yield of the load carrying capacity. Contrasting results were obtained while unloading. In case of unloading the roundwood, the forwarder had to maneuver in the landing site to separate the logs depending on quality classes (felling and processing was made using buck-to-quality method), while the unloading of the energy wood was carried without additional maneuvering of the vehicle. The cause of higher fuel consumption may also be due to increased fuel fluctuations, whose change was recorded by the measuring probe during unloading/loading of larger logs and swinging of the entire forwarder.
When comparing both load types, the lowest fuel consumption was measured at the unloading stage (16.5%) and was slightly higher while driving unloaded (18.3%) and higher while driving loaded (22.2%). Fuel consumption shares in this load type followed the ratio of timeshares of working cycle stages.
When extracting round wood, the use of fuel per m3 was generally lower in comparison with energy wood (
Higher fuel consumption was measured for Valmet 840.2 forwarder in all expressed fuel consumption ratios (
Regarding fuel consumption expressed per total travelled distance, fuel consumption was slightly higher for Valmet 840.2 forwarder (0.69 and 0.66 l 100 m-1 for roundwood and energy wood, respectively) than it was for Valmet 860.4 forwarder (0.65 and 0.64 l 100 m-1 for roundwood and energy wood, respectively). The reason for that is that Valmet 840.2 forwarder was for the majority of travelled distance (1550 m of total 2272 m and 2235 m) driving in bad conditions (mud, melting of the snow, low soil bearing capacity, increase of slip, etc.).
Concerning hourly fuel consumption, Valmet 840.2 forwarder had a higher consumption on both types of load (17.36 and 15.17 l h-1 for roundwood and energy wood, respectively) compared to the Valmet 860.4 forwarder (12.13 and 12.48 l·h-1, respectively). Many authors (
Fuel consumption per ton of transported timber was almost three times higher for Valmet 840.2 forwarder compared to the Valmet 860.4 forwarder (1.29
Fuel consumption expressed per gross volume of roundwood was almost three times higher for Valmet 840.2 compared to the Valmet 860.4 forwarder (1.18
Fuel consumption expressed in l t-1 km-1 during roundwood extraction was higher for Valmet 840.2 (0.56 l t-1 km-1) compared to the Valmet 860.4 forwarder (0.45 l t-1 km-1), while the opposite holds for the extraction of energy wood, where Valmet 840.2 forwarder had lower fuel consumption than Valmet 860.4 (0.78
As expected, both forwarders had higher fuel consumption with higher travelling distances, and the higher increase in consumption was for Valmet 840.2 forwarder (
The extraction conditions at the study site where the Valmet 860.4 forwarder was tested (Debrinja, 64f) were more favorable, as the ground was dry and the wheel slipping was below 6%. Moreover, this sub-compartment is located directly beside the forest road along which were the landing sites for roundwood and energy wood. According to the fuel consumption expressed in l t-1 km-1, the fuel consumption of the Valmet 860.4 forwarder while extracting energy wood was slightly higher compared to the Valmet 840.2 forwarder (0.83
The parameter that indicates the fuel consumption per cycle stage is based on the sum of the fuel consumption per each cycle stage, and the parameter showing the fuel consumption per day was obtained based on the fuel level difference at the end and the beginning of the working day, taking into account the refueling during the day (
According to the expression 1 quoted by
One of the important disadvantage of the differential flow meter is its sensitivity to impurities that may appear in the fuel (
The higher fuel consumption of the Valmet 840.2 forwarder reflects the worse working conditions during the test. Both forwarders had higher fuel consumption (expressed in l t-1 km-1) when energy wood was extracted, because of the lower mass of energy wood compared to the mass of roundwood in the individual load of forwarders.
The increased hourly fuel consumption of the Valmet 840.2 forwarder can be partly due to the older generation engine (Valmet 620 DWRE), that meets the Euro 2 exhaust emission standards, and the older fuel injection system used by the line pump. The Valmet 860.4 forwarder is equipped with a newer generation propulsion engine (Sisu 66 CTA) that meets Euro 3 exhaust emission standards, and with a modern CR (Common Rail) fuel injection system, which is considered more energy-efficient.
The fuel consumption measuring probe is not suitable for scientific research due to the large influence of external factors on the fuel level in the tank. In future studies, a flowmeter should be developed, or the fuel delivery system should be upgraded. The upgrading would consist mainly of installing an additional pump to prevent a fuel supply pressure drop due to the installation of a flowmeter less sensitive to external influences, such as those affecting fuel level measurements with a measuring probe. However, the flowmeter is sensitive to impurities in the fuel that prevent the normal flow. By installing an additional filter, this problem can be solved. The additional filter also has a positive effect on the pressure drop in the fuel supply system which triggers an alarm, warning about the occurrence of engine problems.
The solution is the purchase of a forwarder with a factory-fitted flowmeter for measuring the fuel consumption, for which the manufacturer guarantees precision and unobstructed operation during the service life of the vehicle.
Forwarders (a) Valmet 840.2 and (b) Valmet 860.4 (photo: Z. Pandur).
The ratio of fuel consumption and total travelled distance with the Valmet 840.2 forwarder (Slavir, 143a). (a) Roundwood; (b) energy wood.
The ratio of fuel consumption and total travelled distance with the Valmet 860.4 forwarder (Debrinja, 64f). (a) Roundwood; (b) energy wood.
Dependence of fuel consumption per gross volume of roundwood on the total travelled distances. (a) Valmet 840.2 (Slavir, 143a); (b) Valmet 860.4 (Debrinja, 64f).
Main technical features of researched forwarders. (*) Declared: listed in the prospectus for the basic model; weighted: a real mass of researched forwarders with additional equipment (bigger/stronger hydraulic crane, front pushing board, etc.).
Feature | Valmet 840.2 | Valmet 860.4 |
---|---|---|
Drive equation | 6 x 6 | 8 x 8 |
Mass (kg) - declared/weighted * | 13.800 /16.100 | 16.060 /18.750 |
Load carrying capacity (kg) | 11.000 | 14.000 |
Length (mm) | 9.007 | 9.920 |
Width (mm) | 2.640 | 2.760 |
Height (mm) | 3.800 | 3.906 |
Ground clearance (mm) | 680 | 680 |
Engine type | Valmet 620 DWRE | Sisu Diesel 66 CTA |
Power (kW) at 2.200 rpm | 124 | 145 |
Euro emission standard | Euro 2 | Euro 3A |
Torque (Nm) | 670 Nm at 1.400 rpm | 800 Nm at 1.500 rpm |
Transmission | Hydrostatic-mechanical | Hydrostatic-mechanical |
Length of bunk area (mm) | 4.200 | 4.400 |
Hydraulic crane type | CRF 7 | CRF 14 |
Maximum crane reach (m) | 9.1 | 7.5 |
Tires: front | 600/65 x 34 | 600/55 x 26.5 |
Tires: rear | 600/55 x 26.5 | 600/55 x 26.5 |
Fuel consumption of Valmet 840.2 and Valmet 860.4 forwarders. Values in the same row (for each forwarder separately) marked with the same letter do not represent significant difference according to
Characteristic | Units | Valmet 840.2 | Valmet 860.4 | ||
---|---|---|---|---|---|
Roundwood | Energy wood | Roundwood | Energy wood | ||
Fuel consumption - |
l cycle-1 | 15.61a | 14.81a | 6.22a | 7.09a |
l 100 m-1 | 0.69a | 0.66a | 0.65a | 0.64a | |
l h-1 | 17.36a | 15.17b | 12.13a | 12.48a | |
l t-1 | 1.29a | 1.74b | 0.44a | 0.9b | |
l m-³ | 1.18 | - | 0.42 | - | |
l t-1 km-1 | 0.56a | 0.78b | 0.45a | 0.83b | |
Working cycles | n | 28 | 24 | 57 | 48 |
Load mass | kg | 12.317a | 8.468b | 14.689a | 7.996b |
Load volume | m3 | 13.37 | - | 15.08 | - |
Total extraction distance | m | 2.272a | 2.235a | 1.000a | 1.235b |
Shares of fuel consumption by stages of the working cycle of the Valmet 840.2 forwarder (Slavir, 143a).
Stage | Time share (%) | Share of fuel consumption (%) | Share of travelled distance (%) | Hydraulic crane engagement ( |
||||
---|---|---|---|---|---|---|---|---|
Roundwood | Energywood | Roundwood | Energywood | Roundwood | Energywood | Roundwood | Energywood | |
Driving unloaded | 16.8 | 17.8 | 30.2 | 32.3 | 41.2 | 42.5 | - | - |
Loading | 29.0 | 42.3 | 17.2 | 27.2 | 7.7 | 9.8 | 99 | 163 |
Driving loaded | 19.5 | 20.9 | 28.2 | 28.2 | 42.5 | 44.4 | - | - |
Unloading | 34.7 | 19.0 | 24.4 | 12.3 | 8.6 | 3.4 | 163 | 78 |
Shares of fuel consumption by stages of the working cycle of the Valmet 860.4 forwarder (Debrinja, 64f).
Stage | Time share(%) | Share of fuelconsumption (%) | Share of travelleddistance (%) | |||
---|---|---|---|---|---|---|
Roundwood | Energy wood | Roundwood | Energy wood | Roundwood | Energy wood | |
Driving unloaded | 19.2 | 14.7 | 13.8 | 18.3 | 36.2 | 37.2 |
Loading | 40.6 | 46.5 | 33.2 | 43.0 | 14.5 | 9.1 |
Driving loaded | 22.3 | 22.0 | 31.8 | 22.2 | 41.3 | 51.2 |
Unloading | 17.9 | 16.8 | 21.2 | 16.5 | 8.0 | 2.4 |
Total fuel consumption measured by measuring probe on the Valmet 860.4 forwarder per stages of the working cycle and on a daily level.
Fuel consumption | Roundwood | Energy wood |
---|---|---|
Working cycles (n) | 57 | 48 |
By stages of working cycle (l) | 354.6 | 340.3 |
By day (l) | 416.6 | 372.4 |
Difference (%) | 14.88 | 8.62 |