In memoriam – U spomen
Yuri Gerasimov (1946–2013)
Yuri Gerasimov was born on the 8th August 1964
and passed away on a business trip in Germany on the
30th September 2013.
Yuri graduated in 1986 from the Forest Engineering
Faculty of the Petrozavodsk State University. Then he
worked as a researcher and did his post graduate and
doctorate studies in the Leningrad Forest Engineering
Academy.
In 1995 he was awarded the doctor of science degree by the St. Petersburg Forest Engineering Academy. He served then the Petrozavodsk State University
1995 – 2000, first as a teacher, then as an associate professor and finally as a professor of forest technology.
During that time, he also participated in cooperation
and staff exchange between the Petrozavodsk State
University and the University of Joensuu in Finland.
Yuri moved to the Stora Enso company in 2000, first
as the Head of the Representative Office in Petrozavodsk, and later as the Business Planning Manager in
the St. Petersburg office.
Croat. j. for. eng. 34(2013)2
In April 2004, Yuri moved to Joensuu in Finland
and back to research. He started at the Finnish Forest
Research Institute (Metla) first as a project researcher
in Russian forestry related R&D projects. His task was
to develop methods and tools for the analysis of different forest management practices, harvesting technologies, and wood procurement methods for the
conditions in Northwest Russia. In late 2009, Yuri was
elected for a permanent position in Metla as a senior
researcher.
As a senior researcher, Yuri continued dealing the
above themes, but also including forestry in Central
and Eastern European countries. Based on his excellent and diverse contacts research cooperation
strengthened not only with the Petrozavodsk State
University, but also with many other partners. Metla’s
register on performance reflects his dedication to research: on top of about 150 publications, tens of presentations in conferences and workshops. Last years
were productive. Few articles are still in the peer review process, and several articles were in the planning
phase. Yuri was supposed to present results of one of
the most recent article in Stralsund, Germany, at the
46th International Symposium on Forestry Mechanisation, but he passed away just a few hours earlier.
Yuri was a member of the Russian Academy of
Natural Sciences, member of the Scientific Council
evaluating PhD and DSc thesis in the Petrozavodsk
State University, editor in chief of the refereed journal
Resources and Technology. He was also docent at the
University of Eastern Finland, the School of Forest Sciences.
With respect,
Timo Karjalainen
Professor, Finnish Forest Research Institute
173
Original scientific paper – Izvorni znanstveni rad
Productivity and Cost-Efficiency of Bundling
Logging Residues at Roadside Landing
Juha Laitila, Marica Kilponen, Yrjö Nuutinen
Abstract – Nacrtak
The aim of this case study was to clarify the productivity and cost of a system based on bundling logging residues at the roadside landing with the forwarder-mounted logging residue
bundler. In order to find the bundling productivity, a set of time studies was carried out, in
which several working techniques were tested and evaluated. The cost-efficiency of the roadside
bundling system was compared with the conventional bundling system, wherein the logging
of residue logs is made directly in the terrain and, after bundling, the logging residue logs are
forwarded to the roadside landing with a forwarder. The harvesting cost (bundling and forwarding) of the extracted wood biomass to the roadside landing was calculated for bundling
systems using time study data obtained from this study and productivity models and cost
parameters acquired from the literature.
The productivity of roadside bundling ranged from 48 to 53 logging residue logs per effective
working hour (E0h), depending on the working technique used, and the mean time required to
produce one logging residue log ranged from 83.6 to 92.3 seconds (E0h). The harvesting costs
of the logging residue logs (€/m3) at the roadside landing were 11.5–13.7 €/m3 for the system
based on bundling in terrain and 10.8–17.7 €/m3 for the system based on bundling at the
roadside landing, when the forwarding distance was in the range 100–600 m and the removal of
logging residues was in the range 30–90 m³/ha (m3 = solid cubic metre). According to our results,
bundling at the roadside landing allowed a reduction in harvesting costs, when the forwarding
distance of the logging residues was 100 m or less and removal was beyond 50 m³/ha. The cost
savings were quite small, however, at 0.1–0.7 €/m³.
Keywords: Bundling, logging residue logs, productivity, compaction, harvesting, forest biomass, logging residue bundler
1. Introduction – Uvod
The system, based on logging residue logs and
comminution at a plant was launched into commercial
use in Finland in the beginning of 2000, when the supply of forest biomass to the world’s largest biofuelfired CHP plant – Oy Alholmes Kraft Ab – was developed (Laitila 2000, Poikola et al. 2002). Due to the long
transport distances, large procurement area and enormous annual harvesting volumes, the circumstances
for introducing the novel large-scale production technology were favourable on the west coast of Finland.
In addition, integration of bundle production into the
procurement of industrial roundwood was straightforward, and the synergies were significant because
the CHP plant Alholmens Kraft is located within the
Croat. j. for. eng. 34(2013)2
large pulp-, paper- and sawmill integrate of the forest
industry company UPM (Laitila 2000, Poikola et al.
2002). Another benefit was that all the machines in the
supply system were able to operate independently of
each other, making the system more efficient and reliable (Laitila 2000, Poikola et al. 2002).
In the bundling method (Fig. 1), logging residues
are bundled into cylindrical bales using the compacting device mounted on top of the forwarder deck (e.g.
Laitila 2000, Ranta 2002, Cuchet et al. 2004, Johansson
et al. 2006, Kärhä and Vartiamäki 2006, Stampfer and
Kanzian 2006, Spinelli and Magagnotti 2009, Lindroos
et al. 2010, Spinelli et al. 2012a, Spinelli et al. 2012b).
Feeding and compacting is usually a continuous process, and for these bundling machines (e.g. Timber-
175
J. Laitila et al.
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
Fig. 1 Forwarder-mounted Timberjack/John Deere 1490D logging
residue bundler operating in a clear-cut area
Slika 1. Rad forvardera Timberjack/John Deere 1490D s ugrađenim
bandlerom za šumski ostatak u čistoj sječi
jack/John Deere 1490D, Pika/Pinox RS 2000), compacting can be divided into three phases (Ranta 2002). In
the first phase, the collected logging residues are
pressed by feed rollers. The compacting then continues in a rectangular presser. The last compacting phase
ends with the binding of the pulse-fed logging residue
bundle and, finally, the bundle is cut into the desired
length with a chainsaw. The length of the bundle (logging residue log) can be selected but it is typically
about 3 m with a diameter of 65–75 cm. The average
weight is 418 kg (sd. 111), the solid volume 0.5 m³ (sd.
0.09) and the energy content approx. 1 MWh (sd. 0.17)
(Kärhä and Vartiamäki 2006).
To accrue the benefits of compaction as early as
possible along the supply chain, log-like bundles are
made directly at the stump (Fig. 1) and the bundler
must therefore be installed on a vehicle capable of accessing the cut area (Laitila 2000, Asikainen et al. 2001,
Ranta 2002, Cuchet et al. 2004, Kärhä and Vartiamäki
2006, Spinelli and Magagnotti 2009, Spinelli et al.
2012a, Spinelli et al. 2012b). At the stand, the bundler
drives to the logging residue heap or windrow and
stops to load logging residues into the bundler in-feed.
The bundling unit follows an automatic cycle with actions activated by internal load sensors. Loading and
in-feeding work continue until no more logging residue is within crane reach. Then the forwarder-mounted bundler moves to the next windrow and resumes
the work cycle (Asikainen et al. 2001, Cuchet et al.
2004, Kärhä and Vartiamäki 2006).
In the studies conducted in Finland and France, the
bundling productivities have ranged from 11 to 26 log-
176
ging residue logs per operating working hour (E15h)
(Asikainen et al. 2001, Cuchet et al. 2004, Kärhä and
Vartiamäki 2006). In the most recent Swedish followup study, the average bundling productivity was 28
logging residue logs per effective working hour (E0h)
for the John Deere 1490D logging residue bundler (Eliasson 2011).
After bundling, the logging residue logs are forwarded to the roadside landing with standard forwarders. At the landing, the logging residue logs are
stacked alongside conventional timber assortments
and transported with the standard timber trucks to the
terminal or end-use facility (Laitila 2000, Asikainen et
al. 2001, Ranta 2002, Johansson et al. 2006, Kärhä and
Vartiamäki 2006, Stampfer and Kanzian 2006, Jylhä
and Laitila 2007, Spinelli and Magagnotti 2009, Lindroos et al. 2010, Spinelli et al. 2012a, Spinelli et al.
2012b). Logging residue logs dry well and have good
storage properties if handled correctly (Petterson and
Nordfjell 2009, Eliasson 2011). The unloading of the
logging residue logs takes place at the end-use facility
with similar equipment to that for unloading saw logs
or pulpwood. In the most efficient cases, the logging
residue logs are unloaded directly from the timber
truck to the feeding table of the stationary crusher
(Laitila 2000, Asikainen et al. 2001, Ranta 2002).
In the large-scale procurement of logging residue
chips, bundling has proved to be cost-efficient when
operating with long forwarding and road transportation distances (e.g. Andersson 2000, Laitila 2000,
Asikainen et al. 2001, Kärhä and Vartiamäki 2006,
Ranta and Rinne 2006). However, in current harvesting operations, e.g. in Finland, the average forwarding
distances for logging residues are usually < 300 m,
road transporting distances to CHP plants < 100 km
and the annual consumption of forest chips per CHP
plant almost invariably < 100,000 m³ (solid) (Asikainen
et al. 2001, Laitila et al. 2010, Karttunen et al. 2012), and
the expected breakthrough of logging residue bundling technology was therefore not achieved. Kärhä
and Vartiamäki (2006) underlined that the prerequisite
for increased bundling volumes is a reduction in the
cost of the most expensive sub-stage of the bundling
supply chain, i.e. the bundling itself. This requires,
e.g., improved recovering conditions at bundling sites,
increased bundling productivity and the execution of
bundling operations in two work shifts using an efficient bundler and efficient operator working methods
(Kärhä and Vartiamäki 2006).
A less well-developed alternative in Nordic is to
forward loose logging residues and bundle them at the
landing. Potential benefits of such a bundling process
include a higher concentration of logging residues beCroat. j. for. eng. 34(2013)2
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
J. Laitila et al.
Table 1 Number of bundled logging residue logs per working technique and temperature during the time study
Tablica 1. Broj izrađenih svežnjeva tijekom studija vremena po radnoj tehnici i temperaturi
Working technique I
Working technique II
Working technique III
Working technique IV
Working technique V
Radna tehnika I
Radna tehnika II
Radna tehnika III
Radna tehnika IV
Radna tehnika V
201
193
82
94
113
–10
–3
–22
–3 & –22
–22
No. of logging residue logs
Broj izrađenih svežnjeva
Temperature, C°
Temperatura, C°
cause residue concentration and presentation have
already been recognized as major variables affecting
bundler productivity (Cuchet et al. 2004, Kärhä and
Vartiamäki 2006) and avoidance of requirements for
the expensive bundling vehicles to have off-road capabilities (Wittkopf 2004, Kanzian 2005, Stampfer and
Kanzian 2006, Spinelli and Magagnotti 2009, Lindroos
et al. 2010, Gallagher et al. 2010, Spinelli et al. 2012b).
A truck-mounted bundler (Spinelli and Magagnotti
2009, Lindroos et al. 2010, Spinelli et al. 2012b) would
also be a solution for more cost-efficient recovery of
logging residues from small, scattered cutting areas
due to the smaller relocation costs. One option tested
in a Southern U.S. tree length logging operation, in
order to reduce costs and maximize bundling efficiency, was to adapt the simplified bundler unit for a motorized trailer and feed it by the separate loader at the
landing (Gallagher et al. 2010).
According to Spinelli and Magagnotti (2009), working at the roadside allows for a reduction in machine
moving time from 1–2 min/ton (Cuchet et al. 2004) to
0.3–0.5 min/ton, but this fact alone does not seem to
entail a marked productivity gain; in fact, the forwarder-mounted bundler seems to compensate for this with
a faster bundling pace, which is the result of its capacity to bundle while moving. In this case, the time is
recorded as »moving«, but the machine is also bundling during part of this time, thus maintaining sustained productivity.
2. Aim of the study – Cilj istraživanja
The aim of this case study was to clarify the productivity and cost of a system based on bundling logging residues at the roadside landing with the forwarder-mounted logging residue bundler (John Deere
1490D). In order to find the bundling productivity, a
set of time studies was carried out, in which several
working techniques were tested and evaluated. The
cost-efficiency of the roadside bundling system was
Croat. j. for. eng. 34(2013)2
compared with the conventional bundling system,
wherein bundles are made directly in the terrain, and,
after bundling, the logging residue logs are forwarded
to the roadside landing with a forwarder. The harvesting cost (€/m³) of wood biomass extracted to the road
side landing was calculated for both bundling systems
using time study data obtained from this study, and
productivity models and cost parameters acquired
from the literature (Ranta 2002, Kärhä et al. 2004, Laitila et al. 2010). The bundling system cost comparison
was made at the stand level, and, in the cost comparison, the forwarding distance was in the range 100–600
m and the removal of logging residues was in the
range 30–90 m³/ha.
3. Material and Methods – Materijal
i metode
3.1 Time study of roadside bundling – Studij
vremena izradbe svežnjeva uz cestu
The time study of roadside bundling was conducted in December 2009 at a roadside landing (62°19.398’N,
30°38.691’E) located in the province of North Karelia
in eastern Finland. During the time study, 683 logging
residue logs were bundled and five different working
techniques were tested (Fig. 2, Table 1). The time study
was carried out mainly in natural light during the daytime (7:00–6:00). The sky was cloudless and the temperature range was –3 to –22 C° (Table 1). The ground
had snow cover of 0–1 cm during the experiments (Fig.
3). The length of the bundles was 3 m and the diameter
70 cm. In the time studies, the productivity unit logged
residue logs per effective working hour (E0h).
The bundled logging residues originated from a
clear-cut stand dominated by Norway spruce (Picea
abies), with an average age of the harvested trees of 90
years, height 24 m and diameter (d1.3) 28 cm. The minimum length of the harvested industrial roundwood
was 3 m and the minimum top diameter was 7 cm
(over the bark). The clear cut had been carried out me-
177
J. Laitila et al.
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
Fig. 2 Layout of the bundling study arrangements at the roadside landing using working technique I, II, III, IV or V
Slika 2. Prikaz raspodjele stadija izradbe svežnjeva na pomoćnom stovarištu pomoću radne tehnike I, II, III, IV ili V
chanically in April 2009 using a cut-to-length method
adapted for the recovery of logging residues (Brunberg 1991, Wigren 1991, Wigren 1992, Nurmi 1994). In
July 2009, after drying, »brown« logging residues were
forwarded to the roadside landing and piled into
stacks with a width of 7 m and a height of 5 m (Fig. 3).
The total area of the clear cut was extraordinarily large
(50 hectares), which made it possible to carry out the
bundling study at one stand with homogeneous raw
material and similar bundling conditions for each
working technique at the roadside landing. The bundle properties (moisture, solid content, etc.) were not
studied because they were expected, as estimated by
the author, to be similar for all the studied working
techniques due to the homogenous bundling material
and the same logging residue bundler. It was also
deemed that the properties of the logging residue logs
produced at the roadside landing do not differ from
those produced in the terrain, as the raw material and
compacting unit/bundler are the same.
The layout of the studied working techniques is
described in Fig. 2. In working techniques I and II, two
machines were operating at the roadside landing because the feeding of the bundler was carried out with
a separate loader (forwarder) in order to steer the full
hydraulic capacity of the logging residue bundler into
the bundling process. The bundler was located across
from the logging residue stack, and the loader (forwarder) was on the forest road parallel to the logging
residue stack (Fig. 2 and 3). The piling of the bundles
in the roadside stack was carried out as a separate operation with the loader (forwarder) at the end of the
roadside bundling operation (I) or during the bundling process with the crane of the logging residue
178
bundler (II). In working techniques III, IV & V, the
feeding of the bundler was carried out with the crane
of the logging residue bundler, and one machine was
operating at the landing. The piling of logging residues was carried out either as a separate operation
after bundling (III and IV) or during bundling (V). In
working technique III, the logging residue bundler
was located on the forest road parallel to the logging
residue stack, whereas in working techniques IV and
V, the bundler was located across from the logging
residue stack (Fig. 2).
Fig. 3 Separate loading of logging residues with the Valmet 840.3
forwarder to the feeding table of the John Deere 1490D logging
residue bundler (working methods I and II)
Slika 3. Odvojen utovar šumskoga ostatka forvarderom Valmet
840.3 na opskrbnu traku bandlera za izradbu svežnjeva John Deere
1490D (radna metoda I i II)
Croat. j. for. eng. 34(2013)2
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
The machines used in the study were a John Deere
1490D Eco III logging residue bundler and a Valmet
840.3 eight-wheel forwarder (Fig. 3). The crane models
of the bundler and forwarder were John Deere CF7
and Cranab CRF 8.1 C, and both were equipped with
a special logging residue grapple (e.g. Ranta 2002,
Kärhä and Vartiamäki 2006). Skilful and motivated
machine operators were pre-trained for the studied
working techniques and they had more than five years
working experience in bundling or forwarding logging residues and logging residue logs.
The time study was carried out manually using the
Rufco-900 field computer (Nuutinen et al. 2008). The
output was estimated by counting all the logging residue logs produced during the observation time. The
working time was recorded by applying a continuous
timing method in which a clock runs continuously and
the times for different elements are separated from
each other by numeric codes (e.g. Harstela, 1991). The
logging residue bundler working time was divided
into effective working time (E0h) and delay time (Haarlaa et al. 1984, Mäkelä 1986), which is a common method employed in Nordic work studies. Effective working time was divided into the following work phases
in order of priority:
Loading and bundling: The work cycle began
when the grapple started to move towards the logging
residue stack and ended when a residue bunch was
lifted and placed on the feeding table or into the chamber of the bundler and the feed rollers started to pull
residues into the bundler or the compressing cylinders
of the bundler started to pull residues into the chamber of the bundler.
Bundling (loading is idled): This began when the
feeding rollers or belts of the bundler started to pull
residues into the bundler or the compressing cylinders
of the bundler started to pull residues into the chamber of the bundler and ended when the individual logging residue log was wrapped. The number of binding
points was chosen to be six with double twines, because frozen and dry logging residue is breaking easily and requires more binding.
Cross-cutting (bundling and loading are idled):
This began when a chainsaw emerged from a defence
case and ended when the bundle dropped off.
Moving: This began when the bundler or the separate loader (forwarder) started to move and ended
when the bundler and/or loader stopped moving to
perform other activity. The moving time consisted of
the short move from one work location to another at
the roadside landing.
Piling: The piling of logging residue logs onto the
roadside stack while bundling or as a separate operaCroat. j. for. eng. 34(2013)2
J. Laitila et al.
tion after roadside bundling from the bundle heaps
with the crane of the bundler or the separate loader
(forwarder).
Arrangements: Repositioning of logging residues
on the roadside stack in order to improve the loading
work or shake off snow, ice or other impurities.
Delays: Time not related to productive bundling
work but with the reason for the interruption recorded. The main reasons for the delayed times being less
than 15 minutes were bundler maintenance (e.g. tightening or replacing the sawchain and adding a bundling cord to the wrapping unit of the bundler), organizational delays (e.g. telephone calls) or personal
breaks.
3.2 Cost comparison of bundling methods
Usporedba troškova među metodama izradbe
svežnjeva
The cost comparison of bundling systems was
made at stand level and in the cost comparison, the
forwarding distance was in the range 100–600 m and
the removal of logging residues was in the range 30–90
m³/ha. At the stand, logging residues were stacked in
good heaps and the heaps were located on both sides
of the strip road. The nature and slope of the ground
surface were normal = flat (Tavoiteansioon perustuvat
puutavaran … 1990).
Bundling productivity in terrain was calculated using the time-consumption model made for the Timberjack/John Deere 1490D logging residue bundler
(Kärhä et al. 2004). Bundling productivity at the roadside landing was based on working technique V reported herein. The solid volume of the logging residue
logs was 0.55 m³ (Kärhä et al. 2004) for both bundling
methods. The length of the logging residue logs was 3
m and it was bound at six points. The effective working hour productivity (E0h) of the bundler in terrain or
at the landing was converted into operating hour productivity (E15h) by the coefficient 1.274 (Kärhä et al.
2004). The bundling productivity at the landing was
33.8/E15h logging residue logs and in terrain it was calculated as 17–18/E15h logging residue logs as a function of logging residue removal (30–90 m³/ha).
The figures for the forwarding productivity of the
logging residues and logging residue logs from the
clear cut with a heavy forwarder (Fig. 4) were calculated using the time consumption models presented
in studies by Ranta (2002) and Kärhä et al. (2004), and
the effective working hour productivity (E0h) of forwarding was converted into operating hour productivity (E15h) by the coefficient of 1.224 (Kuitto et al.
1994, Kärhä et al. 2004). The payload of the forwarder
179
J. Laitila et al.
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
productivity of the logging residue logs was in the
range 15.2–30.8 m3/ E15h.
The operating hourly costs of the forwarder and
forwarder-mounted logging residue bundler were
based on the study by Laitila et al. 2010 and updated
to the current cost level (November 2012) with the cost
index of forest machinery »MEKKI« produced by Statistics Finland (http://www.stat.fi/til/mekki/yht_en.
html) in order to guarantee the validity of the cost
comparison results. The operating hourly costs of the
forwarder and logging residue bundler in this study
were 71.8 €/E15h and 85.3 €/E15h, respectively.
Fig. 4 Forwarding of pre-piled logging residues with a heavy forwarder at the stand
Slika 4. Izvoženje neuhrpanoga šumskoga ostatka s teškim forvarderom u sastojini
was set at 7.2 m³ for logging residues and 25 pieces
(13.8 m³) for logging residue logs. The forwarding productivity of the logging residues was in the range
5.5–11.8 m3/E15h as a function of forwarding distance
and removal of the logging residues. The forwarding
4. Results – Rezultati
4.1 Results of the time study – Rezultati studija
vremena
In relative terms, combined loading and bundling
required on average 55–68 % and cross-cutting 12–21 %
of the effective working time (E15h), when bundling logging residues at the roadside landing (Fig. 5). The piling
of logging residue logs took time, 11–13 %, except for
working technique II (0 %), in which piling was carried
out with the crane of the logging residue bundler during the other work phases (Fig. 5). With working tech-
Fig. 5 Relative time consumption of work phases (%), when bundling logging residues at the roadside landing
Slika 5. Relativan utrošak vremena po radnim fazama (%) pri izradbi svežnjeva na pomoćnom stovarištu
180
Croat. j. for. eng. 34(2013)2
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
J. Laitila et al.
Moving time of the loader, s
Premještanje utovarivača, s
Piling of the logging residue logs to the stack, s
Uhrpavanje izrađenih svežnjeva na složaj, s
Moving time of the bundler, s
Premještanje bandlera, s
Arrangements of the logging residue stack, s
Razmještavanje složaja šumskoga ostatka, s
Cross-cutting of the logging residue logs, s
Prerezivanje izrađenih svežnjeva, s
Separate bundling of logging residues, s
Zasebna izradba svežnjeva od šumskoga ostatka, s
Loading and bundling of logging residues, s
Utovar i izradba svežnjeva od šumskoga ostatka, s
Total time, s
Ukupno vrijeme, s
Radna tehnika V
Working technique V
Radna tehnika IV
Working technique
IV
Radna tehnika III
Working technique III
Radna tehnika II
Working technique II
Radna tehnika I
Working technique I
Table 2 Average time consumption of the work phases per logging residue log and working technique
Tablica 2. Prosječan utrošak vremena radnih sastavnica po izrađenom svežnju i radnim tehnikama
2.0
1.2
–
–
–
10.8
–
11.8
9.8
9.4
3.4
2.5
6.2
7.9
5.1
1.2
1.3
2.5
1.2
1.8
11.5
14.9
11.3
13.6
13.2
0.8
3.1
4.6
6.0
8.6
55.5
48.5
55.9
46.8
45.6
85.3
71.6
92.3
85.3
83.6
Grapple load time, s
Vrijeme utovara kliještima, s
Average number of grapple loads per bundle
Prosječan broj utovara kliještima po svežnju
Radna tehnika V
Working technique V
Radna tehnika IV
Working technique IV
Radna tehnika III
Working technique III
Radna tehnika II
16.4
15.5
15.7
15.7
17.1
3.4
3.1
3.6
3.0
2.7
niques I and II, the shares of mere bundling were 1 %
and 4 %, respectively and, with working techniques III,
IV and V, the shares were 5–10 % (Fig. 5). The share of
arrangements was 1–3 % for all the working techniques.
The moving time for the logging residue bundler was
Croat. j. for. eng. 34(2013)2
Working technique II
Radna tehnika I
Working technique I
Table 3 Average time consumption of the loading cycle (grapple load time) and the average number of grapple loads per logging residue log
and working technique used
Tablica 3. Prosječan utrošak vremena ciklusa utovara (vrijeme utovara kliještima) i prosječan broj zahvata hvatalom po izrađenom svežnju i
korištenoj radnoj tehnici
6–9 % of the effective working time when using working techniques III, IV and V (Fig. 5). With working techniques I and II, the total moving time was 6 % out of
which the loader accounted for 2 and the logging residue bundler for 4 % (Fig. 5).
181
J. Laitila et al.
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
Fig. 6 Average time consumption of work phases per logging residue log in seconds
Slika 6. Prosječan utrošak vremena radnih sastavnica po izrađenom svežnju u sekundama
Combined bundling and loading of logging residues at the roadside landing took on average 45.6–55.9
seconds per logging residue log (Fig. 6 and Table 2).
The mean number of crane grapple loads required to
produce a logging residue log ranged from 2.7 to 3.6
and the average grapple load time was in the range
15.5–17.1 seconds per crane cycle (Table 3). The total
mean time required to produce one logging residue
log ranged from 71.6 to 92.3 seconds depending on the
working technique used (Table 2, Fig. 6).
There were no big differences between the working techniques in terms of bundling productivity per
effective working hour (pieces/E0h) during the time
studies and the feeding of the bundler with a separate loader did not improve the bundling productivity compared with the self-loading logging residue
bundler. The productivity of mere bundling was in
the range 48–53 logging residue logs per effective
working hour (E0h) depending on the working technique used (Fig. 7). When calculating the bundling
productivity, the mere bundling included the time
consumption of the work phases loading and bundling, bundling, cross-cutting and arrangements. The
bundling productivity was 45–49 pieces/E0h at the
roadside landing when the moving time of the bundler and loader were included in the effective work-
182
ing time and 39–43 pieces/E0h when the piling time
was included (Fig. 7). The bundling productivity of
working technique III was somewhat lower than that
of the other techniques, but this can be explained by
the fact that the bundler operator fell ill with the flu
on the day of the time study.
4.2 Results of the bundling method cost comparison – Rezultati usporedbe troškova među
metodama izradbe svežnjeva
The harvesting costs of the logging residue logs
(€/m3) at the roadside landing were 11.5–13.7 €/m3 for the
system based on bundling in terrain and 10.8–17.7 €/m3
for the system based on bundling at the roadside landing, when the forwarding distance was in the range
100–600 m and the removal of logging residues was in
the range 30–90 m³/ha (Fig. 8, Table 4, cf. section 3.2 in
the article). According to our results, bundling at the
roadside landing enabled a reduction in harvesting
costs when the forwarding distance of the logging
residues was 100 m or less and the removal was beyond 50 m³/ha (Fig. 8, Table 4). The cost savings, however, were quite small, 0.1–0.7 €/m³. Traditional terrain
bundling was clearly more cost-competitive in all
stand circumstances when the forwarding distance
was more than 200 m (Fig. 8, Table 4).
Croat. j. for. eng. 34(2013)2
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
J. Laitila et al.
Fig. 7 Average time consumption of work phases per logging residue log in seconds
Slika 7. Prosječan utrošak vremena radnih sastavnica po izrađenom svežnju u sekundama
5. Discussion – Rasprava
According to our time study, feeding the bundler
with a separate loader did not improve the bundling
productivity compared with the self-loading logging
residue bundler, when the length of the logging residue logs was 3 m. The main reason for the result is that
the combined loading and bundling work phase was
interrupted after every 3–4 grapple loads to cross-cut
the produced logging residue log, which means that
there was no time for the loading to become a bottleneck
in the bundling system even though the efficiency and
hydraulic capacity of the compacting unit itself would
enable higher productivity. In order to improve the efficiency of a continuous bundling process, either a more
efficient cross-cutting of bundles should be developed,
or the current length of the logging residue logs should
increase within the constraints imposed by the off- and
on-road transportation and durability of the logging
residue logs. In the studies by Spinelli and Magagnotti
(2009), and Gallagher et al. (2010) the highest bundling
productivity was achieved with the longest target
lengths of logging residue logs. In the study by Gallagher et al. (2010), the bundling productivity was 15.9
tons/E0h when the length of the bundles was 2.5 m and
17.2 tons/E0h for a bundle length of 3.5 m.
Croat. j. for. eng. 34(2013)2
The productivity (39–43 pieces/E0h) achieved in this
study is higher than that reported in the others studies
conducted on the truck-mounted logging residue bundler under central European conditions in Germany,
Austria and Italy (Wittkopf 2004, Kanzian 2005, Spinelli and Magagnotti 2009, Spinelli et al. 2012b). In
Germany, Wittkopf (2004) reports productivity of 12
pieces/E15h and in Austria, Kanzian (2005) mentions
productivity of 11.5–15.2 pieces/E0h. In Italy, the productivity varies between 14 and 22 pieces/E0h (Spinelli and Magagnotti 2009). In studies conducted in
Germany and Austria, the length of the logging residue logs was 3 m (Wittkopf 2004, Kanzian 2005),
whereas in Italy, the target lengths were 4 and 3 m
(Spinelli and Magagnotti 2009).
All these studies were conducted on the very same
machine, the Timberjack/John Deere 1490 bundler on
a 6 x 6 MAN truck (Spinelli et al. 2012b). The unit is
powered by the 353 kW engine of the truck and fed by
a Timberjack CF 710 crane. The truck is equipped with
a modified cab incorporating the crane control seat:
this constitutes a second rotating chair mounted to the
right of the driving seat with an extended rear window. The overall weight of the truck-base bundler is
24 tons (Spinelli et al. 2012b).
183
J. Laitila et al.
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
Fig. 8 Harvesting cost of the logging residue logs (€/m3) at the roadside landing as a function of forwarding distance (100–600 m) and biomass
removal (30–90 m3/ha)
Slika 8. Troškovi pridobivanja svežnjeva (€/m3) na pomoćnom stovarištu u ovisnosti o udaljenosti izvoženja (100–600 m) i sječnoj gustoći biomase (30–90 m3/ha)
Table 4 Harvesting cost (€/m3) of logging residue logs at the roadside landing when the bundling is done either in terrain or at the roadside
landing. The removal of logging residues is 30, 50, 70 or 90 m3/ha and the forwarding distance is in the range 100–600 m
Tablica 4. Troškovi pridobivanja (€/m3) svežnjeva na pomoćnom stovarištu kada se svežnjevi izrađuju na sječini ili na pomoćnom stovarištu.
Uklanjanje je šumskoga ostatka 30, 50, 70 ili 90 m3/ha, a udaljenost je izvoženja u rasponu 100–600 m
Terrain
30 m3/ha
Landing
30 m3/ha
Terrain
50 m3/ha
Landing
50 m3/ha
Terrain
70 m3/ha
Landing
70 m3/ha
Terrain
90 m3/ha
Landing
90 m3/ha
Udaljenost izvoženja
Sječina
30 m3/ha
Stovarište
30 m3/ha
Sječina
50 m3/ha
Stovarište
50 m3/ha
Sječina
70 m3/ha
Stovarište
70 m3/ha
Sječina
90 m3/ha
Stovarište
90 m3/ha
100 m
12.4
13.4
11.9
11.9
11.7
11.2
11.5
10.8
200 m
12.7
14.3
12.3
12.7
12.0
12.1
11.9
11.7
300 m
13.0
15.1
12.6
13.6
12.3
12.9
12.2
12.5
400 m
13.3
16.0
12.9
14.5
12.6
13.8
12.4
13.4
500 m
13.5
16.9
13.1
15.3
12.9
14.7
12.7
14.3
600 m
13.7
17.7
13.3
16.2
13.1
15.3
12.9
15.1
Forwarding distance
The original invention of the logging residue bundler was developed by Swedish company Fiberpak AB
in 1995, and the first bundling units were mounted on
standard forwarders as an attachment. In addition, the
bundling unit was operated with a separate control
system and steering of the bundling unit was managed with own independent hydraulic pump. Whereas e.g. in the John Deere 1490D logging residue bun-
184
dlers, steering of the bundling unit is shared with the
hydraulic line and pump of the forwarder crane. Sharing of the steering system with the forwarder crane
limits the maximum power execution for the bundling
unit and in principle the maximum productivity of the
bundling unit is not possible to achieve without installing an independent hydraulic system or stopping
the movements of the forwarder crane completely.
Croat. j. for. eng. 34(2013)2
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
6. Conclusions – Zaključci
According to the results, bundling at the roadside
landing with a forwarder-mounted bundler made it
possible to reduce the harvesting costs to 0.1–0.7 €/m³
when the forwarding distance of the logging residues
was 100 m or less and the removal was beyond 50 m³/
ha. In practical operations, roadside bundling should
be carried out outside the road area because of the
large amount of material (needles, bark, small branches) that will be dropped on the ground while bundling
‘brown’ residues. In addition, road traffic may disrupt
the bundling work, especially on the public road area,
which also limits the usability of truck- and trailermounted logging residue bundlers. In wintertime, the
cover of snow and frozen logging residues are obviously a problem too for a roadside bundling system in
Nordic conditions. In Finland, the average forwarding
distances are close to 300 m (Asikainen et al. 2001,
Jylhä et al. 2010), which also limits the wide implementation of a roadside bundling system.
The results reported in this paper were based on
theoretical time consumption models and cost parameters from earlier bundling and forwarding studies and
rather limited time study data on bundling productivity at the roadside landing, which limits the generalization of the results. The study also focused on the effective working time (E0h), which is only part of the total
working time. Nevertheless, the results give new estimates for the performance and cost competitiveness of
the roadside bundling system in Nordic conditions and
the operators involved in the study were skilled, using
machinery representatives for the current machines in
use. In order to guarantee the reliability of the reported
case study observations (Hellström and Hyttinen 1996),
the results must be compared with the results of similar
case studies, and efforts should be made to verify the
observed phenomenon.
7. References – Literatura
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Brunberg, B., 1991: Tillvaratagande av skogsbränsle – träddelar och trädrester (Harvesting of forest fuels – tree sections
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the use of a John Deere bundling unit in a Southern US logging system. In publication: Proceedings of FORMEC 2010
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Haarlaa, R., Harstela, P., Mikkonen, E., Mäkelä, J., 1984: Metsätyöntutkimus (Forest work study). Department of logging
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Harstela, P., 1991: Work studies in forestry. University of Joensuu. Silva Carelica 18. 41 p.
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Finnish).
Johansson, J., Liss, J.-E., Gullberg, T., Björheden, R., 2006:
Transport and handling of forest energy bundles – advantages and problems. Biomass and Bioenergy 30(4): 334–341.
Jylhä, P., Laitila, J., 2007: Energy wood and pulpwood harvesting from young stands using a prototype whole-tree
bundler. Silva Fennica 41(4): 763–779.
Jylhä, P., Dahl, O., Laitila, J., Kärhä, K., 2010: The effect of
supply system on the wood paying capability of a kraft pulp
mill using Scots pine harvested from first thinnings. Silva
Fennica 44(4): 695–714.
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from the trials with an energy slash bundler in the mountain).Verfahren Energieholzbundeln im gebirge. Universität
fur Bodenkultur Wien, Department fur Wald- und Bodenwissenschaften. 32 p.
Karttunen, K., Lättilä, J., Korpinen, O-J., Föhr, J., Enström, J.,
Ranta, T., 2012: Large scale container supply chain of forest
chips. In publication: Bioenergy from Forest 2012. Book of
proceedings – Bioenergy from Forest 2012 conference. 263 p.
Kuitto, P.-J., Keskinen, S., Lindroos, J., Oijala, T., Rajamäki,
J., Räsänen, T., Terävä, J., 1994: Puutavaran koneellinen hakkuu ja metsäkuljetus (Mechanized cutting and forest haulage). Metsäteho report 410. 38 p.
Kärhä, K., Vartiamäki, T., Liikkanen, R., Keskinen, S. & Lindroos, J., 2004: Hakkuutähteen paalauksen ja paalien metsäkuljetuksen tuottavuus ja kustannukset (Productivity and
cost of slash bundling and bundle forwarding). Metsätehon
raportti 179. 88 p.
Kärhä, K., Vartiamäki, T., 2006: Productivity and costs of
slash bundling in Nordic conditions. Biomass and Bioenergy
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Laitila, J., 2000: Puupolttoaineiden hankinta Oy Alholmens
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Laitila, J., Leinonen, A., Flyktman, M., Virkkunen, M., Asikainen, A., 2010: Metsähakkeen hankinta- ja toimituslogistiikan
haasteet ja kehittämistarpeet (Challenges and development
needs of forest chips procurement and delivery logistics). VTT
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44(3): 547-559.
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Röser, D., 2008: The accuracy of manually recorded time
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screen. Silva Fennica 42(1): 63–72.
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Rinne, S., 2002: The prerequisites of the bundling method in
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2002. Puuenergian teknologiaohjelman vuosiseminaari, Joensuu, 18–19. syyskuuta 2002. VTT symposium 221: 141–56.
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at the roadside in mountain operations. Scandinavian Journal of Forest Research 24: 173–181.
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evaluation of slash bundling under the conditions of mountain forestry. Biomass and Bioenergy 36: 339–345.
Spinelli, R., Lombardini, C., Magagnotti, N., 2012b: Annual
usage and long-term productivity of a truck-mounted slash
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Wigren, C., 1991: Tillvaratagande av trädrester efter
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Wigren, C., 1992: Uttag av trädrester efter slutavverkining
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Sažetak
Djelotvornost izradbe svežnjeva od šumskoga ostatka na pomoćnom
stovarištu – proizvodnost i trošak
U radu se prikazuje istraživanje proizvodnosti i troškova sustava temeljenoga na izradbi svežnjeva od šumskoga
ostatka na pomoćnom stovarištu pomoću forvardera s ugrađenim bandlerom (John Deere 1490D). Radi utvrđivanja
proizvodnosti izradbe svežnjeva proveden je studij vremena u kojem je ispitano i ocijenjeno nekoliko radnih tehnika
(slika 2). Šumski ostatak za izradbu svežnjeva potječe iz sastojine gdje je obavljena čista sječa, uz prevladavanje
obične smreke (Picea abies) s prosječnom dobi stabala od 90 godina, visine 24 m i prsnoga promjera (d1,3) 28 cm.
Tijekom studija vremena izrađena su 683 svežnja od ostatka sječe. Duljina je svežnjeva iznosila 3 m, a promjer 70
cm. Studij je vremena proveden uglavnom u prirodnom svjetlu tijekom dana (7:00–16:00). Nebo je bilo bez oblaka,
a raspon je temperature bio od –3 do –22 °C (tablica 1). Velika je površina radilišta omogućila provedbu studija
izradbe svežnjeva u istoj sastojini s homogenom sirovinom i sličnim uvjetima rada za svaku radnu tehniku na po-
186
Croat. j. for. eng. 34(2013)2
Productivity and Cost-Efficiency of Bundling Logging Residues at Roadside Landing (175–187)
J. Laitila et al.
moćnom stovarištu. Iskusni i motivirani rukovatelji mehanizacije, prethodno osposobljeni za ispitivanu radnu tehniku, imaju više od pet godina radnoga iskustva na izradbi svežnjeva, izvoženju šumskoga ostatka i/ili izvoženju
izrađenih svežnjeva.
Ekonomičnost sustava izradbe svežnjeva na pomoćnom stovarištu uspoređena je s konvencionalnim sustavom
izradbe pri čemu se svežnjevi izrađuju u sastojini (na radilištu), a naknadno se pomoću forvardera izvoze na pomoćno
stovarište. Troškovi pridobivanja (€/m³) dobivene šumske biomase na pomoćnom stovarištu izračunati su za oba
sustava izradbe svežnjeva na temelju podataka dobivenih studijem vremena, modelima proizvodnosti i cijenama
parametara dobivenih iz literature. Trošak sustava izradbe svežnjeva napravljen je na razini sastojine (radilišta), a u
usporedbi troškova korištena je srednja udaljenost izvoženja u rasponu od 100 do 600 metara i uklanjanje ostatka
sječe u rasponu od 30 do 90 m³/ha.
Proizvodnost izradbe svežnjeva
žnjeva
njeva na pomoćnom
ćnom
nom stovarištu
štu
tu (slika
slika 7) kretala se od 48 do 53 svežnja
žnja
nja šumskoga
umskoga ostatka po efektivnom satu rada (E0h), ovisno o radnoj tehnici i prosječnom vremenu potrebnom za proizvodnju jednoga
svežnja (slika 6) koje se kretalo od 83,6 za 92,3 sekunde (E0h). Prosječan broj zahvata hvatalom dizalice potreban za
čno
no vrij
vrijeme
eme utovara kretalo se u rasponu od 15,5 do 17,1 seproizvodnju svežnjeva
žnjeva
njeva kretao se od 2,7 do 3,6, a prosječno
kunde po ciklusu dizalice (tablica 3). Troškovi izradbe svežnjeva (€/m3) na pomoćnom stovarištu (slika 8, tablica 4)
bili su od 11,5 do 13,7 €/m3 za sustav koji se temelji na izradbi svežnjeva u sastojni i od 10,8 do 17,7 €/m3 za sustav
koji se temelji na izradbi svežnjeva na pomoćnom stovarištu kada se udaljenost izvoženja kretala u rasponu od 100
do 600 m, a uklanjanje šumskoga ostatka u rasponu 30–90 m³/ha.
Temeljem dobivenih rezultata izradba svežnjeva
žnjeva
njeva na pomoćnom
ćnom
nom stovarištu
štu
tu omogućuje
ćuje
uje smanjenje troškova
škova
kova pridobivanja kada je srednja udaljenost izvoženja šumskoga ostatka 100 m ili manja i kada je uklanjanje šumskoga ostatka
iznad 50 m³/ha. Uštede su vrlo male, u rasponu od 0,1 do 0,7 €/m³. Tradicionalna izradba svežnjeva u sastojini je
više troškovno kompetitivna u svim sastojinskim okolnostima kada je srednja udaljenost izvoženja veća od 200 m
(slika 8, tablica 4). U praksi izradbu svežnjeva na pomoćnom stovarištu treba provoditi izvan cesta zbog velike količine
materijala (iglice, kora, grančice) koji padne na tlo. Osim toga, cestovni promet može poremetiti izradbu svežnjeva,
pogotovo na javnim cestama, koje ograničavaju iskoristivost kamiona i prikolica s ugrađenim bandlerom. U zimskim
mjesecima pokrov snijega i smrznuti šumski ostaci također su ograničavajući čimbenik za sustav izradbe svežnjeva
uz prometnice, npr. u nordijskim uvjetima.
Ključne riječi: izradba svežnjeva šumskoga ostatka, proizvodnost, šumska biomasa, bandler
Authors’ address – Adresa autorâ:
Juha Laitila, PhD.*
e-mail: [email protected]
Nuutinen Yrjö, PhD.
e-mail: [email protected]
Finnish Forest Research Institute, (Agr. & For.)
Yliopistokatu 6, FI-80101 Joensuu
FINLAND
Received (Primljeno): December 12, 2012
Accepted (Prihvaćeno): March 20, 2013
Croat. j. for. eng. 34(2013)2
Marica Kilponen, MSc.
e-mail:[email protected]
Lappeenranta University of Technology /
John Deere Forestry
Lokomonkatu 21, FI-33900 Tampere
FINLAND
* Corresponding author – Glavni autor
187
Original scientific paper – Izvorni znanstveni rad
Evaluating Efficiency, Chip Quality
and Harvesting Residues of a Chipping
Operation with Flail and Chipper
in Western Australia
Mohammad Reza Ghaffariyan, Mark Brown, Raffaele Spinelli
Abstract – Nacrtak
Roadside chipping is a common harvesting system in Australian plantations, which utilizes
a mobile chipper stationed at the field edge to produce high-quality pulp chips for export. The
studied harvesting system included a feller-buncher, two grapple skidders, a flail-debarker and
a disc chipper. The study goals were to determine machine productivity, operation costs, fuel
consumption, chip quality and measure the amount of slash left in the field after harvesting.
The average productivity for feller buncher and skidder were about 97.26 GMt/PMH0 and
60.22 GMt/PMH0, respectively. The productivity of flail and chipper averaged at 57.80 GMt/
PMH0 and 58.18 GMt/PMH0 in this case study. The transportation productivity averaged
about 57.34 GMt/PMH0. Time studies and regression analysis were used to model machine
productivity. Tree size had significant impact on the feller-buncher productivity, while skidding
distance was a significant variable affecting skidding productivity. Operation costs were
evaluated using the ALPACA (Australian logging productivity and cost appraisal) model.
This paper offers valuable information about the impact of different factors on feller-buncher
and skidder productivity. Application of two skidders resulted in high total operating cost.
Extracting whole trees to roadside yielded a very small amount of remaining slash distributed
on the site.
Keywords: whole tree harvesting, feller-buncher, skidder, flail-debarker, cost, slash
1. Introduction – Uvod
The most common option in the production of
woody biomass is chipping in the forest at roadside
followed by transportation of the chips (Stampfer and
Kanzian 2006). In Denmark in-field chipping is often
used in thinning and small diameter tree harvesting
(Talbot and Suadicani 2005). About 75–80 % of the annual woody biomass production in Sweden is produced in this way (Ranta and Rinne 2006, Junginger
et al. 2005).
Roadside chipping is a common harvesting method in Australian eucalypt plantations. It utilizes a mobile chipper to produce export grade pulp chips at the
plantation. If the fundamental objective of logistical
Croat. j. for. eng. 34(2013)2
efficiency is to handle the largest piece size the least
number of times, roadside chipping must be considered as preferential to any other method. Chips production at the roadside in Australia can be performed
either by debarking the stems at the stump using a
single-grip harvester, or alternatively, by debarking
the stems with a chain flail delimber and debarker at
the forest road prior to chipping (Lambert 2006).
The system of roadside chipping with debarking
at the stump was developed by Eumeralla Pty Ltd and
AFM Pacific in Australia in 1998, for Timbercorp limited. This system uses single grip harvesters to fell,
delimb and debark full tree lengths at the stump and
position them for subsequent extraction. From this
point, a purpose built tree-length forwarder extracts
189
M. R. Ghaffariyan et al. Evaluating Efficiency, Chip Quality and Harvesting Residues of a Chipping Operation ... (189–199)
Table 1 Harvesting equipment for roadside chipping with Husky Precision
Tablica 1. Oprema za pridobivanje drvne sječke strojevima Husky Precision
Operator
experience, years
Hourly machine
cost, $
Pogonskih sati
Iskustvo
rukovatelja, god.
Trošak strojnoga
rada po satu, $
191
4 738
4
240.59
630C (S9)
184
3 811
0.3
278.84
Tigercat
630D (S10)
191
748
0.7
203.07
Husky Precision
FD 2300-4
309
3 993
2
345.68
Husky Precision
HTC 2366
441
8 624
2.5
383.15
Machine type
Make
Model
Power, kW
Hours used
Tip stroja
Proizvođač
Model
Snaga, kW
Tigercat
845C
(shear head:
Tigercat 2001)
Tigercat
Tracked swing-to-tree
feller-buncher
Gusjenični feler bančer
Rubber tired grapple skidder
Kotačni skider s kliještima
Rubber tired grapple skidder
Kotačni skider s kliještima
Flail
Procesor za kresanje grana
i koranje
Chipper
Iverač
the stems to the forest road for stockpiling. Finally, the
full-length, debarked trees are chipped using a chipper at the roadside.
The method of roadside chipping with debarking
at the forest road is currently being used in the Green
Triangle Region, Albany and Bunbury in Australia. In
this system, trees are felled and bunched using a driveto-tree feller-buncher. The felling can also be commonly carried out by a boom-mounted swing-to-tree
feller-buncher, which has the ability to process multiple rows at a time and can place the bunches in the
out-row with less machine movement. The fellerbuncher head can be installed on a rubber-tired or a
tracked based machine. At the roadside, trees are delimbed and debarked using a chain flail delimber/
debarker and then chipped in the trailer. The delimber/debarker can be integrated with the chipper, such
as the Peterson Pacific DDC5000 (DDC), or separate
from the chipper, such as the combination of the Husky Precision Flail and Chipper (F/C). A number of different variations of these machines have been tested
over the years (Lambert 2006).
Two recent studies on roadside chipping operations in Western Australia reported a productivity of
33.90 GMt/PMH0 for the Peterson Pacific chipper (Wiedemann and Ghaffariyan 2010) and 51.70 GMt/PMH0
for Husky precision chipper (Ghaffariyan et al. 2011).
Both studies indicated that the major operational delay was the waiting time for trucks. This delay may be
reduced through improved truck scheduling. The
Husky Precision chipper study (Ghaffariyan et al.
190
2011) was about chipping small trees for biomass usage and no flail was used to debark the trees. The current study investigated the chipper and flail to produce pulp export chip, which is a common system in
Western Australia. To add to the body of knowledge
about the productivity of this harvesting method in
Australia, this study aimed to investigate the efficiency of a road-side chipping system using a Husky Precision chipper.
The objectives of this study were to:
Þ Measure productivity of each machine of the
system,
Þ Estimate the cost of each machine and of the
whole system,
Þ Study impact of different parameters on productivity,
Þ Measure fuel consumption of each machine and
of the whole system,
Þ Measure harvesting residues retained on the site
after logging operation,
Þ Assess the quality of chips produced.
2. Materials and Methods – Materijal i
metode
2.1 Study area – Mjesto istraživanja
The study area was located in a Eucalyptus globulus
(Blue gum) plantation in southwest Western Australia,
58 km from the delivery point for all the products, the
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Albany Plantation Export Company (APEC) chip mill.
The study area was about 1.45 ha of flat terrain. The
diameter at breast height over bark (DBHOB) and total
tree volume averaged at 17.8 cm and 0.21 m3. The
stocking was 711 stems per ha.
Table 1 describes the machine used for the harvesting system. The trees were felled, bunched and skidded to the roadside as whole trees, then processed into
pulp chips, and loaded directly into trucks for transport. The whole trees were processed by a Husky flail.
The trees were delimbed and debarked using the flail.
Then the debarked wood was fed into the chipper. The
trucks used in this study were pocket road train type
with the loading capacity of 60 tonnes. The chipping
residues were returned to the site as »beehives« using
the grapple skidders.
Table 2 Work elements for the feller-buncher, skidder and truck (Acuna and Heidersdorf 2008)
Tablica 2. Definicije radnih elemenata feler bančera, skidera i kamiona (Acuna i Heidersdorf 2008)
Machine
Work elements
Definition
Stroj
Radni elementi
Definicija
Positioning
Zauzimanje položaja
Any time spent for the movement of machine to place to start felling – Svako vrijeme utrošeno za pomicanje
stroja na mjesto početka sječe
Felling-bunching
Sječa i uhrpavanje
Starts when felling head is attached to tree to start cutting. It finishes when operator lays the felled tree on
the ground – Počinje kada sječna glava obuhvati stablo i počinje sjeći. Završava kada rukovatelj položi posječeno
stablo na tlo
Traveling
Premještanje
Begins when the machine starts to travel to next tree and ends when the machine stops moving to perform
some other activity – Počinje kada se stroj krene premještati do sljedećega stabla, a završava kada se stroj
prestane kretati i započinje obavljati neku drugu aktivnost
Clearing
Raščišćavanje
Starts when the machine stops moving or felling/bunching to dispose of non-merchantable material and stops
when feller/bunching or moving recommences – Počinje kada se stroj prestane kretati ili sjeći i uhrpavati radi
raščišćavanja nekomercijalnoga drvnoga amaterijala, a prestaje kada se sječa i uhrpavanje ili kretanje stroja
nastavi
Clear debris
Uklanjanje ostatka
Any time spent for clearing debris and removal to stockpile or return to the block – Svako vrijeme utrošeno za
uklanjanje ostatka nakon iveranja i njegovo uhrpavanje ili vraćanje u sječinu
Travel empty
Vožnja praznoga
Starts when machine commences travel into block and ends when loading of bunch commences – Počinje
kada stroj započinje vožnju u sječinu, a završava kada počinje utovarivati
Loading
Utovar
Starts with grappling the bunch and picking up and ends when travel loaded commences – Počinje sa
zahvaćanjem i podizanjem tovara, a završava s početkom vožnje opterećenoga skidera
Travel loaded
Vožnja punoga
Starts when wheels commence turning after loading, and ends when skid distance to the landing is reached
Počinje kada se kotači skidera počinju okretati nakon utovara, a završava kada se prevali udaljenost privlačenja
do pomoćnoga stovarišta
Unloading
Istovar
Time to drop load and turn around to commence travel empty. Starts when skid distance to deck is reached
and ends when turn around is completed – Vrijeme potrebno za istovar tovara i okretanje prije početka vožnje
praznoga skidera. Počinje kada se prevali udaljenost privlačenja do mjesta istovara, a završava s okretanjem
Loading
Utovar
Begins when chipper starts blowing the chips into truck and ends when truck starts travelling loaded – Počinje
kada iverač započne upuhivati drvnu sječku u kamion, a završava kada puni kamion započinje vožnju
Travel loaded
Vožnja punoga
Starts when loading finishes and truck starts travelling loaded to the mill and ends when unloading starts
Započinje sa završetkom utovara i početkom vožnje punoga kamiona u tvornicu, a završava s početkom istovara
Unloading
Istovar
Starts when travel loaded ends at the mills and ends after being fully unloaded at the time of starting travelling
empty – Započinje sa završetkom vožnje punoga kamiona u tvornici, a završava nakon potpunoga istovara, u
trenutku početka vožnje neopterećenoga kamiona
Travel empty
Vožnja praznoga
Starts when truck driver commences to travel at the end of unloading element. It ends when loading starts
Počinje kada vozač kamiona započinje vožnju na kraju istovara. Završava s početkom utovara
Feller-buncher
Feler bančer
Grapple skidder
Skider s kliještima
Truck
Kamion
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Table 3 Productivity, cost and fuel consumption of roadside chipping with Husky Precision
Tablica 3. Proizvodnost, trošak i utrošak goriva pri iveranju na pomoćnom stovarištu strojevima Husky Precision
Machine
Productivity, GMt/PMH0
Cost, $/GMt
Fuel consumption, l/hr
Fuel consumption, l/GMt
Stroj
Proizvodnost, GMt/PMH0
Trošak, $/GMt
Utrošak goriva, l/h
Utrošak goriva, l/GMt
97.26
2.55
32.09
0.33
60.22
12.02
91.91
1.58
57.80
5.98
44.51
0.77
58.18
6.59
72.14
1.24
14.96
4.19
–
–
–
31.33
–
3.92
Feller-buncher
Feler bančer
Grapple skidder (two skidders)
Skider s kliještima (dva skidera)
Husky Precision flail
Procesor Husky Precision
Husky Precision chipper
Iverač Husky Precision
Truck
Kamion
Total
Ukupno
2.2 Method – Metoda
2.2.1 Time study and modeling – Studij vremena i
modeliranje
The elemental time study method was used to
evaluate machine productivity for the feller buncher,
two grapple skidders and trucks. The felling-bunching
and skidding working cycles were divided into the
specific elements described in Table 2. Personal, mechanical and operational delays were also recorded
during the time study. Productivity was calculated by
the delivered tonnes of chips (GMt) and productive
machine hours, excluding all delays (PMH0). Backward stepwise regression was applied to develop the
productivity predicting equations in SPSS 18. If any
variable had significant impact on the residual mean
square of the models, it was included in the models.
The analysis of variance of each model was used to
verify the significance of the model. The models were
validated using witness samples, and the confidence
intervals for each coefficient were calculated. By recording the total working time and delivered volume,
the productivity of the flail, chipper and trucks were
estimated.
2.2.2 Harvesting costs – Troškovi pridobivanja
The hourly machine cost included fixed, variable
and labor costs. The hourly machine cost for each harvesting machine was modeled using the ALPACA
(Australian Logging Productivity And Cost Apprais-
192
al) calculator, developed by Murphy and Acuna
(2009). Unit cost was determined by dividing hourly
machine cost by the net machine productivity.
2.2.3 Yield and chip quality – Količina i kakvoća
drvne sječke
The yield was based on weighbridge data of the
chips delivered to the mill. Using 8 samples of about
2 kg each, the moisture content of the chips was estimated to calculate the yield in bone dry metric tonnes
(BDMt). The samples were tested for their size classification and bark content according to the APEC export chip specifications.
2.2.4 Assessment of harvest residues – Procjena
količine drvnoga ostatka
There were two types of harvesting residues in this
study; scattered residues left at the stump site and flail
residues piled at roadside. The amount of stump site
residues was estimated using two lines transects 20 m
apart, along which 4 square plots of 1x1 m were established every 20 m. All the slash on each sample plot
was collected manually and weighed with a portable
scale. Roadside residues were taken back to the field
with the skidder and stacked into piles, also called
»beehives«. The »beehives« were evenly distributed
over the site. The bulk volume of 6 samples of »beehives« was determined by measuring the length,
width, height and cross-sectional shape of each pile.
The total number of the »beehives« was about 66. By
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Evaluating Efficiency, Chip Quality and Harvesting Residues of a Chipping Operation ... (189–199) M. R. Ghaffariyan et al.
multiplying the average volume to the number of
»beehives«, the total volume was estimated. No information on bulk density was available to convert the
volume of »beehives« to weight.
3. Results – Rezultati
3.1 Productivity, cost and fuel consumption
Proizvodnost, trošak i utrošak goriva
Table 3 shows the measured productivity, cost and
fuel consumption for each machine engaged in the test
operation. Skidding had the highest cost, and incurred
the highest fuel consumption per GMt. The main reason for using two skidders was to avoid waiting time
for the chipper while extracting the trees and clearing
debris, which might take long time when using one
skidder in the operation.
3.2 Feller-buncher productivity model – Model
za izračun proizvodnosti feler bančera
Tree size significantly impacted the productivity of
the feller-buncher. Increasing tree size resulted in
higher productivity (Fig. 1). The model is significant
at α = 0.05 (Table 4). The model is:
Productivity (GMt/PHM0) = 182.078 + 57.585 × ln
(Tree size (m-3))
R2 = 40.2%, n = 80
Table 5 summarizes the percent incidence of each
work step on total time consumption, for the Tigercat
feller-buncher. Felling and bunching accounted for
over 95% of work time. No delay occurred for the duration of our time study.
3.3 Skidder productivity model – Model za
izračun proizvodnosti skidera
Fig. 1 Impact of tree size on feller-buncher productivity
Slika 1. Utjecaj obujma stabla na proizvodnost feler bančera
Tree size did not have any significant impact on
skidder productivity and therefore it was excluded
from the model. Skidding distance significantly affected the productivity of both skidders (Fig. 2 and 3).
From the ANOVA tables, both models were significant
at α = 0.05 (Tables 6 and 7). The model for the skidder
TC 630C had a higher coefficient of determination
compared to the model for the skidder TC 630D, and
it could explain about 49% of the total variability observed for skidder productivity. The average productivity for the TC 630C skidder was about 28.53 GMt/
PMH0 which was lower than for the TC 630D skidder,
with 31.69 GMt/PMH0 although the skidder 630D covered a longer mean skidding distance (256 m vs. 190 m)
(Table 8).
Table 4 Analysis of variance of productivity model for feller-buncher
Tablica 4. Analiza varijance modela za izračun proizvodnosti feler bančera
Sum of Squares
Df
Mean Square
F
Sig.
Suma kvadrata
Stupnjevi slobode
Varijanca
F-vrijednost
Statistička značajnost
8 502.33
1
8 502.33
52.35
0.00
12 668.22
78
162.41
–
–
21 170.55
79
–
–
–
Regression
Regresijski model
Residual
Rezidual
Total
Ukupno
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3.3.1 Productivity model for Skidder TC 630C
Model za izračun proizvodnosti skidera TC 630C
3.3.2 Productivity model for Skidder TC 630D
Model za izračun proizvodnosti skidera TC 630D
Productivity (GMt/PHM0) = 34.559 – 0.032 ×
Skidding distance (m)
Productivity (GMt/PHM0) = 37.214 – 0.020 ×
Skidding distance (m)
R2 = 49.0%, n = 10
R2 = 38.9%, n = 11
Fig. 2 Impact of skidding distance on the productivity of skidder TC
630C
Slika 2. Utjecaj udaljenosti privlačenja na proizvodnost skidera TC
630C
Fig. 3 Impact of skidding distance on the productivity of skidder TC
630D
Slika 3. Utjecaj udaljenosti privlačenja na proizvodnost skidera TC
630D
Table 5 Work element breakdown for the feller-buncher
Tablica 5. Raščlamba radnih elemenata feler bančera
Share, % – Udio, %
Positioning
Felling & bunching
Travel
Clearing
Delay
Zauzimanje položaja
Sječa i uhrpavanje
Premještanje stroja
Raščišćavanje
Prekid rada
0.3
95.5
4.0
0.2
0.0
Table 6 Analysis of variance of productivity model for skidder TC 630C
Tablica 6. Analiza varijance modela za izračun proizvodnosti skidera TC 630C
Sum of Squares
Df
Mean Square
F
Sig.
Suma kvadrata
Stupnjevi slobode
Varijanca
F-vrijednost
Statistička značajnost
163.17
1
163.17
7.68
0.024
Residual – Rezidual
170.01
8
21.25
–
–
Total – Ukupno
333.18
9
–
–
–
Regression
Regresijski model
194
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From Fig. 3, the longer the skidding distance the
lower the productivity, due to the increased travel time.
The percent incidence of each work element on the
skidding cycle for the two skidders is presented in
Table 9. Nearly half of the work time was spent for
clearing debris. The lowest percentage was for unloading, which accounted for less than 2% of the total skidding time. The delays were mainly due to waiting for
the chipper to unload the bunches in front of the chipper to be accessible for the chipper grapple due to lack
of free space (operational delays). The incidence of
delays was 10 percentage points higher for the skidder
630D than for the skidder 630C.
3.3.3 Husky Precision flail and chipper – Procesor i
iverač Husky Precision
The flail worked for 243 minutes, reaching the average productivity of 57.80 GMt/PMH0. Debarking
accounted for about 92% of total work time. Delays
included waiting for wood (4.5% of total work time),
warm up (1.6% of total work time) and waiting for
chipper as the chipper was waiting for truck (2.0% of
total work time).
The chipper discharged directly into the trucks.
Four trucks were used to transport the chips to the
APEC mill. The average delay-free chipping time per
truck was about 56 minutes. Net productivity averaged 58.18 GMt/PMH0. Effective chipping time accounted for 93 % of total work time. Delays were represented by waiting for wood (4.7% of total work
time), waiting for trucks (0.2%) and warm up (2.0%).
3.3.4 Transportation – Daljinski transport
The transport distance from study area to the
APEC mill gate was 58 km. Mean net productivity and
the payload was 14.96 GMt/PMH0 and 54 GMt, respectively. The average delay-free cycle time for transportation was about 4.58 hours. Elemental time breakdown for transportation is shown in Table 10. Traveling
loaded had the highest incidence on total cycle time
(28 %). Delays consisted almost exclusively of waiting.
3.3.5 Yield and chip quality – Količina i kakvoća
drvne sječke
The study area (1.45 ha) yielded 232 GMt of pulp
chips, corresponding to 160 GMt/ha. Based on moisture content sampling of 43%, the actual yield in dry
mass was equal to 90 BDMt/ha (Mitchell and Wiedemann 2012).
The chip sample analysis showed that bark content
was 0.18%, well within the limits set by APEC specifications (<0.5 %). Table 11 shows that 68% of the chip
mass consisted of particles measuring between 9.5 mm
and 22.2 mm (Mitchell and Wiedemann 2012).
Croat. j. for. eng. 34(2013)2
3.3.6 Harvest residues assessment – Procjena
količine drvnoga ostatka
Scattered stump site residues accounted for
6.4 GMt/ha. In contrast, flail residues returned to the
field and stacked as »beehives« represented 262 m3.
4. Discussion – Rasprava
The productivity of the feller-buncher in this
case study is lower than the average productivity
(138.0 GMt/PMH0) reported for a similar Valmet
445 EXL tracked self-leveling feller-buncher working in
the pine plantations of the South Gippsland coast of
Victoria (Acuna et al. 2011). It is also lower than the
122.2 GMt/PMH0 reported for the clear fell of pine plantation in Southern Tasmania (Ghaffariyan et al. 2012).
The main reason for that is likely to consist in the smaller tree size handled in this study. The fuel consumption
per cubic meter is also lower than the consumption
reported for a large feller-buncher (0.36 l/GMt) by
Johnson et al. 2006. It is also slightly lower than the
consumption of 0.34 l/GMt reported by Ghaffariyan et
al. 2012 for Southern Tasmania, which is consistent
with the lower productivity. The close relationship
between feller-buncher productivity and tree size in
eucalypt clearfell operations is supported by the results obtained in Brazil by Moreira et al. (2004), who
reported a productivity of 33.5 and 36.1 GMt/PMH0
for an average DBH of 9.0 and 10.4 cm, respectively.
Similar results are also reported by Spinelli et al. (2009)
who studied a range of feller-bunchers used for eucalypt clearfell and obtained figures between 14 and
20 GMt/PMH0 for smaller DBH and steeper slopes
than covered by this study.
The average productivity of both skidders in this
study is lower than the productivity (44.6 GMt/PMH0)
of a similar TC 730C grapple skidder used for extracting small whole eucalypt trees in Western Australia
(Ghaffariyan et al. 2011).
Productivity rates in this study are also lower than
the 47.5 GMt/PMH0 reported for whole eucalypt tree
skidding in Brazil (Valverde et al.1996). This could be
the result of the longer skidding distance, smaller payload and residue clearing in our case study. The productivity models estimated by Dodson et al. (2006) for
two Caterpillar rubber-tired grapple skidders working
in western juniper stands included three independent
variables, namely: skidding distance, number of stems
per turn and a dummy variable for stand type (mixed
or not-mixed). Our skidding productivity models contain the skidding distance as a significant variable affecting the skidder productivity.
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Table 7 Analysis of variance of productivity model for skidder TC 630D
Tablica 7. Analiza varijance modela za izračun proizvodnosti skidera TC 630D
Sum of Squares
Df
Mean Square
F
Sig.
Suma kvadrata
Stupnjevi slobode
Varijanca
F-vrijednost
Statistička značajnost
125.02
1
125.02
5.72
0.04
196.59
9
21.84
–
–
321.61
10
–
–
–
Regression
Regresijski model
Residual
Rezidual
Total
Ukupno
Table 8 Descriptive statistics of productivity model – Skidder TC 630C and TC 630D
Tablica 8. Opisna statistika modela za izračun proizvodnosti skidera TC 630C i skidera TC 630D
Skidder type
Minimum
Maximum
Mean
Tip skidera
Najmanja vrijednost
Najveća vrijednost
Aritmetička sredina
Skidding distance, m
TC 630C
60.00
510.00
190.00
Udaljenost privlačenja, m
TC 630D
20.00
555.00
256.04
Tree size, m3
TC 630C
0.14
0.21
0.17
Obujam stabla,m
TC 630D
0.15
0.21
0.17
Productivity, GMt/PMH0
TC 630C
18.50
39.00
28.53
Proizvodnost, GMt/PMH0
TC 630D
22.10
40.30
31.69
3
The productivity rates of both skidders in our case
study are lower than reported productivity of
53.8 GMt/PMH0 for a Caterpillar grapple skidder 525C
in clear felling operations in Eucalypt stands with the
average tree size of 0.178 m3 and average skidding distance of 160 m (Wiedemann and Ghaffariyan 2010).
The skidding distance was longer in our case study,
which resulted in lower productivity. The average
fuel consumption of the two skidders in this study
(0.79 l/GMt) is higher than the fuel consumption reported by Makkonen (2004) for a grapple skidder used
in Canada. However, it is also lower than reported for
large clam bunk skidders (1.17 l/GMt) used in USA
(Johnson et al. 2006).
Flail and chipper were two separate machines operated by two operators at the road side in this study.
The chipper net productivity (58.18 GMt/PMH0) is
slightly lower than recorded for the Morbark chipper
working at roadside (59.4 GMt/PMH0) to chip logs
from first thinning in Pine plantation of South Australia (Ghaffariyan 2012). Tree size and machine power
in this study were higher than for the Morbark chipper
trial, which should have resulted in higher productivity, based on the findings of Spinelli and Hartsough
(2001). They found a direct relationship between chipper productivity, piece size and engine power. The
lower chipping productivity in this study is likely due
to the smaller tree bunches delivered to the chipper as
Table 9 Percent incidence of each work element on the total duration of the skidding cycle
Tablica 9. Postotni udio pojedinoga radnoga elementa u ukupnom trajanju turnusa privlačenja
Skidder type
Tip skidera
Clear debris
Travel empty
Čišćenje ostatka Vožnja praznoga
Load
Travel loaded
Unload
Delay
Utovar
Vožnja punoga
Istovar
Prekid rada
Share, %
TC 630C
49
20
3
18
1
9
Udio, %
TC 630D
43
16
5
15
2
19
196
Croat. j. for. eng. 34(2013)2
Evaluating Efficiency, Chip Quality and Harvesting Residues of a Chipping Operation ... (189–199) M. R. Ghaffariyan et al.
Table 10 Percent incidence of work steps on total transportation cycle
Tablica 10. Postotni udio pojedinoga radnoga elementa u ukupnom trajanju turnusa daljinskoga transporta
Share, % – Udio, %
Loading
Travel loaded
Unloading
Travel empty
Delay
Utovar
Vožnja punoga
Istovar
Vožnja praznoga
Prekid rada
22
28
13
23
14
Table 11 Particle size distribution of chip samples
Tablica 11. Granulometrijska struktura uzoraka drvne sječke
Size class
Razred
>28.6 mm
>22.2 mm
>9.5 mm
>4.8 mm
<4.8 mm
3.36
16.31
68.24
9.88
2.03
Share, % – Udio, %
Bark
Kora
0.18
a result of the hot-decking operation, where chipping/
loading occurred at the time of wood extraction to the
road side. In contrast, the Morbark chipper worked
trees decked in large piles (average height and length
of the piles were 4 m and 66 m, respectively), allowing
for relatively large bunches of wood to be fed into the
chipper. Another factor may be the impact of whole
tree chipping (in our case study delimbed stems from
whole trees by flail) versus log chipping (Spinelli and
Magagnotti 2010). The productivity recorded in this
study is also higher than reported for a Peterson Pacific chipper tested in whole tree chipping for biomass
(33.90 GMt/PMH0) in Western Australia, due to the
smaller tree size of 0.10 m3 in the latter study (Ghaffariyan et al. 2011). In our case study area only four
trucks were loaded, and chipping and trucking were
characterized by a very small sample size.
The amount of scattered stump-site residues
(6.45 GMt/ha) was much lower than reported for sites
harvested by the cut-to-length system. According to
Smethurst and Nambiar (1990) stump-site residues
amounted to 52 GMt/h in a clearfelled Pinus radiata
plantation in Mount Gambier, South Australia. Similarly, Ghaffariyan and Andorovski (2011) report as
much as 70.4 GMt/ha for the stump-site residues left
after the cut-to-length clearfell harvesting of a Eucalyptus nitens plantation in Northern Tasmania. In our case
study, it is important to determine whether the »beehives« are better spread over the whole site or if the flail
residues could rather be refined and used as boiler fuel.
increased total operating costs. Future studies could
compare the use of two skidders with the use of one
skidder only. Long skidding distance, small payload
and spending time for clearing debris resulted in low
productivity of the skidders in this case study. According to the results, the skidding distance had significant
impact upon the productivity of two skidders. Based
on the productivity predicting models, the larger the
tree volume the higher the feller-buncher productivity.
As two separate machines were used for debarking
(Husky flail) and chipping (Husky chipper), the future
studies could also explore the efficiency of integrated
delimber-debarker-chipper units, where the flail and
chipper are combined into one machine, as an initial
trial has indicated that using separate flail and chipper
can result in higher total harvesting cost than using an
integrated delimber-debarker-chipper (Ghaffariyan
and Sessions 2012).
Roadside chipping operation left a small amount of
residues in the stand, being based on whole tree-extraction. The possible impacts of intense slash removal on
site fertility could also be studied in the future.
5. Conclusions – Zaključci
6. References – Literatura
Based on these results, the inclusion of more machines will result in higher cost of operation and higher
fuel consumption. In this case study, using two skidders
Acuna, M., Heidersdorf, E., 2008: Harvesting machine evaluation framework for Australia. CRC for Forestry, Draft Technical Report, 33 p.
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Acknowledgement – Zahvala
This is to acknowledge the following researchers
for their assistance in data collection: Rick Mitchell and
John Wiedemann. The authors would like to thank the
journal reviewers who provided valuable comments
that helped improve this article.
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M. R. Ghaffariyan et al. Evaluating Efficiency, Chip Quality and Harvesting Residues of a Chipping Operation ... (189–199)
Acuna, M., Skinnell, J., Mitchell, R., Evanson, T., 2011: Bunching stems in steep slopes for efficient yarder extraction. CRC
for Forestry Bulletin 17, 3 p.
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Dodson, E. M., Deboodt, T., Hudspeth, G., 2006: Production,
cost, and soil compaction estimates for two Western Juniper
extraction systems. Western Journal of Applied Forestry
21(4): 185–194.
Moreira, F.M.T., de Souza, A. P., Machado, C. C., Minetti, L.
J., Silva, K. R., 2004: Technical and economic analysis of a
feller-buncher in two harvest subsystem of Eucalyptus forests. Revista Árvore 28: 199–205.
Ghaffariyan, M. R., Andorovski, V., 2011: Bundling harvest
residues in shining plantations. CRC for Forestry, Bulletin 15,
3 p. (and Forest Energy observer 2011 online at: http://journal.
forestenergy.org)
Ranta, T., Rinne, S., 2006: The profitability of transporting
uncomminuted raw materials in Finland. Biomass and Bioenergy 30(3): 231–237.
Ghaffariyan, M. R., Brown, M., Acuna, M., Sessions, J., Kuehmaier, M., Wiedemann, J., 2011: Biomass harvesting in Eucalyptus plantations in Western Australia. Southern Forests
73(3–4): 149–154.
Ghaffariyan, M. R., Sessions, J., 2012: Comparing the efficiency
of four harvesting methods in a blue gum plantation in southwest Western Australia. CRC for Forestry, Bulletin 29, 4 p.
Ghaffariyan, M. R., Sessions, J., Brown, M., 2012: Machine
productivity, volume recovery and harvesting residues of a
cut-to-length harvest system in Southern Tasmania. Southern
Forests: a Journal of Forest Science 74(4): 229–235.
Johnson, L. R., Lippke, B., Marshall, J. D., Comnick, J., 2006:
Life-cycle impacts of forest resource activities in the Pacific
Northwest and Southeast United States. Wood and Fiber Science, 37 Corrim Special Issue, 2005: 30–46.
Junginger, M., Faaij, A., Bjorheden, R., Turkenburg, W. C.,
2005: Technological learning and cost reductions in wood fuel
supply chains in Sweden. Biomass and Bioenergy 29(6):
399–418.
Murphy, G., Acuna, M., 2009: Australian logging productivity and cost appraisal model (ALPACA). Internal toolbox,
CRC for Forestry, Hobart, Australia.
Lambert, J., 2006: Growth in blue gum forest harvesting and
haulage requirements in the Green Triangle 2007–2020. CRC
for Forestry Consultant report, 119 p.
Makkonen, I., 2004: Saving fuel in mechanized forestry operations. Forest Engineering Institute of Canada, PointeClaire, QC. Internal Report IR-2004-08, 10 p.
Spinelli, R., Hartsough, B., 2001: A survey of Italian chipping
operations. Biomass and Bioenergy 21: 433–444.
Spinelli, R., Magagnotti, N., 2010: A tool for productivity and
cost forecasting of decentralised wood chipping. Forest Policy and Economics 12: 194–198.
Spinelli, R., Ward, S., Owende, P., 2009: A harvest and transport cost model for Eucalyptus spp. fast-growing short rotation plantations. Biomass and Bioenergy 33: 1265–1270.
Stampfer, K., Kanzian, Ch., 2006: Current state and development possibilities of wood chip supply chains in Austria.
Croatian Journal of Forest Engineering 27(2): 135–145.
Smethurst, P. J., Nambiar, E. K. S., 1990: Distribution of carbon
and nutrients and fluxes of mineral nitrogen after clearfelling
a Pinus radiata plantation. Canadian journal of forest research 20: 1490–1497.
Talbot, B., Suadicani, K., 2005: Analysis of two simulated infield chipping and extraction systems in spruce thinnings.
Biosystems Engineering 91(3): 283–292.
Valverde, S. R., Machado, C., Pereira de Rezende, J., Paulo de
Souza, A., Antiqueira, A., 1996: A technical and economical
analysis of timber skidding using a skidder in a full tree harvesting system. Viçosa, Brasil. Revista Arvore 20(1): 101–109.
Wiedemann, J., Ghaffariyan, M. R., 2010: Preliminary results:
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Bulletin 9, 4 p.
Sažetak
Ocjena učinkovitosti, kakvoće drvne sječke i količine drvnoga ostatka
pri proizvodnji drvne sječke procesorom i iveračem u Zapadnoj Australiji
Iveranje pokretnim iveračem na pomoćnom stovarištu uobičajen je sustav proizvodnje visokokvalitetne drvne
sječke za celulozu u australskim šumskim plantažama. Istraživani sustav pridobivanja drvne sječke činili su feler
bančer, dva skidera s kliještima za privlačenje uhrpane stablovine, procesor za kresanje grana i koranje, diskni iverač
za usitnjavanje okorane deblovine i kamion za prijevoz proizvedene drvne sječke. Skideri su osim za privlačenje
stablovine na pomoćno stovarište korišteni i za vraćanje drvnoga ostatka nastaloga pri proizvodnji drvne sječke u
sječinu i njegovo uhrpavanje.
198
Croat. j. for. eng. 34(2013)2
Evaluating Efficiency, Chip Quality and Harvesting Residues of a Chipping Operation ... (189–199) M. R. Ghaffariyan et al.
Istraživali su se proizvodnost, troškovi i utrošak goriva pojedinih strojeva u sustavu te kakvoća drvne sječke i
količina drvnoga ostatka nakon pridobivanja drvne sječke.
Prosječna proizvodnost stroja za sječu i uhrpavanje iznosila je 97,26 GMt/PMH0, a prosječna proizvodnost skidera
iznosila je 60,22 GMt/PMH0. Proizvodnost procesora i iverača iznosila je prosječno 57,80 GMt/PMH0, odnosno
58,18 GMt/PMH0. Prosječna proizvodnost daljinskoga transporta iznosila je 57,34 GMt/PMH0.
Za konstrukciju modela za izračun proizvodnosti pojedinoga stroja u sustavu pridobivanja korišten je studij
vremena i regresijske analize. Utvrđen je značajan utjecaj obujma stabla na proizvodnost stroja za sječu i uhrpavanje te udaljenosti privlačenja na proizvodnost skidera. Troškovi su procijenjeni primjenom modela ALPACA (Australian logging productivity and cost appraisal).
Ovaj rad donosi važne spoznaje o utjecaju različitih čimbenika na proizvodnost feler bančera te na proizvodnost
skidera. Primjenom dvaju skidera u sustavu pridobivanja, nužnih za održavanje proizvodnosti ostalih strojeva u
sustavu, nastao je visoki ukupni trošak. Pridobivanje sirovine za proizvodnju drvne sječke stablovnom metodom dalo
je vrlo malu količinu drvnoga ostatka preostaloga u sječini.
Ključne riječi: pridobivanje drva stablovnom metodom, stroj za sječu i uhrpavanje, skider, procesor, trošak, drvni
ostatak
Authors’ address – Adresa autorâ:
Mohammad Reza Ghaffariyan, PhD.*
e-mail: [email protected]
University of the Sunshine Coast
Private Bag 12
7001 Hobart
AUSTRALIA
Prof. Mark Brown, PhD.
e-mail: [email protected]
University of the Sunshine Coast
Locked Bag 4
4558 Maroochydore, Queensland
AUSTRALIA
Received (Primljeno): January 22, 2013
Accepted (Prihvaćeno): February 11, 2013
Croat. j. for. eng. 34(2013)2
Raffaele Spinelli, PhD.
e-mail: [email protected]
CNR IVALSA
Via Madonna del Piano 10
50019 Sesto Fiorentino
ITALY
* Corresponding author – Glavni autor
199
Original scientific paper – Izvorni znanstveni rad
Forest Road Access Decisions for Woods
Chip Trailers Using Ant Colony
Optimization and Breakeven Analysis
Storm Beck, John Sessions
Abstract – Nacrtak
Non-conventional products provide opportunities for the forest industry to increase economic value from forests; however, these products may require transport by specialized vehicles.
The existing forest transportation network was not necessarily designed to the road standards
required for these specialized vehicles. Several road modifications can be made to give specialized vehicles access to the forest transportation network including filling the ditch, removing
the superelevation, reversing the superelevation, or reconstructing the roadway. For each investment, there is an associated vehicle that can traverse the road segment if the investment
is made. For scheduling multiple biomass operations over a road network, we use the Ant
Colony heuristic to identify the combination of optimal vehicle choices and road modifications
to effectively transport non-conventional products. These combinations related to a 27% reduction in total transportation costs. For isolated biomass operations, we use breakeven analysis
to make the vehicle selection and road modification option. Decisions for isolated biomass
operations depend on road modification cost, transport volume, and transport costs on forest
and highway roads.
Keywords: ant colony optimization, biomass transport, vehicle accessibility
1. Introduction – Uvod
The production of high valued non-conventional
products, such as utility poles or the production of low
valued products such as chips or hogfuel, provide opportunities for the forest industry to increase economic value from forests. However, most of the forest
transportation system has been designed and built for
long-log, stinger-steered trailers (Sessions et al. 2010)
and there is little engineering record of road design or
location throughout the forest industry (Craven et al.
2011).
This lack of engineering records provides a challenging environment in the assessment of transporting
non-conventional products. The primary challenge to
hauling non-conventional products, on specialized
vehicles, is determining if the vehicle can navigate the
horizontal and vertical geometry unloaded and loaded, as well as turning around near the landing. These
specialized vehicles include truck tractors pulling pole
Croat. j. for. eng. 34(2013)2
trailers with rear self-steering axles, pole trailers with
stinger-steered axles, fifth-wheel chip trailers (with
and without self-steering rear axles), and stingersteered chip trailers. We define a pole trailer as a stinger-steered trailer with a bunk-to-bunk distance longer
than 8.5 m, hauling logs that are longer than 13.7 m.
We focus on the economical assessment of varying
sized chip trailers (chip vans) throughout the forest
transportation network for the remainder of the paper,
although the principles are the same for other specialized trailers.
2. Problem Description – Problematika
Several choices can affect the accessibility of these
specialized vehicles. These choices include temporarily filling the ditch, removing or reversing the superelevation to reduce lateral tire slip, and widening the
roadway. During the dry months, temporarily filling
201
S. Beck and J. Sessions Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215)
the ditches or changing the superelevation of the roadway are options that permit specialized vehicles access. Temporarily filling the ditch provides a greater
road width for the specialized vehicle to pass, usually
0.5 to 1.5 m of extra road width. Single lane forest
roads surfaces are insloped, outsloped, or crowned.
Positive superelevation of the road surface is often
constructed into forest roads to counteract centrifugal
force created by vehicles in curves (Oglesby and Hicks
1982). Negative superelevation of the road surface is
sometimes constructed into curves to adjust the normal forces on the driving axles to permit climbing
steeper grades (Anderson and Sessions 1991). Outsloping a forest road is sometimes used to drain water
from the road surface without diverting water to
ditches and insloping of forest roads is done for safety
when roads are icy (Bowers 2006). During the dry
months, superelevation may not be needed either because side friction is greater and/or cross slope drainage is not an issue; providing an opportunity to alter
the road surface to reduce lateral tire slip toward the
inside of a curve. Two options exist when altering the
superelevation (1) remove the superelevation and (2)
reverse the superelevation. Removing the superelevation reduces the amount of off-tracking that a vehicle
produces by reducing the amount of lateral tire slip
due to gravity (Glauz and Harwood 1991). Reversing
the superelevation could be used to counteract offtracking; allowing the weight of the vehicle and the
effects of gravity on an inclined plane to counter the
effects of off-tracking. Lastly, forest engineers and
Fig. 1 A 13.7 m drop center 5th wheel chip van being loaded on a
forest road in Lane County, Oregon
Slika 1. Poluprikolica za šumsku sječku dugačka 13,7 m (utovar na
sredini prikolice) tijekom utovara na šumskoj cesti u Lane County,
Oregon
202
Fig. 2 A stinger-steered chip van. Photo courtesy of Western
Trailer Company
Slika 2. Samokretna prikolica za šumsku sječku. Slika dobivena od
Western Trailer Company
managers can affect the outcome by redesigning the
roadway to allow these vehicles access along the entire
roadway length. This is achieved by widening the
roadway and removing obstacles close to the roadway
such as standing trees.
Each modification option has an associated cost
and benefit. For example, if a 13.7 m drop center 5th
wheel chip van (Fig. 1) needs an extra half meter of
road width to access a harvest unit, the ditches might
be temporarily filled to allow the 5th wheel chip van
access. If the ditches were not filled, the only vehicle
that might have access to the unit would be a stingersteered chip trailer (Fig. 2). Not only does the amount
of off-tracking vary between vehicles, so does the volume of chips or hogfuel consistent with weight restrictions that these vehicles can haul. The operating cost
and traveling speed vary for each vehicle configuration, creating a multi-dimensional problem.
We look at two cases. The first case involves scheduling multiple biomass operations over a road network, where trucks from several biomass operations
can take advantage of the same road investment. The
second case looks at isolated biomass operations,
where the road investment is used by only one operation. For both cases, mixed integer linear programming
can be used to exactly solve the underlying mathematical problem. However, for the second case it is more
convenient to use a breakeven analysis. For larger
problems of the first case, due to the solution time for
mixed integer programming, heuristics such as Ant
Colony Optimization (ACO) can be used to determine
a high quality solution for vehicle type, path, and road
modifications for transporting biomass. Other useful
heuristics are described by Glover and Kochenberger
(2002), Hoos and Stutzle (2005) and Geem (2009).
Croat. j. for. eng. 34(2013)2
Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215) S. Beck and J. Sessions
3. Mathematical Formulation – Case One
Matematički prikaz – slučaj prvi
The mathematical problem is to minimize the sum
of road modifications and biomass transportation
costs. Let G = (N, A) be a directed network with nodes
N and arcs (i,j) within A. We associate with each node
i within N a number S(i), which indicates the supply
or demand depending on whether S(i) > 0 or S(i) < 0.
The minimal cost problem is then:
Minimize
∑ FC
(i,j) ∈ A
+
∑ ∑VC
t
ij
t
t
ij ×Yij
+
∑ ∑VC
(i,j) ∈ A
t
ij
× Volumeijt
t∈ T
∀ ( i , j ) ∈ A , t ∈T
× Volumeijt
(1)
T
(i,j) ∈ A t ∈ Conservation
of Flow
∑
Volumeijt −
{ ji(i,j) ∈ A}
∑
Volume tji = V t ( i )
{ ji( j,i)∈ A}
∀ i ∈N
(2)
Sale Volumes
V t (i ) = S (i )
∑
∀ i ∈N
(3)
t∈ T
Road Triggers
≥ Volumeij1
∀ (i , j ) ∈ A
(4)
∑
M × Yijt ≥ Volumeij2
∀ (i , j ) ∈ A
(5)
∑
M × Yijt ≥ Volumeij3
∀ (i , j ) ∈ A
(6)
∑M × Y
t
ij
t∈ T
t ∈ T( t ≥ 2 )
t ∈ T ( t = 3)
Decision Variables
Yijt = {0,1}
Volumeijt ≥ 0
∀ ( i , j ) ∈ A , t ∈T
∀ ( i , j ) ∈ A , t ∈T
4. Review of Ant Colony Optimization
Opis optimizacije metodom mravlje
kolonije
The ACO (Dorigo and Stutzle 2004) is based on the
analogy of ants searching for food. Ants randomly
walk in search of food leaving a pheromone behind as
they travel. The pheromone is a scent that influences
other ants to take that path. As more ants travel over
the same path the pheromone increases, increasing the
possibility of an ant choosing that path. This process
continues until all ants are following the same path to
the food source. The ACO heuristic has been used to
solve fixed cost and variable cost forest transportation
problems with side constraints (Contreras et al. 2008).
Outside of the forest industry, this heuristic has been
used to solve vehicle route scheduling problems, capacitated vehicle routing problems, and other scheduling problems (Donati et al. 2008, Rizzoli et al. 2007).
(7)
(8)
Equation (1) is the objective function. FCijt is the
fixed cost to modify link ij to allow truck type t access.
Yijt is a binary variable, zero if the link is not used, and
one if the link is used. VCijt is the round trip variable
cost over link ij in truck type t, ($/tonne). Volumeijt is
the amount of volume crossing link ij in truck type t,
(tonnes). Equation (2) provides conservation of flow
at each node for each truck type. V t ( i ) is the volume
entering each node i for each truck type t, (tonnes).
Equation (3) requires that the total supply or demand
Croat. j. for. eng. 34(2013)2
at each node S ( i ) (tonnes), equal the sum of the volume transported over all truck types. Equation (4) requires that the road modification for truck type 1 (the
lowest standard truck type) be made to at least pass
truck type 1, if there is volume passing over link ij in
truck type 1. Equation (5) requires that the road modification for truck type 2 (the moderate standard truck
type) be made to at least pass truck type 2, if there is
volume passing over link ij in truck type 2. Equation
(6) requires that the road modification for truck type
3 (the highest standard truck type) be made to pass
truck type 3, if there is volume passing over link ij in
truck type 3. Equation (7) requires that the road trigger
for link ij for truck type t be a binary variable, zero or
one. Equation (8) requires that the volume passing
over link ij for truck type t be equal to or greater than
zero.
5. Ant Colony Optimization – Optimizacija
metodom mravlje kolonije
The ACO developed in this paper is designed to
minimize the total transportation cost. The total transportation cost is the sum of the modifications costs
plus the round trip variable costs multiplied by the
volume of each harvest unit. If a truck is loaded at sale
x, it must make it to destination z using the same
truck. If different types of trucks use the same link,
the one with the maximum fixed cost will be applied.
Therefore, if road modifications are applied so that a
16.2 m drop center 5th wheel chip van (Fig. 3) can
navigate the road, no other modifications need to take
203
S. Beck and J. Sessions Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215)
Fig. 3 A 16.2 m drop center 5th wheel chip van near Port Angeles,
Washington
Slika 3. Poluprikolica za šumsku sječku dugačaka 16,2 m s utovarom na sredini u blizini Port Angeles, Washington
place for other truck types. The ACO regards each
road modification option as a separate link. In other
words, between each node, three links exist; one that
has no fixed cost, one that has a moderate fixed cost,
and one that has a large fixed cost; all of which end
up at the same node (Fig. 4). As the algorithm progresses through each set of ants, each ant in each set
has a designated modification option that it will
choose from as it progresses through the network. It
was chosen to have three kinds of ants; a truck type 1
ant, a truck type 2 ant, and a truck type 3 ant to diversify the search. With this formulation, each modification option has its own set of pheromones. The starting pheromones provided an equal probability
choosing each link leaving a node for each truck type.
As the algorithm identifies a lower total cost route
from each sale, the links that are not part of that path
have their pheromones decay. We used a constant decay factor of 25 %.
The ACO was compared to a mixed integer linear
programming model, using a small network (Fig. 4).
The large black circles are the nodes in the network.
The small black circles are the road modification option for the 16.2 m drop center 5th wheel chip van, the
small horizontally hatched circles are the road modification option for the 13.7 m drop center 5th wheel
chip van, and the small white circles are the no road
modification option for the stinger-steered chip van.
In this formulation, three different degrees of road
modification could be applied, no modification, moderate modification, or major modification. The no
modification option will only allow a stinger-steered
chip van access. The moderate modification option
will allow a stinger-steered chip van and a 13.7 m drop
center 5th wheel chip van access. The major modification will allow all three trucks access to the road segment. Each truck has a different hourly operating cost.
The stinger-steered chip van has an estimated hourly
cost of $ 95.37, the 13.7 m drop center 5th wheel chip
van hourly cost is $ 90.95, and the 16.2 m drop center
5th wheel chip van hourly cost is $ 99.79 (Table 1). We
assumed cost per hour is the weighted average hourly
cost and did not vary with speed or road type.
The modification costs vary by the magnitude of
the required modifications. The moderate modification option was assumed to require removing the superelevation within the roadway and filling the ditches to allow the 13.7 m drop center 5th wheel chip van
access. We assumed that these modifications would
cost $ 3,281 per km. The major modification option
Table 1 Chip Van Operating Characteristics for the three truck types
Tablica 1. Tehničke značajke triju promatranih tipova prikolica
Trailers
Prikolice
Volume
Capacity, m3
Speed on Forest Roads
(empty or loaded), km/h
Speed on Highways
(empty or loaded), km/h
Operating Cost, $/h
Modification Cost, $/km
Maksimalna brzina na
Jedinični trošak, $/h Troškovi rekonstrukcije, $/km
autocesti (puna ili prazna),
km/h
Obujam, m3
Maksimalna brzina na
šumskoj cesti (puna ili
prazna), km/h
73.6
16.1
72.4
$ 95.37
$0
93.4
16.1
72.4
$ 90.95
$ 3,281
113.3
16.1
72.4
$ 99.79
$ 9,843
12.8 m Stinger Steered
Samokretna prikolica dugačka
12,8 m
13.7 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m
s utovarom na sredini
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 16,2 m
s utovarom na sredini
204
Croat. j. for. eng. 34(2013)2
Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215) S. Beck and J. Sessions
half of the link length needed to be modified because
forest road curves are approximately half of the transportation network.
Table 2 Sale Nodes
Tablica 2. Mjesta prodaje
Volume of Biomass – Volumen biomase
Harvest Node
Destination Node
Biomass, m3
Mjesto iveranja
Mjesta isporuke
Biomasa, m3
1
10
135,921
2
10
28,883
3
10
175,564
The sale nodes for the small network (Fig. 4) are nodes
1, 2, and 3. The associated amount of biomass for each
sale (chips or hogfuel) is identified in Table 2. All of
the biomass is to be delivered to only one mill (Node
10). The haul and modification costs per link are provided in the appendix (Table 5).
The ACO had a stopping criterion of 1,000 iterations. The heuristic converged on its solution rather
quickly (iteration 282). The optimal solution to this
problem using the ACO is $ 72,140. This amounted to
$ 6,225 in modification costs and $ 65,915 in hauling
costs. The optimal path is shown for each sale in Table
3 and Fig. 4. There were 1,454 trips from Unit 1 to the
Fig. 4 Small example road modification network, adapted from
(Sessions 1985)
Slika 4. Primjer modificirane mreže šumskih prometnica (prilagođeno iz Sessions 1985)
was assumed to require filling the ditches, reversing
the superelevation, and widening the roadway on a
few select curves. These modifications were estimated
to cost $ 9,843 per km (Table 1). We assumed that only
Table 3 The Optimal Path for the Small Network Using Ant Colony Heuristic
Tablica 3. Optimalni pravac izvoženja prema metodi mravlje kolonije
Total Cost – Ukupni troškovi prijevoza
$ 72,139.50
–
Sale 1 – Prodaja 1
Sale 2 – Prodaja 2
Sale 3 – Prodaja 3
Truck Type – Vrsta prikolice
Truck Type – Vrsta prikolice
Truck Type – Vrsta prikolice
13.7 m Drop Center 5th wheel
13.7 m Drop Center 5th wheel
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s utovarom na
sredini
Poluprikolica dugačka 13,7 m s utovarom na
sredini
Poluprikolica dugačka 16,2 m s utovarom na
sredini
Best Node Path – Optimalni pravac izvoženja
Best Node Path – Optimalni pravac izvoženja
Best Node Path – Optimalni pravac izvoženja
1
2
3
5
4
7
6
11
10
7
6
–
10
7
–
–
10
–
Croat. j. for. eng. 34(2013)2
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S. Beck and J. Sessions Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215)
Table 4 The Optimal Path for the Small Network Using Mixed Integer Programming
Tablica 4. Optimalni pravac izvoženja prema metodi mješovitoga cjelobrojnoga linearnoga programiranja
Total Cost – Ukupni troškovi prijevoza
$ 72,154.26
Sale 1 – Prodaja 1
Sale 2 – Prodaja 2
Sale 3 – Prodaja 3
Truck Type – Vrsta prikolice
Truck Type – Vrsta prikolice
Truck Type – Vrsta prikolice
13.7 m Drop Center 5th wheel
13.7 m Drop Center 5th wheel
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s utovarom na
sredini
Poluprikolica dugačka 13,7 m s utovarom na
sredini
Poluprikolica dugačka 16,2 m s utovarom na
sredini
Best Node Path – Optimalni pravac izvoženja
Best Node Path – Optimalni pravac izvoženja
Best Node Path – Optimalni pravac izvoženja
1
2
3
5
4
7
6
11
10
7
6
–
10
7
–
–
10
–
Mill, 309 trips from Unit 2 to the Mill, and 1,550 trips
from Unit 3 to the Mill.
The ACO solution was compared to a mixed integer solution (Table 4, Fig. 5). The mixed integer and
ACO produced similar results; a $ 13 difference between the two approaches. This was the result of
rounding when formulating the mixed integer problem. Both methods used the same truck types and
paths to transport the biomass to the mill. This small
example illustrates that the heuristic appears reasonable for determining near optimal solutions for similar
road modification problems.
6. Application to a realistic forest
transportation network – Primjena na
stvarnoj šumskoj transportnoj mreži
Following the favorable results of the small network, the ACO heuristic was used on the McDonald
Forest, to determine the least cost path for future harvesting activities. McDonald Forest is located 11.3 km
north of Corvallis and is managed by Research Forest
staff, College of Forestry, OSU. McDonald Forest is a
teaching, research and demonstration forest revolving
around four themes. These themes are:
Þ Short Rotation Wood Production with High Return on Investment,
Þ High Quality, Growth Maximizing Timber Production,
206
Þ Visually Sensitive, Even-aged Forest,
Þ Structurally Diverse Forest.
Biomass utilization is gaining interest in western
Oregon and several biomass-powered cogeneration
plants exist within 95 km of McDonald Forest. A major
cost of biomass operations is the transportation cost.
With small profit margins, it is important to determine
the least cost method for transporting biomass from the
woods to the mill. Being able to determine the optimal
trucks and haul routes that would reduce total transportation costs would be important to the decision to
utilize biomass. We applied the ACO heuristic to develop a least cost path from a sample of harvest units
distributed through McDonald Forest. McDonald Forest is approximately 2,914 ha with 113 km of road or
about 37.3 m of forest roads per hectare (Lysne D. and
Klumph, B. OSU College Forests, Corvallis, Oregon,
Personal Communication, December 14, 2011). The
McDonald Forest road network and possible truck
routes through Corvallis are shown in Fig. 6.
Thirty hypothetical timber harvests (sales) were
spread through McDonald Forest (Fig. 6) for the purpose of reducing fuel loading around the urban interface. These timber harvests were assumed to produce
and recover 89.7 green tonnes of biomass per hectare
or 113.3 m3 of biomass with 50 % moisture content. It
was estimated that each sale would harvest between
45 and 95 ha (black triangles in Fig. 6). The destination
node for all of the transported biomass is a biomass
plant in Eugene (48 km south of Corvallis). The estiCroat. j. for. eng. 34(2013)2
Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215) S. Beck and J. Sessions
Fig. 5 Ant Colony Optimal Haul Routes. The bold arrows indicate
optimal haul routes. The large black circles indicate nodes within
the transportation network. The small black circles indicate the road
modification option for the 16.2 m drop center 5th wheel chip van,
the small horizontally hatched circles indicate the road modification
option for the 13.7 m drop center 5th wheel chip van, and the small
white circles indicate the road modification option for the stingersteered chip van
Slika 5. Optimalni pravac izvoženja prema metodi mravlje kolonije.
Podebljane strelice označuju optimalni pravac izvoženja, dok veliki
krugovi označuju raskrižja transportne mreže. Mali tamni kružići označuju šumsku cestu prilagođenu poluprikolici za šumsku sječku dugačkoj 16,2 m s utovarom na sredini, mali vodoravno iscrtkani kružići označuju šumsku cestu prilagođenu poluprikolici za šumsku
sječku dugačkoj 13,7 s utovarom na sredini, dok mali bijeli kružići
označuju šumsku cestu prilagođenu samokretnoj prikolici za šumsku
sječku
Fig. 6 Mixed Integer Optimal Haul Routes. The bold arrows indicate
optimal haul routes. The large black circles indicate nodes within
the transportation network. The small black circles indicate the road
modification option for the 16.2 m drop center 5th wheel chip van,
small horizontally hatched circles indicate the road modification
option for the 13.7 m drop center 5th wheel chip van, and the small
white circles indicate the road modification option for the stingersteered chip van
Slika 6. Optimalni pravac izvoženja prema metodi mješovitoga cjelobrojnoga linearnoga programiranja. Podebljane strelice označuju
optimalni pravac izvoženja, dok veliki krugovi označuju raskrižja transportne mreže. Mali tamni kružići označuju šumsku cestu prilagođenu poluprikolici za šumsku sječku dugačkoj 16,2 m s utovarom na
sredini, mali horizontalno iscrtkani kružići označujuju šumsku cestu
prilagođenu poluprikolici za šumsku sječku dugačkoj 13,7 s utovarom
na sredini, dok mali bijeli kružići označuju šumsku cestu prilagođenu
samokretnoj prikolici za šumsku sječku
mated travel speed on forest roads was 16.1 km/h and
72.4 km/h on major highways (loaded or unloaded).
On public highways, it was assumed that any truck
combination could be used without incurring any
road modification costs.
are the same as Table 1. Once the chip vans were outside of the McDonald Forest, it was assumed that any
chip van could be used without incurring a road modification cost. It was also assumed that adequate turnarounds exist to permit use of each truck type.
The transportation network included 405 nodes
and 2,433 links, including the existing transportation
network and two modification options for each link.
The existing transportation network was assumed to
only permit stinger-steered trailer access. The other
two trailer types required temporary road modification for access similar to the small network problem.
The chip van operating characteristics in this problem
The routes for the 30 sales produced by the ACO
in 10,000 iterations are shown in Fig. 8. For every sale,
the ACO determined that the least cost path used a
16.2 m drop center 5th wheel chip van. The total transportation cost was $ 2,697,920 with $ 254,647 in road
modification costs and $ 2,443,273 in haul costs. The
road modification costs amount to 9 % of the total cost.
If no road modifications had been made, only the
Croat. j. for. eng. 34(2013)2
207
S. Beck and J. Sessions Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215)
Fig. 7 McDonald Forest Road Network, Corvallis, Oregon, USA
Slika 7. Mreža šumskih cesta u šumi »McDonald« Corvallis, Oregon,
SAD
Fig. 8 Optimal route path for all 30 sales, McDonald Forest, Corvallis, Oregon, USA
Slika 8. Optimalni pravac izvoženja za svih 30 turnusa u šumi »McDonald« Corvallis, Oregon, SAD
stinger steered chip van could have been used with a
total transportation cost of $ 3,703,310 (100 % haul
costs). In this example, the ability to modify the roadway to allow larger trucks access to these sales reduced the total transportation cost by 27 %. The ability to reduce transportation costs by 27 % is a large
benefit when margins are as slim as they are in the
biomass market. This implies that being able to reduce
the haul cost with the application of road modifications could have a significant positive impact.
framework to assist in deciding the optimal truck type.
When comparing cost per tonne versus highway haul
kilometers, the 16.2 m drop center 5th wheel chip van
is the most economical (Fig. 9). However, if the forest
transportation network requires modification, the
most economical chip van changes. For illustration, we
assume that loaded and empty vehicles of a given type
travel at the same speed and have the same hourly cost
(Table 1). The cost per tonne including transport and
road investment is:
7. Single Harvest Unit Analysis
– Case Two – Analiza pojedinačne
sječine – slučaj prvi
The network example provides an example of how
several nearby chip or hog fuel sales and the use of
road modifications can reduce overall transportation
costs when considering road investments that benefit
more than one sale. However, the ability to have nearby chip or hog fuel sales may not be practical. For the
case of isolated sales, we provide a decision-making
208
Cost Per Tont =
+
2 × HK × OCt 2 × FK × OCt
+
+
KPHHt × VCt KPH Ft × VCt
FK × PFKt × MCt
H× V
∀ t ∈T (9)
Where:
HK
FK
OCt
distance traveled on highway roads
(one-way), km,
distance traveled on forest roads
(one-way), km,
operating cost of chip van, t ($/hr),
Croat. j. for. eng. 34(2013)2
Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215) S. Beck and J. Sessions
two trucking options) can be calculated for any two
trucking options:
HM =
 2 ×OC b
PFK b × MC b
PKMa × MCa 
2 ×OCa
FK × 
+
−
−

KPH
+
VC
H
V
KPH
VC
H ×V
×
×


b
Fb
Fa
a

2 ×OCa
2 ×OC b 
 KPH × VC − KPH × VC 

Ha
a
Hb
b
(10)
Fig. 9 Comparison of cost per tonne versus highway kilometers
when traveling on highway roads. When traveling over highway
roads or when traveling on the forest transportation network, where
no modifications are required for all vehicles, the most economical
chip van is the 16.2 m drop center 5th wheel chip van. On an 80 km
highway haul, the cost savings is $ 2.71 per tonne comparing a 12.8
m stinger-steered chip van to a 16.2 m drop center 5th wheel chip
van. We assumed each trailer is weight limited
Slika 9. Usporedba troškova prijevoza po toni prema udaljenosti
prijevoza autocestom. Prilikom prijevoza autocestom ili šumskim
cestama gdje nije bilo potrebe za rekonstrukcijom najekonomičnijom
se pokazala poluprikolica za šumsku sječku dugačka 16,2 m s utovarom na sredini. Na 80-om km autoceste ta je poluprikolica 2,71 $
po toni isplativija od samokretne prikolice za šumsku sječku dugačke
12,8 m uz pretpostavku poštivanja ograničenja nosivosti
VCt
volume capacity of chip van, t,
KPHHt average operating speed on highway roads
for chip van, t (km/h),
KPHFt average operating speed on forest roads
for chip van, t (km/h),
PFKt %age of the forest road kilometers that need
to be modified for chip van, t,
MCt forest road modification cost for chip van,
t ($/km),
V
harvest volume per hectare, tonnes/ha,
H
total harvest area, ha.
Equation 9 can be manipulated to compare alternative truck options for the single sale. For example, the
breakeven highway haul distance (the highway distance that provides the same cost per tonne between
Croat. j. for. eng. 34(2013)2
The subscripts »a« and »b« indicate the two trucking options being compared. Equation 10 assumes that
both truck options can be operated on the highway.
Some counties may have restrictions over some roads
that do not permit trucks or trailer combinations over
a maximum length or weight.
The breakeven equation between the 12.8 m stinger-steered chip van and the 16.2 m drop center 5th
wheel chip van, if no road investment is required, is
trivial (Fig. 9). The cost per tonne in the 16.2 m drop
center 5th wheel chip van is always lower than the cost
per tonne in the 12.8 m stinger-steered chip van.
The breakeven highway distance between the
12.8 m stinger-steered chip van and the 13.7 m drop
center 5th wheel chip van for the 90 green tonnes of
biomass per hectare case as a function of in forest kilometers (FK) is (operating characteristics from Table
1 were rounded for ease of illustration):
HM =
 2 × $ 91 0.5 × 3 281 2 × $ 95 
+
−
FK × 
 15 × 29.9
90 × H
15 × 23.6 
 2 × $ 95
2 × $ 91 
 75 × 23.6 − 75 × 29.9 
(11)
Equation (11) is the highway distance (km) needed
to be traveled before the 13.7 m drop center 5th wheel
chip van becomes economical for a given in forest
hauling distance. The breakeven distance for a harvest
area of 50 ha between these two vehicles for 2 km on
forest roads is 17.8 highway km. For distances less
than 17.8 km, it is more economical to use the 12.8 m
stinger-steered chip van. For distances greater than
17.8 km and less than 179.4 km, it is more economical
to use the 13.7 m drop center 5th wheel chip van (Fig.
10). A breakeven analysis of an in forest hauling distance of 15 km is shown in Fig. 11.
For the case of removing 45 green tonnes per hectare (such as a thinning operation) on a harvest unit of
50 ha and the in forest, hauling distance was either
2 km (Fig. 12) or 15 km (Fig. 13). The optimal trucking
option would be the 12.8 m stinger-steered chip van
for highway hauling distances less than 45.7 km, when
hauling on 2 km of forest road and 342.6 km when
hauling on 15 km of forest road. As volume removed
is reduced, the use of road modifications to allow
209
S. Beck and J. Sessions Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215)
close vicinity, the larger transport volume justifies a
greater investment and makes a larger chip van economical.
8. Concluding Remarks – Zaključna
razmatranja
Mixed integer programming and breakeven analysis have been applied for a long time to address forest
transportation problems. The focus of this application
has been in response to the worldwide interest in the
utilization of forest residues for alternative energy. Unlike the primary log market, roads were not built to
extract forest residues and the limited value of these
Fig. 10 Comparison of cost per tonne versus highway kilometers,
when traveling over 2 km on forest road. This comparison uses 90
green tonnes per hectare for a 50 ha harvest unit. Modification
costs are only applied to half of the distance traveled on a forest
road. As the highway haul distance increases, a larger chip van
becomes more economical. In this case, 17.8 km of highway hauling is the breakeven case between a 13.7 m drop center 5th wheel
chip van and a 12.8 m stinger-steered chip van. The 16.2 m drop
center 5th wheel chip van becomes economical over the 13.7 m
drop center 5th wheel chip van at 179.4 km highway hauling
Slika 10. Usporedba troškova prijevoza po toni prema udaljenosti
prijevoza autocestom kada je vožnja šumskom cestom dulja od 2 km.
Dobiveni podaci temelje se na sječnoj površini od 50 ha i 90 t svježe sječke po hektaru. Troškovi potrebni za rekonstrukciju šumskih
cesta izračunavaju se za pola njihove duljine. S povećanjem udjela
vožnje autocestom veća prikolica postaje ekonomičnija. U ovom
slučaju na 17,8 km autoceste poluprikolica za šumsku sječku dugačka 13,7 m s utovarom na sredini postaje ekonomski isplativija od
samokretne prikolice za šumsku sječku dugačke 12,8 m, dok poluprikolica za šumsku sječku dugačka 16,2 m s utovarom na sredini
postaje ekonomski isplativija od poluprikolice za šumsku sječku dugačke 13,7 m s utovarom na sredini na 179,4 km autoceste
larger vehicle access tends to increase transportation
costs per tonne.
From the single harvest unit case, it is apparent that
modifying the transportation network is not always
the economical option. However, in the McDonald
Forest transportation network example, it was cost efficient to modify the network to allow larger vehicles
access. By grouping several biomass harvest units in
210
Fig. 11 Comparison of cost per tonne versus highway kilometers
when each truck must travel 15 km on forest road. This comparison
uses 90 green tonnes per hectare for a 50 ha harvest unit. Modification costs are only applied to half of the distance traveled on a
forest road. As the highway haul distance increases, a larger chip
van becomes more economical. In this case, 133.8 km of highway
hauling is the breakeven case between a 13.7 m drop center 5th
wheel chip van and a 12.8 m stinger-steered chip van
Slika 11. Usporedba troškova prijevoza po toni prema udaljenosti
prijevoza autocestom kada je vožnja šumskom cestom dulja od
15 km. Dobiveni podaci temelje se na sječnoj površini od 50 ha i 90 t
svježe sječke po hektaru. Troškovi potrebni za rekonstrukciju šumskih
cesta izračunaju se za pola njihove duljine. S povećanjem udjela
vožnje autocestom veća prikolica postaje ekonomičnija. U ovom
slučaju na 133,8 km autoceste poluprikolica za šumsku sječku dugačaka 13,7 m s utovarom na sredini postaje ekonomski isplativija
od samokretne prikolice za šumsku sječku dugačke 12,8 m
Croat. j. for. eng. 34(2013)2
Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215) S. Beck and J. Sessions
products will usually not support widespread reconstruction of the forest network. However, strategic
investments in the existing road network - some temporary, some permanent, may be justified. Decision
support for temporary activities, such as filling ditches and changing road cross slopes to enable large vehicle access, has not been available in the literature.
When these ideas were applied to schedule multiple biomass operations over a common road net-
Fig. 12 Comparison of cost per tonne versus highway kilometers
when traveling over 2 km on forest road. This comparison uses 45
green tonnes per hectare for a 50 ha harvest unit. Modification costs
are only applied to half of the distance traveled on a forest road. As
the highway haul distance increases, a larger chip van becomes
more economical. In this case, 45.7 km of highway hauling is the
breakeven case between a 13.7 m drop center 5th wheel chip van
and a 12.8 m stinger-steered chip van. Not shown, the 16.2 m drop
center 5th wheel chip van becomes economical over the 13.7 m drop
center 5th wheel chip van at 368.9 km highway hauling
Slika 12. Usporedba troškova prijevoza po toni prema udaljenosti
prijevoza autocestom kada je vožnja šumskom cestom dulja od 2 km.
Dobiveni podaci temelje se na sječnoj površini od 50 ha i 45 t svježe sječke po hektaru. Troškovi potrebni za rekonstrukciju šumskih
cesta izračunaju se za pola njihove duljine. S povećanjem udjela
vožnje autocestom veća prikolica postaje ekonomičnija. U ovom
slučaju na 45,7 km autoceste poluprikolica za šumsku sječku dugačka 13,7 m s utovarom na sredini postaje ekonomski isplativija od
samokretne prikolice za šumsku sječku dugačke 12,8 m, dok poluprikolica za šumsku sječku dugačka 16,2 m s utovarom na sredini
postaje ekonomski isplativija od poluprikolice za šumsku sječku dugačke 13,7 m s utovarom na sredini na 368,9 km autoceste
Croat. j. for. eng. 34(2013)2
Fig. 13 Comparison of cost per tonne versus highway kilometers
when traveling over 15 km on forest road. This comparison uses 45
green tonnes per hectare for a 50 ha harvest unit. Modification
costs are only applied to half of the distance traveled on a forest
road. As the highway haul distance increases, a larger chip van
becomes more economical. In this case, the 12.8 m stinger-steered
chip van is the most economical for highway hauling distances less
than 342.6 km
Slika 13. Usporedba troškova prijevoza po toni prema udaljenosti
prijevoza autocestom kada je vožnja šumskom cestom dulja od 15 km.
Dobiveni podaci temelje se na sječnoj površini od 50 ha i 45 t svježe sječke po hektaru. Troškovi potrebni za rekonstrukciju šumskih
cesta izračunaju se za pola njihove duljine. S povećanjem udjela
vožnje autocestom veća prikolica postaje ekonomičnija. U ovom
slučaju samokretna prikolica za šumsku sječku dugačka 12,8 m najekonomičnija je do 342,6 km autoceste
work, the ACO heuristic obtained an optimal solution
to a small problem; and when applied to a more realistic problem, quickly provided a solution. As transport volume increases, more could be spent on road
modifications to allow larger truck capacity access. Being able to modify the forest transportation network
to accommodate larger trucks access could greatly reduce hauling costs. Decisions for isolated biomass operations depend on road modification cost, transport
volume, and transport costs on forest and highway
roads. Breakeven analysis can be used to determine
the optimal vehicle type. Further research is required
to determine if the associated costs used in this paper
accurately represent the road modification costs required to allow these non-standard trucks access.
211
S. Beck and J. Sessions Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215)
Appendix – Dodatak
9. References – Literatura
Donati, A. V., Montemanni, R., Casagrande, N., Rizzoli, A.
E., Gambardella, L. M., 2008: Time Dependent Vehicle Routing Problem with a Multi Ant Colony System. European
Journal of Operational Research 185(3): 1174–1191.
4
Glauz, W. D., Harwood, D. W., 1991: Superelevation and
Body Roll Effects on Offtracking of Large Trucks. Transportation Research Record 1303, Transportation Research Board
of the National Academies.
Gover, F., Kochenberger, G., 2003: Handbook of Metaheuristics. Kluwer Academic Publishers.
1
4
1
4
1
5
Poluprikolica dugačka 13,7 m s
utovarom na sredini
17.91
2,600
Poluprikolica dugačka 16,2 m s
utovarom na sredini
19.66
7,800
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
6.14
0
5.86
850
6.43
2,550
12.28
0
11.71
1,700
12.85
5,100
6.14
0
5.86
850
13.7 m Drop Center 5th wheel
1
5
Poluprikolica dugačka 13,7 m s
utovarom na sredini
16.2 m Drop Center 5th wheel
1
5
Rizzoli, A. E., Montemanni, R., Lucibello, E., Gambardella,
L. M., 2007: Ant colony Optimization for Real-World Vehicle
Routing Problems: From Theory to Applications. Swarm
Intelligence 1: 135–151.
2
1
Sessions, J., Wimer, J., Costales, F., Wing, M. G., 2010: Engineering Considerations in Road Assessment for Biomass
Operations in Steep Terrain. Western Journal of Applied Forestry 25(3): 144–153.
0
16.2 m Drop Center 5th wheel
Hoos, H., Stutzle, T., 2005: Stochastic Local Search, Foundations and Applications. Morgan Kaufmann Publishers.
Sessions, J., 1985: A Heuristic Algorithm for the Solution of
the Variable and Fixed Cost Transportation Problem. Society
of American Foresters Symposium, Athens, Georgia 324–
336.
18.79
13.7 m Drop Center 5th wheel
Dorigo, M., Stutzle, T., 2004: Ant Colony Optimization. The
MIT Press.
Geem, Z., 2009: Music-Inspired Harmony Search Algorithm.
Springer–Verlag.
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
Troškovi rekonstrukcije, $/pravac
1
Modification Cost, $/Link
Truck Type
Vrsta prikolice
Troškovi prijevoza po turnusu, $/prikolica/pravac
Craven, M., Wing, M., Sessions, J., Wimer, J., 2011: Assessment of Airborne Light Detection and Ranging (LiDAR) for
use in Common Forest Engineering Geomatic Applications.
M.S. Thesis, Oregon State Universtiy, College of Forestry,
Corvallis. Retrieved from Oregon State University: <http://
hdl.handle.net/1957/21803
Šifre pravaca
izvoženja
Round Trip Haul Cost, $/Truck/Link
Contreras, M. A., Chung, W., Jones, G., 2008: Applying Ant
Colony Optimization Metaheuristic to Solve Forest Transportation Planning Problems with Side Constraints. Canadian Journal of Forest Research 38(11): 2896–2910.
Link Identifier
To – Do
Bowers, S., 2006: Managing Woodland Roads, A Field Handbook. Oregon State University Extension Service, Oregon
State University, Corvallis, Oregon.
Table 5 Haul and Modification Cost for the Small Network
Tablica 5. Troškovi prijevoza i rekonstrukcije
From – Od
Anderson, P., Sessions, J., 1991: Factors affecting the maximum grade a truck can climb around a curve. In: Proceedings, Fifth International Conference on Low Volume Roads.
Transportation Research Board, National Research Council,
Washington, D.C. TRR 1291, Volume 2: 15–19.
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
13.7 m Drop Center 5th wheel
2
1
Poluprikolica dugačka 13,7 m s
utovarom na sredini
16.2 m Drop Center 5th wheel
2
1
2
4
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
13.7 m Drop Center 5th wheel
2
212
4
Poluprikolica dugačka 13,7 m s
utovarom na sredini
Croat. j. for. eng. 34(2013)2
Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215) S. Beck and J. Sessions
16.2 m Drop Center 5th wheel
2
4
3
2
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
4
11
13.7 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s
utovarom na sredini
4.13
600
4.54
1,800
6.43
2,550
9.39
0
4
11
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 16,2 m s
utovarom na sredini
8.96
1,300
5
4
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
7.95
0
4
13.7 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s
utovarom na sredini
7.58
1,100
8.32
3,300
13.7 m Drop Center 5th wheel
3
2
Poluprikolica dugačka 13,7 m s
utovarom na sredini
16.2 m Drop Center 5th wheel
3
2
3
4
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
5
9.83
3,900
6.50
0
5
4
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 16,2 m s
utovarom na sredini
6.20
900
5
6
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
3.61
0
6
13.7 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s
utovarom na sredini
3.45
500
3.78
1,500
13.7 m Drop Center 5th wheel
3
4
Poluprikolica dugačka 13,7 m s
utovarom na sredini
16.2 m Drop Center 5th wheel
3
3
4
7
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
6.80
2,700
5
6.32
0
5
6
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 16,2 m s
utovarom na sredini
6.03
875
5
8
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
6.14
0
8
13.7 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s
utovarom na sredini
5.86
850
6.43
2,550
13.7 m Drop Center 5th wheel
3
7
Poluprikolica dugačka 13,7 m s
utovarom na sredini
16.2 m Drop Center 5th wheel
3
4
7
5
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
6.61
2,625
9.03
0
5
8
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 16,2 m s
utovarom na sredini
8.61
1,250
6
7
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
5.42
0
7
13.7 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s
utovarom na sredini
5.17
750
6
7
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 16,2 m s
utovarom na sredini
5.67
2,250
6
8
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
6.50
0
6
8
13.7 m Drop Center 5th wheel
Poluprikolica dugačka 13,7 m s
utovarom na sredini
6.20
900
6
8
16.2 m Drop Center 5th wheel
Poluprikolica dugačka 16,2 m s
utovarom na sredini
6.80
2,700
13.7 m Drop Center 5th wheel
4
5
Poluprikolica dugačka 13,7 m s
utovarom na sredini
th
16.2 m Drop Center 5 wheel
4
4
5
6
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
9.45
3,750
6.14
0
5.86
850
13.7 m Drop Center 5th wheel
4
6
Poluprikolica dugačka 13,7 m s
utovarom na sredini
th
16.2 m Drop Center 5 wheel
4
4
6
11
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
Croat. j. for. eng. 34(2013)2
5
6.43
4.34
6
2,550
0
213
S. Beck and J. Sessions Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215)
7
6
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
1.81
0
1.72
250
16.2 m Drop Center 5th wheel
8
9
8
10
th
13.7 m Drop Center 5 wheel
7
6
Poluprikolica dugačka 13,7 m s
utovarom na sredini
16.2 m Drop Center 5th wheel
7
6
7
8
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
8
Poluprikolica dugačka 13,7 m s
utovarom na sredini
1.89
750
6.50
0
6.20
900
8
10
8
7
10
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
8
10
9
10
6.80
2,700
9.03
0
8.61
0
9
10
Poluprikolica dugačka 13,7 m s
utovarom na sredini
8
10
9
Poluprikolica dugačka 16,2 m s
utovarom na sredini
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
9
10
11
6
9.45
0
5.06
0
4.82
700
11
9
Poluprikolica dugačka 13,7 m s
utovarom na sredini
18.60
0
Poluprikolica dugačka 16,2 m s
utovarom na sredini
20.41
0
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
9.03
0
Poluprikolica dugačka 13,7 m s
utovarom na sredini
8.61
0
Poluprikolica dugačka 16,2 m s
utovarom na sredini
9.45
0
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
0.36
0
6
Poluprikolica dugačka 13,7 m s
utovarom na sredini
0.34
50
0.38
150
16.2 m Drop Center 5th wheel
11
13.7 m Drop Center 5th wheel
8
Poluprikolica dugačka 13,7 m s
utovarom na sredini
13.7 m Drop Center 5th wheel
16.2 m Drop Center 5th wheel
7
0
16.2 m Drop Center 5th wheel
13.7 m Drop Center 5 wheel
10
19.51
13.7 m Drop Center 5th wheel
th
7
2,100
16.2 m Drop Center 5th wheel
16.2 m Drop Center 5th wheel
7
12.8 m Stinger
Samokretna prikolica dugačka 12,8 m
5.29
13.7 m Drop Center 5th wheel
13.7 m Drop Center 5th wheel
7
Poluprikolica dugačka 16,2 m s
utovarom na sredini
6
Poluprikolica dugačka 16,2 m s
utovarom na sredini
Sažetak
Odlučivanje o izvoznim pravcima prikolica za šumsku sječku uz optimizaciju
metodom mravlje kolonije i analizu prekretnice troškova
Nekonvencionalni (sekundarni) šumski proizvodi pružaju mogućnost povećanja ekonomske vrijednosti šume,
dok transport takvih proizvoda u nekim slučajevima zahtijeva prijevoz specijaliziranim vozilima. Zbog činjenice da
postojeća šumska prometna infrastruktura uglavnom nije dizajnirana prema standardima koje specijalizirana vozila
zahtijevaju potrebno je raditi izmjene (rekonstrukcije) na šumskim cestama (zatrpavanje odvodnih jaraka, proširivanje
i rekonstruiranje kolničke konstrukcije) kako bi se takvim vozilima omogućio pristup šumi. Svaku izmjenu kolničke
konstrukcije potrebno je prilagoditi tehničkim karakteristikama specijaliziranih vozila koja će naposljetku tom
šumskom cestom i prometovati. U ovom su radu promatrani različiti transportni sustavi za (1) višestruko izvoženje
biomase, (2) pojedinačno izvoženje biomase.
214
Croat. j. for. eng. 34(2013)2
Forest Road Access Decisions for Woods Chip Trailers Using Ant Colony Optimization... (201–215) S. Beck and J. Sessions
U slučaju višestrukoga izvoženja biomase primijenjena je metoda mješovitoga cjelobrojnoga linearnoga programiranja i metoda temeljena na principu mravlje kolonije »Ant Colony Optimization« (ACO). Obje su metode korištene na malom uzorku prikazanom na slici 4. Jedina razlika između tih dviju metoda iznosi $ 13, a nastala je tijekom
izračuna (zaokruživanja) kod metode mješovitoga cjelobrojnoga linearnoga programiranja (tablice 3 i 4). Metoda
ACO primijenjena je pri određivanju optimalnoga specijaliziranoga vozila (prikolice) te pri izboru optimalnoga
pravca izvoženja za 30 hipotetski odabranih mjesta iverenja u šumama »McDonald« u Corvallisu, Oregon, Sjedinjene Američke Države (slika 7). Metodom ACO utvrđeno je da su ukupni troškovi prijevoza najmanji prilikom korištenja najveće prikolice za šumsku biomasu, što razumijeva najveću rekonstrukciju šumske ceste na pravcima izvoženja. Na dionicama gdje nije bila potrebna izmjena kolničke konstrukcije ukupni troškovi prijevoza manji su za
27 %.
Pri pojedinačnom izvoženju biomase primijenili smo prikladniju analizu prekretnice troškova. Analiza prekretnice troškova pretpostavlja da su pravci izvoženja poznati, dok su varijable operativne karakteristike prikolice za
šumsku biomasu te troškovi izgradnje pripadajuće šumske ceste s uračunatim troškovima rekonstrukcije šumske
ceste (jednadžba 9). Pomoću jednadžbe 10 može se utvrditi na kojoj su udaljenosti (autoceste) troškovi transporta kod
promatranih dviju opcija jednaki. U ovom smo radu procijenili četiri različita slučaja, čistu sječu i prorede s kratkim
i dugim duljinama privlačenja. Utvrđeno je da se zbog povećanja privlačenja drvnih sortimenata te zbog potreba za
izmjenom kolničke konstrukcije pri korištenju većega kamiona nadmašuje korisnost povećanoga obujma biomase po
tovaru većega kamiona. Osim toga, zbog smanjenja obujma biomase po hektaru (proreda) te troškova rekonstrukcije
pojedine šumske ceste potreban je dulji transport autocestom (veća udaljenost) da bi veći kamion bio ekonomičan.
Ovom je analizom utvrđeno da rekonstrukcija šumskih cesta nije uvijek ekonomičan izbor.
Ključne riječi: optimizacija metodom mravlje kolonije, transport šumske biomase, pristupačnost vozilima
Authors’ address – Adresa autorâ:
Received (Primljeno): October 24, 2012
Accepted (Prihvaćeno): December 30, 2012
Croat. j. for. eng. 34(2013)2
Storm Beck, MSc. *
e-mail: [email protected]
Prof. John Sessions, PhD.
e-mail: [email protected]
Oregon State University
Department of Forest Engineering, Resources and
Management
Oregon State University
Corvallis, Oregon 97331
USA
* Corresponding author – Glavni autor
215
Original scientific paper – Izvorni znanstveni rad
Planning Forest Opening
with Forest Roads
Janez Krč, Jurij Beguš
Abstract – Nacrtak
The article presents the model for determining inaccessible forest areas by density of forest
roads. The model is based on the GIS analysis of the distances between the existing network
of public and forest roads and inaccessible forest areas, sizes of excluded forest areas, and forest
site potentials. In order to increase forest road density, the following must be done: (1) construct
connecting roads to the inaccessible forest areas and (2) construct new forest roads with different density in the excluded inaccessible forest areas. The model provides the minimum size
of the inaccessible area located at least 300 m away from the existing forest and public road.
The selected inaccessible forest areas are first analyzed according to their size – plot size of at
least 30 ha is used as a model default size suitable for economically justified construction of
the access road that connects the existing road network to the inaccessible forest area. The
analysis showed that there are still 210,385 ha of inaccessible forests in Slovenia according to
the model criteria. According to the research of regional units conducted by forest experts and
based on the determination of priorities for the next ten-year forest management plan, the
construction of 758 km of new forest roads is planned at the national level.
Keywords: forest road, density, forest operation, model, forest management plan
1. Introduction – Uvod
The construction of forest road network is considered as the key element for successful forest management. It has the biggest impact on the forest production function, since it enables and also technologically
defines the forest operations in the majority of cases.
The importance of forest roads or forest road network
can also be considered in terms of comparison, i.e. asset values that occur in forest operations. The simplified model can be of assistance where the forest, as a
piece of land, is considered as fixed asset, whereas the
forest stand, road network and working means represent the current assets – all used in forest operations.
In view of the above mentioned factors, the forest
management should provide the sustainability of
these factors. The current asset values (forest stand,
road network and working means) are in the approximate value interrelation of 100:10:1. The relation is
calculated for the model example covering 2667 ha
taking into account the following assumptions:
Þ Stand: value 45,142,000 € (timber value 60 EUR/m3,
volume 282 m3/ha) (SURS: Gozd in gozdarstvo
2013), (Poročilo o gozdovih za leto 2011, 2012);
Croat. j. for. eng. 34(2013)2
Þ Forest roads: value 4,300,000 € (construction costs
65 EUR/m, road density 24,8 m/ha) (Robek et al.
2007), (Gozdnogospodarski in lovsko upravljalski
načrti območij za obdobje 2011–2020, 2012);
Þ Working means: value 500,000 € (efficiency
80 m3/day, utilization 200 days/year).
The calculation was made for the projected model
of forest operations with the capacity of modern working means serving as a referential value (harvester and
forwarder). The average annual volumes of allowable
cut of 6m3/ha/year were applied for the calculation of
the necessary utilization of the available capacity of
modern working means. On the basis of the above
model assumptions, the necessary forest cutting area
for forest operations is well congruent with the size of
the average forest district in Slovenia and volumes of
allowable cuts defined in the forest management plans
(Poročilo o gozdovih za leto 2011, 2012).
The relations show the great importance of systematic approach to the issue of forest opening conducted
on a strategic and detailed level. The strategic or general level is implemented at various levels of forest
management planning. This should replace the current
approach of integrated planning of opening the forests
217
J. Krč and J. Beguš
with forest roads that called for the preparation of »Perspective programs for integrated opening of forests«
(Program odpiranja gozdov z gozdnimi prometnicami,
1990), studies that have not been successfully implemented anywhere in Slovenia. Today, these studies can
be of a great assistance and are widely used as reference points to conduct the tests of methodology presented in this article. In the forest management plans
prepared by Slovenia Forest Service (SFS), the priority
areas of opening are determined within the strategic
planning of forest road construction. These areas represent the surfaces where the forest roads should be
constructed. Due to legal procedures of adopting forest
management plans, they do not include detailed routes
of forest roads. At a higher level of forest management
planning, i.e. at the level of regional forest management
plans, the priority opening areas are not determined.
However, the strategic evaluation should include the
volume of new forest road construction that would
provide the necessary forest road network from the
point of view of timber harvesting.
1.1 Previous research – Dosadašnja istraživanja
Expert and scientific literature have been dealing
with the issue of estimation of forest opening together
with the evaluation of the density of the existing forest
road network for a relatively long time (Matthews
1942, quoting Chung et al. 2008).
The research of forest opening frequently includes
the relations between skidding costs and the costs of
forest road construction and maintenance. Frequently,
these estimations apply the assumption about the equal
distribution of logging operations in a certain area. As
a result, the optimum density and position of a forest
road network are determined. These are calculated according to the differential ratios of timber skidding
costs. Skidding costs are primarily dependant on the
applied skidding method and skidding distances (Krč
1999, Košir 2000). Some studies deal with the optimum
forest road network layout on the basis of the shortest
path between the appropriately distributed timber
sources (timber stacks at forest road) in a certain area
– i.e. from the point of view of further timber transport
(Anderson et al. 2004, Dean 1997).
An attempt of Preliminary Planning of Forest Road
Systems Using Digital Terrain Models was conducted
by Liu and Sessions (Liu et al. 1993). They set the optimal road alignment using a three step method (The
first step includes the identification of possible road
segments, the second step deals with the minimization
of the sum of construction, maintenance and transport
costs, while the third displays the results to provide
the verification of result by operation planner).
218
Planning Forest Opening with Forest Roads (217–228)
The ecosystem approach to road issues was comprehensively treated by Lugo and Gucinski (2000).
They proposed the unified ecosystem approach to
road management using an environmental gradient
analysis based on three main parameters (ecological,
socioeconomic and physical).
Similar to our problem, Demir (2007) tried to find
a systematic solution for the remaining portion of forest road network in Turkey. He used specific functional planning criteria for different forest road network
systems (production forest, reforestation forest and
national parks). The determination of road density in
the production forest was differentiated by growing
stock (20 m/ha for stands over 250 m3/ha and 10 m3/ha
under 250 m3/ha, respectively).
Previous studies also state different definitions of
primary forest openness. In Croatia there are different
levels of primary openness determined according to
the planning level (global : local) and definition purpose (planning, research work). The openness has also
been determined according to the relief regions (lowlands, hilly, highlands, Karst). The planned openness
(from minimal to the target) according to relief region
and projected plan is determined in the interval between 7 and 30 m/ha (Pentek et al. 2007).
The issue of including the road sections (public and
forest roads) into the selection of productive values in
terms of timber harvesting is dealt with by Pentek et
al. (2011). Also the position of forest road plays an important role when estimating the level of forest openness. Thus, the length of productive and connecting
roads is differentiated. According to Dobre (1995), the
productive forest road length is considered when:
Þ Road runs through the forest;
Þ Road runs along the forest;
Þ Forest is located less than 200 m from the road
– there are no obstacles for skidding operations;
Þ Non-forest zone is longer than 200 m, but shorter than 200 m along the road.
The data from recent studies were applied and
partly adjusted for the preparation and verification of
the following model for planning the necessary forest
opening with forest roads.
1.2 Purpose and aims of planning the necessary
forest opening with forest roads – Svrha
i ciljevi planiranja potrebne otvorenosti
šumskim prometnicama
At a strategic level, in forestry management planning of opening the forest with forest roads, the main
question is related to the target density and consequently the total length of forest roads. This means
Croat. j. for. eng. 34(2013)2
Planning Forest Opening with Forest Roads (217–228)
that the answer should include the quantity of new
forest roads that will reach the goals set at different
levels of planning. Basically, two questions are relevant: where the new forest roads need to be constructed, and how many kilometers of forest roads are still
necessary. It is estimated that these two answers suffice at the strategic level, i.e. regional level.
In Slovenia, the contents related to the planning of
forest opening with forest roads are legally defined.
Thus, the Article 3 of the Regulation on Forest Infrastructure (Pravilnik o gozdnih prometnicah, 2009) differentiates the strategic and detailed level of opening.
The strategic level, i.e. the level of forest management
planning defines the priority areas for forest opening
with forest roads, whereas the detailed level includes
making the elaborate of nought line definition. Furthermore, the Article 10 of the Forest Act (Zakon o
gozdovih, 1993 and following) states that the concept
of forest infrastructure is shown in the spatial part of
forest management plan of regional unit. At a lower
level of forestry management planning – forest management plan for forest management unit provides the
concept and overview for forest infrastructure. The
detailed scope for planning, construction, and maintenance of forest roads is regulated by the Regulation
on Forest Infrastructure.
Despite some previous attempts, the strategic and
integrated planning of providing forest opening with
forest roads on the basis of special programs/studies
has never been truly successful and never really implemented on the national level. Current regulations try
to solve the actual situation by implementing the regulations on the strategic/general planning of forest
opening with forest roads to the forest management
plans of forest management units with the determination of preferential areas for forest road construction.
Due to formal reasons1, the routes of future forest
roads are not defined in the forest management plans,
and it is, therefore, hard to make an objective evaluation of how many forest roads should still be constructed to provide the optimum operation of forest
production simply by applying the currently known
approaches. The plans include certain actual and target forest road densities that show the level of forest
opening with forest roads, but still this data insufficiently indicates further actions. Preferential opening
areas show the locations where new forest roads
should be necessary, but this still does not mean that
The routes of individually planned forest roads should not be
drawn in the forest management plans, since then each plan
would require the environmental impact assessment.
1
Croat. j. for. eng. 34(2013)2
J. Krč and J. Beguš
the new forest road construction would not be possible elsewhere. However, the strategic decision-making
should not overlook the data of how many forest roads
are still needed, i.e. not just the mere location but also
the quantity that would provide the realization of the
set goals. This requires a unified approach to the planning that would provide the decision-making based
on the objective evaluation of needs for the increasing
forest road density.
According to the legal provisions and relevant issue, the accessory tool was developed that provides a
quick, unified, and consistent evaluation of all forests
from the point of view of forest accessibility necessary
for performing forest operations. This tool consequently enables the exclusion of inaccessible areas and
hence the sequence of opening, i.e. increasing forest
road density, is determined in gradual steps.
It is estimated that the present model tool is a step
forward, since its consistent procedure helps to define
the location of inaccessible forests with the quantification of needs for opening.
2. Materials and methodology – Materijal
i metodologija
Slovenia is located between 45°25’–46°52’ N latitudes and 13°35′–16°35′ E longitudes. Slovenia is surrounded by neighboring countries (Italy, Austria,
Hungary and Croatia) and the Adriatic Sea. It covers
an area of 2,027,300 hectares and has a 43 km long
coastline. It belongs to the group of the smallest EU
countries (the longest width of 257 km is in the East–
West direction, while the smallest range of 78 km is
between the North-South direction). Slovenia has four
geographical regions (Pannonian on the East, Mediterranean on the South-West, Alpine on the North, and
Dinaric on the South part of the country). The total
forest area in Slovenia is 1,184,369 hectares. This figure
represents 58.4% of the total area. High quality forests
prevail, while the coppice forests spread only over
39,432 hectares and account for 3.3% of the total forest
area. According to 2011 figures, the share of coniferous
forest in the total growing stock is 46.2%, whereas the
deciduous forest covers 53.8 %. The total annual increment amounts to 8,265,936 m3, whereas the annual
allowable cut equals 5,498,733 m3 (Poročilo o gozdovih
za leto 2011, 2012). According to the data of the current
forest management plans for regional units (Gozdnogospodarski in lovsko upravljalski načrti območij za
obdobje 2011–2020, 2012), forests in Slovenia are accessible by forest roads (12,023 km) and primary prevention fire roads (489 km), which means 12,512 km or
10.6 m/ha of roads density in total. The forest area is
219
J. Krč and J. Beguš
additionally also accessible by public roads, which
could be suitable for forestry operations and wood
transport. In total, the Slovenian forests are accessible
by 29,244 km of roads, with a road density of 24.8 m/ha.
2.1 Data selection and analysis – Odabir
podataka i analiza
The model was developed according to the results
of previous studies and new technological trends that
have influenced the needs for additional forest roads.
The model performed the geographical analysis of
three main influential factors: (1) distance from the forest to the existing productive forest road or public road
that provides forest accessibility, (2) forest site potentials
(Košir 1975), and (3) surfaces of potentially inaccessible
forests. The areas for further forest construction of forest
roads were determined by applying the skidding distance and site potential factors. Then the priority of
opening was determined for individually selected inaccessible areas that met the criterion of minimum size.
The criteria for area selection, suitable for road construction according to the values of influential factors,
were somewhat adjusted in terms of previous research
results, regulations, and practice (Dobre 1995):
(1) distance between the forest and the road has
been increased, i.e. to 300 m,
(2) minimum inaccessible area size (30 ha) has been
determined,
(3) also the public roads that can be used as productive roads for forest production have been included.
The following general data of forestry information
system were applied:
Þ Forest and public roads suitable for forest production and primary forest fire prevention
roads with the status of a forest road (hereinafter referred to as »forest road«). Public roads
suitable for forest production have been determined with the intersection of public road linear
layer and border of the forest area. Herein, the
condition has been included that the section includes 200 meter of influential buffer zone
around the public roads. The final classification
of public roads has been determined with the
in-situ examination and confirmation of Slovenia Forest Service specialists.
Þ Forest-stand map with the map of forest border.
Þ Map of protective forests and forests with special purpose.
Þ Geo-encoded data on forest sections.
Þ Map of forest plant associations, acquired from
the digital data on forest sections (spatial and
attributive part).
220
Planning Forest Opening with Forest Roads (217–228)
2.2 Procedure of model preparation and
application – Postupak pripreme i primjene
modela
The preparation and basic processing of the selected
data from the forestry information system is conducted
first. The data preparation provides the necessary information for the determination of the position and scope
of inaccessible forests in a specific area. The tools for
raster processing of spatial data and DBMS modules
(Database Management System) are applied for the
data analysis. The attributive data are processed with
DBMS modules – in terms of input data preparation as
well as in terms of determination of the selected areas
that are smaller than minimum projected surface for
additional increasing the forest road density. The combination of basic as well as derived spatial vector and
raster data of forestry informational system are applied
for map preparation. Maps of model-wise inaccessible
forests acquired from data processing of forest information system then serve as the basis for in-situ evaluation
of the suitability of computerized model results, executed by foresters at the SFS local unit level.
The process can be divided into the following steps
(Fig. 1):
1. Determination of all areas with inadequate forest
road network – low access areas.
2. Exclusion of inaccessible areas that are smaller
than 30 ha (model-default as the minimum size
of inaccessible forest area that needs further increasing of the forest road density).
3. Determination of the necessary road density per
hectare. The road density is defined by site potentials (Table 1). Each surface was given the additional 300 meters of forest road for the connection to the existing road network.
4. Preparation of the numbered list of the low access areas with inadequate forest road network
in the attributive form, simultaneously shown on
the map (identification key is the serial number
of the low access area).
5. The examination of suitability of the low access
areas and the determination/selection of reasonable low access areas (i.e. the exclusion of low
access areas that cannot be considered suitable
for further increasing of forest road density on
the basis of computerized model and input data
quality).
6. Determination of low access areas where roads
should be constructed with priority in the tenyear period while the forest management plan
for the regional unit is in force, in order to achieve
the set goals. The determination is defined by
forest management goals and by the total length
Croat. j. for. eng. 34(2013)2
Planning Forest Opening with Forest Roads (217–228)
J. Krč and J. Beguš
Fig. 1 Main steps of the model for determining the necessary forest road density
Slika 1. Glavni koraci modela za određivanje potrebne šumske otvorenosti šumskim prometnicama
of forest roads that should be constructed for this
purpose (determination of priority low access
areas during the validity of the forest management plan).
2.3 Definition of conditions for determining low
access areas – Definiranje uvjeta za
utvrđivanje nedovoljno otvorenih površina
Further in the text, the main characteristics are given
of the model preparation and of the process for acquiring influential data used for the evaluation of the areas
requiring higher forest road density. All forest and public roads (suitable for forest production) and primary
forest fire prevention roads were assigned an influential
buffer zone of 300 meters according to the relief conditions, thus determining an area suitable for providing
good forest accessibility. It was estimated that skidding
method (tractor or cable skidder) does not play a crucial
role and does not influence the width of the influential
buffer zone. Thus, the cable skidding operation over the
distance of 400 m and tractor skidding over the distance
of 600 m was encompassed (distance from the standing
tree to the road). The areas outside this zone are poorly
accessible by roads.
The map of low access areas was made on the basis
of road intersection and 300 meter buffer zone. It determines the necessary locations of forest road construction (areas outside 300 meter buffer zone along
the forest roads). Since the information layer intersections offered areas of different sizes, also with very
small areas included, the size limit area had to be deCroat. j. for. eng. 34(2013)2
termined to get a reasonable idea of forest road construction. The estimation showed that the smallest low
access area where the construction of forest roads
would be reasonable was 30 ha. It would be unreasonable to construct forest roads on smaller areas or in
other words it would be more reasonable to provide
their opening with skid trails.
During the development of this method, the result
of suitability had to be checked with a referential
study. The Study of Integrated Forest Opening with
Forest Roads, i.e. »Program of Forest Opening with
Forest Roads« (hereinafter referred to as »Program«),
developed by the Regional Unit Kočevje in 1990 (Pro-
Table 1 Target forest road densities (TFR) according to the level of
the forest site potentials
Tablica 1. Ciljana gustoća šumskih prometnica (CGŠP) prema razinama potencijala šumskoga područja
Site potentials
Target forest road density, m/ha
Potencijal područja
Ciljana gustoća šumskih cesta, m/ha
< 5*
0
5–8
15
9–11
20
>12
25
*The exception is the Karst region where the opening was planned also for the
areas with the lowest level of site potentials (fire protection function).
* Iznimka je krško područje gdje je otvaranje planirano kao za područja s najnižom
razinom potencijala područja (protupožarna funkcija).
221
J. Krč and J. Beguš
gram odpiranja gozdov z gozdnimi prometnicami,
1990), was used as the referential study. The study
map was compared with the model map of areas that
needed opening. The method was also presented to
the forest road specialists and field foresters at the Regional Unit Kočevje and thus the independent opinion
on the applied methodology had been acquired already in the process of model development. The comparison of the study and the map of 300 m zone
showed a high degree of accordance of inaccessible
areas in terms of both location and shape. Also the
Planning Forest Opening with Forest Roads (217–228)
length of necessary forest roads established by the Program was examined and a relatively high degree of
agreement was confirmed – the Program foresaw the
construction of 331 km of forest roads, whereas the
model offered the result of 376 km.
To establish the final result, i.e. the required length
of forest roads to be constructed, it was necessary to
determine the required forest road length for each selected area of 30 ha or larger. The assumption was accepted that the management of better forest sites was
more intensive, thus justifying the higher forest road
Fig. 2 Example of the map with the numbered selected areas in the Regional Unit Kočevje with road network at the regional level
Slika 2. Primjer karte s obrojčanim odabranim područjima u Upravi šuma Kočevje s cestovnom mrežom na razini Uprave
222
Croat. j. for. eng. 34(2013)2
Planning Forest Opening with Forest Roads (217–228)
J. Krč and J. Beguš
Table 2 Example of the selected areas list in the Regional Unit Kočevje according to the level of site potentials with the planned length of
new roads
Tablica 2. Primjer popisa odabranih područja u Upravi šuma Kočevje prema razinama potencijala područja s planiranim duljinama novih cesta
No.
Br.
1
3
Level of site potentials, selected areas, ha
New Forest Roads, km
Razina potencijala područja, odabrana područja, ha
Nove šumske prometnice, km
5
7
9
11
15
17
New
Access
Total
Nove
Pristup
Ukupno
1
0
0
0
0
143
448.75
0
0
11.84
0.3
12.14
2
0
0
0
0
116.5
355.25
0
0
9.44
0.3
9.74
3
0
0
0
88.5
164
207.25
0
0
8.75
0.3
9.05
4
0
0
0
0
255.5
190.75
0
0
8.93
0.3
9.23
5
0
0
34.25
26.5
169
43.75
0
169.5
9.40
0.3
9.70
...
174
0
0
0
0
15.5
14.75
0.75
0
0.62
0.3
0.92
175
0
0
0
0
0
31
0
0
0.62
0.3
0.92
176
0
0
0
0
30.5
0.25
0
0
0.62
0.3
0.92
177
0
0
1
0
25.75
4
0
0
0.61
0.3
0.91
178
0
0
5.5
0
24.5
0
0
0
0.57
0.3
0.87
densities (Table 1). The level of the forest site potentials
was acquired from the forestry information system defined on the basis of forest vegetation associations
(Košir 1975). The value of forest site potential is a rank
that represents the relative ratio of forest vegetation associations based on forest site production potential. The
ranks are scaled from 1 to 17. The most productive rank
is 17, while the least productive one is 1. The value is
assumed as a long-term management goal, determined
by the composition of tree species which is close to the
potential natural state of forest stand (Košir et al. 2006).
When each area was adjusted with the necessary
forest road length, the numbered list of these areas
needed to be prepared. As the attributive basis, this list
was connected to the graphic information layer (Table
2, and Fig. 2) with all areas appropriately numbered.
The attributive list of the selected areas includes the
data on the site potentials and data on forest road
lengths. The list is necessary to provide clear and precise positioning of the areas in the region.
In the next phase of the method, it is necessary to
assess the suitability of the selected areas. Not all forest
areas that are more than 300 m away from forest roads
are appropriate for opening. Apart from the minimum
area size factor (30 ha), the shape of the selected areas
must also be taken into account. The typical example
are the areas between two roads that can be very narrow and long; this is especially obvious for forest
roads that run along both sides of long ridges – Number 34 in Fig. 3.
Croat. j. for. eng. 34(2013)2
This is the stage where the estimation with the application of computer tools does not suffice, and the
estimation of the in-situ experts is required. They decide which areas are actually suitable for opening. All
the selected areas the experts find unsuitable for opening, mainly due to their shape, are excluded from the
list and map.
The final, adjusted model product is represented
in the form of thematic map and table, which offer
spatial and quantitative recapitulation of the data on
the structure of the excluded inaccessible forests according to the site conditions and calculated new forest road lengths for every selected area. Additionally,
the access roads are included connecting the inaccessible sections with the existing forest road network.
3. Results – Rezultati
Table 3 shows the results of the described model at
the national level (Slovenia). It presents the quantities
of model-wise excluded inaccessible areas by regional
units of Slovenia Forest Service and site potentials
(Košir 1975). Then the necessary scope of new forest
road construction is calculated for regional units to
achieve the target road density according to the site
potentials of the excluded surfaces and in the extent
shown in Table 1. The scope of construction in the
model is divided into the access roads and the road
network that provides the forest opening. The length
is determined according to the forest operations on the
basis of target forest road density.
223
J. Krč and J. Beguš
Planning Forest Opening with Forest Roads (217–228)
Fig. 3 Example of the area section numbered 170 unsuitable for additional opening
Slika 3. Primjer izdvojenoga područja s brojem 170 koji je neprikladan za daljnje otvaranje
The analysis in the Karst area additionally included
the forests with lower site potentials, where the construction of primary fire-prevention roads is planned.
The majority of inaccessible areas were excluded
on the sites with lower site potentials, while only a
good third of the total length was excluded on the sites
with the site potential level higher than 10. This only
confirms the established fact that the forests located at
better sites had the priority for the construction of forest roads in the past. Nowadays, more attention has to
be paid to the medium potential sites.
All the necessary forest roads cannot be constructed in the following management period, since the
evaluation is a long-term one and in terms of the present timber harvesting technology it represents the final
solution of the forest roads density. Thus, the final
product determines the areas that must be made accessible to reach the management goals, set in the current plan. That is why the priority areas for increasing
forest road densities are defined together with the nec-
224
essary length of new forest roads. After the final examination of the specialists of SFS in the regional units
and after the determination of priorities, the final result is shown in Table 4.
In general, less than a fifth (17 %) of forest roads
has to be constructed in Slovenia to ensure optimal
forest accessibility. Here the area of Regional Unit
Sežana stands out, i.e. the area of Slovenian Istra, Brkini and Kras, as it was neglected in terms of forest road
construction. However, the forest roads and primary
fire prevention roads are very important in this area,
representing the key element of fire protection safety.
That is why the sites with lower site conditions were
also included in the calculation of forest road construction in this area.
4. Discussion – Rasprava
The model for planning the necessary forest opening with forest roads provides a consistent and comCroat. j. for. eng. 34(2013)2
Planning Forest Opening with Forest Roads (217–228)
J. Krč and J. Beguš
prehensive evaluation of the locations and necessary
lengths of new-built forest roads for strategic and tactical forest management planning at the regional as
well as the national level. Further in the text, certain
characteristics are presented together with recommendations for further model development and research
work in the field of forest opening with forest roads.
The basis for differentiation of target forest road
densities is the potential situation and forest site potentials, i.e. the projected potential of forest sites based
on plant associations – and not the current situation of
forest stands wood volumes. That is why some deviations can occur from the established guidelines, which
presume higher forest road network density in better
stands (evaluated according to the growing stock).
Thus, the model serves to adjust the forest road density to the site conditions – regardless of the current
level of potential forest site exploitation.
The problem of access, connecting roads leading
into the selected inaccessible areas is dealt with in a
unified and simplified way. It is an approximation that
will be definitively longer (minimum distance for the
access road is included) in the majority of cases, since
this method variant failed to include the coefficient of
road winding factor, whereas in larger excluded areas
the possibility was also foreseen of a greater number
of connecting (access) roads to the selected inaccessible forest area.
The adjusted criteria for the selection of inaccessible forest areas were used with the purpose to determine the priorities for locations with relatively long
distance from forest to roads in terms of skidding operations. Thus, the smallest area, entitled to further
investments in road network from forest funds, was
provided. The additional motive for criteria adjustment is due to the fact that the consequences of technological progress have also been taken into consideration. The development of logging and skidding
technology also generates larger quantities of timber
to be transported (on wheels) in the skidding operations. The share of ecologically and economically disadvantageous ground skidding is thus decreasing
compared to the transport on wheels, causing the increase of the acceptable distance of timber skidding.
In comparison with ground skidding, timber transport
is a more ecological, faster, and more efficient method
of timber skidding. It is expected that the longer distance between forest and road is also justified because
the model does not include public cart tracks and all
types of skid trails with road elements.
The gap between the current construction scope
and the need for new forest road construction on the
Table 3 Results of model calculation for increasing forest road density at the national level and its structure according to the regional units
Tablica 3. Rezultati izračuna modela za povećanje gustoće šumskih cesta na nacionalnoj razini i njihova struktura po upravama šuma
Site potentials, excluded surfaces, ha
Area, Regional Unit
Potencijal područja, isključene površine, ha
Područje, uprava šuma
Total (Slovenia)
Ukupno (Slovenija)
Tolmin
New Forest Roads, km
Nove šumske prometnice, km
New
Access
Total
Nove
Pristup
Ukupno
5
7
9
11
13
15
17
24197
36784
68126
76570
830
832
3046
3926.35
540.90
4467.25
4106
13997
9328
1794
0
2
37
494.95
57.90
552.85
Bled
1056
4216
1067
1575
0
0
1
131.96
26.70
158.66
Kranj
2639
3750
4690
2122
0
226
542
251.29
37.50
288.79
Ljubljana
5779
2296
16204
6428
3
241
470
591.60
84.00
675.60
Postojna
1576
2392
7057
6463
813
0
179
354.70
36.00
390.70
Kočevje
595
810
5563
11193
0
166
220
365.84
53.40
419.24
Novo Mesto
518
339
6374
24453
0
0
474
641.21
63.30
704.51
Brežice
385
336
3720
6540
0
0
15
216.38
34.20
250.58
Celje
Nazarje
1575
632
1129
876
2153
1218
223
1300
0
0
0
129
84
149
90.18
79.94
23.40
14.70
113.58
94.64
Slovenj Gradec
137
222
994
181
2
41
58
31.40
8.70
40.10
Maribor
825
2062
1607
2502
11
28
819
146.91
30.30
177.21
Murska Sobota
4376
786
1838
11797
0
0
0
350.13
18.30
368.43
Kras
0
3573
6314
1
0
0
0
179.89
52.50
232.39
Croat. j. for. eng. 34(2013)2
225
J. Krč and J. Beguš
Planning Forest Opening with Forest Roads (217–228)
Table 4 Presentation of the necessary and priority construction of forest roads and primary fire-prevention roads – regional forest management plans 2011–2020
Tablica 4. Prikaz otvaranja potrebnim i prioritetnim šumskim cestama i primarnim protupožarnim cestama – planovi uprava za gospodarenje
šumama 2011–2020.
Primary fire prevention roads
Forest roads – Šumske ceste
Regional Unit
Uprava šuma
Necessary for optimum
opening
Primarne protupožarne ceste
Priority lengths of opening in
the next decade – priority areas
Necessary for optimum
opening
Priority lengths of opening in
the next decade – priority areas
Potrebno za optimalnu
otvorenost
Prioritetne duljine otvaranja
u sljedećem desetljeću
– prioritetna područja
205
–
–
Potrebno za optimalnu
otvorenost
Prioritetne duljine otvaranja
u sljedećem desetljeću
– prioritetna područja
370
km
Tolmin
Bled
96
25
–
–
Kranj
240
80
–
–
Ljubljana
125
22
–
–
Postojna
149
21
120
50
Kočevje
376
58
–
–
Novo Mesto
365
50
–
–
Brežice
197
30
–
–
Celje
91
9
–
–
Nazarje
35
17
–
–
Slovenj Gradec
41
16
–
–
Maribor
101
45
–
–
Murska Sobota
117
40
–
–
Sežana
450
140
440
325
Total – Ukupno
Total forest and fire roads
2,753
758
560
375
Ukupno šumskih i
protupožarnih cesta
3,313
1,133
–
–
basis of the present model is wide and obvious (Robek
et al. 2007). Slovenia Forestry Service keeps the database on forest roads, i.e. Records of Forest Roads (RFR)
that is also legally defined in the Forest Act and the
Regulation on Forest Infrastructure. The user interface
has also been developed to enable the maintenance of
the database, designed as relation base (Beguš 2002).
The data on the new constructions or increasing of
forest road density are systematically acquired
through RFR. The scope of new constructions is relatively small, since 2011 witnessed only 2.5 km of new
forest roads (Poročilo o gozdovih za leto 2011, 2012).
Therefore, the recapitulation of the model calculation
has been prepared on the level of larger spatial units
(forest management units), which provides the evaluation of the necessary road construction scope to meet
the target density, defined in the model. According to
the existing forest road construction dynamics in Slo-
226
venia, it is reasonable to include in the model a procedure, which will enable experts to define priorities for
opening up inaccessible forests that can be realistically achieved during the validity of forest management plans.
Apart from the included influential factors (forest
sites and skidding distances), further model development should also include additional factors related to
the decision-making, planning and maintainance of
road network. Some of these factors are: forest road
construction and maintenance costs, forest operation
technology, timber skidding methods, current stand
structures, relief characteristics, skidding trail construction and maintenance costs as well as restrictions
and needs depending ecologic and social forest functions. Also the forest ownership or socio-economic and
size category of forest ownership definitely plays an
important part.
Croat. j. for. eng. 34(2013)2
Planning Forest Opening with Forest Roads (217–228)
5. Conclusions – Zaključci
The present model is a tool giving satisfactory results at the strategic (national) level and is also applicable at lower forest management planning levels. The
model provides the possibility to determine the need
for construction of new forest roads on specific areas
– not only the target density. In our opinion, the most
prominent added value of the model application (in
view of the existing planning process) lies in its spatial
determination of the needs for the additional forest
opening (by forest roads).
We also assume that the model can be used in different circumstances and also at the international
level. Its practical applicability was proven on the national level elaborating Regional Forest Management
Plans in Slovenia (Gozdnogospodarski in lovsko upravljalski načrti območij za obdobje 2011–2020, 2012).
The contemporary perspective offers the following
development possibilities of the present model:
Þ Inclusion of relief characteristics (e.g. recognition of ridge points),
Þ Exclusion of protected sections (differentiating
the length of forest roads according to different
levels of protection),
Þ Differential model evaluation of road construction on different mostly rock surfaces,
Þ Inclusion of timber skidding direction (shorter
under; longer above the road with exception of
cable skidding),
Þ Differentiation of the smallest size of low access
areas according to site potentials,
Þ Estimation of forest functions according to forest
road density,
Þ Determination of priorities according to the actual accessibility (public cart tracks),
Þ Preparation of the module for forest road density optimization (e.g. logging and skidding
costs according to construction and maintenance costs of forest roads).
From the point of view of the model development,
there are still many possibilities for improvement of the
presented tool that would also facilitate the preparation
of regional forest management plans. The development
result will be a more complex model that would show
a more reliable and detailed first version of low access
areas and calculation of the necessary forest road densities and length of new road construction.
J. Krč and J. Beguš
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družbeno planiranje in Inštituta za gozdno in lesno gospodarstvo pri Biotehniški fakulteti, Ljubljana, 145 p.
Košir, B., Krč, J., 2000: Where to Place and Built Forest Roads
– Experience From the Model. Journal of Forest Engineering
11(1): 7–19.
Košir, B., Košir, Ž., Krč, J., 2006: Natural composition of tree
species as a basis for model development of stumpage price.
Croatian Journal for Forest Engineering 27(2): 71–80.
Krč, J., 1999: Modelni izračun vpliva ceste na povečanje vrednosti donosa gozda, Zbornik gozdarstva in lesarstva 59, Ljubljana, 121–139.
Lugo, A. E., Gucinski, H., 2000: Function, effects, and management of forest roads. Forest Ecology and Management 133(3):
249–262.
Matthews, D., 1942: Cost control in the logging industry.
McGraw-Hill Book Company, New York, 374 p.
Pentek, T., Nevečerel, H., Pičman, D., Poršinsky, T., 2007: Forest road network in the Republic of Croatia – Status and perspectives. Croatian Journal for Forest Engineering 28(1): 93–
106.
Pentek, T., Pičman, D., Nevečerel, H., Lepoglavec, K., Papa, I.,
Potočnik, I., 2011: Primary forest opening of different relief
areas in the Republic of Croatia. Croatian Journal for Forest
Engineering 32(1): 401–416.
6. References – Literatura
Poročilo o gozdovih za leto 2011, Zavod za gozdove Slovenije (Slovenia Forest Service) (http://www.zgs.gov.si/slo/zavod/
informacije-javnega-znacaja/letna-porocila/index.html) (Accessed: 1 August 2012).
Anderson, A. E., Nelson, J., 2004: Projecting vector-based road
networks with a shortest path algorithm. Canadian Journal of
Forest Research 34(7): 1444–1457.
Robek, R., Klun, J., 2007: Recent developments in forest traffic
way construction in Slovenia. Croatian Journal for Forest Engineering 28(1): 83–89.
Croat. j. for. eng. 34(2013)2
227
J. Krč and J. Beguš
Planning Forest Opening with Forest Roads (217–228)
Program odpiranja gozdov z gozdnimi prometnicami, 1990,
Gozdno gospodarstvo Kočevje, Kočevje 1990
Pravilnik o gozdnih prometnicah, 2009, Uradni list RS št. 4,
Ljubljana 2009.
SURS: Gozd in gozdarstvo (http://www.gozd-les.com/vsebina/odkupne-cene-hlodovine) (Accessed 1. January 2013).
Zakon o gozdovih, 1993, Uradni list RS no. 30.
Sažetak
Planiranje potrebne šumske otvorenosti šumskim prometnicama
U radu je predstavljen model koji određuje neotvorene šumske površine temeljeći se na analizama postojeće mreže
javnih i šumskih cesta provedenima pomoću GIS-a te analizama potencijalnih bonitetnih staništa u neotvorenim šumama.
Unaprjeđenje gustoće cesta ostvaruje se preko dva oblika nadgradnje cestovne mreže: (1) izrada spojnih cesta do
neotvorenih šumskih područja i (2) izgradnja novih šumskih cesta različite gustoće na izdvojenim područjima neotvorenih
šuma. Dakle, model daje minimalnu veličinu neotvorene površine, koja se nalazi najmanje 300 metara od postojeće ceste.
Izdvojena se područja neotvorenih šuma najprije analiziraju iz aspekta njihove veličine – površina od minimalno 30 ha
uzeta je kao primjerena za izgradnju pristupnih cesta koje povezuju postojeću cestovnu mrežu s neotvorenom šumskom
površinom. Povećanje gustoće cesta, gradnjom novih šumskih cesta, ovisi o šumskom ekosustavu pri čemu uzimamo u
obzir njegov RK kao pokazatelj bonitetnog potencijala neotvorene šumske površine. S obzirom na bonitet staništa definirane su različite gustoće cestovnih mreža na izdvojenim neotvorenim šumskim područjima.
Model je testiran na primjeru Uprave šuma Kočevje gdje je već bio izrađen »Program otvaranja šuma šumskim
prometnicama«, koji je pri testiranju rezultata analize poslužio kao referencija. Podrobnije je model analiziran na području
gospodarske jedinice Kočevska reka gdje smo rezultate modela predstavili stručnom osoblju Zavoda za šume Slovenija,
Uprava šuma Kočevje, i napravili procjenu usklađenosti između rezultata modela i ocjene stručnjaka, koja je prethodno
dobivena terenskom procjenom položaja šumskih cesta u analiziranoj gospodarskoj jedinici Kočevska reka.
Sukladno važećim podacima šumskogospodarske osnove (šumskogospodarske i lovnogospodarske osnove za razdoblje
od 2011. do 2020. godine) Slovenija ima 12 023 km šumskih cesta i 489 km protupožarnih cesta. Gustoća šumskih i
protupožarnih cesta iznosi 10,6 m/ha. Šume su dodatno otvorene javnim cestama, koje u pojedinim odsjecima služe za
šumarske radove, pa je tako šumska površina u Sloveniji otvorena s ukupno 29 244 km cesta, što znači da je gustoća
cesta 24,8 m/ha.
Predstavljena analiza pokazala je da je u Sloveniji, prema kriterijima modela, još 210 385 ha neotvorenih šumskih
površina. Stručnjaci u upravama šuma Zavoda za šume u daljnjem su postupku odabrali prioritetne površine na kojima
je u idućih 10 godina gospodarenja potrebno izgraditi 758 km novih šumskih cesta.
Ključne riječi: šumske prometnice, gustoća cesta, šumske operacije, model, plan gospodarenja šumama
Authors’ address – Adresa autorâ:
Received (Primljeno): August 16, 2012
Accepted (Prihvaćeno): December 30, 2012
228
Assoc. Prof. Janez Krč, PhD.*
e-mail: [email protected]
Biotechnical Faculty
Department of Forestry and Renewable Forest
Resources
Večna pot 83
1000 Ljubljana
Jurij Beguš, MSc.
e-mail: [email protected]
Slovenia Forest Service
Večna pot 2
1000 Ljubljana
SLOVENIA
* Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Original scientific paper – Izvorni znanstveni rad
Fuel Consumption in Timber Haulage
Radomír Klvač, Josef Kolařík, Marcela Volná, Karel Drápela
Abstract – Nacrtak
The paper presents an assessment of road timber transport by trucks, which included 132
truck-and-trailer units – three types of trucks (Tatra, Mercedes Benz and Iveco) with a selection of trailers in the Czech Republic. The main aim of this work was to establish the effect of
hauling distance in the individual types of timber-transport units on the fuel consumption
per 100 km and on the specific fuel consumption per one transported cubic metre of timber.
Any decrease of fuel consumption per unit of production can enhance environmental profile
of secondary transport. Freight transport recorded conspicuous changes in the last ten years,
and the analysis presented in this work provides important information useful in the planning
and organization of road timber transport. During the study period, obsolete and inadequate
truck-and-trailer units were continuously replaced with new units, which resulted in a considerable reduction in fuel consumption per unit of production (0.5 L/m3 ub).
Keywords: haulage road, timber transport, truck, truck-and-trailer unit, fuel consumption
1. Introduction – Uvod
Timber transport from the roadside landing to the
customer represents a very demanding phase in the
chain of timber supply in terms of energy and cost. It
is characterized by several specific factors that influence its implementation and differentiate it from the
goods transport by trucks. In general, we can say that
it is a one-way haulage, where it is very difficult or
even impossible to utilize the timber-transport unit in
its return run. The machines are specifically designed
and can be used only to a limited extent for the haulage of other goods. Also, they have to drive a larger
part of the hauling distance on forest roads. Holzleitner (2009) and Holzleitner et al. (2011) studied the operation of timber-transport units by using the GPS/GIS
system and concluded that the share of their travel on
forest roads was 14%. The machines often have to
drive deep into the forests and have to be adapted accordingly. They have to work in difficult field conditions and therefore they are very frequently affected
by them as well as by extreme seasonal weather. This
is why the trucks are often equipped with the multiple-wheel drive and heavy-duty engines. These specific technological requirements considerably increase
fuel consumption of timber-transport units.
Svenson (2011) mentioned a range of technical factors directly affecting the fuel consumption of timberCroat. j. for. eng. 34(2013)2
transport units and classified them into the following
groups: vehicle characteristics, trailer characteristics,
road geometry, road surface, goal speed, gear change,
driving behavior, weather and road surface conditions.
The above factors of technical and technological
character have a considerable influence on the average
fuel consumption of timber truck-and-trailer units,
which may be double as compared with the common
road goods transport by trucks (Devlin 2010).
The number of information systems specialized in
goods or bus transportation is high in the Czech Republic but the number of information systems specialized in timber transport is low. Hauling timber from
the roadside landing features problems such as heterogeneity of the transported material, difficult utilization of vehicles at their return run, seasonal character
of operations, climatic effects – all these resulting in a
high rate of »empty« drives. Data processing, transport optimization and necessity of flexible response to
unexpected situations put high requirements both on
the information system and on timber haulage managers. This is why an information system was designed,
which tries to respond to the absence of information
systems in the field of timber haulage (Klvač 2006).
From the economic point of view, the share of timber haulage in total timber supply chain costs may
reach more than 30% (Favreau 2006). He mentions that
229
R. Klvač et al.
transport is the biggest cost item in round wood costs
in Canada. In Sweden, Svenson (2011) says that 35%
of total transportation costs are related to the fuel consumption of timber trucks. Economic data provided
by the contractor of timber-transport units, which
were the subject of our study, demonstrated that diesel
fuels accounted for the highest share in total costs
(30%), followed by depreciation and leasing (20%) and
repairs and maintenance (16%). Wages (15%), overhead costs (13%) and other costs (5%) followed. The
objective of implementation of the information system
was to conduct a basic analysis of individual types of
timber-transport units and based on the acquired data
to find primary relations affecting transport efficiency
and thus to find ways how to reduce the cost of timber
haulage.
Any decrease of fuel consumption per unit of production can enhance environmental and economy
profile of secondary transport. As the fuel cost makes
the largest part of total timber haulage costs, the aim
of this work is to analyze the fuel consumption in the
individual types of truck-and-trailer units used in timber transport. Any replacement of obsolete and inadequate truck-and-trailer units by new more efficient
units can result in a considerable reduction of fuel consumption per unit of production.
2. Material and methods – Materijal
i metode
A »tailor made« information system was designed
in 2003, which can receive orders placed by customers,
support the decision-making process of dispatchers by
using suitable truck-and-trailer units (TTU), make records of hauling performance, monitor production in
progress and summarize data in the form of databases.
In 2004, the system was characterized in the form of
diagrams so that designers would be capable of meeting customer requirements (Klvač 2006). This information system was designed for larger companies with a
greater number of vehicles dislocated on remote workplaces. All workplaces had an access to the system via
client and worked with data on multiple levels related
to the position in company or business interrelationship. Each position/client type had centrally set rights
and responsibilities in the system. A timber transport
company implemented the system at the beginning of
2005 and data on each individual transportation case
started to be recorded from the end of the same year.
The data was summarized for each TTU in monthly
intervals for purposes of analytical assessment by the
company management. The monthly indicators of
TTUs were used in this study.
230
Fuel Consumption in Timber Haulage (229–240)
The structure of the assessed data related to this
study was as follows:
Þ Truck-and-trailer unit, inventory number provided for non-commutability of data,
Þ TTU operational centre,
Þ Trailer, inventory number,
Þ Total travel distance, km,
Þ Travel unloaded, km,
Þ Travel loaded, km,
Þ Backhauling, % of kilometers driven loaded,
Þ Volume of transported timber, m3 ub; softwood
and hardwood,
Þ Number of loads per month and per day,
Þ Average size of load, m3 ub,
Þ Average hauling distance – one way distance, km,
Þ Fuel consumption in liters per month.
Parameters that were calculated based on the above
data were as follows:
Þ Average fuel consumption per unit of production, llm3 ub
Þ Average fuel consumption per 100 km, ll100 km
All data were checked at first and records containing gross errors caused by human factor at recording
were eliminated. Then the data were imported and
organized within the spreadsheet software (Microsoft
Excel) and subsequently summarized for individual
types of TTUs. In the period 2005 – 2009, considerable
changes occurred in the fleet of timber transport units
with obsolete TTUs being put out of operation and
replaced by new TTUs where necessary. Old and technically unfit Liaz TTUs were taken out of service first.
As the amount of data on these TTUs was not representative, the Liaz type of TTU was not statistically
evaluated in this study. Types of truck-and-trailer
units assessed in this study were Iveco (represented
by models ASTRA, MP260 and STRALIS), Tatra (represented by Tatra 815 only), Mercedes Benz (models
3344, 3341, 2644 and 3348). The data were aggregated
and analyzed according to truck manufacturers.
The initial analysis was made with the use of pivoting (contingency) tables and graphs. GraphPad Prism
5 (Motulsky 2007) was used for non-linear regressions.
The software enables a very flexible choice of the regression model, it has very good graphical capabilities
and provides the possibility to compute and draw confidence intervals of the model. Prism 5 can eliminate
outliers with the ROUT method (Motulsky and Brown
2006). This method is based on a new robust non-linear regression combined with outlier rejection. It is an
adaptive method that gradually becomes more robust
as the method proceeds. Press et al. (1988) based their
Croat. j. for. eng. 34(2013)2
Fuel Consumption in Timber Haulage (229–240)
R. Klvač et al.
2 548. The total number of TTUs assessed in the period
2005 – 2009 was 134 and the units were operated at
different places in the Czech Republic. In the period
2003 – 2004, we monitored only 21 trucks; this number
increased in 2005 to 90. In the following years, the fleet
was gradually renewed and some old vehicles were
put out of operation. This is why the number of trucks
monitored in 2006, 2007 and 2008 was 87, 80 and 71,
respectively. In 2009, the process of renewal was completed and the final number of trucks was 51 of which
45 were Mercedes Benz.
In the period under study (Table 1), more than 3.4
million cubic meters of timber were hauled from the
roadside landing to the conversion depot, directly to
customers or to the siding railway. They were recorded and assessed - softwood accounted for 92% and
hardwood for 8% of the total volume. Total diesel consumption of monitored TTUs was 6.8 million liters.
The fuel consumption is not broken down to the
amount used directly in timber haulage and the
amount used indirectly, i.e. driving to the working
place or driving to the workshop for repair. The share
of »empty kilometers« in the total number of driven
kilometers was 47%. Average backhauling of TTUs
(loaded vehicles) was 53%. The presented values represent and summarize a total of 136 292 cases of timber
transport.
The average hauling distance was changing in the
course of years depending on activities of the company operating the trucks. From 2005, the number of
timber yards was decreasing and the amount of timber handled at the roadside landing was increasing as
well as the timber haulage from the landing directly
to the customer. The average hauling distance was
robust fitting method on the assumption that variation
around the curve follows a Lorenzian distribution
rather than a Gaussian distribution. The Marquardt
non-linear regression algorithm was adapted to accommodate the assumption of a Lorenzian (rather
than Gaussian) distribution of residuals. After fitting
a curve using robust non-linear regression, a threshold
is needed for deciding when a point is far enough from
the curve to be declared an outlier. All methodology
is described in detail in Motulsky and Brown (2006).
The authors state that their method identifies outliers
from non-linear curve fits with reasonable power and
few false positives (less than 1%).
In all cases, the logarithmic function used for the
regression model was in the following form:
y = a  ln(x) + b
(1)
Where:
x
explaining (independent) variable,
y
explained (dependent) variable,
a, b coefficients.
The respective statistical assessments include a, b
coefficients established by the regression analysis, 95%
confidence interval (shaded in the graphs), R2 – determination coefficient, number of analyzed points and
number of outliers.
The respective dependencies are presented in summary diagrams in Microsoft Excel, in which only regression curves were plotted.
3. Results – Rezultati
The total number of assessed records (i.e. monthly
performances of various truck-and-trailer units) was
Table 1 Mean values for all monitored TTU types
Tablica 1. Značajke promatranih kamionskih skupova
Softwood – Crnogorica
3 161 533
Hardwood – Bjelogorica
256 638
Empty kilometers – Vožnja praznim kamionom, km
5 172 109
Volume of transported timber, m3 – Obujam transportiranoga drva, m3
3 418 171
Total distance, km – Ukupno prijeđena udaljenost, km
11 032 534
Fuel consumption, l – Potrošnja goriva, l
6 811 604
–
–
136 292
–
–
Average fuel consumption, l/m3 – Prosječna potrošnja goriva, l/m3
2.19
–
–
Average consumption, l/100 km – Prosječna potrošnja goriva, l/100 km
67.4
–
–
Average hauling distance*, km – Prosječna udaljenost turnusa*, km
45.05
–
–
Number of cycles – Broj turnusa
Kilometers driven loaded – Vožnja punim kamionom, km 5 860 425
* One way distance – * U jednom smjeru
Croat. j. for. eng. 34(2013)2
231
R. Klvač et al.
Fuel Consumption in Timber Haulage (229–240)
Table 2 Trends of important indicators in all TTU types in the studied period
Tablica 2. Trendovi i važne karakteristike promatranih kamionskih skupova u vremenu istraživanja
Year – Godina
2005
2006
Average fuel consumption, l/m – Prosječna potrošnja goriva, l/m
2.32
2.06
1.87
2.67
3.08
Average fuel consumption, l/100 km – Prosječna potrošnja goriva, l/100 km
69.51
68.4
70.94
61.22
61.36
Average hauling distance*, km – Prosječna udaljenost turnusa*, km
39.31
37.6
36.87
65.76
74.21
Average size of load, m3 – Prosječni obujam tovara, m3
20.59
23.45
25.96
26.13
27.57
53
48
48
52
49
3
3
Average backhauling**, % – Prosječna transportna udaljenost punoga kamiona**, %
2007
2008
2009
* One way distance – * U jednom smjeru
** % of kilometers driven loaded – ** Udio s obzirom na udaljenost turnusa
Table 3 Outputs and indicators of individual TTU types
Tablica 3. Tehničke karakteristike promatranih kamionskih skupova
TTU type – Model kamionskoga skupa
IVECO
TATRA
MB*
Average fuel consumption, l/m – Prosječna potrošnja goriva, l/m
2.26
1.93
2.71
Average fuel consumption, l/100 km – Prosječna potrošnja goriva, l/100 km
66.74
72.25
58.31
Average hauling distance**, km – Prosječna udaljenost turnusa **, km
48.97
28.98
76.11
Average loads per day – Prosječan broj turnusa po danu
2.96
3.25
2.98
25.21
22.84
28.38
51
46
55
3
3
3
3
Average size of load, m – Prosječan obujam tovara, m
Average backhauling*** – Prosječna transportna udaljenost punoga kamiona ***
Total, km – Ukupno, km
903 845
4 014 736
6 055 543
Volume of hauled timber, m3 – Obujam transportiranoga drva, m3
285 683
1 701 892
1 408 446
* MB: Mercedes-Benz
** One way distance – **U jednom smjeru
*** % of kilometers driven loaded – *** Udio s obzirom na udaljenost turnusa
increasing towards the end of the study period – see
Table 2. The lowest distance was achieved in 2007 due
to the Kyrill gale disaster when a substantial part of
all TTUs were concentrated to work in affected areas,
where the trucks mostly transported timber over
short hauling distances, which considerably affected
the annual average hauling distance. The average size
of load was markedly increasing during the years
thanks to changes in the fleet because the newly used
TTUs of Mercedes Benz type featured a considerably
higher capacity than the other assessed TTU types
(Table 3).
Table 2 shows that the increasing average hauling
distance resulted in the increasing average fuel consumption per unit of production and that the fleet renewal brought a gradual decrease in the fuel consumption per 100 km. In 2008 and 2009, when the
Mercedes Benz type of TTU started to dominate the
fleet, the average fuel consumption per 100 km
dropped dramatically by 9%. A detailed survey of indicators and outputs by individual types of timber
232
transport units is presented in Table 3, where the
prominent indicator is the load size.
Backhauling considerably affects transport efficiency; average backhauling increased depending on
average hauling distance, which was favorably affected by the easier coordination of loads by dispatchers. Over short hauling distances, timber transport
from the forest is operated more or less in one-way
direction; backhauling is often unrealistic and the
trucks are additionally burdened by driving to their
workplace and to repair or maintenance workshops.
This is why its efficiency is below 50%. With the increasing of the hauling distance, the possibility of finding suitable backhauling increases and the effect of
driving to the workplace or repair is minimized (Fig.
1). Extremely low values mostly resulted from loading
into wagons (when the vehicle was used for loading
wagons) and its number of empty kilometers increased
due to frequent drives within the terminal (timber
yard). On the other hand, extremely high values resulted from a nearly ideal relation when empty kiloCroat. j. for. eng. 34(2013)2
Fuel Consumption in Timber Haulage (229–240)
R. Klvač et al.
Fig. 1 Dependence of backhauling on hauling distance (all TTU types)
Slika 1. Udio vožnje punim kamionom po turnusu (svi promatrani
modeli kamionskih skupova)
Fig. 3 Relation between fuel consumption per 100 km and hauling
distance for the Tatra type of TTU
Slika 3. Odnos između potrošnje goriva na 100 km i duljine turnusa
za kamionski skup Tatra
Fig. 2 Relation between fuel consumption per 100 km and hauling
distance for the Iveco type of TTU
Slika 2. Odnos između potrošnje goriva na 100 km i duljine turnusa
za kamionski skup Iveco
Fig. 4 Relation between fuel consumption per 100 km and hauling
distance for the Mercedes-Benz type of TTU
Slika 4. Odnos između potrošnje goriva na 100 km i duljine turnusa
za kamionski skup Mercedes-Benz
meters represented only driving on forest roads and
very short travels for another load. Details of regression analyzes were as follows: Best-fit values a = 8.352,
b = 19.19; Std. Error a = 0.1920, b = 0.6994; 95% Confidence Intervals a = 7.976 to 8.728, b = 17.82 to 20.56; R
square 0.4500; Outliers (excluded, Q = 1.0 %) 3.
Croat. j. for. eng. 34(2013)2
233
R. Klvač et al.
Fuel Consumption in Timber Haulage (229–240)
Table 4 Results of regression analyses of the relation of fuel consumption per 100 km and hauling distance
Tablica 4. Rezultati regresijske analize potrošnje goriva na 100 km i duljine turnusa
TTU type
Model kamionskoga skupa
* Regression coefficients of equation
Border coefficients, 95%
* Regresijski koeficijenti jednadžbe
Granični koeficijenti, 95 %
y = a × ln(x) + b
Confidence Intervals – Faktor pouzdanosti
R2
Range of × value
Raspon × vrijednosti
a
b
a
b
Iveco
–15.47
123.4
–17.14 ; –13.81
117.2; 129.6
0.6102
10 – 132
Tatra
–13.96
116.7
–15.30 ; –12.61
112.3 ; 121.0
0.2390
10 – 131
MB
–10.42
101.7
–11.25 ; –9.576
98.12 ; 105.3
0.4397
12 – 178
* x – hauling distance – Duljina turnusa
y – fuel consumption per 100 km – Potrošnja goriva na 100 km
Table 5 Results of regression analyses of the relation of fuel consumption per unit of production (m3) and hauling distance
Tablica 5. Rezultati regresijske analize potrošnje goriva po jedinici proizvodnje (m3) i duljine turnusa
TTU type
Model kamionskoga skupa
* Regression coefficients of equation
Border coefficients, 95%
* Regresijski koeficijenti jednadžbe
Granični koeficijenti, 95 %
y = a × ln(x) + b
Confidence Intervals – Faktor pouzdanosti
R2
Range of × value
Raspon × vrijednosti
a
b
a
b
Iveco
0.9842
–1.399
0.8887; 1.080
–1.756 ; –1.043
0.6601
10 – 132
Tatra
1.335
–2.444
1.280; 1.391
–2.624 ; –2.265
0.6311
10 – 131
MB
1.531
–3.749
1.460; 1.601
–4.048 ; –3.450
0.7025
12 – 178
* x – hauling distance – Duljina turnusa
y – fuel consumption per unit of production, m3 – Potrošnja goriva po jedinici proizvodnje, m3
Fig. 5 Relation between fuel consumption per 100 km and hauling distance for all types of TTUs
Slika 5. Odnos između potrošnje goriva na 100 km i duljine turnusa za sve promatrane kamionske skupove
234
Croat. j. for. eng. 34(2013)2
Fuel Consumption in Timber Haulage (229–240)
R. Klvač et al.
Fig. 6 Relation between fuel consumption per unit of production
(m3) and hauling distance for the Iveco type of TTU
Slika 6. Odnos između potrošnje goriva po jedinici proizvodnje (m3)
i duljine turnusa za kamionski skup Iveco
Fig. 7 Relation between fuel consumption per unit of production
(m3) and hauling distance for the Tatra type of TTU
Slika 7. Odnos između potrošnje goriva po jedinici proizvodnje (m3)
i duljine turnusa za kamionski skup Tatra
3.1 Average fuel consumption in relation to
driven distance including the effect of uploading and unloading and proportion of
time spent on forest roads – Prosječna
potrošnja goriva po prijeđenom kilometru
uključujući utovar, istovar te udio vožnje
šumskom cestom
roads due to harsh terrain conditions, limited speed
(lower gear) and worse road quality that decreases
with the increasing hauling distance. None of these
Average fuel consumption per 100 km is markedly
higher in the older TTU types such as Iveco and Tatra
in particular (see Table 3). It is also synergy affected by
uploading and unloading times as well as by the hauling distance. If the hauling distance is shorter, the average consumption per 100 km is markedly higher
than over longer distances due to the effect of uploading and unloading. During the uploading and unloading, the engine of the truck (energy source) drives the
hydraulic crane and the consumption of fuel thus increases without a change in driven kilometers. According to company workers (personal communication), the loading time was different when loading
stems or timber shortened to transportation length
(max. 35 min.) and when loading stacked assortments
up to 8 m (max. 50 min.).
The second effect is the proportion of time spent
on forest roads. The shorter journey meant a higher
proportion of travel time spent on forest roads. The
trucks have a higher fuel consumption on forest
Croat. j. for. eng. 34(2013)2
Fig. 8 Relation between fuel consumption per unit of production
(m3) and hauling distance for the Mercedes-Benz type of TTU
Slika 8. Odnos između potrošnje goriva po jedinici proizvodnje (m3)
i duljine turnusa za kamionski skup Mercedes-Benz
235
R. Klvač et al.
Fuel Consumption in Timber Haulage (229–240)
Fig. 9 Relation between fuel consumption per unit of production (m3) and hauling distance for all types of TTUs
Slika 9. Odnos između potrošnje goriva po jedinici proizvodnje (m3) i duljine turnusa za sve promatrane kamionske skupove
two aspects can be eliminated to determine the influence of each separately. In other words, as the two
aspects are inseparable part of timber haulage, the
assessment was made including the impact of them
both.
Both effects also correspond to the average number
of daily delivered loads with respect to hauling distance i.e.: 4 deliveries at 10.7 km average hauling distance, 3 at 38 km and 2 at 200 km, respectively.
Regression equations of fuel consumption for the
respective TTUs are presented in Figs. 2 – 4 including
discerned outliers and including confidence interval
of 95% reliability. The regression equations are plotted
in a comprehensive graph (Fig. 5) for the comparison
of individual TTU types. The regression curves are
drawn in the interval of hauling distances in which
TTU types were operating. The results of regression
analyses for individual types of timber transport units
are presented in Table 4.
3.2 Average fuel consumption per unit of
production (hauled cubic meter) – Prosječna
potrošnja goriva po jedinici proizvodnje
(prevezeni kubni metar)
In this case, too, the respective types of truck-andtrailer units were assessed separately (Figs. 6 – 8). The
average fuel consumption per unit of production (m3)
was conspicuously different in the individual TTU
236
types, the reason for the difference being mainly the
effect of hauling distance and the size of TTU load.
The greater the hauling distance, the higher was the
fuel consumption per unit of production; at the same
time, the greater the vehicle capacity, the lower was
the average fuel consumption. The two factors act in
synergy and there are other impacts to be expected,
too, such as seasonal character of the work, effect of
the operator, etc. Results of regression analyses for
individual types of timber transport units are presented in Table 5.
The comprehensive diagram in Fig. 9 shows regression equations for the respective types of timber
transport units. The regression curves are plotted only
within the hauling distance interval in which the values used in the regression analysis occurred. Tatra
type trucks showed unambiguously the highest fuel
consumption per unit of production.
4. Discussion and conclusion – Rasprava
sa zaključcima
The above graphs (Figs. 2 – 5) show the dependence of fuel consumption per 100 km on average
hauling distance of the individual TTU types. The
average hauling distance ranged from 10 – 180 km.
Older Iveco and Tatra trucks in particular had a considerably higher fuel consumption per 100 km, which
Croat. j. for. eng. 34(2013)2
Fuel Consumption in Timber Haulage (229–240)
supposedly resulted from the fact that their hauling
distances were relatively short (38 km) and loading
and unloading was more frequent. Thus, due to more
frequent loading and unloading, the fuel consumption increased although it did not show in the travel
distance. The average fuel consumption per 100 km
of Mercedes-Benz TTUs was markedly lower, because the hauling distances were apparently higher.
Another aspect affecting the fuel consumption together with this factor was the proportion of driving
on forest roads, which decreases with the increasing
hauling distance i.e. loading is limited within one
working day. Fig. 5 shows that the fuel consumption
per 100 km decreases with the increasing hauling
distance. The third very important factor is the engine category. Mercedes Benz Trucks were Euro 3 and
Euro 5 class, which should guarantee lower fuel consumption. However, this is not as visible as expected
and further detailed analysis of Mercedes Benz truck
is necessary. Other impacts, such as the seasonal
character of work, locality (road quality, relations),
human factor in loading/unloading, equipment operators, drivers, etc. could not be identified but their
influence can be anticipated at least to some extent.
The authors consider that the volume of data is representative for estimating the mean values of fuel
consumption.
Svenson (2011) informs that in Sweden the average fuel consumption per 100 km is 58 liters but does
not mention the hauling distance, which could be
corresponding to 65 km according to the results of
our study. Although the value is highly speculative,
it might be realistic for such a vast country as Sweden
even if it is by 40% higher than the average hauling
distance of 45 km established in this study. It is however fully comparable with values recorded in 2008
and 2009, when the timber transport company that
provided the data focused on longer hauling distances. Similar conditions as in the Czech Republic can
be expected in Austria, where Holzleitner (2009)
claims the average hauling distance of 51 km, which
is in line with the values detected in this study.
Fuel consumption can be reduced in different
ways. Considerate driving may considerably reduce
the fuel consumption. By a program that can monitor
the driving regime, the Tom Tom Corporation can
identify inappropriate driving manners and demonstrate a more economical regime (personal communication Tom Tom). Lofroth and Lindholm (2005)
mention further possibilities of fuel economy, e.g.
that haulage trucks can reduce their fuel consumption by 5 – 10% simply by fitting a wind deflector and
by removing all unnecessary items such as signCroat. j. for. eng. 34(2013)2
R. Klvač et al.
boards, extra air horns, extra lamps and other unnecessary accessories.
Average fuel consumption per unit of production
(m3) is first of all affected by the hauling distance and
by the load size – the two factors acting in synergy.
The higher is the vehicle capacity, the lower is the
average consumption per unit of production, and the
greater is the hauling distance, the higher is the fuel
consumption per unit of production. Further to the
above, the Tatra TTUs would have the lowest fuel
consumption per unit of production if the average
values of TTU types from global assessment were
compared without a more detailed analysis (see Table 3). Nevertheless, this view of the problem would
be rather naïve, because these are the average values
for the entire 5-year monitoring period and they are
related to anaverage hauling distance calculated for
the whole period of the study. Therefore, it is necessary to compare the average fuel consumption based
on data presented in Fig. 9. The Tatra truck-and-trailer unit has the highest average fuel consumption per
unit of production in relation to the hauling distance,
the likely reason being the average size of load but
also the construction of the machine, which is designed for difficult, inaccessible terrains and is fitted
with older engine types.
By contrast, the Mercedes-Benz TTUs exhibited
the highest average fuel consumption per unit of production (approx. 3 liters per cubic meter) in the global assessment (Table 3), which resulted from the long
hauling distance in the monitored period. However,
it can be concluded from Fig. 9 that the MercedesBenz TTUs are more economical in terms of fuel consumption per unit of production with the load size
playing once again the most important role. The load
size in the Mercedes-Benz TTUs was approximately
5 m3 greater than in the Tatra TTUs. Further to the
above, it can be concluded that the timber transport
units cannot be evaluated only according to summarized data (Table 3) but that more detailed analyses,
such as in Figs. 6 – 8, are absolutely necessary.
The issue of relations between the individual indicators is very complex and it would be certainly
useful to conduct a detailed survey within the respective types of trucks e.g. in relation to hauling distance, loading capacity, trailer type or region in which
the TTU operated. All activities connected with the
detailed characterization of these relations are focused on fuel economy. This direction is also obvious
from the activities of FP Innovation, where the socalled StarTrack was designed aimed at reducing
machine weight and providing maximum loading
capacity. The specifications placed on the research
237
R. Klvač et al.
truck considered the local operating conditions and
included the following requirements: heavy-duty
aluminum rims, smaller fuel tank (but the right size
for one shift), aluminum cab protector, central tire
inflation (CTI), on-board weighing, in-cab auxiliary
heater, on-board computer, single tractor frame rail,
lightweight multi product semi-trailer and road
maintenance management system. All these innovations resulted in the following improvements:
Þ The Star Truck had a higher payload by 9.8%
and consumed only 1% more fuel,
Þ The Star Truck transported 8.6% more products
per liter of fuel,
Þ The Star Truck fuel cost per ton was by 8% lower than in the control truck,
Þ Tire wear was by 40% lower in the Star Truck
due to CTI. (Anon. 2012)
The reduced fuel consumption per unit of production aims at mitigating the environmental pollution
caused by emissions of greenhouse gases (GHGs).
Fuel consumption by trucks is one of the largest contributors of these emissions. Komor (1995) informs
that in the U.S.A., trucks account for over 80% of the
freight energy use and 19% of US oil consumption.
Plans to improve the technical efficiency through new
technologies, careful driving and optimal driving
conditions can increase the efficiency by 50 to 70%.
Bandivadekar et al. (2008) believe that the increase in
the consumption of oil for transport in the U.S.A. is a
challenging environmental problem that needs to be
addressed in terms of reducing fuel consumption
based on drivers’ behavior rather than concentrating
on the improvement of vehicle performance through
new propulsion technologies and new fuels in the
shorter term. Other methods leading to reduced fuel
consumption are decision support systems and use of
telemetry in combination with GPS/GIS. An example
may be the study published by Devlin et al. (2007).
The amount of timber extracted in the Czech Republic per year is about 15 million m3. Adequate fleet
changes, improved optimization and technical modifications may be used to reduce fuel consumption per
unit of production by 0.5 – 1.0 liter. This would bring
a reduction of fuel consumption in timber haulage by
0.75 – 1.5 million liters of oil in the Czech Republic.
Devlin (2010) claims that each liter of oil burnt in the
truck-and-trailer unit is responsible for 2.67 kg of carbon dioxide emitted into the atmosphere. Based on
the emission factors established by Lewis (1997), we
can state that each liter of oil is responsible for additional 0.25 kg CO2 emitted during the production and
distribution. Thus, saving 1.5 million liters of oil
equivalent would result in a reduction of CO2 emis-
238
Fuel Consumption in Timber Haulage (229–240)
sions into the atmosphere of 4.4 million tons. The unambiguous conclusion is that optimization and use of
adequate TTU types in timber transport from the
roadside landing can significantly contribute to the
mitigation of the negative impact of forest machinery
on the environment.
Acknowledgement
The paper was prepared within the framework of
research projects of the Ministry of Education of the
Czech Republic nos. MSM 6215648902 and OC10041,
Mendel University internal project IGA and of the
COST Action FP0902. The authors also wish to express
their thanks to contractors for providing the possibility of data collection.
5. References – Literatura
Anon., 2012: FP Inovation. Timber Transport Research –
FERIC’s Star Truck Project. Logging-on newsletter. Available
on http://www.loggingon.net/timber-transport-researchferics-star-truck-project_news_op_view_id_43
Bandivadekar, A., Cheah, L., Evans, C., Groode, T., Heywood, J., Kasseris, E., Kromer, M., Weiss, M., 2008: Reducing
the fuel use and greenhouse gas emissions of the US vehicle
fleet. Energy Policy 36(7): 2754–2760.
Devlin, G., 2010: Fuel consumption of timber haulage versus
general haulage. Harvesting/Transportation No. 22. COFORD, 6 p.
Devlin, J. G., McDonnell, K., Ward, S., 2007: Timber haulage
routing in Ireland: an analysis using GIS and GPS. Journal
of Transport Geography 16(1): 63–72.
Favreau, J., 2006: Six key elements to reduce forest transportation cost. FERIC. Available on http://www.forac.ulaval.ca/
fileadmin/docs/EcoleEte/2006/Favreau.pdf
Holzleitner, F., 2009: Analyzing road transport of roundwood with a commercial fleet manager. In: Prknová H (ed)
Formec 2009. Kostelec nad Černými lesy: Czech University
of Life Sciences Prague, p. 173–181. ISBN 978-80-213-1939-4.
Holzleitner, F., Kanzian, Ch., Stampfer, K., 2011: Analyzing
time and fuel consumption in road transport of round wood
with an onboard fleet manager. Eur J Forest Res 130(2): 293–
301.
Klvac, R., 2006: Draft of Information system for timber haulage. In Charvát K (ed) Information Systems in Agriculture
and Forestry. Praha: ČZU Praha, p. 1-8. ISBN 80-213-1494-X.
Komor, P., 1995: Reducing energy use in US freight transport. Transport Policy 2 (2): 119–128.
Lofroth, C., Lindholm, E. L., 2005: Reduced fuel consumption on roundwood haulage rigs. Skogforsk. Resultat no. 23.
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Motulsky, H. J., 2007: GraphPad Prism Version 5.0. Regression Guide. GraphPad Software. Inc.. San Diego. 294 p.
Motulsky, H. J ., Brown, R. E., 2006: Detecting outliers when
fitting data with nonlinear regression – a new method based
on robust nonlinear regression and the false discovery rate.
BMC bioinformatics. Available on http://www.ncbi.nlm.nih.
gov/pubmed/16526949.
Press, W. H., Teukolsky, S. A., Vettering, W. T., Flannery, B.
P., 1988: Numerical Recipes in C. The Art of Scientific Computing. New York. Cambridge University Press.
Svenson, G., 2011: The impact of road characteristics on fuel
consumption for timber trucks. In Ackerman P, Ham H,
Gleasure E (eds) Proceedings of 4th Forest Engineering Conference: Innovation in Forest Engineering – Adapting to
Structural Change. Stellenbosch University, p. 172. ISBN 9780-7972-1284-8.
Sažetak
Potrošnja goriva pri prijevozu drvnih sortimenata
U ovom je radu istraživana pristupačnost drvnih sortimenata prijevozu kamionskim skupovima, a istraživala su
se 132 kamionska skupa i tri modela kamiona (Tatra, Mercedese Benz i Iveco) s različitim vrstama kamionskih
prikolica.
Svako smanjenje potrošnje goriva po jedinici proizvodnje može povećati okolišni i ekonomski profil sekundarnoga prijevoza. S obzirom na to da na gorivo otpada najveći dio troškova koji nastaju pri prijevozu drvnih sortimenata, cilj je ovoga rada bio analizirati potrošnju goriva promatranih kamionskih skupova korištenih za prijevoz.
Svaka zamjena zastarjeloga i neučinkovitoga kamionskoga skupa novim učinkovitijim kamionskim skupom može
rezultirati značajnim smanjenjem potrošnje goriva po jedinici proizvodnje.
Glavni je cilj ovoga rada bio ustanoviti na koji način prijevozna udaljenost (duljina jednoga turnusa) kod
promatranih kamionskih skupova utječe na potrošnju goriva na 100 km te na specifičnu potrošnju goriva po prevezenom kubnom metru drva.
Dizajniran je informacijski sustav koji može primati narudžbe od naručitelja i koji pruža potporu dispečerima
pri donošenju odluka da bi se odabrao najpogodniji kamionski skup. Sustav također bilježi podatke o pojedinom
turnusu, zbraja ih te ih pohranjuje u baze podataka.
Početna je obrada podataka napravljena usporedbom velikoga broja tablica i grafikona. Za nelinearnu regresiju koristili smo se programom GradhPad Prism 5. Taj program omogućuje vrlo fleksibilan izbor regresijskoga
modela, ima vrlo dobre grafičke mogućnosti i moguće je ubaciti i ucrtati intervale pouzdanosti pojedinih modela.
Navedeni program eliminira ekstreme metodom »ROUT«.
U vrijeme istraživanja više od 3,4 milijuna kubnih metara drva prevezeno je od pomoćnoga stovarišta do
glavnoga stovarišta, krajnjega korisnika ili do željezničke pruge. U ukupnom obujmu prevezenoga drva udio je
crnogorice bio 92, a bjelogorice 8 %. Ukupan utrošak goriva za promatrane kamionske skupove iznosio je 6,8
milijuna litara.
Na potrošnju goriva po jedinici proizvodnje (m3) najviše utječu duljina turnusa i obujam tovara. Ta dva
čimbenika djeluju u sinergiji. Što je veći obujam tovarnoga prostora kamionskoga skupa, manja je prosječna potrošnja goriva po jedinici proizvodnje, dok s druge strane, što je veća udaljenost pojedinoga turnusa, veća je i
prosječna potrošnja goriva po jedinici proizvodnje.
Zastarjeli i neadekvatni kamionski skupovi tijekom istraživanoga razdoblja stalno su zamjenjivani novim i
učinkovitijim, zbog čega je primijećeno značajno smanjenje prosječne potrošnje goriva (0,5 l/m3) po jedinici proizvodnje.
Smanjenje potrošnje goriva po jedinici proizvodnje u konačnici znači smanjenje emisije stakleničkih plinova
te ublažavanje štetnoga utjecaja na okoliš. Sagorijavanjem jedne litre goriva u motoru kamionskoga skupa u atmosferu se ispušta 2,67 kg ugljičnoga dioksida te bi se smanjenjem potrošnje goriva za 1,5 milijuna litara smanjila i emisija ugljičnoga dioksida u atmosferi za 4,4 milijuna tona. Nedvosmisleni je zaključak ovoga rada da se pri
odabiru kamionskih skupova za prijevoz drvnih sortimenata, tj. njihovom optimizacijom, može značajno pridoniCroat. j. for. eng. 34(2013)2
239
R. Klvač et al.
Fuel Consumption in Timber Haulage (229–240)
jeti ublažavanju negativnih utjecaja šumskih strojeva na okoliš. Cestovni je promet u posljednjih deset godina
zabilježio velike promjene, a analiza predstavljena u ovom radu daje važne informacije korisne u planiranju i organizaciji cestovnoga prijevoza drvnih sortimenata.
Ključne riječi: šumska cesta, prijevoz drvnih sortimenata, kamionski skup, potrošnja goriva
Authors’ address – Adresa autorâ:
Received (Primljeno): February 18, 2013
Accepted (Prihvaćeno): August 06, 2013
240
Assoc. prof. Radomír Klvač, PhD.*
e-mail: [email protected]
Mr. Josef Kolařík
e-mail: [email protected]
Mrs. Marcela Volná
e-mail: [email protected]
Assoc. prof. Karel Drápela, PhD.
e-mail: [email protected]
Mendel University in Brno
Faculty of Forestry and Wood Technology
Department of Forest and Forest Products Technology
Zemedelska 3
613 00 Brno
CZECH REPUBLIC
* Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Original scientific paper – Izvorni znanstveni rad
Work Ability Index of Forestry Machine
Operators and some Ergonomic Aspects
of their Work
Matija Landekić, Ivan Martinić, Matija Bakarić, Mario Šporčić
Abstract – Nacrtak
This paper provides the results of an applied research of forestry machine operators related to
their work ability index (WAI) and some ergonomic aspects of their everyday work. A questionnaire on work environment and working ability was conducted in the year 2012 and included
machinery operators employed in the state forestry company Croatian Forest Ltd. and in
private forestry companies. Descriptive statistics and comparisons have been carried out regarding work ability index and frequency response of the respondents. The first part of the
results presents a) profile of respondents b) organization of operators’ work activities and their
education, c) impact of tiredness and d) impact of psychological and social factors on operators’
work ability. The second part of the results presents a) work ability results in relation to demographic categories of respondents and b) examination of differences between work ability
indexes by groups of descriptive variables. Regarding the educational aspect of the sampled
machine operators, the results showed insufficient level of adequate specialized education.
Higher level of mental demands required to perform the job was rated with the operators
employed in private companies. Demographic parameters of the respondents negatively affect
the working and functional ability of forestry machine operators, and the value of operators’
WAI decreased considerably within the groups depending on work experience in the private
forestry sector.
Keywords: forestry, machine operators, work ability index, working environment
1. Introduction – Uvod
Skidding and/or forwarding of timber are considered to be technically demanding, the most expensive,
and together with felling and cutting, the riskiest everyday operations in forestry. Within the process of
timber harvesting, a group of work operations during
skidding/forwarding, which are also called the primary transport (Poršinsky 2005), are defined as removal of whole trees or their parts from the felling site
(stump) to the roadside landing using a forest machine. Requirements for volume and quality of forest
works, especially works concerning skidding and forwarding, are ever increasing. At the same time, forest
work and supporting logistics processes become more
complex, and certification of forest management goes
with a wide number of requirements on the quality of
performance, especially in terms of stand protection
Croat. j. for. eng. 34(2013)2
and biodiversity conservation (Kostenholtz et al. 2008),
as well as social and safety standards of workers in
direct production. Development of forest technology
at the end of the 20th century and structural changes in
forestry sector (market growth, denationalization, etc.)
have led to a significant reduction in the number of
employees in the state forestry sector and also to the
development of new business models in some segments, such as exploitation of forests, where entrepreneurship plays a dominant role.
Forest contractors become an important link between forest owners and wood industry (Šporčić 2005)
in Europe and in Croatia. In the period 2000–2010,
there has been a visible increase in contractors’ services in the state forests of the Republic of Croatia
(RC). Contractors have a constant share of 41.83% in
skidding/forwarding operations, which means that
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M. Landekić et al.
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
the company Croatian Forests Ltd. Zagreb (in charge
for the management of state forests) extracts with its
own mechanization approximately 58.17% of timber
(Landekić et al. 2011b). The volume of services that
private contractors provide to private forest owners in
Croatia is not registered and no reliable data concerning these activities are available. Engagement of forest
contractors and transition to contract work brings
some benefits (flexibility, better financial result, better
work performance due to specialization, etc.), but also
defects such as insufficient investment in equipment
and training, questionable professional level of work,
low safety level, questionable effectiveness of workers’
health care, ineffective labor inspection (Šporčić et al.
2009) and potentially less skillful machine operators
in the private sector.
The key role for ensuring competitiveness of timber extraction (skidding/forwarding), but also for
achieving a satisfying level of safety and efficiency in
forest production, lies in work ability and working
techniques used directly by forestry machine operators (Martinić et al. 2011). Vaguely specified legal responsibility of forest contractors and inefficiency of
labor inspection leads to negligence of basic safety
standards, which may result in inadequate working
environment and reduced working ability of operators
employed in private forestry sector. This is why in this
paper the ergonomic aspects were investigated and
compared of the working environment and working
ability of forestry machine operators who are employed by private contractors in forestry on the one
side, and those employed in the state company Croatian Forests Ltd. Zagreb (CF Ltd.) on the other side.
The working ability of operators is researched and
presented through the work ability index (WAI), and
the ergonomic characteristics of the working environment are measured through the respondents’ answers
on the training process, exposure to physical hazards
(noise and vibration), impact of fatigue on work ability and also on their assessment of psychological and
social factors of the working environment.
2. Issues and objectives of research
Problematika i ciljevi rada
Forest work is highly dangerous and risky, and the
work environment that implies working outdoors
hides many hazards. The group of work operations
related to timber skidding and/or forwarding is technically demanding, the most expensive, and after felling and cutting to length the most risky among everyday forest operations (Ranogejec et al. 2010). Insight
into the real conditions of work safety and humaniza-
242
tion of work activities in timber extraction, in the form
of ergonomic, technical and organizational solutions,
is a starting point for the process of improving ergonomic features of the working environment and work
ability of machine operators in forestry.
Satisfactory ergonomic level in terms of working
environment and high working ability of forestry machine operators, in compliance with safety rules for
mechanized skidding, seems crucial for creating safe
working conditions in order to prevent physical fatigue, monotony of work and work-related injuries.
Analysis of ergonomic characteristics of the working
environment and numerical evaluation of machine
operators’ work ability in forestry is the first step in the
evaluation of the current situation, which should later
result in proposing the necessary measures to improve
the safety system and security levels of timber extraction. The main task of this research is to determine the
work ability index (WAI) of machine operators employed in the state and private forestry sector and to
establish the ergonomic features of the working environment, as well as opportunities to improve the current situation in forestry operations.
3. Material and methods – Materijal
i metode
Forest machine operators in Croatian forestry, employed by the state-owned company Croatian Forests
Ltd. as well as those employed by private forest contractors, are the primary object of research. Investigation of ergonomic requirements of the working environment and research on work ability of machine
operators engaged in timber extraction included the
current theoretical understanding and views of operators using the survey method. The source and model
used to create a survey questionnaire were the documents under the title »The Machine Operator Current
Opinions and the Future Demands on Technical Ergonomics in Forest Machines« (Walker et al. 2001). Another
relevant source refers to a document under the title
»Work Ability Index« (Tuomi et al. 1998), which was
developed by the Finnish Institute of Public Health.
3.1 Survey method and structure of
the measuring instrument – Metoda anketiranja i struktura mjernoga instrumenta
The survey method is a process based on a survey
questionnaire, which investigates and collects data,
information, views and opinions about the subject of
research (Čekić 1999). There are numerous ways to
conduct a survey questionnaire, and some of the most
used are as follows: on-line or web surveys, e-mail
Croat. j. for. eng. 34(2013)2
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
surveys, computer-aided telephone interviewing, etc.
The answer to a particular question from the survey is
valuable to the extent to which it is associated with the
opinion or attitude on a topic. Questionnaires, in relation to interviews, are usually viewed as a more objective research tool that can produce generalizable results because of large sample sizes (Oppenheim 1992).
For the investigation of the working environment
ergonomics and work ability of forestry machine operators, the questionnaire developed by the Department of Forest Engineering at the Faculty of Forestry
in Zagreb was used. The survey was conducted during
the year 2012 as a part of activities on the project entitled »Licensing and Certification for Acquiring European
Standards of Safety and Quality at Forestry Work« initiated and financed by Croatian Forests Ltd. Before the
questionnaire was distributed, all required steps and
preparations had been performed with the goal to ensure reliability and credibility of the survey.
The questionnaire consists of five structural parts,
and contains 48 questions. The first structural part of
the questionnaire is related to the collection of personal data about respondents (gender, age, qualifications, etc). The second part of the questionnaire covers
the current employment and organization of machine
operators’ daily work activities. The third section of
the questionnaire examines the presence and development of disease and fatigue, while the fourth section
is related to the impact of psychological and social factors on forestry machine operators. Within the first
four structural parts, questions were designed to measure separate variables. The fifth part of the questionnaire involves the assessment of work ability index
(WAI) for forestry machine operators through 7 standardized questions. In the questionnaire, the following answers to the questions were used: a) yes/no answer b) multiple answers c) Likert scale evaluation and
d) questions with open answers.
Stratified sampling method was used to divide up
the population (N = 150) into two smaller non-overlapping sub-groups: (a) operators in CF Ltd. (N = 75) and
(b) operators in private forest companies (N = 75). In
each sub-group a simple random sample was done by
Sample Size Calculator. During the analysis and processing of collected data, the following methods were
used: statistical method, method of generalization,
description and comparison. Graded, collected and
summarized data for the assessment of working and
functional abilities of forestry machine operators (the
fifth part of the questionnaire) are expressed through
the work ability index (WAI). Database for entry of
collected data, systematization, verification of input
accuracy and primary processing of data was made in
Croat. j. for. eng. 34(2013)2
M. Landekić et al.
Microsoft Office Excel. Statistical analysis was performed using statistical software: Statistica 8 and SPSS
17.0 – Statistical Package for Sociological Research.
Rank correlation was used to measure the relationship
between variables and alternative nonparametric analysis of variance (Kruskal–Wallis test) was used to test
the differences between groups of variables. Based on
individual observations, generalized conclusions were
drawn up using the analysis of a limited number of
subjects in the base sample.
3.2 Work ability index in general – Indeks radne
spremnosti općenito
Working and functional ability cannot be objectively measured with a single instrument. It always
requires an assessment based on data obtained from
several different sources (medical examination, survey, testing, etc.). Work Ability Index (WAI) is an instrument designed for practical application, widely
used by healthcare workers or health and safety employees, like a help tool for determining employees
working competence, as a basis for further measurements (Tuomi et al. 1998). WAI is a result of workers
own assessment of his or her work readiness. The instrument, developed by the Finnish Institute of Public
Health, is easy and quick to use, cyclically repeatable,
results are obtained quickly and can be used for monitoring on the level of individuals or groups (e.g. department, age or professional groups, etc.). It is applicable within health and safety system, where it
shows how well an employee is able to perform his
daily job duties. It can be used for the assessment of
working and functional ability in the framework of
medical examination or as a survey at the workplace.
The instrument based on a questionnaire is intended
for workers support: a) where it can be used at an
early stage to ensure proper measures to maintain
working readiness or b) it can help in determining
workers who need healthcare support at work. Responding to a series of seven questions (Table 1),
which take into account physical and mental demands
of the job, it gives the result ranging between 7 and 49
points (Table 1), which illustrates numerically the
working and functional ability of each participant.
This approach establishes optimal conditions to prevent premature reduction of work ability.
Steps and measures directed toward restoring
work ability or additional evaluations of work ability
are needed by those whose work ability is graded poor
(maximum score 27). For those whose work ability is
moderate (score 28–36), measures to help improve
work ability are recommended. Workers with a good
work ability index (score 37–43) should receive instructions on how to maintain their work ability. Those
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Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
Table 1 Items of the Work Ability Index (Ilmarinen 2007)
Tablica 1. Stavke indeksa radne spremnosti (Ilmarinen 2007)
Items – Stavka
Range – Raspon
1
Current work ability compared with the lifetime best – Sadašnja radna spremnost u odnosu na najbolju životnu
0–10
2
Work ability in relation to the demands of the job – Radna spremnost u odnosu na zahtjeve posla
2–10
3
Number of current diseases diagnosed by a physician – Broj bolesti koje je dijagnosticirao liječnik
1–7
4
Estimated work impairment due to diseases – Procijenjena radno umanjenje zbog bolesti
1–6
5
Sick leave during the past year (12 months) – Broj dana bolovanja u protekloj godini (12 mjeseci)
1–5
6
Own prognosis of work ability 2 years from now – Vlastita prognoza radne sposobnosti za buduće 2 godine
1–7
7
Mental resources – Mentalni resursi
1–4
whose work ability is excellent (44–49) should also be
informed about which work and life-style factors
maintain work ability and which factors weaken it
(Tuomi et al. 1998). The index can also be used to predict the threat of disability in the near future.
4. Results and findings of research
Rezultati i nalazi ispitivanja
In the present study, analysis of opinions and attitudes of the forestry machine operators included: a)
profile analysis of the respondents in the study; b)
main findings of the second, third and fourth structural part of the questionnaire related to the working
environment of machine operators, c) values of the
machine operators work ability index and comparison
of WAI with demographic categories of respondents.
4.1 Profile of respondents – Profil ispitanika
Forestry machine operators employed in the state
and private forestry sector were selected as participants in the research conducted on the ergonomic features of the working environment and work ability
index. First, 75 questionnaires were delivered to forestry machine operators employed in working units
engaged in mechanization, transport and building,
and also to the forest offices which have their own
mechanization, within forest administration Požega,
Našice, Zagreb and Karlovac, as a part of the company
Croatian forests Ltd. Another 75 questionnaires were
delivered to machine operators employed in private
forestry sector, which were engaged in timber extraction on the territory of the forest administration
Našice, Zagreb and Sisak at the time of survey. 44.67%
of forestry machine operators answered the questionnaire (Table 2), which is satisfactory feedback in terms
of the research.
244
The profile and characteristics of the operators surveyed in the state forestry sector, according to several
criteria (gender, age group, qualifications), roughly
correspond to the total number of employees working
as machine operators in the company Croatian forests
Ltd. Zagreb. A higher share of younger machine operators is visible in private forestry sector. Also, within the sample, difference in the level of machine operators’ education is notable. In the private sector, the
operators’ education level is significantly higher than
that of operators employed in Croatian forests Ltd.
(Table 2).
4.2 Aspect of Working Environment of Forestry
Machine Operators in Croatia– Aspekt
radnoga okoliša kod rukovatelja mehanizacijom u Hrvatskoj
To plan for and control environmental and ergonomic aspects of forestry machine operators work, it
is necessary to know what impacts them and where
these impacts come from. Consequently, ergonomic
characteristics of the working environment are examined and presented through the attitudes of the forest
machinery operators concerning a) education and organization of operators work activities, b) impact of
tiredness and c) impact of psychological and social
factors on operator work ability. Identification and efficient management of environmental aspects and impacts should result in positive influence on employees
in practice and also in significant environmental improvements.
4.2.1 Employment, education and organization of
work activities – Zaposlenost, osposobljenost i
organizacija rada
For decades, training and periodically checking the
qualification of forestry machine operators have been
considered as the key activities for ensuring the work
Croat. j. for. eng. 34(2013)2
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
M. Landekić et al.
Table 2 General information about the respondents
Tablica 2. Opći podatci o ispitanicima
Type of interviewees – Vrsta ispitanika
Forestry machine operators (private and state sector)
Rukovatelji šumarskom mehanizacijom (privatni i državni sektor)
Number of respondents – Broj odgovora
67 (44.67%)
Time of research – Vrijeme ispitivanja
During 2012 – Tijekom 2012. godine
Profile of interviewees – Profil anketiranih zaposlenika
Croatian Forests Ltd.
Private forest company
Hrvatske šume d.o.o.
Privatna šumarska tvrtka
39 (52.00%)
28 (37.33%)
N
%
N
%
Gender
Male – Muški
39
100.00
28
100.00
Spol
Female – Ženski
0
0.00
0
0.00
<25
1
3.00
7
25.00
25–35
10
26.00
7
25.00
35–45
14
36.00
8
29.00
45–55
12
31.00
5
28.00
55<
2
5.00
1
4.00
Unqualified (worker) – Nekvalificirani (radnik)
18
46.00
5
18.00
Level of education
Qualified (worker) – Kvalificirani (radnik)
6
15.00
9
32.00
Stručna sprema
Secondary education – Srednja školska sprema
15
38.00
12
43.00
University degree – Visoka stručna sprema
0
0.00
2
7.00
Age group
Dobna skupina
quality and safety of operational forest work. In most
European countries, regulations oblige employers to
provide adequate training to each person using the
working tools and machines (Medved 1998). The research results of professional education of operators in
the sample (Table 3) show that 56.41% of operators in
CF Ltd., and 33.00% of operators employed by private
contractors have no adequate professional experience
or specialized education. The reason why the level of
education is low is the lack of formal regulations and
bodies that provide certification of knowledge and
skills of forestry machine operators in Croatia.
Knowledge, skill and experience in operating forest machinery are the basic items in the operator career
development. By comparing the professional experience of the respondents (Fig. 1), it can be seen that
operators employed by the company CF Ltd. have on
average more work experience as forwarder operators,
skidder operators and as forest cutters. The reason for
this result is noticeably older population of respondents employed by the CF Ltd. (average age mean in
CF Ltd = 42.33 years, and in private sector = 35.79
years) with about 1/3 higher overall professional exCroat. j. for. eng. 34(2013)2
Fig. 1 Professional experience of operators by workplace
Slika 1. Godine profesionalnoga iskustva rukovatelja prema mjestu
rada
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Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
Table 3 Type of education related to machine control
Tablica 3. Vrsta obrazovanja vezana uz upravljanje mehanizacijom
Offered response – Ponuđeni odgovor
Croatian Forests Ltd.
Private forest company
Total
Hrvatske šume d.o.o.
Privatna šumarska tvrtka
Ukupno
N
%
N
%
N
%
Self-educated – Samoobrazovan
22
56.41
9
33.00
31
48.00
Vocational experience – Strukovno iskustvo
9
23.08
17
63.00
25
38.00
Specialized education – Specijalističko obrazovanje
8
20.51
1
4.00
9
14.00
length method (almost always with forwarders),
through stemwood, halfwood to whole tree methods.
Adequate work organization can proactively act to
increase the level of performance of the forestry machine operators. Research results on work techniques
training for the mechanized timber extraction (Table
4) show that the operators employed by private contractors have a higher level of training (29.85%). Exposure to excessive noise and vibration in the working
environment was rated with 32.14% by respondents
employed in the private sector and 41.03% by respondents employed in CF Ltd (Table 4). The lack of personal protective equipment (PPE) was rated with
32.14% by respondents employed by private contractors, and 50.00% said that they do not use it every day
to the full extent. On the other hand, in the company
CF Ltd. only 5.13% of the respondents indicated a lack
of personal protective equipment, and 43.59% said
that they do not use it every day to the full extent. The
occurrence of pain and discomfort (Table 4) caused by
the position of the body when working was noted by
16 operators employed in CF Ltd. and 12 operators
employed in the private forestry sector.
Fig. 2 Number and average age of machinery operated by sampled
operators
Slika 2. Broj i prosječna dob mehanizacije kojom upravljaju uzorkovani rukovatelji
perience in forestry (Fig. 1). On the other hand, the
sample shows that operators employed by the CF used
more commonly skidders for timber extraction (Fig.
2), and that the average age of machines (forwarders
and skidders) is considerably lower than the age of
machinery owned by private contractors in forestry.
In timber extraction, different methods are applied for
removing different forms of assortments: from cut-to-
246
4.2.2 The impact of fatigue and development of
disease among respondents – Utjecaj zamora i
razvoj bolesti kod ispitanika
Tiredness and fatigue can have a significant adverse
impact on organizational efficiency and productivity
as well as operators’ health and safety. Assessment of
the impact of physical fatigue on the quality and productivity of machine operators (Fig. 3) is valued with
five answers on Likert scale. Operators employed in
CF Ltd. believe that fatigue significantly (very much
– 41.03%) affects the quality and productivity of the
work compared to those employed by the private contractor (17.86%). Higher percentage of the rates
»much«, »medium« and »little« is recorded by the operators employed in the private forestry sector (Fig. 3).
Jobs with an increased risk, especially for the development of work-related diseases, require medical
Croat. j. for. eng. 34(2013)2
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
M. Landekić et al.
Table 4 Rating of organizational factors during work of machine operators (answer share, %)
Tablica 4. Ocjena organizacijskih čimbenika u radu rukovatelja mehanizacijom (udio odgovora, %)
Organizational factors – Organizacijski čimbenici
Croatian Forests Ltd.
Private forest company
Hrvatske šume d.o.o.
Privatna šumarska tvrtka
Yes – Da
No – Ne
48.72
38.46
41.03
All PPE provided – Osiguranost svih OZS
Ful use of PPE – Uporaba OZS u punoj mjeri
Work techniques training in mechanized timber extraction
Osposobljavanje radnim tehnikama pri mehaniziranom privlačenju
Exposure to excessive noise and vibration
Izloženost prekomjernoj buci i vibracijama
First-aid kit and fire extinguisher in the machine
Kutija prve pomoći i protupožarni aparat u stroju
Appearance of pain and discomfort caused by body position at work
Pojava boli i neugode uzrokovana položajem tijela pri radu
Don't know
Don't know
Yes – Da
No – Ne
12.82
78.57
14.29
7.14
25.64
33.33
32.14
39.29
28.57
94.87
5.13
0.00
64.29
32.14
3.57
53.85
43.59
2.56
50.00
50.00
0.00
97.44
2.56
0.00
85.71
14.29
0.00
58.97
41.03
0.00
50.00
42.86
7.14
Ne znam
Ne znam
research, the symptoms of headache were noticed by
17 participants, and the appearance of symptoms of
insomnia was noted by 11 participants employed by
the company CF Ltd. A high proportion of respondents said that the symptoms of headache were associated with work (Table 5). A smaller percentage of
respondents employed by private contractors reported
the appearance of symptoms, but they put the emphasis on the connection between these symptoms and the
daily work activities and demands at work (Table 5).
Fig. 3 Rating the impact of fatigue on the quality and productivity
of machine operator work
Slika 3. Ocjena utjecaja zamora na vrsnoću i proizvodnost rukovatelja mehanizacijom
supervision of employees for early detection, monitoring and treatment of health disorders partially caused
by exposure to physical and mental challenge, and
hazards at work (Macan et al. 2012). As part of the
Croat. j. for. eng. 34(2013)2
4.2.3 Impact of psychological and social factors on
forestry machine operators – Utjecaj
psihološko društvenih čimbenika na rukovatelje šumarskom mehanizacijom
Psychological and social factors of the working environment may have a direct impact on the health and
safety of forest machine operators, as well as on productivity. One of the most important tasks of employers is to keep the mental load and strain of employees
at acceptable levels, all with the long-term goal of diminishing the probability of occurrence and development of mental stress (Landekić et al. 2011a). According to the rating of mental job demands by forestry
machine operators (Fig. 4), the results show a significant proportion of large and very large (46.42%) mental demands of the job performed by operators employed in private companies in relation to the operators
employed in the state–owned company CF Ltd.
The reason for the increased mental demands of
the job indicated by the operators employed in a pri-
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Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
Table 5 Headaches and insomnia symptoms experienced by forestry machine operators
Tablica 5. Pojava simptoma glavobolje i nesanice kod rukovatelja mehanizacijom u šumarstvu
Croatian Forests Ltd. – Hrvatske šume d.o.o.
Private forest company – Privatna šumarska tvrtka
Headache – Glavobolja
Insomnia – Poremećaj spavanja
Headache – Glavobolja
Insomnia – Poremećaj spavanja
17 respondents (43.59%)
11 respondents (28.21%)
10 respondents (35.71%)
5 respondents (17.86%)
17 ispitanika (43,59 %)
11 ispitanika (28,21 %)
10 ispitanika (35,71 %)
5 ispitanika (17,86 %)
Work–related
Work–related
Work–related
Work–related
Povezano s poslom
Povezano s poslom
Povezano s poslom
Povezano s poslom
Yes – Da
No – Ne
Yes – Da
No – Ne
Yes – Da
No – Ne
Yes – Da
No – Ne
70.59%
29.41%
45.46%
54.54%
70.00%
30.00%
60.00%
40.00%
resulted in almost equal frequency response of forest
workers employed in the private sector and in CF Ltd.
Influence of the working climate within the operators’
working environment, expressed through business
solidarity, working atmosphere, good relationship
with superiors and colleagues, is evaluated in Table 6.
The results show a higher proportion of affirmative
answers (often and always) on the subject of freedom
to make own decisions while working and the existence of a sense of solidarity by the operators employed in private companies. On the other hand, a
greater proportion of affirmative answers (often or
always) were recorded by operators employed in CF
Ltd. regarding good working atmosphere and good
relationship with superiors and colleagues (Table 6).
4.3 Work Ability Index of Forestry Machine
Operators – Indeks radne spremnosti rukovatelja šumarskom mehanizacijom
Fig. 4 Rating of job mental demands by forestry machine operators
Slika 4. Ocjena mentalne zahtjevnosti posla kod rukovatelja šumarskom mehanizacijom
vate company (Fig. 4) can be partially linked with the
results in Table 6 related to time pressure, working
climate, acquiring new skills or knowledge and some
other factors of the working environment explored in
this paper. Relative frequency of responses related to
time pressure at work is presented in Table 6. The percentage share of responses shows a greater presence
of time pressure at work for operators employed in a
private company (often or always – 32.14%). Evaluation of acquiring new skills or knowledge (Table 6)
248
Work ability index is a tool in the form of a questionnaire used for the self-assessment of employees.
Focus is put on employees and their job readiness in
relation to the requirements of their current job position. It also highlights the need to adapt working conditions to the capacities and capabilities of employees.
Mean score of the work ability index of machine operators, employed in Croatian forests Ltd. and in private companies, is shown in Table 7. The results of the
WAI average score show a negligible difference between the operators employed in the private sector
and in state forestry sector. They have good work ability (score 37–43), which should be kept at the existing
level.
For a more detailed insight into work ability, a thorough examination of opinions and attitudes of forestry machine operators included as follows: (a) correlation analysis of work ability index (WAI) with
Croat. j. for. eng. 34(2013)2
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
M. Landekić et al.
Table 6 Evaluation of some psychological and social factors of the working environment, %
Tablica 6. Procjena nekih psihološko-društvenih čimbenika radnoga okoliša, %
Questions – Pitanja
Do you feel the time pressure due to the volume of work?
Osjećate li vremenski pritisak zbog opsega posla?
Do you learn new things at work?
Učite li nove stvari na poslu?
Does your job require skills?
Zahtijeva li Vaš posao vještinu?
Does your job require ingenuity?
Zahtijeva li Vaš posao domišljatost?
Do you have any freedom to decide at work?
Imate li slobodu odlučivanja u radu?
Is the atmosphere at work pleasant?
Je li atmosfera na poslu ugodna?
Is there a sense of solidarity?
Postoji li osjećaj solidarnosti?
I have a good relationship with my superiors?
Slažete li se dobro s nadređenim?
I have a good relationship with my colleagues?
Slažete li se dobro s kolegama?
Croatian Forests Ltd.
Private forest company
Hrvatske šume d.o.o.
Privatna šumarska tvrtka
Never
Rarely
Often
Always
Never
Rarely
Often
Always
Nikad
Rijetko
Često
Uvijek
Nikad
Rijetko
Često
Uvijek
20.51
66.67
12.82
0.00
17.86
50.00
21.43
10.71
10.26
33.33
35.90
20.51
0.00
32.14
42.86
25.00
2.56
23.08
74.36
0.00
17.86
21.43
53.57
7.14
2.56
2.56
38.46
33.33
0.00
28.57
25.00
46.43
5.13
25.64
41.03
30.77
10.71
17.86
35.71
35.71
0.00
10.26
43.59
46.15
0.00
10.71
50.00
39.29
2.56
12.82
33.33
51.28
0.00
7.14
67.86
25.00
0.00
2.56
25.64
71.79
0.00
3.57
42.86
53.57
0.00
0.00
17.95
82.05
0.00
3.57
46.43
50.00
Table 7 Work ability index of forestry machine operators – CF Ltd. and private contractors
Tablica 7. Indeks radne spremnosti rukovatelja šumarskom mehanizacijom – HŠ d.o.o. i privatni izvoditelji
Indicator
Number of operators
Minimum
Maximum
Arithmetic mean
Standard deviation
Pokazatelj
Broj rukovatelja
Minimum
Maksimum
Aritmetička sredina
Standardna devijacija
39
24.00
49.00
38.46
5.70
28
24.00
48.00
38.11
5.39
WAI (CF Ltd.)
IRS (HŠ d.o.o.)
WAI (private contractors)
IRS (privatni izvoditelji)
demographic indicators of the respondents and (b)
testing the WAI difference among a group of descriptive variables.
4.3.1 Correlation of work ability index and demographic parameters of respondents – Mjere
povezanosti indeksa radne spremnosti i
demografskih parametara ispitanika
This section shows testing the strength and direction of respondent demographic parameters and work
Croat. j. for. eng. 34(2013)2
ability index. Correlation and influence are reviewed
with the aim of gaining a more comprehensive understanding of the relation between the work of forestry
machine operators and their functional ability (WAI)
depending on work experience, age and weight of the
workers. Spearman’s rank correlation coefficient was
used to assess the degree and direction of the relation
between the derived indicators.
The indicator of machine operator work ability index negatively correlated with three demographic
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Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
Table 8 Rank correlation of work ability index of machine operators and demographic parameters
Tablica 8. Korelacija ranga indeksa radne spremnosti i demografskih parametara rukovatelja mehanizacijom
Variable
Indicator
Age
Mass
Work experience in forestry
Work ability index
Varijabla
Pokazatelj
Godine života
Masa
Radno iskustvo u šumarstvu
Indeks radne spremnosti
Age
rs
1.000
0.238
0.769**
–0.525**
Godine života
p
–
0.052
0.000
0.000
Mass
rs
0.238
1.000
0.335
–0.247*
Masa
p
0.052
–
0.006
0.044
1.000
–0.443**
–
0.000
**
Work experience in forestry
rs
0.769
Radno iskustvo u šumarstvu
p
0.000
**
**
**
0.335
0.006
*
**
Work ability index
rs
–0.525
–0.247
–0.443
1.000
Indeks radne spremnosti
p
0.000
0.044
0.000
–
* Correlation is significant at the 0.05 – Korelacija je značajna na razini 0,05;
** Correlation is significant at the 0.01 – Korelacija je značajna na razini 0,01
the work ability index and work experience in forestry
was medium negative (r = -0.443; n = 67; p<0.01), where
a higher level of work ability index was recorded with
machine operators with less experience in forestry,
and the calculated coefficient of determination (r² =
0.196) indicated that work experience accounted for
19.6% of the variance in the respondents answers regarding the indicator of work and functional ability.
The relation between the work ability index of machine operators and the mass of respondents resulted
in a small negative correlation (r = -0.2474; n = 67;
p<0.05).
Fig. 5 Mean value of WAI by three age groups
Slika 5. Srednja vrijednost IRS prema trima dobnim grupama
variables. The relationship of work ability index and
age of the respondents resulted in a strong negative
correlation (Table 8), r = -0.525; n = 67; p<0.01, where a
high level of work ability index was recorded with
younger machine operators. The calculated coefficient
of determination (r² = 0.275) showed that age accounted for 25.5% of the variance in the respondents answers regarding the indicator of work and functional
ability. Strength and direction of relationship between
250
4.3.2 Testing the diference of WAI between groups
of descriptive variables – Ispitivanje razlika
indeksa radne spremnosti prema opisnim
varijablama
Using the database of respondents, differences
were tested between the work ability index and selected descriptive variables. The following descriptive
variables were used: a) age group and b) group of
work experience in forestry. The homogeneity of variance between groups of data was tested with Levene’s
test (p>0.05), where on the basis of test significance
level a further testing of WAI difference was conducted with parametric and/or nonparametric techniques.
Due to inadequacy of variance homogeneity, alternative nonparametric analysis of variance (Kruskal–
Wallisov test) was used to test the difference of work
ability index among three groups of respondents according to age. Also, differences in work ability index
were examined between the four groups of respondents regarding work experience in forestry.
Croat. j. for. eng. 34(2013)2
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
M. Landekić et al.
Table 9 Testing the difference between WAI groups using the Kruskal–Wallis H test
Tablica 9. Ispitivanje razlika IRS između grupa pomoću Kruskal–Wallisova H-testa
Chi-square
Degrees of freedom
Sample size
P-value
Hi-kvadrat
Stupnjevi slobode
Veličina uzorka
P-vrijednost
Age of respondents – Godine života
16.897
2
67
0.000**
Work experience in forestry – Radno iskustvo u šumarstvu
14.776
3
67
0.002**
Descriptive variable – Opisne varijable
** The difference is significant at 0.01 – Razlika je značajna na razini 0,01
Groups by age:
Þ group 1: less than 35 years of age;
Þ group 2: from 36 to 45 years of age;
Þ group 3: more than 46 years of age;
Testing the score values of work ability index
among defined groups of respondents resulted in the
following statistically significant differences (Table 9).
Statistically significant difference was determined
among the age groups (p<0.01), where operators with
less than 35 years of age have the highest level of work
ability index (median – Md = 41.00) compared to their
older colleagues (Fig. 5). Subsequent testing of the difference using the Mann-Whitney U test showed that the
median value of WAI in group 1 (<35 years) (Md = 41.00,
N = 25) was significantly different from group 3 (>46
years of age) (Md = 35.50, N = 20), U = 64.50; z = -4.255;
p = 0.000. A statistically significant difference was not
confirmed between group 2 and group 1. Forestry
machine operators with more than 46 years of age employed in the state sector (CF Ltd) showed a significantly better working and functional ability in relation to
operators working in the private forestry sector (Fig. 6).
Forestry machine operators with less than 10 years
of experience in forestry had the highest level of work
Fig. 6 WAI of machine operators in private and public sector by age
groups
Slika 6. IRS rukovatelja mehanizacijom u privatnom i državnom
sektoru prema dobnim grupama
Fig. 7 Mean value of WAI by four groups of working experience in
forestry
Slika 7. Srednja vrijednost IRS prema četirima grupama radnoga
staža u šumarstvu
Groups by work experience in forestry:
Þ group 1: 0–10 years of work experience;
Þ group 2: 11–20 years of work experience;
Þ group 3: 21–30 years of work experience;
Þ group 4: 31–40 years of work experience.
Croat. j. for. eng. 34(2013)2
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M. Landekić et al.
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
Fig. 8 WAI of machine operators in private and public sector by
groups of work experience
Slika 8. IRS rukovatelja mehanizacijom u privatnom i državnom
sektoru prema grupama radnoga staža
ability index (Md = 41.00) in comparison to colleagues
with more years of experience (Fig. 7). Using the
Mann-Whitney U test, testing of differences showed
that the median value of WAI in group 1 (<10 years of
service) (Md = 41.00; N = 35) was significantly different
from group 2 (Md = 37.00; n = 19) U = 196.50; z = –2.473;
p = 0.013, group 3 (Md = 33.00; N = 8) U = 65.00;
z = –2.704; p = 0.007 and group 4 (>31 years of service)
(Md = 34.00; N = 4) U = 15.500; z = -2.238; p = 0.011. The
research has also shown that the indicator of employees work ability in the state sector slightly increases
with years of service, while in the private sector it declines with years of service (Fig. 8).
5. Discussion and conclusions – Rasprava
i zaključci
The study was designed with the purpose of determining the limits of forestry machine operators’ working and functional ability and acquiring insights in
some ergonomic aspects of their working environment
in forestry production. The investigated education
level of machine operators showed a lack of specialized education. In an effort to overcome the weaknesses of the national training system, the Croatian
forestry sector needs to look at examples of good practices implemented by the European countries, and at
252
measures advocated by Martinić et al. (2011), regarding the establishment of a national center for forestry,
which would enable the implementation of the certification process of machine operator training in forestry. Also, it is necessary to develop the safety culture
in the forestry sector through the development of personal responsibility for the safety, use of personal protective equipment and establishment of joint responsibility on safety including the management and
employees.
Psychological and social aspects of the working
environment of machine operators resulted in a higher level of mental demands on the job with the operators employed in private forest companies. A higher
proportion of time pressure due to the volume of work
and poor working climate in the workplace of operators employed in the private forestry sector goes in
favor of the obtained results on mental demand. Psychological and social factors of the working environment can influence the operators’ productivity, and
therefore one of the most important tasks of employers
is to keep the mental load and strain of employees at
acceptable levels (Landekić et al. 2011a).
Demographic parameters of the respondents (age,
work experience in forestry and weight) negatively
affect the working and functional ability (WAI) of forestry machine operators. Machine operators with less
than 35 years of age and with less than 10 years of
experience in forestry have the highest level of work
ability index, which is significantly different (p<0.01)
from the WAI in the oldest groups. Lower work ability of the respondends in the oldest group, according
to Ilmarinen at al. (2005), can be related to the health
(symptoms) and functional capacity (physical) or
work factors (mental strain) at the workplace of machine operators. According to age groups, machine
operators working in private companies, with more
than 46 years of age, have a considerably lower WAI
compared to operators employed by the company CF
Ltd. Also, within the groups formed by work experience in forestry, a visible reduction in the level of WAI
(moderate rating) is observed with operators working
in private companies, which indicates the need for
measures required to improve the current situation.
The responses of all machine operators and the analysis presented in this paper represent an important
contribution in the process of developing a model of
security measures for the improvement of health and
safety system in timber extraction through education
on work ability index and responsibilities that need to
be implemented in private and state forestry sector.
Such approach helps to identify potential work-related health risks in order to implement appropriate
Croat. j. for. eng. 34(2013)2
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
measures aimed at reducing the possibility of declining the working capacity of employees and preventing
their early retirement. Maintenance and/or improvement of the working and functional ability of forestry
machine operators can and needs to be carried out
through periodical training during the whole working
life.
M. Landekić et al.
ment for Forestry, Freiburg, Germany, September 26 – October 1, 2011. (In press)
Macan, J., Kerner, I., Šetek, J., 2012: Smjernice za zdravstvene
preglede zaposlenih u izdanju hrvatskog društva za medicinu rada hrvatskog liječničkog zbora. Arh Hig Rada Toksikol, 63, 555–558.
6. References – Literatura
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Area of Occupational Safety in Forestry?, Croatian journal
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Medved, M., 1998: Nezgode in tveganje pri poklicnem in
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Čekić, Š., 1999: Osnovi metodologije i tehnologije izrade
znanstvenog i stručnog djela. FSK, Sarajevo, 73.
Oppenheim, A. N., 1992: Questionnaire design, interviewing, andattitude measurement. New York City: St. Martin‘s
Press.
Ilmarinen, J., Tuomi, K., Seitsamo, J., 2005: New dimensions
of work ability. Proceedings of 2nd International Symposium
on Work Ability: Assessment and Promotion of Work Ability, Health and Well-being of Ageing Workers. Volume 1280,
Pages 1–436 (June 2005) Verona, Italy.
Ilmarinen, J., 2007: The Work Ability Indeks (WAI). Occupational Medicine, 57 (Source: http://occmed.oxfordjournals.
org)
International Business Machines (IBM) Corporation, 2008:
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Kastenholz, E., Dyduch, C., Fitzgerald, R., Hudson, B., Jaakkola, S., Lidén, E., Monoyios, E., et all., 2008: Guide to good
practice in contract labour in forestry. Report of the UNECE/
FAO Team of Specialists on Best Practices in Forest Contracting. Food and Agriculture Organization of the United Nations, Rome, 1–54.
Landekić, M., Martinić, I., Lovrić, M., Šporčić, M., 2011a: Assessment of Stress Level of Forestry Experts with Academic
Education, Coll Antropol 35(4): 1185–1191.
Landekić, M., Martinić, I., Lovrić, M., Zečić, Ž., Šporčić, M.,
Vusić, D., 2011b: Private Entrepreneurship in the Forestry
Sector of the Republic of Croatia – Status and Perspectives.
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Poršinsky, T., 2005: Djelotvornost i ekološka pogodnost forvardera Timberjack 1710 pri izvoženju oblovine iz nizinskih
šuma Hrvatske. Disertacija, Šumarski fakultet Sveučilišta u
Zagrebu, Zagreb, 1–170.
Ranogajec, B., Klarić, D., Zagudajev, J., Perakić, S., Plantak,
S., Pavlić, V., Koščević, V., Mundweil, V., Tomašić, Z., 2010:
Upute za rad na siguran način pri privlačenju i prijevozu
drveta. Hrvatske šume d.o.o. Zagreb 2010, 1–62.
StatSoft, Inc., 2007: Statistica 8® software.
Šporčić, M., 2005: Uvid u neka gledišta poduzetništva u
šumarstvu Europe. Šumarski list, 129(5–6): 287–298.
Šporčić, M., Martinić, I., Landekić, M., Lovrić, M., Svakidan,
M., 2009: Prikaz stanja poduzetništva u šumarstvu srednje i
istočne Europe. Nova mehanizacija šumarstva, 30(1): 37–46.
Tuomi, K., Ilmarinen, J., Jahkola, A., Katajarinne, L., Tulkki,
A., 1998: Work Ability Indeks. Finnish Institute of Occupational Health, Helsinki 1998, 1–22. (Source: http://www.
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Walker, M., Tobisch, R., Weise, G., 2005: The Machine Operator Current Opinions and the Future Demands on Technical Ergonomics in Forest Machines. Institutionen för skogens
produkter och marknader, Sveriges lantbruksuniversitet
(SLU), 1–73.
Sažetak
Indeks radne spremnosti rukovateljâ šumarskom mehanizacijom i neki ergonomski aspekti njihova rada
U radu se analiziraju neki ergonomski aspekti radnoga okoliša te se numerički vrednuje radna spremnost rukovateljâ šumarskom mehanizacijom kao prvi korak u ocjeni trenutačnoga stanja. Pritom je metodom anketiranja tijekom
2012. godine istražen i analiziran a) indeks radne spremnosti (eng. Work Ability Index) (tablica 1) te b) ergonomski
aspekt radnoga mjesta rukovateljâ šumarskom mehanizacijom za državni (Hrvatske šume d.o.o.) i privatni šumarski
sektor.
Croat. j. for. eng. 34(2013)2
253
M. Landekić et al.
Work Ability Index of Forestry Machine Operators and some Ergonomic Aspects... (241–254)
Prvi dio rezultata obuhvaća a) profil ispitanika (tablica 2), b) organizaciju rada rukovateljâ mehanizacijom i
njihovo obrazovanje (tablica 3 i 4), c) utjecaj umora (slika 3) i d) utjecaj psiholoških i socijalnih čimbenika na radnu
sposobnost rukovateljâ (slika 4). Na temelju nalaza istraživanja prikazanih u radu potvrdilo se da se u šumarskom
sektoru Republike Hrvatske, kako u državnom tako i u privatnom, vrlo malo sredstava, znanja i truda ulaže u osposobljavanje, sigurnost i zdravlje radnika. Prevladavaju nekvalificirani radnici (tablica 3) koji upravljaju vrlo skupim
strojevima bez osnovnoga strukovnoga i specijalističkoga obrazovanja. Razlog je tomu nepostojanje zakonskih instrumenata u smislu obvezne certifikacije znanja i vještina za rukovatelje šumarskom mehanizacijom u RH, a posljedično
i manjak organizacije pratećega sustava certifikacije. Također, rezultati istraživanja pokazuju da zaposlenici nisu
obrazovani kako izvoditi radove uza što manje fizičkoga i psihičkoga opterećenja (slika 3 i 4), te kako postići optimalnu dinamiku dnevnoga rada u pogledu održavanja tjelesne kondicije, koncentracije i dr. Radnicima koji upravljaju
šumarskim strojevima u većini slučajeva osigurana su propisana osobna zaštitna sredstva, ali većina ih se ne koristi
njima ili se koriste njima na neispravan način (tablica 4). Drugi dio rezultata vezan uz numeričko vrednovanje radne
spremnosti rukovateljâ obuhvaća a) odnos radne spremnosti rukovateljâ prema demografskim kategorijama ispitanika (tablica 7 i 8) i b) pregled razlika između indeksa radne spremnosti prema odabranim opisnim varijablama (slika
5, 6, 7 i 8). Ključni parametri ispitanika (godine života, radno iskustvo u šumarstvu, masa ispitanika) negativno
utječu na radnu i funkcionalnu spremnost (IRS) rukovateljâ šumarskom mehanizacijom (tablica 8). Rukovatelji
mehanizacijom zaposleni u privatnom sektoru s više od 46 godina života imaju zamjetno niži IRS u usporedbi s
rukovateljima zaposlenim u HŠ d.o.o. (slika 5 i 6). Također, unutar grupa prema radnomu iskustvu vidljivo je smanjenje vrijednosti IRS (srednje bodovano) te su potrebne mjere za unapređenje postojećega stanja (slika 7 i 8).
Zaključno, na temelju rezultata dani su prijedlozi za unapređenje istraživanih čimbenika radne spremnosti rukovateljâ šumarskom mehanizacijom. Kao nužna mjera poboljšanja potreban je cjelovit i kvalitetan postupak osposobljavanja kojim će se rukovatelji šumarskom mehanizacijom upoznati s opasnostima i štetnostima u procesu privlačenja
drveta, s vrstama i razinom opterećenja pri radu te osposobiti za rad uporabom sigurnoga načina rada i optimalne
radne tehnike. Samo korektni radni postupci povezani sa zadovoljavajućom razinom radne sposobnosti mogu preduhitriti nastanak tjelesnih ozljeda i zdravstvenih tegoba rukovateljâ. U nastojanju da se riješe slabosti državnoga sustava
obuke radnika, hrvatsko se šumarstvo treba ugledati na primjere dobre prakse iz zemalja u europskom okruženju, a
prema modelu Martinića i suradnika (2011) sa središnjom ulogom nacionalnoga centra za šumarstvo rada koji bi po
svom osnutku trebao biti središte sustava za provedbu procesa certificiranja rukovatelja mehanizacijom u šumarstvu
Ključne riječi: šumarstvo, rukovatelji mehanizacijom, indeks radne spremnosti, radni okoliš
Authors’ address – Adresa autora:
Received (Primljeno): March 13, 2013
Accepted (Prihvaćeno): September 11, 2013
254
Matija Landekić, MSc.
e-mail: [email protected]
Prof. Ivan Martinić, PhD.
e-mail: [email protected]
Matija Bakarić, MSc.
e-mail: [email protected]
Asst. Prof. Mario Šporčić, PhD.*
e-mail: [email protected]
Forestry Faculty of Zagreb University
Department of Forest Engineering
Svetošimunska 25
HR – 10 000 Zagreb
CROATIA
*Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Original scientific paper – Izvorni znanstveni rad
Time Consumption of Skidding
in Mature Stands Performed by Winches
Powered by Farm Tractor
Janusz M. Sowa, Grzegorz Szewczyk
Abstract – Nacrtak
The aim of the present research was to determine the characteristics of time consumption in
skidding by winch. The research was conducted in pine, fir, spruce and beech mature stands. It
covered the operation of skidding from the stand to the skid trail at the distance of up to 50 m. A
time study was performed for skidding operations, timber volume and thinning intensity. The
average time consumption of skidding in the operational time, assessed in the examined mature
stands, amounted to approximately 18 min/m3. Significant differences were observed in frequency levels between early thinnings (24 min/m3) and late ones (13 min/m3). The operational
time structure for skidding by winch was characterized by a large share of auxiliary time: 71%.
Out of that time, 30% was used for attaching and detaching the load and 36% for the transfer.
Approximation was also done of the multiple regression equations. The equations described
changes in skidding time consumption, i.e. the Empirical Efficiency Index (EST). The changes
depended on environmental factors (stand, cutting category), elements of the working day structure (the share of a given time category in a shift) and task intensity (ratio of the number of
harvested trees per area unit). The strongest correlations between the EST and the analyzed
variables were observed for the factors related to the percentage of time required for attaching and
detaching the load and factors related to operation intensity.
Keywords: work consumption, timber harvesting technologies, skidding, forest utilization
1. Introduction – Uvod
In the mid-1990s in Poland, the market economy
led to the privatization of almost 100% of the felling
work (Więsik 2000). This economy has entirely
changed the idea of timber harvesting. In Poland,
small, one- or two-person forest enterprises with insufficient capital prevail. Certification of forest enterprises has been conducted in recent years with the support
of the State Forests’ administration (Kapral 2000). One
of the crucial aspects of assessment is the method of
performing forest operations in accordance with the
applicable regulations and standards. For many reasons, it is very important to know the appropriate time
standards for performing a specific operation. This is
often underestimated although it is useful for both
foresters and forest enterprise owners. It allows for
proper arrangement of tender procedures and for rational planning of operations that are to be carried out.
Croat. j. for. eng. 34(2013)2
The amended Catalogues of Forest Work Time
Standards, which have been in force in the State Forests units since 2003, are also useful for forest entrepreneurs. The tabular data in these standards present
the average working conditions in the field. The data
characterize the tasks connected with specific technological systems and timber harvesting technologies.
Most studies treat modeling of time consumption
(productivity) in specific forest operations or in whole
harvesting technologies as a relation between the volume of the harvested timber and a selected category
of effective working time. This increases the precision
of inference. On the other hand, it does not allow for
assessing the joint effect of all factors on a given variable. The real picture of the phenomenon can be
shown by the multi-criterion consideration of the analyzed relations.
255
J. M. Sowa and G. Szewczyk
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
The objective assessment of a given technology is
connected with measuring the time of the examined
operations. Full examination of the time needed to obtain a product (effective time, operational time, shift
time) allows for complete assessment of the operations. The present research assumes that the operational time will provide a sufficient generalization. In
each case, it is crucial to find the categories of time
which significantly affect time consumption in a shift.
This is the way to indicate the operations, which
should be focused on, at the stage of shift optimization. The above-mentioned interdependence of specific categories of time should be reflected in their
percentages, because they show specific features of a
given technology and a given stand.
The introduction of work time standards has always attracted much interest (Cserjes 1989, Lukačka
1989, Döhrer 1998, Grzegorz 2003, Derek 2004, Kusiak
2006). Standardization has often been understood only
as an element of control. However, it is also a tool used
to plan properly the performance of economic tasks.
For this reason, the use of time consumption catalogues by the State Forests encourages critical assessment of their standards.
The present research on skidding with the use of
cable winches powered by farm tractors, commonly
used in Polish forestry, shows the current technical
capabilities of timber harvesting as performed by
small forest enterprises with insufficient capital. The
farm tractor is the most common equipment used for
work in agriculture (in the broad sense of the term),
and therefore also in forestry (Gil 2007). In Poland,
about 65% of skidding operations are performed with
the use of tractors.
2. Research aim and scope – Cilj
istraživanja
3. Methods – Metode istraživanja
Due to the changing technical capacities of timber
harvesting and considering the necessity to update the
quantification of the multi-criteria influence of the selected factors on the level of time consumption, an attempt was made to provide a preliminary assessment
of this phenomenon. Constructing a time consumption model for different timber harvesting technologies would allow for making realistic time standards
for performing individual operations and for undertaking research on such standardization that would be
useful for both the State Forests as the employer and
for forest enterprises as contractors.
The aim of the present study was to determine the
characteristics of time consumption of skidding by
Fransgård winch powered by a farm tractor (referred
to as WINCH below). The modeling consisted in approximating the mathematical functions described by
the following relation (1):
ESTwinch = f(stand structure, task intensity,
elements of working day structure)
where:
ESTwinch – the synthetic index of Empirical Technological Efficiency at the work stand: WINCH
256
(1)
The present research was conducted in pine, beech,
fir and spruce stands. The scope of the operations, limited to the stands of early and late thinning, made it
possible to optimize the time consumption model in a
group of stands that had the highest share of area and
volume. In such stands the performance of timber harvesting operations is particularly difficult, especially
concerning the part of skidding operations from the
stem to the skid trail. This is affected by the spatial
structure of such stands as well as by the volume and
dimensions of logs. In the stands of middle age classes,
the largest problems occur with the determination of
the appropriate levels of time standards, used in job
tenders by the State Forests.
The research plots of the present research were
situated within the Regional Directorate of the State
Forests in Cracow, the Regional Directorate of the State
Forests in Katowice and the Forest Experimental Station in Krynica (Tab. 1).
In the areas chosen for their full density and uniformity of forest taxation features (breast-height diameter, height) and for their species composition, experimental plots of 0.5 ha and dimensions 50 × 100 m each
were set up so that the longer side of each plot was
adjacent to the skid trail. On each plot, at 32 circular
plots of 50 m2 each, complete stock-taking was done
of all trees thicker than 7 cm.
The equipment used in the present research was
Fransgård V6000GS winch powered by a Pronar 5112
farm tractor. The timber was harvested in the tree
length system (TLS) (Laurow 2000). Cable skidding
was performed in the direction towards the skid trail
at the maximum distance of 50 m. No additional
equipment, such as skidding tongs or skidding sledge,
was used to facilitate skidding and each item was attached to the collective rope by means of standard attachment ropes with slide locks. One collective rope
was used for the skidding of maximum 6 logs. The
winch operator performed the skidding from the skid
Croat. j. for. eng. 34(2013)2
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
J. M. Sowa and G. Szewczyk
152a
6.49
245c
9.19
250d
1.74
Bor
Mountain forest
Fir
Planinska šuma
Jela
Mountain forest
Fir
Planinska šuma
Jela
Mountain forest
Fir
Planinska šuma
Jela
Mountain forest
Fir
Planinska šuma
Jela
Mixed mountain forest
Beech
Mješovita planinska šuma
Bukva
Mountain forest
Beech
Planinska šuma
Bukva
Mixed mountain forest
Spruce
Mješovita planinska šuma
Smreka
Mixed mountain forest
Spruce
Mješovita planinska šuma
Smreka
trail. The basic technical data of Fransgård V6000GS
winch powered by a Pronar 5112 farm tractor are presented in Table 2.
A constant time study of the operations was conducted with the working day method during skidding
(Monkielewicz and Czereyski 1971, Sajkiewicz 1981).
Time was measured with the use of PSION Workabout
Croat. j. for. eng. 34(2013)2
0.9
45
0.7
47
1.0
47
1.1
Crown density
Sklop
6.37
Mješovita šuma četinjača
Stocking of stand
Obrast
333b
Pine
Age , yr
Dob, god.
8.07
Species
Glavna vrtsa drveća
300c
Forest site type
Vrsta šume
5.62
Moist mixed coniferous forest
25
Full crown closure
Gust sklop sastojine
Moderate crown closure
Umjereno gust sklop sastojine
Full crown closure
Gust sklop sastojine
Moderate crown closure
Umjereno gust sklop sastojine
Broken crown closure
97
Nepotpuno sklopljena sastojina
97
0.6
47
1.1
70
1.1
25
1.0
60
1.2
Broken crown closure
Nepotpuno sklopljena sastojina
Moderate crown closure
Umjereno gust sklop sastojine
Moderate crown closure
Umjereno gust sklop sastojine
Full crown closure
Gust sklop sastojine
Moderate crown closure
Umjereno gust sklop sastojine
Large timber, m3/ha
Zrela stabla, m3/ha
Kasne
316g
Bor
Stand quality – Bonitet
Late
26.01
Mješovita šuma
Height, m
Srednja visina stabla, m
Nowy Targ
Early
Rane
45b
Fresh Mixed broadleaved forest Pine
DGB, cm
Srednji prsni promjer, cm
Kasne
Forest area, ha
Površina šume, ha
Late
Compartment
Odjel/odsjek
Rane
Forest district
Gospodarska jedinicat
Sucha
LZD
Early
Wał Ruda
Late
Kasne
Wał Ruda
Kasne
30.46
Dominikowice Dominikowice
Gorlice
Late
48a
Małastów
Early
Rane
4.96
Małastów
Early
Rane
58d
Juszczyn
Kasne
5.19
Tylicz
Late
68d
Stańcowa
Thinning
Prorede
Early
Rane
Stańcowa
Dąbrowa Tarno-wska
Forest Inspectorate
Šumski predjel
Table 1 Characteristics of stands on sample plots
Tablica 1. Sastojinske značajke na pokusnim plohama
13
12
Ia
140
22
20
Ia
200
18
17
I
202
18
17
I
73
45
21
III
146
36
24
III
239
15
19
I
182
30
26
I
444
7
8
I.5
10
24
23
I
503
computer with specialist »Timing« software for conducting time studies (Sowa et al 2007). The registered
duration of specific operations was assigned to given
categories according to BN-76/9195-01 in the National
Forest Equipment System (Botwin 1993). The outline
of the classification of the operational work time and
the adopted symbols are presented in Table 3.
257
J. M. Sowa and G. Szewczyk
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
Table 2 Technical data of Fransgard V6000GS winch powered by
a Pronar 5112 farm tractor
Tablica 2. Značajke vitla Fransgard V6000GS i ATP-a Pronar 5112
Fransgard V6000GS
1.
2.
3.
4.
5.
6.
7.
8.
9.
Height / width, mm
860/1700
Visina / širina, mm
Weight, kg
550
Težina, kg
Pulling force, kN
60
Vučna sila, kN
Power consumption, kW
37–67
Potrebna snaga, kW
Rope diameter, mm
11
Promjer užeta, mm
Rope length, m
50–120
Duljina užeta, m
Winding speed (at 540 min-1), m/s
Brzina užeta (pri 540 okretaja/min), m/s
Height (without safety shield), mm
Visina (bez zaštitnoga okvira), mm
Total height, mm
Tc =
0.5–1.3
1660
2400
Ukupna visina, mm
Pronar 5112
10.
11.
12.
13.
Dimensions: length / width / height, mm
Dimezije: duljina / širina / visina, mm
Front/rear wheel track
4130/1960/2560
1570-1730/15001800
Prednji/stražnji kotači
Weight, kg
4040
Težina vozila, kg
Diesel 60 kW/2300
min-1
Engine type – Vrsta motora
Where:
I
– number of trees before felling on circular plots,
L
– number of trees removed from circular plots,
Wiip – index of quantitative harvesting intensity,
Wmip – index of harvesting intensity in terms of volume
(Wmip = timber volume removed from circular
plots / timber volume before felling on circular
plots *100 %).
The Wsip index, expressed in this way, reflects spatial distribution of the harvested volume on a timber
handling site. For specific stands, the Wszt index, which
described the number of trees removed from 1 ha, was
determined.
In order to obtain more stable results, time consumption was calculated by relating the obtained timber volume to the operational time T02 (4) (Giefing and
Gackowski 2001).
T02
M
(4)
Where:
Tc – time consumption,
T02 – operational time,
M – timber volume.
In order to achieve accordance of the time consumption, calculated for specific sections, with the
normal distribution as well as due to the lack of uniformity of variance, analysis of differences of the mean
values of time consumption was conducted using the
parametric t-Student test. Examination of the dependence of the time consumption observed at work
stands on stand characteristics, felling intensity indexes, timber characteristics and factors of the working day structure was conducted using multiple regression procedures. The significance of null
hypotheses H0 was determined for the level of significance α = 0.05. Statistical calculations were done using
STATISTICA 6 PL program.
4. Results – Rezultati
On completion of the field work, the volume of the
obtained timber was calculated, stock-taking was performed of the trees remaining on the circular plots and
the intensity of planned thinning was determined (2),
(3).
Wiip =
I
× 100
L
Wsip =
258
Wiip
Wmip
(2)
(3)
The research was carried out in 24 plots, 3 in each
selected stand for each thinning category. Felling intensity was determined at 768 measurement points (circular research plots), where stock-taking of 4,360 trees was
performed. The harvesting resulted in the removal from
the circular plots of 620 trees, which constituted about
14% of their number and 145 m3, i.e. over 9% of the
volume of trees recorded before the operation.
Table 4 presents the mean values of the index of the
total harvesting intensity Wsip, calculated for the analyzed conditions.
Croat. j. for. eng. 34(2013)2
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
J. M. Sowa and G. Szewczyk
Table 3 Work time classification
Tablica 3. Turnus rada
T02 – Operativno vrijeme rada
T02 – Operatio-nal work time
T1
Effective worktime
Efektivno radno vrijeme
T21
T2
Auxiliary time
Pomoćna vremena rada
Time of skidding
T13
Vrijeme privlačenja drva
Time of waiting for help in task execution or for the end of other activities
Vrijeme čekanja (za pomoć pri radnoj operaciji ili da završi neka druga radna operacija)
T22
T23
T24
Time of walking in workplace
Vrijeme kretanja radnika po radilištu
Time of load attachment and detachment
Vrijeme vezanja i odvezivanja drva
Time of unlocking skidded timber
Vrijeme oslobađanja zapelih tovara
Table 4 Indexes of quantitative harvesting intensity Wiip and the
total harvesting intensity Wsip in the analyzed stands
Tablica 4. Udio broja (Wiip) i volumena (Wsip) posječenih stabala na
primjernim plohama
Fig. 1 The structure of operational work time for skidding performed
with the farm tractor
Slika 1. Udjeli vremena tijekom radnoga turnusa
The Wiip index reached higher values in the early
thinning stands. Its level ranged from 9.7 to 16. In all
cases, the percentage of the number of removed trees
was always higher than the volume removed. The
analyzed index reached the highest values in early
thinning in beech and pine stands. The highest value
Wsip, i.e. 2.09, was observed in spruce stands in late
thinning whereas the lowest one, amounting to 0.79,
was observed for the late thinning in beech stands. The
mean Wsip values were by almost 20% higher in early
thinning stands. The highest values were observed in
Croat. j. for. eng. 34(2013)2
Stand – Sastojina i vrsta prorede
Wiip
Wsip
Beech, late thinning – Bukva, kasne prorede
8.45
0.79
Fir, late thinning – Jela, kasne prorede
8.86
1.25
Pine, late thinning – Bor, kasne prorede
10.12
1.18
Spruce, late thinning – Smreka, kasne prorede
8.06
2.09
Beech, early thinning – Bukva, rane prorede
16.00
1.33
Fir, early thinning – Jela, rane prorede
10.66
1.43
Pine, early thinning – Bor, rane prorede
13.70
1.29
Spruce, early thinning – Smreka, rane prorede
9.70
1.86
Early thinning – Rane prorede
11.74
1.50
Late thinning – Kasne prorede
9.09
1.30
Total – Ukupno
10.77
1.47
spruce stands (Wsip = 2.09 in late thinnings and
Wsip = 1.86 in early thinnings), where in both categories
the Wsip was much higher than in the other cases. The
Wsip index, when calculated individually for each research plot, was then included in the equations of regression describing the time consumption of timber
harvesting (EST).
During harvesting and skidding operations, a time
study was conducted for the operations performed
during work on the research plots. The measurement
base of the duration of the distinguished operation
259
J. M. Sowa and G. Szewczyk
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
Fig. 2 Time consumption calculated for the analyzed work-stand
Slika 2. Operativno vrijeme rada
categories included 7,034 cases whose total time exceeded 70 hours. Part of the measured shift time (the
time category) was included in the equations describing the time consumption of timber harvesting (EST).
The coefficient of the use of the operational shift time
was on the level of approximately 0.75, which points
to considerable reliability of the equipment used and
to good work organization. Fig. 1 presents the percentages of operations observed in the operational time at
the examined work-stand.
The examined skidding operations were characterized by a very high (36%) share of the time of walking
in the workplace (T22). When walking, the winch operator extended the collective rope and fastened a few
skidded logs with attachment ropes (between 4 and 6
at a time), which imposed long walking times. The
skidding operation itself was not time-consuming (T13
amounted to 20%) but the auxiliary operations of attaching and detaching logs increased the time consumption considerably (30%). Fig. 2 presents the time
consumption calculated for the analyzed work-stand.
The results of the differentiation analysis of the mean
time consumption values in subsequent sections are
presented in Table 5.
260
Skidding operations were performed with the
mean time consumption of 18.45 min/m3, which was
a value close to the time consumption observed in the
skidding technology where winches were powered
by chainsaw (Szewczyk 2009). The mean time consumption of skidding was low. Under such conditions, low timber volume was achieved in the early
thinning. Statistically significant differences were observed between the levels of time consumption in the
early-thinning stands (24.59 min/m3) and the latethinning stands (13.10 min/m3). The lowest time consumption was observed in late-thinning pine stands
(9.85 min/m3) and the highest in early-thinning beech
stands (31.31 min/m3).
The level of time consumption is one of the factors
that allows for determination of usefulness of a given
technology to perform specific forest management
tasks. For this reason, the term time consumption will
be replaced below by another, proposed by the present
authors, namely EST – the synthetic index of Empirical
Technological Efficiency (Szewczyk 2010). In this case,
the EST coefficient is the time consumption assessed
on the basis of stand parameters, skidded timber,
working day structure. The parameters of the equaCroat. j. for. eng. 34(2013)2
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
J. M. Sowa and G. Szewczyk
Table 5 Significance of differences between the mean time consumption values in the operational time for skidding with the use of the farm
tractor in stands with late (right up) and early (left down) thinning
Tablica 5. Razlike u srednjim vremenima privlačenja drva u ranim i kasnim proredama (SD – značajna razlika, ID – beznačajna razlika)
Species – Vrsta drveća
Pine – Bor
Beech – Bukva
Fir – Jela
Spruce – Smreka
X
ID; p = 0.07
ID; p = 0.12
ID; p = 0.07
Beech – Bukva
SD*; p = 0.02
X
ID; p = 0.70
ID; p = 0.15
Fir – Jela
SD; p = 0.04
ID; p = 0.10
X
ID; p = 0.06
Spruce – Smreka
ID; p = 0.16
ID; p = 0.78
ID; p = 0.31
X
Pine – Bor
tions (Tab. 6) allowing for the approximation of the
EST level were estimated for factors related to the features of the stand, skidded timber and elements of the
working day structure. Table 6 also presents the values: R, R2, Std error, test values and the probability
level p.
In the applied model, most variables were stable
(terrain features) while others, related to the stand (intensity indexes Wsip, Wszt) and to the working day structure (percentages of times T13, T22), were taken into consideration. Selection of a set of independent variables in
equations approximating the work consumption level
was based on the assumption that it should be jointly
influenced by factors related to: stand structure (stand,
cutting category - early or late thinning), elements of the
working day structure (the share of specific time categories in a shift) and volume of harvested timber. Therefore, developing the equations generally consisted in
removing those factors that did not significantly affect
the estimated time consumption from the widest possible range of independent variables. It was always
done so as to make all groups of variables visible in the
equations. To sum up, the method applied was multiple
backward stepwise regression.
Table 6 Parameters of the regression equations of the EST index
Tablica 6. Regresijska analiza indeksa EST
Nr.
Br.
1
2
3
Equation – accuracy of adjustment
Independent variables
Parametri regresije
Nezavisne varijable
EST
R
Early thinning
Rane prorede
Late thinning
Kasne prorede
Total
Ukupno
0.66
0.78
R2pop
0.41
0.59
F
p
21.98 0.00
29.35 0.00
Error ±
Pogreška ±
14.36
3.93
Variable – Varijable
B
Beta
b
Error std.
Constant
50.34
–
T22, %
-129.1
Wszt
t
p
6.61
7.61
0.00
-0.64
20.30
-6.36
0.00
0.04
0.25
0.02
2.55
0.01
Constant
11.84
–
2.09
5.65
0.00
T13, %
27.43
0.30
7.72
3.55
0.00
T22, %
-27.27
-0.47
4.98
-5.48
0.00
Wsip
2.39
0.41
0.51
4.71
0.00
Constant
30.85
–
3.36
9.18
0.00
6.62
0.22
2.84
2.33
0.02
T22, %
-75.43
-0.49
10.90
-6.91
0.00
Wszt
0.03
0.26
0.01
2.71
0.01
0 = Late thinning – Kasne prorede
0.64
0.39
Croat. j. for. eng. 34(2013)2
26.69 0.00
11.73
1 = Early thinning – Rane prorede
Pogreška
261
J. M. Sowa and G. Szewczyk
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
Predicting the level of time consumption on the
basis of the volume of a single piece of timber, the
number of pieces skidded in a single cycle and e.g. the
skidding distance obviously yield fairly precise results
under specific stand conditions. However, such an approach does not consider the spatial distribution of the
volume of skidded timber on a plot or the method of
work in a shift. Such factors are included in the model
proposed in the present study.
The strongest correlations between the EST level at
the work-stand of the WINCH OPERATOR in mature
stands were found for the following variables: walking
time T22 (β = -0.49) and Wszt (β = 0.26). The estimated
time consumption in early-thinning stands should be
by about 6 min/m3 higher in comparison with latethinning stands. An increased share of walking time
T22 in a shift results in a decrease in time consumption
(parameter -75.43), which at first sight seems incorrect
as the T22 time is the auxiliary time rather than the effective time. However, it must be noted that at the
analyzed work-stand this time is connected with walking in order to attach to the rope several logs, which
are then skidded together as a bunch. Thus its higher
share results in higher volume of one load of skidded
timber, which lowers the level of time consumption.
This phenomenon was better visible in the case of assessing the EST in early-thinning stands (βT22 = -0,64),
which is understandable considering lower volume of
a single log. This would point to the need to carry out
skidding of whole bunches of logs on a rope in stands
of younger age classes.
The analyzed spatial relation (multiple independent variables) is presented in this study as a polynomial relation of the first degree of multiple variables.
For the purpose of assessing the time consumption for
forestry operations, the linear regression model is the
most frequently used by researchers (Häberle 1990,
Samset 1990, Lukáč et al. 2000, Bibliuk 2004, Messingerová 2005, Sowa et al. 2009, Sowa and Szewczyk 2008,
Szewczyk 2010). The total time consumption of timber
harvesting technologies, taking into consideration the
various operations involved, may be assessed by totaling appropriate multiple regression equations calculated for specific operations (Zečić and Marenče 2005).
This may be the method of predicting the level of time
consumption for different technological variants (logical from the point of view of work organization).
In the present study, the EST index was expressed
as several linear functions of multiple variables. There
are always two groups of variables, which generally
characterize a stand and the character of stand management operations (the first group), as well as the
percentages of the selected elements of the working
262
day structure in the operational time, describing the
basic characteristics of timber harvesting technologies
(the second group). Their changes are due to differentiation of stand features and, since the examined times
are generally the skidding times, they complement the
variables included in the first group. Such a comprehensive approach is an innovative solution, proposed
by the present authors.
5. Conclusions – Zaključci
The average time consumption of skidding by
means of the cable winch powered by a farm tractor
in the operational time, assessed in the examined mature stands, amounted to approximately 18 min/m3.
Significant differences were observed in the levels of
time consumption between early thinning (about
24 min/m3) and late thinning (13 min/m3). Differences
in measurements of time consumption between early
and late thinnings could have resulted from different
volumes of single timber pieces and from different
distances between trees that remained in the stand.
The structure of the operational time of skidding
by means of the cable winch in mature stands was
characterized by a large share of auxiliary times T2:
80%, of which the walking time T22 accounted for as
much as 36% while load attaching and detaching T23
accounted for 30% of the time.
An equation of multiple regression was elaborated
for the purpose of describing the changes in the level
of time consumption of skidding, namely the Empirical
Technological Efficiency index (EST). The EST depends
on environmental factors (stand, felling category), elements of the working day structure (the share of an
appropriate time category in a shift), characteristics of
the harvested timber (volume) and operation intensity
(the Wiip indexes of quantitative harvesting intensity
and the Wsip index of total harvesting intensity). The
strongest correlations between the EST and the analyzed variables were established for the factors connected with the percentage of walking time T22, which
is related to the binding of a larger number of timber
pieces, skidded in a single cycle.
High time consumption of the examined skidding
technology and a large share of the time of waiting for
help indicate difficult work conditions in stands of
middle age classes, where the skidded logs are frequently blocked and problems occur in connection
with controlling the skidding from the skid trail.
The measurements of thinning intensity, used for
the approximation of the EST, may be determined
prior to forest management operations based on the
Croat. j. for. eng. 34(2013)2
Time Consumption of Skidding in Mature Stands Performed ... (255–264)
data from the Forest Management Regulations and
Standing Timber Assessment. It allows for the rational
design of the most effective technological solutions.
This makes it possible to apply the results directly in
given field conditions of timber harvesting.
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Time Consumption of Skidding in Mature Stands Performed ... (255–264)
Sažetak
Utrošci vremena prilikom privlačenja drva ATP-om u proredama
zrelih sastojina
Ovim se istraživanjem raščlanio utrošak vremena prilikom privlačenja drva adaptiranim poljoprivrednim traktorom Pronar 5112 s ugrađenim vitlom Fransgård V6000GS u ranim i kasnim proredama. Značajke vozila i
pripadajućega vitla prikazane su u tablici 2. Istraživanje je provedeno u državnim šumama grada Krakówa, Katowica i pokusnih šumskih sastojina u Krynici u zrelim borovim, jelovim, smrekovim i bukovim sastojinama (značajke
sastojina prikazane su u tablici 1). Sastojine su odabrane zbog zadovoljavajuće gustoće sklopa i dimenzija stabala.
Postavljene su pokusne plohe veličine 50 × 100 m (0,5 ha površine) tako da je dulja stranica pokusne plohe bila prislonjena uz traktorsku vlaku. Na svakoj plohi postavljene su 32 plohice, površine 50 m2 svaka, na kojima su izmjerena
sva stabla deblja od 7 cm prsnoga promjera. Korištena je stablovna metoda izradbe drva, a duljina skupljanja drva
vitlom bila je do najviše 50 m. Proveden je studij rada i vremena pri privlačenju drva te je prosječno (operativno)
vrijeme iznosilo 18,85 min/m3. Vrijeme radnih operacija mjerilo se pomoću računala PSION Workabout i programskoga paketa »Timing«. Turnus rada prikazan je kroz efektivno vrijeme rada (privlačenje drva) i pomoćna vremena
(vrijeme čekanja, kretanje radnika po radilištu, vezanje tovara i odvezivanje privučenoga drva), što je i prikazano u
tablici 3. Uočene su značajne (signifikantne) razlike prilikom privlačenja drva u ranim (24,59 min/m3) i kasnim (13,10
min/m3) proredama (tablica 5). Udio je pomoćnih vremena najveći, čak 71 %, od čega 30 % pripada vezanju i
odvezivanju tovara, a 36 % kretanju radnika po radilištu (slika 1 prikazuje postotne udjele vremena radnih operacija). Udio ukupnoga vremena, ovisno o vrsti prorede (rane/kasne) i mjestu istraživanja, prikazan je na slici 2. Regresijska analiza izmjerenih vremena prikazuje utjecaj pojedinih čimbenika radilišta na proizvodnost, tzv. empirijski
indeks učinkovitosti, tj. EST. Razlike nastaju zbog sastojinskih prilika (tablica 1), sastavnica turnusa rada i količine
posječenoga drva Wiip i Wsip (intenziteti sječe prikazani su u tablici 4). Najjača združenost podataka primijećena je
između vremena potrebnoga za vezanje i odvezivanje tovara i intenziteta sječe u pojedinoj sastojini.
Ključne riječi: utrošak vremena, privlačenje drva, tehnologije pridobivanja drva, korištenje šuma
Authors’ address – Adresa autorâ:
Prof. Janusz M., Sowa, PhD.
e-mail: [email protected]
Grzegorz Szewczyk, PhD.*
e-mail: [email protected]
Agricultural University of Cracow
Faculty of Forestry
Department of Forest and Wood Utilization
Al. 29 Listopada 46
31-425 Kraków
POLAND
Received (Primljeno): September 24, 2012
Accepted (Prihvaćeno): January 11, 2013
264
*Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Original scientific paper – Izvorni znanstveni rad
Long Term Repair and Maintenance Cost
of some Professional Chainsaws
Angela Calvo, Marco Manzone, Raffaele Spinelli
Abstract – Nacrtak
A sample of 44 professional chainsaws was used to determine service life and maintenance
cost for this type of equipment. Data were sourced from a large workshop, catering for regional forest crews in north western Italy. Chainsaw service life exceeded 3000 hours, and
spread over a period of 6 to 9 years. Under these conditions, maintenance cost averaged 820 €,
or about 120 % of the investment cost. Annual usage was highest and maintenance cost lowest for mid-size chainsaws, in the 2 to 3.5 kW power class. Models at the two extreme ends
(i.e. < 2 kW and >3.5 kW) configured as specialist tools, which resulted in a lower usage and
a higher maintenance cost per hour. The largest number of interventions (45% of the total)
concerned the engine and the carburettor. The average chainsaw in the sample underwent 31
maintenance interventions over its service life. The cost per intervention varied between 7 and
50 €. Intervention cost was highest for engine work, and the lowest for overhaul. Overall, parts
accounted for two-thirds of the cost, and labour for the remaining third. This study offers
information about chainsaw service life and maintenance cost, obtained with scientific methods and hence suitable for general use.
Keywords: logging, harvesting, biomass
1. Introduction – Uvod
Italian forestry is characterized by steep terrain,
ownership fragmentation and the application of closeto-nature management criteria, such as continuouscover forestry (Mason et al. 1999). All these factors tend
to slow down the inevitable introduction of mechanized harvesting (Febo et al. 1997), determining the current prevalence of labor-intensive operations (Magagnotti et al. 2012). Under these conditions, versatile
low-investment machinery offers a suitable balance between capital and labor inputs (Picchio et al. 2009). For
these reasons, chainsaws and modified farm tractors are
the backbone of the Italian forest machine fleet (Spinelli et al. 2013). In fact, motor-manual felling with
chainsaws is also used in the Nordic countries, where
it is favored by small-scale operators, especially when
dealing with biomass production (Laitila et al. 2007).
Many studies have addressed the productivity and
cost of low-investment operations, based on chainsaws and farm tractors (Spinelli and Magagnotti 2012).
However, most of these studies are relatively weak on
Croat. j. for. eng. 34(2013)2
costing. One of their main weaknesses is the adoption
of conventional assumptions, which may not reflect
current practice (Rozt 1987). The international scientific literature offers no updated information about the
annual use, service life and maintenance cost of these
machines. Year after year, authors use the same assumptions, originating from practical experience
gained several decades ago, when both chainsaws and
farm tractors were much different from the chainsaws
and farm tractors we use today (Ward et al. 1985).
When chainsaws are concerned, studies offer general cost estimates, often obtained from secondary
sources (Long et al. 2002, Mousavi et al. 2006). Most of
these estimates date back to the early ‘80s (Miyata
1980). In fact, chainsaws are no longer considered in
the updated versions of earlier machine rate compendia (Brinker et al. 2002). The only recent study offering
good detail about chainsaw cost concerns its use in
sawmilling – not in forestry practice – and therefore
represents a peculiar case (Smorfitt et al. 2006).
While the international scientific community is
working at improving cost methods for use at a glob-
265
A. Calvo et al.
Long Term Repair and Maintenance Cost of some Professional Chainsaws (265–272)
al scale, very few people are working at developing
reliable input assumptions. As a result, the lack of
quality inputs may thwart all attempts to enhance the
accuracy of machine cost estimates.
Therefore, the goal of this study was to provide
reliable information on the service life and maintenance cost of professional chainsaws used in forest
operations.
2. Materials and methods – Materijal
i metode
The study was conducted in cooperation with a
regional forest administration in north western Italy.
The regional administration maintains its own logging
crews, tasked with performing silvicultural operations
in public forests. Regional crews are specifically
trained for the task, and must attend several training
courses depending on the task. Before using a chainsaw, operators must attend chainsaw use and maintenance courses. Individual chainsaw operators are responsible for the good use and maintenance of the
machines they are assigned, and they are equipped
accordingly. Operators conduct all minor maintenance, and especially the daily and weekly routines.
Major maintenance after severe failure or fatigue is
performed by professional mechanics at a centralized
workshop. All maintenance interventions conducted
in this workshop are recorded in a logbook, together
with information about chainsaw type, model, serial
number, age and worked hours. Therefore, it is possible to reconstruct all maintenance interventions conducted over the whole service life of each chainsaw in
the regional fleet, as well as the duration of their service life.
For this study, we have collected and organized all
the information available in the workshop logbook. It
contained data about 44 chainsaws, as shown in Table
1. All chainsaws in the study were professional models, produced by the two largest chainsaw manufacturers, and namely: Husqvarna (25 units) and Stihl (19
units). The data represented light, medium and heavy
chainsaws. However, the data pool was not balanced
in terms of machine size and make, which prevented
proper comparisons between types and makes. The
characteristics of the machines in the regional fleet reflected those of local forests and silviculture, which
justified a strong bias in favor of medium-size chainsaws. Furthermore, the uneven distribution of age
classes between makes depended on the variable success of the two chainsaw makes with public bids.
For the purpose of this study, maintenance interventions have been categorized into eight main classes, corresponding to the main constructive elements
of a chainsaw and/or intervention type. The following
categories were separated: general overhaul; engine
repairs; crankcase repairs; carburettor issues; starter;
electric system; chain and chain bar; safety devices.
Intervention cost was calculated by summing the
costs of labor and spare parts. The former was estimated to 24 € per hour, taxes and benefits included.
The latter was the actual cost indicated in the repair
bills, after discounting to present value.
Statistical analysis of data was conducted with the
Tukey-Duncan test at the 5% level, and with linear
regression (SAS 1999).
Table 1 Chainsaw characteristics in the study
Tablica 1. Karakteristike motornih pila uključenih u istraživanje
Displacement
Avg. use
Interventions
Power
Guide bar
Snaga
Vodilica
Prosječna
upotreba
cm3
kW
cm
Hours – Sati
n
Class
Make
Model
Machines
Razred
Proizvođač
Model
Uređaji
Obujam
cilindra
n
Zahvati
Heavy – Teške
Stihl
MS660
8
91.6
5.2
50
2 850
315
Medium – Srednje
Stihl
MS440
7
70.7
4.0
45
3 600
190
Medium – Srednje
Husqvarna
272XP
7
72.2
3.6
45
3 400
441
Medium – Srednje
Husqvarna
262XP
7
62.0
3.4
45
4 200
130
Medium – Srednje
Husqvarna
266XP
7
67.0
3.2
45
4 700
196
Light – Lagane
Stihl
MS200
4
35.2
1.8
35
1 000
103
Light – Lagane
Husqvarna
335XPT
4
35.2
1.6
35
400
13
266
Croat. j. for. eng. 34(2013)2
Long Term Repair and Maintenance Cost of some Professional Chainsaws (265–272)
Fig. 1 Frequency of the number of interventions by intervention type
Slika 1. Učestalost broja intervencija prema vrsti zahvata
Overall, this study contains information about 1 388
maintenance interventions, corresponding to a total
expenditure of 36 970 €.
3. Results – Rezultati
The service life of the chainsaws in the data pool
ranged between 400 and over 4000 hours, with a
A. Calvo et al.
weighed average of 3 175 hours. Service life was significantly higher for medium-size chainsaws, than for
the other types. Light chainsaws were characterized
by a very low utilization, and especially the lightest
type (Husqvarna 335 XPT). That depended on the almost exclusive use for park maintenance, and on the
relatively young age of the machines in the study,
which had been bought two years earlier and were still
in service. Average machine age was 8 years, with
wide variations. Resulting average utilization was 400
hours per year.
The largest number of interventions (45% of the
total) was made on the engine and the carburettor, and
generally consisted of carburettor diaphragm replacements and piston-cylinder kit substitutions. In contrast, very few interventions concerned the starter (Fig.
1). The average chainsaw in our data pool underwent
31 maintenance interventions over an average service
life of 3 175 hours.
The cost per intervention varied between 7 and 50 €
(Fig. 2). It was highest for engine work, and lowest for
overhaul. As an average, the total cost per chainsaw
was 840 €, over the whole service life considered in this
study. The largest share of this cost was related to
engine, carburettor and chain/bar issues. Overall, parts
accounted for two-thirds of the cost, and labor for
the remaining third. Assuming that the average investment cost of the chainsaws in the study pool was 700 €,
Fig. 2 Average cost per intervention and machine, by intervention type
Slika 2. Prosječan trošak po intervenciji i uređaju prema vrsti zahvata
Croat. j. for. eng. 34(2013)2
267
A. Calvo et al.
Long Term Repair and Maintenance Cost of some Professional Chainsaws (265–272)
then cumulative repair and maintenance amounted to
120% of investment cost.
Conducted at the 5% level, the Tukey-Duncan test
allowed grouping machines in three categories, as a
function of the number of interventions per machine
(Fig. 3). Machines with a power exceeding 3.5 kW
were characterized by a significantly higher number
of interventions per machine. The number of interventions was lowest for chainsaws with a power below
2 kW. Machines with a power between 2 and 3.5 kW
were in between, requiring more maintenance than
smaller machines, but less maintenance than larger
ones. Overall, average maintenance time over the
whole machine life was 18 hours for machines with
power above 3.5 kW, 8 hours for machines with power between 2 and 3.5 kW, and 6 hours for machines
with power below 2 kW. Statistical analysis also
showed that the total number of interventions was independent from machine life: chainsaws in the intermediate power class (i.e. 2 kW > power > 3.5 kW) had
a longer service life than heavier chainsaws, but underwent fewer interventions.
Overall, chainsaw maintenance incurred a cost between 0.13 and 0.50 € per hour (Table 2). Again, statistical analysis showed that machines could be divided
into three groups. Chainsaws in the intermediate power class (i.e. > 2 and < 3.5 kW) incurred a significantly
lower maintenance cost than all the other chainsaws.
Chainsaws with a power below 2 kW or above 3.5 kW
incurred a maintenance cost of 0.36 € per hour, i.e.
more than twice as large as incurred in the intermediate power class (i.e. 14 € hour–1). In this respect, there
were no significant differences between chainsaws in
the two extreme power classes.
Table 2 Maintenance cost
Tablica 2. Troškovi održavanja
Power – Snaga
Cost – Troškovi
kW
€ hour–1
5.2
0.38
4.0
0.26
3.6
0.45
3.4
0.13
3.2
0.14
1.8
0.50
1.6
0.21
4. Discussion – Rasprava
Service life is much longer than indicated in previous studies, which quote between 1000 (Miyata 1980)
and 2000 hours (Piegai et al. 2010; Spinelli and Mag-
Fig. 3 Number of interventions by intervention type and chainsaw power class (P)
Slika 3. Broj intervencija prema vrsti zahvata i razredu snage motorne pile (P)
268
Croat. j. for. eng. 34(2013)2
Long Term Repair and Maintenance Cost of some Professional Chainsaws (265–272)
agnotti 2011). Annual use is much below the 1 000
hours quoted by Miyata (1980), but in line with the 500
hours reported by Piegai et al. (2010) and Spinelli and
Magagnotti (2011). The very long service life is probably related to the peculiar strategies of public agencies, which are often equipped with their own repair
workshops and tend to internalize repair costs. In that
case, maintaining the workshop is a fixed cost, and
reducing the cost of repairs by a more frequent machine turnover may not lead to any savings in terms
of overall management cost. Extended service life is
consonant with an accumulation of repair and maintenance cost, eventually exceeding the investment
cost. Even if extending service life for such a long time
may prove economically viable, one should check the
effect of machine aging on ergonomic performance,
especially for what concerns vibration and noise
(Martinić et al. 2011). Further studies should clarify if
proper maintenance can prevent the decay of ergonomic performance, despite use and age.
It is also worth noticing that the utilization of medium-size chainsaws is significantly higher than the
use of the extreme models. That is compatible with the
higher versatility of machines in the central class,
which are used more frequently. Both light and heavy
chainsaws configure as specialist tools, used for special jobs only.
Frequent use may partly explain the lower maintenance cost of chainsaws in the intermediate power
class: both the operators and the mechanics were very
familiar with these machines, which facilitated preventive maintenance, diagnostics and repairs. Furthermore, spares were more readily available, due to the
larger number of machines in use. Differences in maintenance cost between power classes may also be explained by their different use, and the resulting different solicitations. Heavy chainsaws were used mostly
for felling large trees, whereas small chainsaws were
used in arboriculture, especially for pruning and delimbing. Medium-size chainsaws were the most versatile, used for a variety of jobs, and especially felling
and processing. For this same reason, machines in the
different power classes would have different construction characteristics, with light chainsaws being generally less sturdy than heavy or medium-size models, in
view of their less intense use. This may have an effect
on machine reliability and duration. Part of the variability may also be explained by individual model
design: some models may have a better design than
others, leading to differences in maintenance frequency and cost.
As to hourly cost, the only available comparison is
the figure reported by Smorfitt et al. (2006), which
Croat. j. for. eng. 34(2013)2
A. Calvo et al.
amounts to 0.27 € hour–1, after discounting to 2013 values and converting Australian dollars to European
currency. That fits well into our 0.13 – 0.50 € hour–1
bracket, and offers a close match to the 0.36 € hour–1
specifically found for heavy chainsaw models, such as
those used in the Australian study. Despite their specific regional source, the hourly costs obtained from
this study may be suitable for general use, or at least
for representing a wider reality than actually probed.
By itemizing maintenance frequency and cost, our
study may point chainsaw manufacturers towards
specific problem areas, where technological development is especially urgent. At present, engine and carburettor maintenance are still the most frequent and
expensive. In their quest for lighter and more powerful
engines, chainsaw manufacturers should not forget
reliability, which is still a main issue. In contrast, the
maintenance of compulsory safety devices (throttle
safety catch, chain brake, etc.) incurs very little cost,
denying earlier complaints that the (then) new devices would represent an additional complication, and
the possible cause of further malfunctions.
Unfortunately, this study could not establish a clear
relationship between chainsaw age and maintenance
cost. Hourly maintenance cost is supposed to increase
with machine use, as a result of fatigue and general
decay. Estimating this relationship in numerical terms
would have helped decisions about the eventual decommissioning of older machines, for substitution
with new models. However, the workshop bills contained no indication of the hours worked at the time
of repair, and their dates were often unreliable. Consequently, it was impossible to associate maintenance
costs with the hours worked by each machine, as needed for developing a predictive model. Future studies
should address this subject, which is extremely important for operation managers.
Finally, readers must recall that our study concerns
major maintenance performed at a workshop, and not
daily maintenance conducted in the field. However,
field maintenance is generally minor, and consists of
sharpening, cleaning and small repairs. We can safely
assume that the largest component of field maintenance cost is labor, which is accounted for by including maintenance with delay time, as normally done in
field studies (Magagnotti and Spinelli 2012).
5. Conclusions – Zaključci
This study offers information about chainsaw service life and maintenance cost, obtained by scientific
methods and suitable for general use. Contrary to previous assumptions, the service life of professional
269
A. Calvo et al.
Long Term Repair and Maintenance Cost of some Professional Chainsaws (265–272)
chainsaws can exceed 3 000 hours and span over up to
8 years. During this period, a chainsaw will undergo
about 30 maintenance interventions, for a cost that is
1.2 times its purchase price. Engine and carburettor
maintenance accounts for the largest number of interventions and the highest share of total maintenance
cost. Versatile chainsaws in the intermediate (> 2 kW
and < 3.5 kW) power class are characterized by the
highest annual use and the lowest maintenance cost.
Mason, B., Kerr, G., Simpson, J., 1999: What is continuous
cover forestry? Forestry Commission Information Note 29.
Forestry Commission, Edinburgh. 8p.
6. References – Literatura
Picchio, R., Maesano, M., Savelli, S., Marchi, E., 2009: Productivity and energy balance in conversion of a Quercus
cerris L. coppice stand into high forest in central Italy. Croat
J For Eng 30: 15–26.
Brinker, R., Kinard, J., Rummer, B., Lanford, B., 2002: Machine rates for selected forest harvesting machines. Circular
296 (Revised). Alabama Agricultural Experiment Station,
Auburn University, AL. 32p.
Febo., P, Pipitone., F, Peri., G., 1997: The preservation of Sicilian forests with poorly mechanized logging processes. J Agr
Eng Res 67: 229–233.
Laitila, J., Asikainen, A., Nuutinen, Y., 2007: Forwarding of
whole trees after manual and mechanized felling bunching
in pre-commercial thinnings. Int J For Eng 18: 29–39.
Long, C., Wang, J., McNeel, J., Baumgras, J. (2002): Production and cost analysis of a feller-buncher in central Appalachian hardwood forest. Proceedings of the 25th COFE meeting, Auburn, Alabama. 5p.
Miyata, E. 1980: Determining fixed and operating cost of
logging equipment. General Technical Report NC-55. Forest
Service North Central Forest Experiment Station, St. Paul,
MN. 14p.
Mousavi, R., Nikouy, M., Uusitalo, J., 2011: Time consumption, productivity, and cost analysis of the motor manual tree
felling and processing in the Hyrcanian Forest in Iran. J Forestry Res 22: 665–669.
Piegai, F., Fratini, R., Pettenella, D., 2010: Costi macchina.
Confronto tra diversi metodi di calcolo. Supplemento scientifico degli approfondimenti di Sherwood – Foreste ed Alberi
Oggi, Compagnia delle Foreste, Arezzo, Italy. 30p.
Rozt, C., 1987: A standard model for repair costs of agricultural machinery. Appl Eng Agr 3: 3–9.
SAS Institute Inc, 1999: StatView Reference. SAS Publishing,
Cary, NC. ISBN-1-58025-162-5. p. 84–93.
Smorfitt, D., Harrison, S., Herbohn, J., 2006: Short-run and
long-run costs for milling rainforest cabinet wood timbers.
Australian For 69: 223–232.
Magagnotti, N., Spinelli, R., Güldner, O., Erler, J., 2012: Site
impact after motor-manual and mechanised thinning in
Mediterranean pine plantations. Biosys. Eng. 113: 140–147.
Spinelli, R., Magagnotti, N., 2011: The effects of introducing
modern technology on the financial, labour and energy performance of forest operations in the Italian Alps. For Pol
Econ 13: 520–524.
Magagnotti, N., Spinelli, R. (Ed.) 2012: COST Action FP0902
– Good practice guideline for biomass production studies.
CNR IVALSA. Florence, Italy. ISBN 978-88-901660-4-4. Available on line at: www.forestenergy.org. 41 p.
Spinelli, R., Magagnotti, N., 2012: Wood extraction with farm
tractor and sulky: estimating productivity, cost and energy
consumption. Small Scale For 11: 73–85.
Martinić, I., Landekić, M., Šporčić, M., Lovrić, M., 2011: Forestry at the EU’s doorstep – how much are we ready in the
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Spinelli, R., Magagnotti, N., Facchinetti, D., 2013: A survey
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and 4 WD tractors. Trans ASAE 28: 1074–1076.
Sažetak
Dugoročni troškovi popravaka i održavanja profesionalnih motornih pila
Šumarstvo u Italiji obilježavaju strmi tereni, usitnjeno vlasništvo i primjena kriterija u gospodarenju bliskih
prirodi. Svi ti čimbenici pomalo usporavaju neizbježno uvođenje mehaniziranoga pridobivanja drva i pridonose
trenutačnomu prevladavanju radno intenzivnih operacija. U takvim uvjetima raznovrsna relativno jeftina mehanizacija pruža odgovarajuću ravnotežu između kapitalnih ulaganja i radnih resursa. Zbog toga motorne pile i adaptirani poljoprivredni traktori čine okosnicu talijanske šumske mehanizacije. Motorno-ručno obaranje s motornim
pilama primjenjuje se također i u nordijskim zemljama, gdje je popularno kod malih izvoditelja šumskih radova, osobito u slučajevima vezanim uz proizvodnju biomase.
270
Croat. j. for. eng. 34(2013)2
Long Term Repair and Maintenance Cost of some Professional Chainsaws (265–272)
A. Calvo et al.
Mnoga su istraživanja razmatrala proizvodnost i troškove nisko investicijskih operacija na temelju motornih pila
i poljoprivrednih traktora. Ipak, većina je tih istraživanja relativno nepouzdana što se tiče troškova. Jedna od njihovih
glavnih slabosti je prihvaćanje konvencionalnih pretpostavki koje možda ne odražavaju sadašnju praksu. Međunarodna
znanstvena literatura ne nudi nove podatke o godišnjoj uporabi, uporabnom vijeku i troškovima održavanja ovih
strojeva. Iz godine u godinu autori se koriste istim pretpostavkama poteklim iz praktičnoga iskustva stečenoga prije
nekoliko desetljeća, kada su se i motorne pile i poljoprivredni traktori znatno razlikovali od motornih pila i traktora
koji se danas upotrebljavaju.
Kada se promatraju motorne pile, istraživanja daju opće procjene troškova, često dobivene iz sekundarnih izvora.
Većina tih procjena potječe iz ranih 80-ih. Ustvari, motorne pile više nisu uključene u ažuriranim verzijama ranijih
pregleda zastupljenosti strojeva. Jedina novija studija s detaljnim troškovima motornih pila odnosi se na primjenu u
pilanama, ali ne i u šumarstvu.
Dok međunarodna znanstvena zajednica radi na poboljšanim troškovnim metodama za primjenu na globalnoj
razini, vrlo je malo ljudi angažirano na razvoju pouzdanih ulaznih pretpostavki. Kao rezultat, nedostatak kvalitetnih
ulaza može omesti sva nastojanja da se unaprijedi točnost procjena o troškovima strojeva. Zbog toga je cilj ovoga
istraživanja bio pružiti vjerodostojnu informaciju o uporabnom vijeku i troškovima održavanja profesionalnih motornih pila u šumskim radovima.
Istraživanje prikazano u radu provedeno je u suradnji s regionalnom šumskom upravom u sjeverozapadnoj
Italiji. Regionalna šumska uprava servisira vlastite sjekačke ekipe, zadužene za obavljanje poslova u javnim šumama.
Regionalne su ekipe posebno uvježbane za radne zadaće i moraju pohađati nekoliko tečaja osposobljavanja ovisno o
vrsti zadaće. Prije korištenja motorne pile rukovatelji moraju polaziti tečaj o uporabi i održavanju motorne pile. Sami
su sjekači individualno odgovorni za pravilno korištenje i održavanje pila za koje su se zadužili, i za to su odgovarajuće opremljeni. Sjekači provode sve manje održavanje i osobito uobičajene dnevne i tjedne postupke.
Velike popravke i održavanje zbog ozbiljnih kvarova ili dotrajalosti obavljaju profesionalni mehaničari u središnjoj radionici. Svi se popravci i održavanje u toj radionici bilježe i evidentiraju u dnevniku, zajedno s podacima o tipu
motorne pile, modelu, serijskom broju, starosti i radnim satima. Stoga je moguće rekonstruirati sve zahvate na održavanju svake motorne pile u regiji te trajanje njihova uporabnoga vijeka.
Za ovo su istraživanje prikupljene i organizirane sve informacije dostupne u dnevniku radionice. To je obuhvatilo podatke o 44 motorne pile. Sve su motorne pile u istraživanju bile profesionalni modeli, koje su proizvela dva
najveća proizvođača motornih pila: Husquarna (25 jedinica) i Stihl (19 jedinica). U podacima su zastupljene i lake,
srednje i teške motorne pile. Ipak, podaci u bazi nisu ujednačeni s obzirom na veličinu i proizvođače strojeva, što je
onemogućilo odgovarajuće usporedbe između tipova pila i proizvođača. Karakteristike motornih pila u regionalnoj
upravi odražavaju značajke lokalnih šuma i njihova uzgajanja, što objašnjava veliku zastupljenost srednje velikih
pila. Nadalje, neravnomjerna razdioba starosnih razreda između modela ovisna je o različitom uspjehu dvaju
proizvođača motornih pila na javnim natječajima.
Za potrebe istraživanja postupci su održavanja kategorizirani u osam glavnih razreda ovisno o glavnim konstruktivnim elementima pile i/ili vrsti intervencije. Razdvojene su ove kategorije: opći pregled, popravci motora, popravci
kućišta radilice, pitanja rasplinjača, starter, električni sustav, lanac i vodilica, sigurnosni uređaji. Troškovi održavanja
i popravaka izračunati su zbrajanjem cijene rada i rezervnih dijelova. Prethodno je procijenjeno na 24 € po satu,
uključujući porez i doprinose. Potonje predstavljaju stvarne cijene navedene u računima popravaka nakon diskontiranja na sadašnju vrijednost. Istraživanje je obuhvatilo podatke za 1388 zahvata na održavanju, što odgovara ukupnim
troškovima od 36 970 €.
Rezultati pokazuju da uporabni vijek motornih pila premašuje 3 000 sati i da traje od 6 do 9 godina. U takvim
su uvjetima troškovi održavanja prosječno iznosili 820 € ili oko 120 % troška investicije. Godišnja je uporaba bila
najviša, a troškovi održavanja najmanji za srednje velike motorne pile u razredu od 2 do 3,5 kW snage. Modeli na
dva ekstremna kraja (tj. < 2 kW i > 3,5 kW) kao specijalistički alati rezultirali su manjom uporabom i višim troškovima
održavanja po satu. Najveći dio popravaka (45 % od ukupnoga broja) odnosi se na motor i rasplinjač. Prosječna
motorna pila u uzorku prošla je 31 zahvat održavanja tijekom svoga uporabnoga vijeka. Trošak po zahvatu iznosio je
između 7 i 50 €. Trošak je popravaka bio najveći za rad na motoru, a najniži za opći pregled. Rezervni su dijelovi
iznosili dvije trećine ukupnoga troška, a rad preostalu trećinu.
Razvrstavanjem učestalosti i troškova održavanja provedeno istraživanje može uputiti proizvođače motornih pila
prema specifičnim problemskim područjima, gdje je tehnološki razvoj osobito nužan. Trenutačno su popravci motora
i rasplinjača još uvijek najčešći i najskuplji. U njihovoj potrazi za lakšim i snažnijim motorima proizvođači ne bi
trebali zaboraviti pouzdanost koja je i dalje glavno pitanje. S druge strane održavanje obaveznih sigurnosnih uređaja
(kočnica lanca i sl.) izaziva vrlo malo troška, što pobija prijašnje prigovore da novi uređaji mogu biti dodatna komplikacija i mogući izvor daljnjih kvarova.
Croat. j. for. eng. 34(2013)2
271
A. Calvo et al.
Long Term Repair and Maintenance Cost of some Professional Chainsaws (265–272)
Nažalost, provedeno istraživanje nije moglo utvrditi jasnu vezu između starosti motornih pila i troškova
održavanja. Pretpostavlja se da trošak održavanja po satu raste s uporabom pile kao rezultat dotrajalosti i općega
trošenja. Procjena toga odnosa u brojčanim iznosima pomogla bi u donošenju odluka o eventualnom otpisivanju
starijih strojeva radi zamjene novim modelima. Međutim, računi radionice nisu sadržavali bilješke o učinjenim
radnim satima u trenutku popravka, i njihovi su datumi često bili nepouzdani. To je onemogućilo povezivanje troška
održavanja s radnim satima svake motorne pile, kao što je potrebno za razvoj prediktivnoga modela. Buduća bi
istraživanja trebala razmotriti to pitanje koje je iznimno važno za operativno rukovođenje.
Također na umu treba imati da je istraživanje obuhvatilo samo velike popravke obavljene u mehaničkoj radionici,
bez dnevnoga održavanja koje se obavlja na terenu. Međutim, terensko je održavanje općenito manje i sastoji se od
oštrenja, čišćenja i sitnih popravaka. Sa sigurnošću se može pretpostaviti da najveći dio u trošku terenskoga održavanja
čini ljudski rad, koji je unaprijed uračunat uključivanjem održavanja motorne pile u dodatno vrijeme sječe i izrade,
kako je to uobičajeno kod terenskih istraživanja. Provedeno istraživanje ipak pruža podatke o uporabnom vijeku i
troškovima održavanja motornih pila, koje su dobivene znanstvenim metodama i stoga su pogodne za opću primjenu.
Ključne riječi: sječa, pridobivanje drva, biomasa, motorne pile, uporabni vijek, troškovi održavanja
Authors’ address – Adresa autorâ:
Assoc. Prof. Angela Calvo, PhD.
e-mail: [email protected]
Marco Manzone
e-mail: [email protected]
Università degli Studi di Torino
DEIAFA sez. Meccanica
Via Leonardo da Vinci 44
Grugliasco (TO)
ITALY
Received (Primljeno): March 17, 2013
Accepted (Prihvaćeno): April 4, 2013
272
Raffaele Spinelli, PhD.*
e-mail: [email protected]
CNR IVALSA
Via Madonna del Piano 10
Sesto Fiorentino (FI)
ITALY
* Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Original scientific paper – Izvorni znanstveni rad
Self-Levelling Feller-Buncher Productivity
Based on Lidar-Derived Slope
Muhammad Alam, Mauricio Acuna, Mark Brown
Abstract – Nacrtak
The purpose of the study was to examine the ability of LiDAR (Light Detection and Ranging)
to derive terrain slope over large areas and to use the derived slope data to model the effect of
slope on the productivity of a self-levelling feller-buncher in order to predict its productivity
for a wide range of slopes.
The study was carried out for a self-levelling tracked feller-buncher in a 24-year old radiata
pine (Pinus radiata) plantation near Port Arthur, Tasmania, Australia undertaking a clear
felling operation. Tree heights and diameter at breast height were measured prior to the harvesting operation. Low intensity LiDAR (>3 points m-2) flown in 2011 over the study site was
used to derive slope classes. A time and motion study carried out for the harvesting operation
was used to evaluate the impact of tree volume and slope on the feller-buncher productivity.
The results showed the ability of LiDAR to derive terrain slope classes. The study found that
for an average tree volume of 0.53 m3, productivities of 97 m3 PMH0-1 (Productive Machine
Hours excluding delays) and 73 m3 PMH0-1 were predicted for the moderate slope (11–18°)
and steep slope (18–27°), respectively. The difference in feller-buncher productivity between
the two slope classes was found to result from operator technique differences related to felling.
The productivity models were tested with trees within the study area not used in model development and were found to be able to predict the productivity of the feller-buncher.
Keywords: Tasmania, productivity, self-levelling feller-buncher, LiDAR, mechanised harvesting system, slope
1. Introduction – Uvod
The productivity and efficiency of a mechanised
harvesting system is affected by a number of factors
including forest stand characteristics (stand density,
undergrowth), tree characteristics (tree size or piece
size, tree form, crown size), terrain variables (slope,
rocks, woody debris, ground roughness, ground
strength, streams and drainage features, roads, etc.),
operators’ experience, skill & work technique and machinery limitations or design (Brunberg et al. 1989,
Lageson 1997, Nurminen et al. 2006, Visser et al. 2009).
Knowledge of the impact of these factors on the productivity and efficiency of forest harvesting machines
can assist in predicting their performance under different conditions in a cost-effective way and lead to
more productive harvesting operations.
Tree size (volume or weight) has been determined
by many studies to be the most influential factor afCroat. j. for. eng. 34(2013)2
fecting the productivity of forest harvesting machines
(e.g. Brunberg et al. 1989, Kellogg and Bettinger 1994,
Acuna and Kellogg 2009). However, slope is the primary determinant of travel speed and stability of harvesting machines (Davis and Reisinger 1990). Increasing slope has been shown to be a significant factor in
decreasing the productivity of a range of forest harvesting equipment (Stampfer 1999, Stampfer and
Steinmüller 2001, Simões and Fenner 2010, Zimbalatti
and Proto 2010). In addition, rubber-tyred harvesting
machines are generally restricted to slopes <19° whereas tracked machines can operate on slopes up to 27°,
with some specialised tracked machines able to operate on steeper slopes (e.g. the Valmet Snake (Stampfer
and Steinmüller 2001)).
Previous harvester productivity studies have usually extrapolated stand-level slope information from a
limited number of points manually measured with
273
M. Alam et al.
Self-Levelling Feller-Buncher Productivity Based on Lidar-Derived Slope (273–281)
clinometers across the study site or used DTMs (Digital
Terrain Models) derived from contours (e.g. Acuna and
Kellogg 2009, Oliveira Júnior E. D. de. et al. 2009). LiDAR is a well-recognised technology for the production
of high quality DTMs (Ackermann 1999, Wehr and Lohr
1999), which can be used to visualise and calculate slope
(Giles and Franklin 1998) and as an input into harvest
planning (Reutebuch et al. 2005). LiDAR slope maps
have been shown to be very accurate and of high resolution compared with DTMs derived from contour
maps (Vaze and Teng 2007). Use of LiDAR to generate
accurate, broad area DTMs makes it possible to predict
the impact of slope on forest harvesting machine productivity across an entire forest estate using models
relating productivity to slope.
Self-levelling feller-bunchers have recently been
introduced in parts of Australia and New Zealand for
harvesting operations in steep terrain (Acuna et al.
2011). Self-levelling feller-bunchers have advantages
over conventional feller-bunchers such as reducing the
risk of tilting, increased lifting capacity and increased
operator comfort during downhill operations (MacDonald 1999, Acuna et al. 2011). The objective of the
study was to use LiDAR-derived slope from readily
available low cost LiDAR data to develop a relationship between slope and the productivity of a self-levelling feller-buncher, and then to use this relationship
to predict the productivity of the feller-buncher for
other areas, where slope had been estimated using
similar LiDAR data.
2. Material and methods
Materijal i metode
2.1 Study site – Mjesto istraživanja
The study was located near Port Arthur, Tasmania,
Australia (Latitude/Longitude: 43°10’10” S / 147°47’
20” E). The stand was 24-year-old radiata pine plantation of 1057 trees ha-1 with no undergrowth. The study
site was an area of approximately 1 hectare within a
plantation being clearfelled for pulp wood production.
Tree spacing was 2.5 m × 4 m and lightly branchy trees
were good in forms and quality. The site had never
been thinned. The forest floor consisted of moist, soft
and clay loamy soils. There were some dolerite rocks
that accounted for the ground roughness. Ground
slope was between 7–27° with an average of 21°.
One hundred and two trees of normal growth and
forms covering the range of heights at the study site
were selected and their heights were measured with a
Vertex hypsometer and Impulse 200 laser to the nearest 0.1 m. The diameter at breast height (DBH, cm) of
274
Table 1 Means and value ranges for pre-harvest tree measurements
Tablica 1. Raspon i prosječne vrijednosti izmjere stabala prije sječe
Mean
Range
Arit. sredina
Raspon
Height – Visina, m
26.1
10–37
DBH – Prsni promjer, m
0.29
0.10–0.46
Basal area – Temeljnica, m2
0.07
0.01–0.16
0.61
0.06–1.84
3
Volume – Obujam, m
all trees on the study site was measured with a diameter tape to the nearest 1 cm. A height-diameter model derived from the measured tree heights was used to
estimate heights of the remaining trees. Each tree had
a unique number painted on the stem to allow it to be
identified during the time and motion study. A volume
function supplied by Norske Skog, Australia was used
to estimate each tree merchantable volume (m3).
Means and value ranges for pre-harvest tree measurements are presented in Table 1.
2.2 Airborne LiDAR system – Sustav LiDAR
LiDAR data covering the study site was supplied
by Forestry Tasmania, with the specifications presented in Table 2. This LiDAR data was available as it had
been collected for the purpose of resource and land
management used by Forestry Tasmania that manages native and plantation forests in the region. LiDAR
data supplied in .LAS format were classified into
ground and non-ground points. LiDAR data accuracy
was verified by the data provider.
A DTM was constructed with a cell size of 2 m using ground LiDAR points and slope was derived from
the DTM using ArcGIS 10. The terrain slope classification used by the Forestry Commission UK (1996)
(Level = 0–6º, Gentle = 6–11º, Moderate = 11–18º, Steep
= 18–27º, Very steep = >27º) was adopted in the study
because: (i) the classes are based around operational
considerations, (ii) there was no widely accepted terrain classification system in use in Australia, (iii) this
classification is very similar to that used by the Forest
Practices system in Tasmania (Forest Practices Board
2000) of Hilly =12–19º, Steep = 20–26º, Very Steep =27º
and above and (iv) it is an internationally recognised
classification.
2.3 Time and motion study – Studij rada
i vremena
An operator with twelve years experience (two
years with current machine) carried out the harvesting
Croat. j. for. eng. 34(2013)2
Self-Levelling Feller-Buncher Productivity Based on Lidar-Derived Slope (273–281)
M. Alam et al.
Table 2 LiDAR parameters and scanning system settings
Tablica 2. Parametri LiDAR-a i postavke sustava snimanja
LiDAR attribute – Obilježja LiDAR-a
Values – Vrijednosti
Date of flight – Datum leta
25/05/2011
System – Sustav
ALTM (Airborne Laser Terrain Mapping) Gemini
Beam divergence – Odstupanje pulsa
0.20 milliradian
Footprint diameter – Prostorna rezolucija
20 cm
Laser mode – Mod lasera
Single pulse
-2
>3 m (1 , 2nd, 3rd and last) (2.3–3.2)
Pulse return density (range) – Gustoća povratka pulsa (raspon)
st
Horizontal accuracy – Horizontalna točnost
0.15 m
Vertical accuracy – Vertikalna točnost
0.15 m
Pulse rate frequency – Frekvencija pulsa
70 kHz
Table 3 Description of time elements
Tablica 3. Opis radnih sastavnica
Time elements – Radne sastavnice
Moving time: Begins when the feller-buncher or the boom starts to move to a tree and ends when machine head is clamped on the tree
Premještanje: Započinje kada feler bančer ili dizalica započinje s pomicanjem i završava kada sječna glava zahvati stablo
Felling time: Starts when the feller-buncher head clamps on to the tree stem and ends when the tree touches the ground
Sječa: Započinje kada sječna glava zahvati stablo te završava kada posječeno stablo dodirne tlo
Stacking time: Starts when the feller-buncher grabs a log and ends when it drops the log onto the pile
Uhrpavanje: Započinje kada feler bančer zahvati deblo i završava u trenutku kada ga ispusti na složaj
Cycle time: Starts when the feller-buncher commences moving to a tree and ends when the feller-buncher completes felling the tree
Vrijeme turnusa: Započinje premještanjem feler bančera ka stablu i završava kad feler bančer posječe stablo
Delay: Any interruption to the harvesting operation spending extra time. The cause of the delay (e.g. operational, personal, mechanical, or study induced)
is recorded
Prekidi: Svako prekidanje pridobivanja drva koje izaziva dodatni utrošak vremena. Uzroci su prekida (npr. povremeni radovi, osobni, kvarovi ili izazvani
istraživanjem) zabilježeni
operation with a self-levelling tracked feller-buncher,
Valmet 475EXL fitted with a Quadco hotsaw accumulating head. It was manufactured in 2004 and had
worked for 7751 hours. The Valmet 475EXL is designed to operate on uneven ground and on steep
slopes.
The harvesting operation was recorded using a
digital video camera in mainly fine and sunny conditions on the 4th April 2011. Several brief episodes of
drizzly rain occurred, but did not disrupt the harvesting operation and filming.
The operator was observed to fell trees in a 4 row
swath directly uphill (moving at right angles to the
Croat. j. for. eng. 34(2013)2
contours) or on side-hill (moving parallel to the contours) on gentle & moderate terrain and downhill on
steep terrain. In fact, terrain conditions largely dictated tree harvesting pattern in steep and moderate
steep slope areas. Trees were laid out in the previously harvested area at right angles to the direction of
harvester movement for subsequent processing into
logs. The length of each swath was approximately 100
m. One to three trees were felled at each stop.
To avoid issues associated with GPS (Global Positioning System) accuracy and performance under tree
cover, following the harvesting operation GPS locations of 100 stumps along the border of the study site
275
M. Alam et al.
Self-Levelling Feller-Buncher Productivity Based on Lidar-Derived Slope (273–281)
were recorded with a standard GPS measuring device.
Coordinates of stump locations were used to locate the
harvest area on the LiDAR-derived DTM.
Timer Pro Professional software (www.acsco.com)
was used to extract each time element from the video
recording (Table 3). Time elements unrelated to tree
size and slope including stacking, brushing, clearing
and any delays were excluded from the analysis because of their random occurrences.
In order to develop feller-buncher productivity
models for each slope class, the following steps were
carried out:
Þ Stump locations on the boundary and tree spacing measurements in the plantation area were
used to interpolate the locations of remaining
trees using ArcGIS 10.
Þ One hundred and twenty-six trees in the moderate slope area and 124 trees in the steep slope
area of the study site were selected for model
development using previously derived LiDAR
slope. Trees with normal growth and forms
were selected from both slope areas and selection was limited to trees that could clearly be
identified as being in the allocated slope class.
There was insufficient area of gentle slope at the
study site for productivity modelling.
Þ For estimated location of each tree in the study
area, both tree volume and slope class were allocated.
Þ Time consumptions of each tree for slope classes
were estimated from the time and motion study.
Þ A correlation between tree volumes and time
consumptions for each slope class was established, which in turn was used to formulate a
productivity model.
Þ Prior to model development, mean tree sizes for
each slope class were compared using a t-test
(p<0.05).
2.4 Data analysis – Obrada podataka
Productivity models for the feller-buncher were
developed based on the cycle times for the trees se-
Fig. 1 LiDAR-derived slope class (Field tree distribution and Field measured tree rows refer to approximate locations)
Slika 1. Razredi nagiba terena izvedeni iz LiDAR-ovih snimaka (terenske izmjere redova i pojedinih stabala odnose se na približne položaje)
276
Croat. j. for. eng. 34(2013)2
Self-Levelling Feller-Buncher Productivity Based on Lidar-Derived Slope (273–281)
lected in each slope area to determine whether slope
significantly affected feller-buncher productivity.
M. Alam et al.
chosen and verified to be similar to those of model
development areas. The productivity of the fellerbuncher for each of these trees was calculated using
cycle time and tree volume and was estimated using
the productivity models developed for each slope
class. For each slope class, the calculated and estimated productivity values were compared using a paired
t-test. Linear regression [Y = a + b(X)] analysis was
performed to predict productivity of the feller-buncher for each slope class, where X is the independent
variable, field measured productivity; Y is the dependent variable, predicted productivity and a & b are the
regression coefficients. Statistical software Excel 2007
was used to perform analyses.
Productivity (m3 PMH0–1) was estimated using
the following formula:
Productivity = (volume / cycle time) * 60
Where,
Volume – tree volume (m3) estimated from field
measurements
Cycle time (min) – refer to Table 3.
PMH0 – Productive Machine Hours excluding
delay time
Regression models were developed for each slope
class and tested to determine the best-fit models using
their mean Bias, Mean Absolute Deviation (MAD),
RMSE (Root Mean Square Error), R2 and the distribution of the residuals. The best-fit models for each slope
class were compared using an F-test (p < 0.05) (Motulsky and Christopoulos 2003).
3. Results – Rezultati
Field measured stump locations (coordinates) were
used to locate the harvest area on the LiDAR-derived
DTM. The LiDAR-derived slope range for the study
site was 7–27° with a mean slope of 19°, which was
found to be comparable to field measurements of the
study site. The slope of the study site was classified
into three classes: gentle slope (7–11°), moderate slope
(11–18°) and steep slope (18–27°) (Forestry Commission UK 1996) (Fig. 1). Several small areas (maximum
8 m × 6 m) of over 27° slope were added to the steep
slope class as they were too small to affect the productivity of the feller-buncher.
The relationship between tree volume and moving
& felling times for each slope class was tested using
linear regression to determine whether tree volume was
a potential covariate in a one-way Analysis of Covariance (ANCOVA). If it was found not to be, a one-way
Analysis of Variance (ANOVA) would be performed. A
general linear model was used to analyse the ANCOVA
and/or ANOVA models (Minitab 16, Minitab Ltd.).
Mean felling and moving times for each slope class
were compared by a post hoc analysis of the means
using Tukey’s test in order to identify the impact of each
time element on feller-buncher productivity.
Mean tree volumes in the moderate and steep slope
areas were not significantly different (Table 4).
As there were very few instances of stacking time
during the study, it was excluded from cycle time. Two
trees were cut and accumulated in head in two occasions and they were also excluded from the analysis
while developing the model to be consistent with
overall tree selection technique. In the steep slope areas, a number of trees had fallen on other trees during
harvest operation and the operator was observed to
In order to test whether the productivity models
developed in the study were able to accurately predict
the productivity of the feller-buncher when felling
trees elsewhere on the study site, thirty-five trees not
used in the model development process were randomly selected from each slope class. Topographic variability and slope ranges of model testing areas were
Table 4 Summary tree volume (m3) statistics for each slope class
Tablica 4. Statistički prikaz obujma stabala za svaki razred nagiba terena
3
Mean volume – Srednji obujam, m
SD – Standardna devijacija, m3
3
Volume range – Raspon obujma, m
Count – Veličina uzorka
Croat. j. for. eng. 34(2013)2
Moderate slope (11–18°)
Steep slope (18–27°)
Umjereni nagib (11–18°)
Strmi nagib (18–27°)
0.55
0.51
0.26
0.26
0.05–1.12
0.13–1.20
126
124
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M. Alam et al.
Self-Levelling Feller-Buncher Productivity Based on Lidar-Derived Slope (273–281)
Table 5 Model coefficients and goodness of fit statistics for the feller-buncher productivity model for each slope class
Tablica 5. Koeficijenti modela i dobrota statističke prikladnosti modela proizvodnosti feler bančera za svaki razred nagiba
Model coefficients – Koef. modela
Goodness of fit statistics – Dobrota statističke prikladnosti
b0
b1
MBE
MAD
RMSE
R2
Moderate slope – Umjereni nagib (11–18°)
12.3
3.8
2.5
24.0
34.7
0.60
Steep slope – Strmi nagib (18–27°)
10.8
3.5
2.0
17.7
25.8
0.61
drag them out in the processing areas. The model form
that best fitted the data was a natural logarithm transformation of processed volume and the square root of
productivity:
(Productivity)1/2 = β0 + β1 * ln (Processed volume)
As the models were developed based on the square
root of the dependent variable, the goodness of fit
measures for the productivity models were calculated
from back-transformed model outputs (Scott and Wild
1991). Model coefficients and fit statistics are shown in
Table 5.
Productivity of the feller-buncher was strongly correlated with tree volume in both slope areas (Fig. 2).
Productivity was greater (97 m3 PMH0-1) for the moderate slope class (11–18°) than that (73 m3 PMH0-1) for
the steep slope class (18–27°) at the pooled mean tree
volume of 0.53 m3. The difference between the productivity models was statistically significant (p<0.05).
Fig. 2 Productivity of the feller-buncher against tree volume for
moderate slope (11–18°) and steep slope (18–27°)
Slika 2. Ovisnost proizvodnosti feler bančera o obujmu stabla za
umjereni (11–18°) i strmi (18–27°) nagib
Feller-buncher moving and felling times were separately found to be poorly related to tree volume and
thus a one-way ANOVA was performed. The data for
the felling and moving times were found to satisfy the
ANOVA assumptions. Mean felling times for each
slope class were significantly different, whereas there
was no significant difference between mean moving
times for each slope class (Table 6).
The mean feller-buncher productivity, predicted
using the slope class productivity models for trees not
used in the model development, was not significantly
Table 6 Feller-buncher mean felling and moving times, standard deviations (SD), min. and max. values for slope classes at the study site
Tablica 6. Deskriptivna statistika vremena sječe i premještanja za razrede nagiba istraživane sječine
Najveća vrijednost
Maximum
Najmanja vrijednost
Minimum
Standardna devijacija
Standard deviation
Aritmetička sredina
Mean
Najveća vrijednost
Moving time, sec – Vrijeme premještanja, s
Maximum
Najmanja vrijednost
Minimum
Standardna devijacija
Standard deviation
Aritmetička sredina
Mean
Felling time, sec – Vrijeme sječe, s
Moderate slope – Umjereni nagib (11–18°)
9.7
5.4
4.9
56.4
11.6
7.7
3.5
44.6
Steep slope – Strmi nagib (18–27°)
14.3
8.4
5.9
56.8
12.4
6.6
4.7
45.8
278
Croat. j. for. eng. 34(2013)2
Self-Levelling Feller-Buncher Productivity Based on Lidar-Derived Slope (273–281)
Fig. 3 Predicted productivity as a function of measured productivity for moderate slope (11–18°) and steep slope (18–27°) of the
model testing areas
Slika 3. Predviđena proizvodnost kao funkcija izmjerene proizvodnosti za umjereni (11–18°) i strmi (18–27°) nagib istraživane sječine
different from the mean feller-buncher productivity
calculated from cycle times and tree volumes for the
same trees (p<0.05). Measured productivity was found
to be strongly correlated with predicted productivity
for each slope (Fig. 3).
4. Discussion and Conclusion – Rasprava
sa zaključcima
The productivity of the feller-buncher in the current
study was found to decrease in the steeper slope class,
which was consistent with the findings of previous
studies (e.g. FPInnovations 2008, Oliveira Júnior E. D.
de. et al. 2009). However, there is considerable variation
amongst the previous studies in the degree of decrease
in productivity with increasing slope, which implies
factors other than slope are influencing the results. In
the current study, the decrease in productivity between
steep slope (18–27°) and moderate slope (11–18°) was
24% whereas Acuna and Kellogg (2009) found no sigCroat. j. for. eng. 34(2013)2
M. Alam et al.
nificant difference in the productivity of a feller-buncher across a slope range from <10º to 20º and FPInnovations (2008) showed a 30% reduction in productivity
between 6–11º slopes and 11–18º slopes based on modelled results from a number of feller-buncher studies.
The greatest decrease in feller-buncher productivity
was reported by Oliveira Júnior E. D. de. et al. (2009),
who found an 80% decrease in productivity for a
tracked feller-buncher between 0 and 27º slopes. This
large productivity drop was explained by the difference
in soil type (e.g. »agri-loose« soil) and difficulties in handling larger trees on steep terrain. Other potential factors accounting for the variation between the study results may include machine characteristics, operator skill
and the number of stems removed per hectare, because
travelling time between trees may increase disproportionately with increasing slope. These factors, however,
were not investigated in this study.
To isolate the cause of the productivity differences
between the slope classes in the current study, the
cycle time components (moving and felling times),
were further analysed. The study found felling time to
be the main driver for the variation in productivity,
which was the result of the operator spending significantly more time per tree (over 4 seconds) felling trees
in the steep slope area (Table 6). Terrain conditions
largely dictated the harvesting pattern and observations indicated it had a greater impact on steeper
slopes within the steep slope classification. Since operating the machine on an uphill slope is slightly more
comfortable and productive (Howe 2011), the operator
was observed to fell trees uphill by predominantly extending the boom and moving the feller-buncher in
the moderate slope areas and lay them out for processing primarily using the boom, whereas, in the
steep slope areas the operator drove downhill to fell
each tree and then back uphill to deposit them in suitable areas, preferably those with moderate slope, for
processing. In the steep slope areas, the operator also
spent time dragging out a number of trees that had
fallen on other trees. The combination of these factors
contributed to higher time consumption when felling
trees in the steep slope areas.
The study did not investigate whether soil strength
was an influential factor affecting the machine’s stability and traction in the steep slope areas, although the
soil in the steep slope areas was observed to be muddy
compared with that in the gentle and moderate slope
areas. Stampfer and Steinmüller (2001) demonstrated
that the locomotion of the harvester was dependent on
the terrain slope and the soil bearing capacity. Therefore, consideration of the soil bearing capacity, while
evaluating slope effects on harvester productivity, may
be an area for future research.
279
M. Alam et al.
Self-Levelling Feller-Buncher Productivity Based on Lidar-Derived Slope (273–281)
The models developed in the study were able to
predict the productivity of the feller-buncher felling
trees from each slope class on the study site where the
topographical features and slope ranges were similar
to model development areas. This suggests that the
models can be used to predict the productivity of the
feller-buncher operating in other areas of radiata pine
plantation with tree volume between 0.06–1.84 m3 and
slope between 11–27°. The models may not be applicable where topographic variability is significantly
different (higher or lower) from the model development areas, because the assignment of trees for each
slope class based on the methodology used in the
study may not represent the exact locations, which
excluded the use of trees on the boundary of the slope
classes and where slope was very variable and different slope variability will potentially influence the operator approach. In addition to being able to estimate
terrain slope, LiDAR has been demonstrated by a
number of researchers to be able to accurately predict
tree volume (e.g. Hyyppa et al. 2001, Persson et al.
2002). However, the LiDAR point density in these
studies was considerably greater than that for the current study, which targeted using readily available LiDAR data in the interest of exploring a methodology
that would be cost-effective for practical application.
Acknowledgement – Zahvala
We acknowledge the support of Mrs. Sandra Hetherington and her team of Norske Skog, Tasmania, Australia and Rick Mitchell (Western Australia Plantation
Resources) for organising harvest operation required
for data acquisition. We also acknowledge the support
of Mr. David Mannes (Forestry Tasmania) for providing LiDAR data.
5. References – Literatura
Ackermann, F., 1999: Airborne laser scanning-present status
and future expectations. ISPRS Journal of Photogrammetry &
Remote Sensing 54(2-3): 64–67.
Acuna, M., Kellogg, L., 2009: An evaluation of alternative cutto-length harvesting technology for native forest thinning in
Australia. International Journal of Forest Engineering 20(2):
17–25.
Acuna, M., Skinnell, J., Evanson, T. Mitchell, R., 2011: Bunching with a self-levelling feller-buncher on steep terrain for
efficient yarder extraction. Croatian Journal of Forest Engineering 32(2): 521–531.
Brunberg, T., Thelin, A., Westerling, S., 1989: Basic data for
productivity standards for single-grip harvesters in thinning
operations. Report No 3, The Forest Operations Institute of
Sweden, p. 21
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Davis, C. J., Reisinger, T. W., 1990: Evaluating Terrain for harvesting Equipment Selection. Journal of forest Engineering
2(1): 9–16.
Forest Practices Board, 2000: Forest Practices Code, Forest
Practices Board, Hobart, Tasmania. Australia 7100.
Forestry Commission UK, 1996: Terrain Classification. Available: http://www.biomassenergycentre.org.uk [Accessed 22
January 2013].
FPInnovations, 2008: Feller-buncher studies. Progress Report
#12, Saint-Jean Pointe-Claire, QC, H9R 3J9, Canada.
Giles, P. T., Franklin, S. E., 1998: An automated approach to
the classification of the slope units using digital data. Geomorphology 21(3–4): 251–264.
Howe, D., 2011: Cut to length on difficult terrain. Available:
http://www.forestrysolutions.net/userfiles/File/CTL%20harvesting%20FOCUS%20PRESENTATION%20Dereke.pdf [Accessed 18 January 2013].
Hyyppa, J., Kelle, O., Lehikoinen, M., Inkinen, M., 2001: A
segmentation-based method to retrieve stem volume estimates from 3-dimensional tree height models produced by
laser scanner. IEEE Transactions on Geoscience and Remote
Sensing 39(5): 969–975.
Kellogg, L. D., Bettinger, P., 1994: Thinning productivity and
cost for mechanized cut-to-length system in the Northwest
pacific coast region of the USA. International Journal of Forest
Engineering 5(2): 43–54.
Lageson, H., 1997: Effects of thinning type on the harvester
productivity and on the residual stand. Journal of Forest Engineering 8(2): 7–14.
MacDonald, A. J., 1999: Harvesting systems and equipment
in British Columbia, FERIC Handbook, ISSN 0707-8355, No.
HB-12, p. 197.
Motulsky, H. J., Christopoulos, A., 2003: Fitting models to
biological data using linear and nonlinear regression: A practical guide to curve fitting. GraphPad Software Inc. San Diego,
CA.
Nurminen, T., Korpunen, H., Uusitalo, J., 2006: Time consumption analysis of the mechanized cut-to-length harvesting
system. Silva Fennica 40(2): 335–363.
Oliveira Júnior, E. D. de., Seixas, F., Batista, J. L. F., 2009: Fellerbuncher productivity in eucalyptus plantation on steep
ground terrain. Floresta 39(4): 905–912.
Persson, A., Holmgren, J., Soderman, U., 2002: Detecting and
measuring individual trees using an airborne laser scanner.
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925–932.
Reutebuch, S., Andersen, H., McGaughey, R., 2005: Light Detection and Ranging (LIDAR): An emerging tool for multiple
resource inventory. Journal of Forestry 103(6): 286–292.
Scott, A., Wild, C., 1991: Transformations and R2. The American Statistician 45(2): 127–129.
Simões, D., Fenner, P., 2010: Influence of relief in productivity
and costs of harvester. Scientia Forestalis 38(85): 107–114.
Stampfer, K., 1999: Influence of terrain conditions and thinning regimes on productivity of a track-based steep slope
harvester. In: Proceedings of the International Mountain LogCroat. j. for. eng. 34(2013)2
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ging and 10th Pacific Northwest Skyline Symposium, Corvallis, Oregon: 78–87.
Stampfer, K., Steinmüller, T., 2001: A new approach to derive
a productivity model for the harvester Valmet 911 Snake. In:
Proceedings of the International Mountain Logging and 11th
Pacific Northwest Skyline Symposium, Seattle, WA, p. 254–
262.
Vaze, J., Teng, J., 2007: High Resolution LiDAR DEM – How
good is it? In: MODSIM 2007 International Congress on Modelling and Simulation.
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Visser, R., Spinelli, R., Saathof, J., Fairbrother, S., 2009: Finding
the »Sweet-Spot« of mechanised felling machines. In: Proceedings of USA: 32nd Annual Meeting of the Council on Forest Engineering (COFE), Kings Beach, CA, p. 10.
Wehr, A., Lohr, U., 1999: Airborne laser scanning – an introduction and overview. ISPRS Journal of Photogrammetry and
Remote Sensing 54(2–3): 68–82.
Zimbalatti, G., Proto, A. R., 2010: Productivity of forwarders
in South Italy. In: FORMEC 2010, Forest Engineering: Meeting
the Needs of the Society and the Environment, Padova–Italy.
Sažetak
Proizvodnost feler bančera sa žiroskopskom kabinom temeljena na nagibu
terena izvedenom iz LiDAR-ovih snimaka
Cilj je istraživanja bio ocijeniti mogućnost uporabe LiDAR-ovih snimaka za određivanje nagiba terena na velikim
površinama te ispitati djelovanje nagiba na proizvodnost feler bančera sa žiroskopskom kabinom.
Istraživanje je provedeno u čistoj sječi plantaže smolastoga bora (Pinus radiata) u Tasmaniji, u blizini Port
Arthura (Australija). Plantaža je bila u dobi od 24 godine. Korišten je feler bančer sa žiroskopskom kabinom, opremljen gusjenicama.
Visina i prsni promjer stabala mjereni su prije sječe. Upotrijebljene su LiDAR-ove snimke niskoga intenziteta (>3
točke po m2) iz 2011. godine kako bi se odredio nagib terena. Pri sječi i izradbi obavljen je i studij rada i vremena radi
određivanja proizvodnosti vozila, a u ovisnosti o obujmu posječenih stabala i nagibu terena.
Rezultati istraživanja dokazuju primjenjivost LiDAR-ovih snimaka za raščlambu nagiba terena. Može se zaključiti
da je za stablo prosječna drvnoga obujma od 0,53 m3 proizvodnost feler bančera sa žiroskopskom kabinom bila 97 m3/h
(ne uključujući prekide rada) na terenu umjerena nagiba (11–18°) odnosno 73 m3/h (ne uključujući prekide rada) na
strmijim terenima (18–27°). Razlika u proizvodnosti vozila zasniva se na različitim postupcima pri sječi i izradi koje
je radnik morao obavljati ovisno o nagibu terena. Modeli proizvodnosti temelje se na stvarno posječenom i izrađenom
drvnom obujmu.
Ključne riječi: Tasmanija, proizvodnost, feler bančer sa žiroskopskom kabinom, LiDAR, strojna sječa, nagib
Authors’ address – Adresa autorâ:
Received (Primljeno): February 8, 2013
Accepted (Prihvaćeno): June 3, 2013
Croat. j. for. eng. 34(2013)2
Muhammad Alam*, PhD. Student
e-mail: [email protected]
University of Melbourne
500 Yarra Boulevard
Richmond, Australia 3121
Mauricio Acuna, PhD.
e-mail: [email protected]
Australia Forest Operations Research Alliance (AFORA)
University of the Sunshine Coast
Hobart, Tasmania, 7001, Australia
Prof. Mark Brown, PhD.
e-mail: [email protected]
Australia Forest Operations Research Alliance (AFORA)
University of the Sunshine Coast
Maroochydore DC, Queensland, 4558 Australia
*Corresponding author – Glavni autor
281
Original scientific paper – Izvorni znanstveni rad
Performance, Capability and Costs
of Motor-Manual Tree Felling in Hyrcanian
Hardwood Forest
Meghdad Jourgholami, Baris Majnounian, Nosratollah Zargham
Abstract – Nacrtak
Motor-manual tree felling is the most labor-intensive component of all harvesting operations
and frequently represents a bottleneck in wood production. The study of motor-manual tree
felling was carried out in two compartments in the Namkhaneh district of Kheyrud Forest.
The objects of this study were as follows: time study of tree felling operations, estimate of
chainsaw productivity and costs, development of a regression model in uneven-aged stand
using single-tree selection methods. The factors affecting total felling time regression model
(increasing order of importance) were DBH of harvested trees, direction of felling regarding
the lay and inter-tree distance. The hourly production of chainsaw felling with and without
delay time was 56.4 cubic meters per hour (13 tree/hour) and 80.7 cubic meters per hour
(19 tree/hour), respectively. Productivity of chainsaw felling increased in relation to tree DBH
as power relation. The cost of chainsaw felling with and without delay time was 0.55 and
0.39 USD/m3, respectively. The cost of felling increased as simple exponential equation when
DBH of harvested trees decreased. However, the unit felling cost for chainsaw operation decreased as the tree size increased. Total felling cycle time without delay averaged 3.14 minutes
and with delay time it averaged 4.5 minutes. Productivity was more sensitive to DBH than
felling direction and inter-tree distance.
Keywords: tree felling, time study, regression model, production, cost
1. Introduction – Uvod
Hyrcanian forest in northern Iran is an example of
biodiversity, with endemic and endangered species,
and a diverse range of economic and social conditions.
About 45% of the Hyrcanian forests are located in
mountainous areas, where forest lands are not readily
accessible with ground-based logging equipments.
Felling, limbing and bucking are all done at the stump
site. Motor-manual systems are used by workers
equipped with chainsaws (Sobhani and Staurt 1991).
Chainsaw felling is often associated with large trees
and steep or rough terrain. It is used for areas where
ground-based machines cannot travel or where the
trees are too large for mechanical felling. Due to larger diameter and crowns of hardwoods, and the relatively steep terrain in the Hyrcanian forest, motormanual tree felling is still the only system used in the
Croat. j. for. eng. 34(2013)2
region (Sarikhani 2008). The capital investment required for motor-manual felling is several hundred
times less than for mechanical felling, and the felling
costs per cubic meter are usually lower as well. Despite these differences, other factors such as terrain
and timber conditions and total system productivity
dominate the choice between the two systems for large
contractors (MacDonald 1999, Sessions et al. 2007).
Harvesting starts with the cutting down of trees
with hand tools, chain saws, or mechanized felling
machines. Felling is the most dangerous part of the
harvesting operation (Conway 1976, ILO 1998, Heinimann 2004, Sessions et al. 2007). Larger trees generally must be felled manually with a chainsaw. In Hyrcanian forest regions, trees were large and heavy with
huge crowns. They fall with a tremendous force,
which can uproot the neighboring trees; and stems
283
M. Jourgholami et al.
Performance, Capability and Costs of Motor-Manual Tree Felling... (283–293)
may shatter, bounce, and roll uncontrollably. Therefore, motor-manual felling operations are the most
hazardous part of harvesting operations for the labor
forces in this forest. They are also a major cause of
damage to the forest stand and result in the generation
of a large amount of wood waste. The objective of the
tree felling operation is to fell the tree with minimum
damage, to avoid damaging surrounding trees, to
minimize soil and water impacts, and to position the
tree or logs for the next phase of harvesting. Directional felling is a specific tree-felling technique, in
which the direction of fall is determined by the operator prior to cutting. Where possible, trees should be
felled in the direction of existing canopy gaps in order
to reduce damage to nearby standing timber. In general, trees should be felled either towards or away
from skid trails, preferably at an oblique angle to the
skidding direction (FAO 1976, Dykstra and Heinrich
1996, MacDonald 1999).
Hartsough et al. (2001) developed the felling time
prediction model based on the tabular data of felling
time per tree collected on clear cutting of secondgrowth timber. Kluender and Stokes (1996) developed
a nonlinear model to predict felling time for different
harvesting prescriptions, using variables as distance
from previous tree, proportion of basal area removed
and DBH. Lortz et al. (1997) conducted an analysis of
southern pine felling with chainsaw and produced
several equations for estimating felling time and productivity. They found that factors affecting total felling
time were DBH of harvested stems, inter-distance, and
harvest intensity. Wang et al. (2004) conducted a time
study on central Appalachian hardwood forest consisting of motor-manual felling and cable skidding.
They reported that felling time was mainly affected by
diameter at breast height and distance between harvested trees. This study showed that productivity of
chainsaw felling was 362 ft3 per productive machine
hour (PMH) with a unit cost of $8.0/100 cubic feet.
Rummer and Klepac (2002) conducted a time study to
compare two harvesting systems; mechanized and
motor-manual felling operations. This study showed
that the harvester was about as productive as a manual crew of five. Also, they reported that there is a
strong trend of increasing cycle time as tree size increases and a regression equation was developed to
predict total cycle time as a function of tree diameter.
Li et al. (2006) conducted a simulation study for comparing production and cost of felling among chainsaw,
harvester, and feller-buncher. They found that the unit
felling cost for chainsaw operation decreased as the
tree size increased.
Few previous studies have addressed the production and cost of motor-manual tree felling in Hyrca-
284
nian hardwood stands. Nikooy (2007) developed a
productivity model for chainsaw felling in Caspian
hardwood forests, which included variables such as
diameter at breast height and the distance among harvested trees. This study reported that productivity of
tree felling with and without delay time was 53 and 67
cubic meters per productive machine hour (PMH),
respectively. Behjou et al. (2009) conducted a time
study on Hyrcanian forests. They found that felling
time per tree was most affected by diameter at breast
height and by the distance among harvested trees. The
gross and net production rate was 20.6 m3 and 26.1 m3
per hour/one person, respectively. The objective of this
study was to: conduct a continuous time study on
motor-manual tree felling with a chainsaw in a Hyrcanian hardwood forest, employing regression techniques to develop models for elemental times and
cycle time of chainsaw felling, and estimate the production rates and costs of chainsaw felling.
2. Study sites and methods – Mjesto i
metode istraživanja
The research was carried out in two compartments
219 and 223 located in Namkhaneh District within
Kheyrud Educational and Research Forest. The altitude ranges from 1 000 to 1 135 m and the forest lies
southwest. The slope ranges from 10 to 70% with an
average of 40%. The average rainfall ranged from 1 420
to 1 530 mm/year, with the heaviest precipitation in
the summer and fall. The average daily temperatures
ranged from a few degrees below 0°C in December,
January, and February to +25°C during the summer.
This area is dominated by natural forests containing
native mixed deciduous tree species such as Fagus orientalis Lipsky, Carpinus betulus L., Acer velutinum
Boiss., and Alnus subcordata (Jourgholami 2013). The
management method is mixed un-even aged high forest with single and group selective cutting regime.
Trees to be removed are felled, limbed and topped
motor-manually. Felled trees are bucked and processed with chainsaws into logs, sawn-lumber and
pulpwood. The logs 5 to 15 meter long are extracted
by wheeled cable skidders to the roadside landings.
The fuel wood is extracted by mules. Also, in steep
terrain that cannot be reached by skidders, logs are
processed to sawn-lumber and then hauled by mules
(Jourgholami 2012). Table 1 summarizes some characteristics of the study site.
Felling was performed using a STIHL chainsaw
with 4-hoursepower (hp) engine and bar length of
70 cm (Fig. 1). The field study was conducted from
January to February 2011 on Kheyrud Forest during
Croat. j. for. eng. 34(2013)2
Performance, Capability and Costs of Motor-Manual Tree Felling... (283–293)
M. Jourgholami et al.
Table 1 Study site description
Tablica 1. Mjesto istraživanja
Compartment
Area
Odjel
Površina
ha
Trees per ha
Broj stabala po ha
Volume
Total felled trees
Total volume of felled trees
DBH of felled trees
Obujam
Ukupan broj posječenih stabala
Etat (sječna gustoća)
Prsni promjer
m3/ha
num. (t/ha) – broj (stabala/ha)
m3 (m3/ha)
cm
3
219
27
173
504
270 (10 t/ha)
872.3 (32 m /ha)
20–135
223
56
123
301
181 (3 t/ha)
719.5 (13 m3/ha)
20–135
Table 2 Main work phases that make up total felling time
Tablica 2. Faze radova sječe
Work elemental function
Definition – Opis radnih zahvata
Radni zahvati
Walk to tree – Prilazak stablu
Acquire
Čišćenje okoliša oko stabla i
određivanje smjera rušenja
Undercut – Izrada zasjeka
Backcut – Potpiljivanje
Wedging – Zabijanje klinova
Refuel and Service
Punjenje goriva, maziva i popravak
Delays – Zastoji
Begins when the sawyer starts toward the tree to be cut and ends when the sawyer reaches to the tree
Prilazak stablu počinje kada šumski radnik sjekač krene prema doznačenomu stablu i završava kada dođe do njega
Begins when the sawyer starts clearing around the tree and decides where the tree will fall and ends when the
sawyer is ready to cut the tree
Priprema počinje kada šumski radnik sjekač počne čistiti okoliš oko stabla, zatim odlučuje o smjeru rušenja stabla te
završava kada je radnik spreman za sječu stabla
Begins when the sawyer starts to make a wedge-shaped notch in the base of the tree to ensure that it accurately
faces the felling direction and ends when the sawyer starts backcut
Radni zahvat započinje izradom kosoga reza zasjeka, u odabranom smjeru rušenja stabla, a završava kada je sjekač
spreman za potpiljivanje
Begins when the sawyer starts cutting the opposite side of the direction of fall and ends when the tree hits the ground
Radni zahvat počinje prilikom prerezivanja stabla sa suprotne strane od zasjeka i završava kad se stablo sruši na zemlju
Begins when the co-sawyer starts to enter the wedge-shaped blade to the cutting gap and ends when the tree falls
in the predetermined direction
Radni zahvat započinje kada pomoćni radnik sjekač počne postavljati klinove u potpiljak te završava kad se stablo
sruši na zemlju
Maintenance and refueling – Održavanje motorne pile i punjenje goriva i maziva
Personal delay, Technical delay, and Operational delay – Osobni prekidi rada, tehnički prekidi rada i povremeni radovi
winter; cold occasionally affected worker utilization
percentages. The power-saw team normally consists
of three men: a feller, an assistant, and a helper. Time
and operational variables were measured using a stopwatch and recorded on paper (Bjorheden and Thompson 1995, Wang et al. 2004). A work cycle for each operation consisted of certain elemental functions and
factors. The time for each function and value of each
factor were measured in the field. Elemental time functions for chainsaw felling are shown in Table 2.
Harvesting factors or operational variables for
chainsaw felling measured in the field include disCroat. j. for. eng. 34(2013)2
tance to tree (cm), tree species, diameter at breast
height (DBH) (cm), walk to tree slope (%), slope at tree
stump (%), and direction of felling: code 1: felling to
lean; code 2: felling sideways to the lean (0° to 90°);
code 3: felling opposite the lean (90° to 180°)). A total
of 233 cycles for chainsaw felling were observed in the
field. Local volume equations of Namkhaneh district
were used to compute the volume of felled trees. The
SPSS 14.0 statistical program was applied to develop
regression equation of time consumption. A regression
analysis with the stepwise method between operational variables (independent variables) was per-
285
M. Jourgholami et al.
Performance, Capability and Costs of Motor-Manual Tree Felling... (283–293)
Fig. 2 Effect of DBH on felling time without delay of tree felling
Slika 2. Utjecaj prsnoga promjera na vrijeme sječe stabla, bez radnih zastoja
formed on the time study data collected for chainsaw,
to determine independent variables that were significant in estimating total felling time (p = 0.01). Regression techniques were also employed to develop models for elemental times, felling cycle time and
productivity of chainsaw felling.
Total felling time was analyzed in stages (Lortz et
al. 1997). First, each work elemental function (phase)
was fit to a linear equation (Y = a + bX) using DBH as
independent variable. Then, other operational variables were added to the model to show how these factors influence the felling time, and to give a more reliable model of motor-manual felling operation.
3. Results and discussion – Rezultati i
rasprava
Fig. 1 Starting to undercut (A and B), cutting the backcut and
wedging (C) in the study area
Slika 1. Šumski radnik sjekač započinje izradu zasjeka (A i B), potpiljivanje i zabijanje klinova (C)
286
DBH of felled trees ranged from 20 to 135 centimeters and averaged 52.3 centimeters, while the volume
per felled tree was between 0.2 to 29.7 cubic meters
with an average of 4.27 cubic meters (Table 3). Distance
between harvested trees varied from 2 to 105 meters
with an average of 25.4 meters. A felling cycle consists
of the following elements: walk to tree, acquire, undercut, backcut, wedging, refuel and service, and delay
times. Total felling time varied from 0.6 to 29.65 minutes with an average of 4.5 minutes, while total felling
time without delay ranged between 0.6 to 10.1 minutes
with an average of 3.14 minutes per cycle (Table 3).
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M. Jourgholami et al.
min
Tree diameter
Prsni promjer stabla
Volume
Obujam
Walk
Hod do stabla
Acquire
Čišćenje okoliša i
određivanje smjera rušenja
Izrada zasjeka
Undercut
Izrada završnoga reza
Backcut
Wedging
Zabijanje klinova
Refuel & service
Točenje goriva i popravak
Delay free time
Factor
Vrijeme bez zastoja
Table 3 Statistics of operational variables of motor-manual felling in the field study
Tablica 3. Statistika operativnih varijabli u provedenom istraživanju ručno-strojne sječe
m3
cm
0.09
0.22
20
Maximum
10.1
3.5
4.17
3.49
5.72
2.15
2.82
29.7
135
Std. dev.
1.95
0.56
0.49
0.62
1.01
0.21
0.43
5.23
24.59
Nagib kod panja
Factor
code*
%
šifra*
Mean – Srednja vrijednost
m
Pers. Delay
0.05
Osobni prekidi rada
0.06
Tech. Delay
0.13
Tehnički prekidi rada
0
Oper. Delay
0
Operativni prekidi rada
0.6
Ukupni prekidi rada
Minimum
Total delay
52.34
Ukupno vrijeme sječe
4.22
Total felling time
0.66
Inter-tree dis.
0.23
Udaljenos između
doznačenih stabala
1.25
Nagib tijekom hoda do
stabla
0.74
Walk to tree slope
0.1
Slope at stump
0.15
Smjer obaranja
3.14
Direction of felling
Mean – Srednja vrijednost
min
1.31
26.07
28.5
25.43
4.5
1.36
0
0.17
1.18
Minimum
1
5
5
2
0.6
0
0
0
0
Maximum
3
70
65
105
29.65
24.36
0
20.21
24.36
Std. dev.
0.55
15.29
14.36
16.6
4.99
4.16
0
1.48
3.9
*code (felling direction as described in text) – šifra (odabrani smjer rušenja stabla kako je opisano u tekstu)
Time of the walk to the tree averaged 0.66 minutes
and ranged between 0.09 to 2.82 minutes. Since the
walk to the tree is directly related to stand density and
harvesting method (Single-selection method), it was
significantly different depending on the distance between felled trees. Acquire time averaged 0.23 minutes
and ranged between 0.05 and 2.15 minutes per cycle.
Time of undercut varied from 0.06 to 5.72 minutes
with an average of 1.25 minute per cycle s. Backcut
time ranged from 0.13 to 3.49 minutes and averaged
0.74 minutes per cycle. Some trees needed no wedging
time. However, a maximum of 4.17 minutes was taken
to direct large trees. Refuel and service time averaged
0.15 minutes per cycle. A total of 55 delays was observed during motor-manual felling in the field study.
The delay times were ranged from 0 to 24.36 and averaged 1.36 minutes per cycle.
Croat. j. for. eng. 34(2013)2
The relation between tree size and total cycle time
is shown in the scatter diagram in Fig. 2. There is a
strong trend of increasing cycle time as tree size increases. A regression equation was developed to predict total cycle time as a function of tree diameter.
Other independent variables were tested and were not
significantly related to the total cycle time (Fig. 3–5).
The stepwise analysis has revealed that tree diameter (DBH) significantly affects the felling cycle time
(Fig. 3). Therefore, we have developed a regression
model of the total felling time without delay using tree
diameter, direction of felling, and inter-distance of
felled trees as an independent variable (Eq. 1). On the
other hand, the total felling time was best described
by DBH, direction of felling, and distance between
felled trees. Statistical significance was checked by an
287
M. Jourgholami et al.
Performance, Capability and Costs of Motor-Manual Tree Felling... (283–293)
Fig. 3 Relation between DBH and total cycle time without delay for
felling per cycle
Slika 3. Odnos između prsnoga promjera i ukupnoga vremena sječe, bez radnih zastoja
Fig. 5 Effect of DBH on backcut time of tree felling per cycle
Slika 5. Utjecaj prsnoga promjera na vrijeme potpiljivanja stabla
Table 4 ANOVA for regression model developed for motor-manual
tree felling
Tablica 4. ANOVA za regresijski model razvijen za ručno-strojnu sječu
Factor
Fig. 4 Effect of DBH on undercut time of tree felling per cycle
Slika 4. Utjecaj prsnoga promjera na vrijeme izrade zasjeka
F-test of the overall fit and t-tests for individual parameters (Table 4).
T = –1.1997 + 0.05844DBH + 0.63097DF + 0.001778D (1)
288
SS
df
MS
f
Sig.
Regression
621.44
3
2078.15
182.2
<0.0001
Residual
260.3
229
1.14
Total
881.74
232
Where:
T
DBH
DF
D
R2
= total felling time without delay (min)
= diameter at breast height (cm)
= direction of felling (1–3 or 0°–180°)
= distance between felled trees (m)
= 0.705, Adjusted R-square = 0.701; Number
of observations = 233
The multiple correlation coefficient of the model
shows that 70.5% of the total variability can be explained by the model. The significance level and Fvalue in the table with the analysis of the model variance confirms that the model makes sense at the
probability level of 0.05.
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M. Jourgholami et al.
The production of felling with chainsaw can be obtained by using the production and time data as follow:
Production =
TFV
TFV
Where:
TFV = total felling volume, m3
TFT = total felling time, hour
The hourly production (m3/hr) with delay time was
56.34 m3/hour. The measured production for motormanual felling without delay times was 80.7 m3/hour.
Hourly production of felling without delay times was
higher than production (m3/hour) with delay times.
Also, the hourly production of chainsaw felling with
and without delay time was 13 trees per hour and 19
trees hour, respectively. The relation between tree size
and felling production is shown in the scatter diagram
in Fig. 6. There is a strong trend of increasing production as tree size increases.
We calculated the hourly cost ($/hr) of motor-manual felling using the cost estimation model developed
by the Forest, Range and Watershed Management Organization of Iran (1999). A purchase price of USD
1 400 was used in the chainsaw cost estimation model,
and the annual interest rate of 18.5%. A chainsaw life
of 3 years was assumed. Insurance and tax rate and
utilization rate were set at 5% and 83%, respectively.
The hourly machine cost was estimated at USD 31.26.
Table 5 summarizes the estimates of machine costs for
chainsaws.
As a result, the average felling cost per cubic meter,
including the delay time, was USD 0.55/m3, while the
average felling cost without delay was estimated at
USD 0.39/m3. The cost of chainsaw felling with and
without delay time was 2.34 and 1.64 USD per tree,
Fig. 6 Effect of DBH on felling productivity
Slika 6. Utjecaj prsnoga promjera na proizvodnost sječe
respectively. Approximately 25% of the total operating
hours were identified as delay times during the time
study, which results in an average machine utilization
rate of 75%.
The effect of each variable used in the model on the
felling time was studied by changing one variable in
its range and retaining the other variables constant at
their average. Fig. 7 shows the effect of operational
variables on felling costs. Increasing tree diameter and
direction of felling will increase felling costs per cycle.
The effect of tree size on unit cost of motor-manual
felling tree is shown in Figure 8. DBH classes of 20 to
50 centimeters have a dramatic effect on felling costs,
USD/hour
USD/satu
0.47
0.2
Croat. j. for. eng. 34(2013)2
0.07
0.73
0.47
13
1.06
14.53
16
Total hourly machine rate
Trošak radnoga sata
Hourly labor cost
Ukupni materijalni troškovi
Subtotal (Operating)
Lanac i oštrač lanca
Chain and file
Gorivo i mazivo
Fuel and lubricant
Održavnje i popravak
Maintenance and repair
Ukupni fiksni troškovi
Operating costs – Materijalni troškovi
Subtotal (Fixed)
Porez i osiguranje
Tax and insurance
Kamata
Interest
Amortizacija
Depreciation
Vrsta troška
Cost elements
Fixed costs – Fiksni troškovi
Ukupni trošak radnoga sata stroja
Table 5 Calculation of motor-manual felling costs
Tablica 5. Izračun troškova ručno-strojne sječe
31.26
289
M. Jourgholami et al.
Performance, Capability and Costs of Motor-Manual Tree Felling... (283–293)
Fig. 7 Effect of tree diameter (DBH) on felling costs
Slika 7. Utjecaj prsnoga promjera na troškove sječe
in Fig. 9. On average, during a cycle most time was
spent on undercut, which accounted for 27.9% of the
total time. Personal delay (rest and meal time) accounted for approximately 26.3% of the time. Backcut
and walk to tree accounted for 16.5% and 14.6% of the
total cycle time, respectively. Acquire accounted for
less than 5% of the total cycle time. Technical delay
accounted for only 3.9% of the total time, while refuel
and service and wedging time accounted for about
3.4% and 2.3%, respectively.
Undercut, backcut and delay time were the most
important time-consuming elements in felling. This
suggests that the productivity could be increased by
diminishing the time consumption of these elements.
Delay time is an inseparable part of each work phase
in harvesting in Iran. Delay time accounted for approximately 30% of gross-effective hour. Technical
delays, such as sharpening and dealing with the chain
of a chainsaw breaking, accounted for approximately
4% of the delay time. One of the reasons for a long
delay time was the use of old and obsolete equipment,
unsuitable and incorrect filling of the chain saw
(Mousavi 2009).
Operational delay accounted for the largest share
that needs to be considered. Operation delay may relate to management, supervision, and equipment
Fig. 8 Effect of tree diameter on unit cost of motor-manual tree
felling
Slika 8. Utjecaj prsnoga promjera na jedinične troškove sječe
ranging from USD 1.2 to 0.2 per m3. With the classes
above 50 cm class, the felling costs for the chainsaw
changed constantly.
During the study period, felling time was divided
into elemental time functions (work phases) as shown
290
Fig. 9 Percentage of time distribution of tree felling elements
Slika 9. Postotna distribucija vremena radnih zahvata prilikom sječe
stabala
Croat. j. for. eng. 34(2013)2
Performance, Capability and Costs of Motor-Manual Tree Felling... (283–293)
M. Jourgholami et al.
availability. A felling group might not have had all the
necessary tools needed for work, which caused a prolonged delay as they had to borrow the tools from the
neighboring groups. Activities such as the chain breaking and filing as well as pinching in the kerfs can be
part of the working time (Sarikhani 2008), however, in
this study it is considered as a technical delay. If we
take into account these activities as a part of effective
working hour, productivity of felling decreases approximately by 3.6%. Walking is the first element of
the felling work cycle. Silvicultural treatment is one of
the most important factors influencing time consumption of walking. In the single tree selection method,
there were more trees in the forest than in the shelter
wood and clear cutting method, and hence more time
was required (Lortz et al. 1997, Mousavi 2009). In this
study, only 14% of the gross-effective hour was related
to walking time.
In some areas, the skid trails were not marked, so
the operator was free to choose the direction. It may
increase skidding time and cost. It is recommended to
mark skid trails before felling (Nikooy 2007, Mousavi
2009). The higher percentage of backcut is related to
the use of a wedge to lead the tree in the specified direction in order to prevent damage to the residual
stand and breakage to the tree being felled. The results
showed that the stump diameter, direction of felling
and distance were the most important variables affecting the felling time. Tree diameter and inter-tree distance influenced the time consumption of felling, productivity, and unit cost of felling. A study by Kluender
and Stokes (1996) showed similar results. They found
that tree diameter is the most important factor in estimating the felling time, while the distance between
trees and harvesting intensity were also important.
However, productivity of felling may be influenced
by the operator skills, silvicultural method, tree species, stand composition, undergrowth trees and seedlings, weather condition, coldness of weather, age and
brands of chainsaws, chain condition, and lean of the
tree as well as slopes (Nikooy 2007, Sarikhani 2008,
Mousavi 2009). However, the influences of all these
factors were not documented in this study but they
were mentioned by Conway (1976).
sumption and productivity of felling. Inter-tree distance also influences the time consumption and productivity of felling. The productivity of felling trees
with a large diameter is higher than the productivity
of felling trees with a small diameter.
4. Conclusion – Zaključak
Jourgholami, M., 2012: Small-scale timber harvesting; mule
logging in Hyrcanian Forest. Small-scale Forestry 11(2):
255–262.
Motor-manual tree felling is a highly variable operation. There are many factors influencing the felling
productivity. This paper identifies the most significant
variables that should be recognized prior to harvesting. It has been proved that the stump diameter of the
tree is the most influential factor affecting time conCroat. j. for. eng. 34(2013)2
Acknowledgements – Zahvala
This paper is a one of the results of the research
project No. 88001084, which was carried out in the period 2010–2012 in the Hyrcanian forest in northern
Iran. The authors would like to acknowledge the financial support of the Iranian National Science Foundation (INSF).
6. References – Literatura
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Bjorheden, R., Thompson, A. M., 1995: An International Nomenclature for Forest Work Study. Paper presented at the
XX IUFRO World Congress, Tampere, 6–12 August 1995.
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Conway, S,. 1976: Logging practices. Miller Freeman Publication. USA. 465 p.
Dykstra, D. P., Heinrich, R., 1996: FAO model code of forest
harvesting practice. FAO. Rome. 97 p.
FAO, 1976: Harvesting planted forests in developing countries. A manual on techniques, roads, production and costs.
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Forest, Range and Watershed management Organization,
1999: Instruction for Preparing Harvesting Plan, 39 p. (in
Persian).
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model for small trees in natural stands in the Interior Northwest, Forest Products J 51(4): 54–61.
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Iran, 240 p. (in Persian).
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central Appalachia. Forest Prod J 56(3): 81–86.
Lortz, D., Kluender, R., McCoy, W., Stokes, B., Klepac, J.,
1997: Manual felling time and productivity in southern forests. Forest Prod J 47(10): 59–63.
MacDonald, A. J., 1999: Harvesting Systems and Equipment
in British Columbia. FERIC Handbook No. HB-12. B.C. Ministry of Forests. Forestry Division Services Branch. Production Resources. 595 Pandora Avenue. Victoria, BC V8W 3E7.
211 p.
Mousavi, R., 2009: Comparison of productivity, cost and environmental impacts of two harvesting methods in Northern
Iran: short-log vs. long-log, Ph.D. thesis, University of Helsinki, Finland.
Nikooy, M., 2007: Production optimization and reduction
impact on forest by preparing harvest planning in Nav, Iran.
Ph.D. thesis, Tehran University, 165 p. (in Persian)
Rummer, R., Klepac, J., 2002: Mechanized or hand operations: which is less expensive for small timber? Published in
Small Diameter Timber: Resource Management, Manufacturing, and Markets proceedings from conference held February 25–27, 2002 in Spokane, Washington. Compiled and
edited by D.M. Baumgartner, L.R. Johnson, and E.J. DePuit.
Washington State University Cooperative Extension. 268 p.
Sarikhani, N., 2008: Forest utilization. Tehran University
Press, Tehran. 728 p. (in Persian).
Sessions, J., Boston, K., Murphy, G., Wing, M. G., Kellogg,
L., Pilkerton, S., Zweede, J. C., Heinrich, R., 2007: Harvesting
operation in the Tropics. Springer-Verlag, Berlin, Heidelberg.
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Sažetak
Izvedba, mogućnosti i troškovi ručno-strojne sječe stabala
u šumi tvrdih listača Hyrcanian
Zbog velikih promjera krošanja te zbog prilično strmoga terena u hirkanskim šumama stabla se sijeku isključivo
ručno-strojnom metodom. Ciljevi su ovoga istraživanja: provesti studij rada i vremena ručno-strojne sječe u tvrdim
listačama, primjenom regresijskih funkcija razviti modele vremena radnih zahvata ručno-strojne sječe te procijeniti
proizvodnost i troškove ručno-strojne sječe. Istraživanje je provedeno u odjelima 219 i 223 koji se nalaze u okrugu
Namkhaneh unutar nastavno-pokusne šume Kheyrud. Za sječu je stabala korištena motorna pila STHIL s četiri
konjske snage te vodilicom od 70 cm. Istraživanje je provedeno zimi od siječnja do veljače 2011. godine. Zimsko vrijeme, osobito hladnoća, ponekad utječu na radni učinak radnika sjekača. Radni se ciklus sastojao od određenih radnih
zahvata i drugih čimbenika. Vrijeme za svaki radni zahvat i vrijednost svakoga čimbenika mjereno je na istraživanom
radilištu. Čimbenici koji utječu na sječu ili operativne varijable za sječu koje su mjerene u istraživanju su udaljenost
od stabla (cm), vrsta drveća, prsni promjer (cm), nagib po kojem se radnik kreće prilikom dolaska do stabla (%),
nagib terena kod panja (%), smjer rušenja stabla. Ukupno su snimljena 233 radna ciklusa sječe stabla. Za izradu
regresijskih jednadžbi korišten je statistički program SPSS 14.0. Rezultati provedene analize ukazuju na povećanje
radnoga ciklusa s povećanjem dimenzija stabla. Postupna analiza podataka pokazala je značajan utjecaj prsnoga
promjera na vrijeme sječe, te je stoga razvijen regresijski model za izračun ukupnoga vremena sječe, bez zastoja, na
osnovi prsnoga promjera stabla, smjera rušenja te međusobne udaljenosti doznačenih stabala. Proizvodnost (m3/h)
sa zastojima rada iznosila je 56,34 m3/h. Izmjerena proizvodnost za ručno-strojnu sječu, bez zastoja rada, iznosila je
80,7 m3/h. Proizvodnost (m3/h) bez zastoja rada iznosila je više nego proizvodnost sa zastojima rada. Povećanje dimenzija stabala značajno utječe na povećanje proizvodnosti. Kao krajnji rezultat analize prosječni trošak ručno-strojne
sječe, sa zastojima rada, iznosio je 0,55 USD/ m3, dok je prosječan trošak ručno-strojne sječe bez zastoja rada iznosio
0,39 USD/ m3. Povećanje prsnoga promjera stabla te smjer rušenja utjecat će na povećanje troškova ručno-strojne
sječe po proizvodnom ciklusu. Stabla prsnih promjera od 20 do 50 cm imaju značajan utjecaj na troškove ručno-strojne
sječe, koji se kreću u rasponu od 1,2 do 0,2 USD/ m3. Na vrijeme izrade zasjeka, završnoga reza te vremena zastoja
otpada najveći dio vremena radnoga ciklusa. U ovom su radu predstavljene najvažnije varijable koje utječu na ručno-
292
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Performance, Capability and Costs of Motor-Manual Tree Felling... (283–293)
M. Jourgholami et al.
strojnu sječu te ih je prije provođenja radova ručno-strojne sječe potrebo vrednovati. Dokazano je da su promjer
panja i udaljenost između doznačenih stabala najutjecajniji čimbenici potrošnje vremena i proizvodnosti prilikom
sječe. Proizvodnost pri sječi stabala većih promjera veća je nego pri sječi stabala manjih promjera.
Ključne riječi: sječa stabala, studij rada i vremena, regresijski model, proizvodnost, troškovi
Authors’ address – Adresa autorâ:
Received (Primljeno): February 12, 2012
Accepted (Prihvaćeno): July 12, 2013
Croat. j. for. eng. 34(2013)2
Asst. Prof. Meghdad Jourgholami, PhD.
e-mail: [email protected]
Prof. Baris Majnounian, PhD.*
e-mail: [email protected]
Assoc. Prof. Nosratollah Zargham, PhD.
Department of Forestry and Forest Economics
Natural Resources Faculty
University of Tehran
P.O. Box: 31585 – 4314, Karaj
IRAN
*Corresponding author – Glavni autor
293
Original scientific paper – Izvorni znanstveni rad
Effects of Cutting Patterns of Shears on
Occlusion Processes in Pruning
of High-Quality Wood Plantations
Enrico Marchi, Francesco Neri, Marco Fioravanti, Rodolfo Picchio, Giacomo Goli,
Giuseppina Di Giulio
Abstract – Nacrtak
Arboriculture plantations aim to produce high-quality wood. In order to investigate the type
and extent of mechanical injury that pruning causes to tree cambium as well as the effects on
the healing process, different types of shear were selected and used in an eight-year-old Quercus robur L. plantation. The amount of removed, detached and crushed bark was assessed by
means of image analysis immediately after pruning. After 15 months, the effect of different
cutting patterns on the healing process was investigated by measuring the area of the pruned
branch covered by woundwood (HI1). Five years after pruning, the same analysis was performed above and below bark (HIo5 and HIu5) and a number of parameters were assessed in
order to quantify the quantity and quality (symmetry) of woundwood growth and the healing
time for sealing. The action of pruning tools depends on cutting pattern and branch diameter.
The greater the diameter, the longer the healing time. The double-blade tool caused less injury
and showed the fastest healing process. The use of double blade pruning tools is thus recommended to improve the performance of wood quality production in arboriculture plantations.
We also recommend the healing index HI1 for an early assessment of pruning damage.
Keywords: pedunculate oak, pruning tools, agroforestry, wood quality, occlusion
1. Introduction – Uvod
Forest trees have been pruned for centuries in order to increase wood quality and to shape the tree
(O’hara 2007). Pruning meets different objectives, such
as: fuelwood production; aesthetic improvement;
dead branch removal, reduction or prevention of the
attack of pathogens. However, the most important
purpose of tree pruning is usually to increase the quality of the log to be used in sawing, peeling or slicing
operations (O’hara 2007, Kupka 2007), in particular in
plantation to produce high quality wood (Springmann
et al. 2011). The main aim is to get at least 2.5 m of stem
length without knots or related defects in logs with a
diameter larger than 30–40 cm (Mohni et al. 2008). In
fact, on average, the butt log represents 90% of a tree’s
economic value (Kronauer 2009) and knot should be
limited to the inner 8–10 cm of the log diameter. This
suggests the need for early pruning.
Croat. j. for. eng. 34(2013)2
After accurate pruning action, the wood growth
will likely be free of defects and will consequently
achieve greater wood quality than unpruned trees.
Nevertheless, branch cutting is a stressful action for
trees (Springmann et al. 2011) and pruning should
avoid a sudden reduction of the total leaf area, so that
the growth increment is kept regular. A severe pruning
or pruning that removes foliage solely from the upper
crown will improve stem form and reduce the size of
the defected core thereby increasing clearwood production (Medhurst et al. 2006). However, it may also
reduce tree growth or stimulate a tree response by developing secondary shoots (Alcorn et al. 2008), thus
having a negative effect on clearwood production.
The effects of pruning on wood quality involve a lot
of factors: e.g. pruning season, pruning methods, tree
species, as well as the diameter of the cut branches,
which in high quality arboriculture plantation should
295
E. Marchi et al.
Effects of Cutting Patterns of Shears on Occlusion Processes in Pruning ... (295–304)
be lower than 3 cm (DeBell et al. 2006, Dujesiefken et
al. 1998, 2005, Nicolescu and Kruch 2009).
Many studies on tree pruning concern the methods
of branch removal and subsequent compartmentalization (Shigo and Marx 1977) and wound occlusion.
These studies show contrasting results. Several works
indicate that a cut close to the stem is effective for
pruning trees for a more rapid occlusion and to enhance wood quality by avoiding infections of fungi or
bacteria (Brodie and Harrington 2006, DeBell et al.
2006). Other studies indicate that for a proper pruning
the branch collar should not be removed from the
stem, thus improving compartmentalization response
(Shigo 1984, Dujesiefken et al. 1998, Smith 2006).
A more rapid occlusion in trees with faster radial
growth rates, both conifers and broadleaves, was observed (Roth 1948, O’Hara and Buckland 1996, Petruncio et al. 1997). Some studies revealed a more rapid
occlusion after pruning live branches than dead
branches and dead branches occluded more rapidly if
the branch collar was intentionally injured during
pruning (Brodie and Harrington 2006).
The mechanical injuries caused to the bark along
the perimeter of the cutting section affect the healing
process, they may favour abnormal wood coloration/
discoloration and/or pathogen attacks, and, ultimately,
they reduce timber quality and value (Pearce 2000,
Dujesiefken et al. 2005, Brunetti et al. 2006, Nocetti et
al. 2011).
Infection from fungal decay organisms has always
been a concern with pruning. However, many authors
found little or no evidence of decay in broadleaved trees
in the northern hemisphere (Chiu et al. 2002, DeBell et
al. 2006) and sometimes found less decay in pruned
trees than unpruned trees (Skilling 1958). Nevertheless,
pruning of thicker branches may cause extensive discolouration and decay in the trunk even though the cuts
are made correctly (Dujesiefken et al. 1998).
In this considerable international body of literature
on tree pruning, there is a dearth of studies on the effects of pruning tools. Very few studies performed
until now consider the effect of pruning tool cutting
pattern (Baldini et al. 1997, Marchi and Rossi 2007,
Schatz et al. 2008). Other studies on different pruning
tool cutting patterns were focused only on the force
requirements for manual pruning (Crossland et al.
1997, Parish 1998). The use of different cutting patterns
in fact could result in different occlusion time, wounding patterns, wood defects, defects extension into the
bole, and decay.
The aim of this paper was to investigate the relation
between pruning tools cutting patterns and the me-
296
chanical injury to tree bark in Quercus robur L. plantation, and to analyze the effect of the cutting pattern of
pruning tools on occlusion processes. These results
will help to minimize direct and indirect unfavorable
pruning effects on wood quality, and to give a contribution in improving research on the methods of
branch removal and subsequent wound occlusion.
2. Materials and Methods – Materijal
i metode
A pruning operation was carried out in an eightyear-old plantation located in S. Barbara (Arezzo –
Central Italy – 43°34’59.49” N, 11°28’23.39” E). It was
a mixed stand of Q. robur, as the main species, and
Alnus cordata, as a secondary species. The planting pattern was square with 3 meters between the trees and
the main and the secondary species were alternate
along the row and between the rows.
In the pruning campaign, carried out in April 2006,
three shears with different cutting patterns were used
(Fig. 1): bypass (BP), draw cut (DC) and double blade
(DB). The shears were selected to represent the range
of tool designs currently used in Italy. Thirteen trees
of Q. robur (Table 1) were selected for a total of 36
branches cut by each shear. For every single tree the
branches were cut with the same shear. For each
branch cut the diameter, the height above ground and
the angle with reference to the North were measured
(the first with a caliper, the second with a measuring
tape and the last one using a Minerva compass) in
order to be able to locate the cuts subsequently.
In pruning, the cut left the branches bark ridge and
the branch collar intact; only branches less than 3.5 cm
in diameter were cut. To evaluate mechanical injury,
each cutting section was photographed with a macroobjective. The camera was parallel to the cut surface.
The amount of bark injury to the section perimeter was
estimated by means of a CAD software (AutoCAD
2002, Autodesk Inc., USA). The bark injury (BI) was
quantified by measuring the angle included in the arc
of the injured section perimeter (Fig. 2).
Fifteen months later, the cutting sections were rephotographed with the same method and they were
compared with the pictures taken after pruning. The
area of each cutting section covered by callus and
woundwood (HA) was determined by means of an
image analysis software (ImageJ 1.39u, National Institute of Healh, USA), and then compared with the
total area of each wound after pruning (TA). A healing
process index (HI) was calculated as a ratio between
HA and TA.
Croat. j. for. eng. 34(2013)2
Effects of Cutting Patterns of Shears on Occlusion Processes in Pruning ... (295–304)
E. Marchi et al.
Table 1 Characteristics of the Quercus robur trees at the time of pruning (2006): DBH, diameter at breast height, and diameter and height above
ground level of the pruned branches (S.E. and N). The values of felled trees refer to 2006. DBH was measured overbark on standing trees in 2006
and underbark on crosscut sections in 2011. The differences among groups were not statistically significant (Kruskal-Wallis test, p-level 0.05)
Tablica 1. Značajke stabala hrasta lužnjaka u vrijeme orezivanja grana (2006): DBH, prsni promjer; promjer orezanih grana i visina grana od
tla (standardna pogreška i N). Vrijednosti se odnose na 2006. godinu. Prsni je promjer mjeren s korom na dubećim stablima 2006. godine i bez
kore na isječcima 2011. godine. Razlike među grupama nisu bile statistički značajne (Kruskal-Wallisov test, p-level 0.05)
DB
All trees in 2006
Sva stabla 2006.
BP
DC
DB
Trees felled in 2011
Stabla posječena 2011.
BP
DC
Tree DBH, mm
Branch diameter, mm
Height a.g.l., cm
Prsni promjer stabla, mm
Promjer grane, mm
Visina od tla, cm
50.0
15.7
152.9
(4.6 N = 5)
(0.1 N = 36)
(7.8 N = 36)
60.2
15.7
142.9
(13.3 N = 4)
(0.1 N = 36)
(10.2 N = 36)
61.4
17.0
147.9
(2.7 N = 4)
(0.1 N = 36)
(10.6 N = 36)
48.2
15.7
164.7
(8.1 N = 3)
(0.1 N = 21)
(12.4 N = 21)
65.8
15.8
143.6
(16.7 N = 3)
(0.1 N = 32)
(11.3 N = 32)
61.0
17.0
147.9
(2.7 N = 4)
(0.1 N = 36)
(10.6 N = 36)
Fig. 1 Outline of cutting pattern
Slika 1. Izgled načina rezanja
Five years after the pruning campaign (March
2011), ten pruned trees were cut for a total of 21, 32 and
36 cutting sections for DB, BP and DC, respectively.
The cutting sections were re-photographed and measured in order to compare them with the previous
results and pictures (taken immediately after pruning
Croat. j. for. eng. 34(2013)2
Fig. 2 Example of the method used for measuring the damage to
cambium in fresh cuttings. The injury was quantified by measuring
the angle included in the arc of the injured section perimeter
Slika 2. Primjer metode korištene za mjerenje oštećenja kambija na
svježim prerezima. Ozljeda je kvantificirana mjerenjem kuta kružnoga
isječka na čijem se luku nalazi oštećenje
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Effects of Cutting Patterns of Shears on Occlusion Processes in Pruning ... (295–304)
Fig. 3 Asymmetrically (a) and symmetrically (b) healed cuts, and cross section (c) with detail of: distance between cutting section and underbark stem perimeter (SC) and thickness of entrapped cork layer (DW)
Slika 3. Asimetrično (a) i simetrično (b) zarasli rezovi te presjek (c) s detaljima: udaljenost mjesta reza od plašta debla bez kore (SC) i debljina
urasle kore (DW)
and fifteen months after pruning) by measuring overbark HI (HIo5). Moreover the cutting sections that had
not completely healed were counted and measured.
The symmetry of the healing process for each cutting
tool was measured and a symmetry index (HSI) was
calculated as a ratio of the lower and higher value of
the distance between the perimeter of the cutting section and the contact line of callus (an asymmetrically
healed cut is shown in Fig. 3a and a symmetrical
healed cut is shown in Fig. 3b). Some pruned brunches (4 for DB, 4 for BP and 9 for DC) were no longer
visible overbark; for these branches the HSI was not
calculated. The distances were measured by a ruler to
the nearest 0.5 mm. Then, the bark over the cutting
sections was carefully removed in order to measure
the area of each cutting section covered by woundwood (HAu).The healing process index underbark
(HIu5) was then calculated as a ratio between (HAu)
and the total area of each woody section after pruning.
Finally, each stem was crosscut at the knot level
and the knots were analyzed. Two, two and four knots
obtained by DB, BP and DC, respectively, were no longer recognized. On each cross section the following
variables were measured (Fig. 3c): distance between
the cutting section of the branch when pruned and
underbark stem perimeter (SC); thickness of entrapped cork layer (DW); number of years to complete
the healing process (HT). In relation to the unhealed
knots, in order to not exclude these cases from the
analysis, we considered that the unsealed branch
would seal in 1 more year, i.e. a value of 6 years was
adopted. A damaged woundwood index (DWI) was
calculated as a ratio between DW and SC.
298
The value of underbark DBH in 2006 and 2011 was
measured for each felled tree on the cross section at
1.3 m above ground. The values of SC, DW and DBH
were measured by a ruler to the nearest 0.5 mm.
Data were checked for normality (KolmogorovSmirnov test) and homogeneity of variance (Levene
test). The Kruskal-Wallis non-parametric multiplecomparison test was used to test differences between
non normally distributed variables (Sprent and Smeeton 2001, Lo Monaco et al. 2011, Picchio et al. 2009),
e.g. tree diameter, branch height above ground, HI1,
HIu5, HSI, SC, DWI, and HT. In order to test the differences between the characteristics of trees and branches at the time of pruning (2006), the same test, i.e.
Kruskal-Wallis, was also applied to cut branch diameter. A one-way ANOVA was applied to determine the
effects of cutting pattern on the extent of injury immediately after pruning (2006), and differences were
tested by the Tukey HSD test. All differences were considered as significant when p ≤ 0.05. A multiple linear
regression was applied to test the relation between
type of pruning tools, years for the healing process to
be complete and branch diameter. All statistics used
the Statistica 7.0 software (StatSoft, Tulsa OK, USA).
3. Results – Rezultati
Non-significant statistical differences were found
in the diameter at breast height (DBH), in the diameter
of the cut branches and in the height above ground
level of the branches of the thirteen trees in 2006 and
of the ten felled trees in 2011 (Table 1).
Croat. j. for. eng. 34(2013)2
Effects of Cutting Patterns of Shears on Occlusion Processes in Pruning ... (295–304)
E. Marchi et al.
3.1 Mechanical injury immediately after pruning
Mehanička ozljeda neposredno nakon
orezivanja
Three kinds of bark injury were found over the cutting section perimeter, namely: crushing, i.e. the bark
appeared to be more compact; detaching, i.e. the bark
was separate from the wood; and removal, where
some bark parts were missing. The cutting pattern did
not significantly affect the kind of injury (data not
shown), while the extent of injury varied in the following order: DB < DC < BP (p < 0.001) (Fig. 4).
3.2 Healing process after 15 months – Proces
zarašćivanja nakon 15 mjeseci
The cutting pattern significantly affected HI1 (p <
0.001). Cuts made using double blade tools showed a
quicker healing process, while draw cut and bypass
showed a slower and similar healing process (Fig. 5).
72% of the branches cut by DB completely healed
their wounds (HI1), and 19% closed 90% of the wound.
In contrast, just 11% and 8% of branches cut by BP and
DC respectively attained complete healing (Fig. 6a).
Callus and woundwood developed in a quite circular pattern in the healing process of cuts made by
double blade tools, whereas when using bypass and
Fig. 5 Healing process index (HI1) fifteenth month after pruning
(2007) for different cutting patterns (+/– S.E.). Different letters
show significant differences (Kruskal-Wallis multi-comparison test,
p < 0.05, N = 36)
Slika 5. Indeks procesa zarašćivanja (HI1) petnaest mjeseci nakon
orezivanja (2007) za različite načine rezanja (+/– standardna pogreška). Različita slova pokazuju signifikantne razlike (Kruskal-Wallisov multiusporedni test, p < 0.05, N = 36)
draw cut tools they developed an irregular shape (Fig.
7). In particular, 50% of the branches cut by draw cut
shears developed callus and woundwood mainly on
one side, i.e. the side cut by the blade (data not shown).
3.3 Healing process 5 years later – Proces
zarašćivanja nakon pet godina
Fig. 4 Damage assessed immediately after pruning (2006) for different cutting patterns (+/– S.E.). Different letters show significant
differences (Tukey HSD test, p<0.05, N = 36)
Slika 4. Oštećenje ustanovljeno neposredno nakon orezivanja (2006)
za različite načine rezanja (+/- standardna pogreška). Različita slova
pokazuju signifikantne razlike (Tukey HSD test, p < 0.05, N = 36)
Croat. j. for. eng. 34(2013)2
In 2011, cuts by DB confirmed their better ability to
seal in shorter time periods. 100% of DB branches were
completely healed, contrasting with only 90.6% of BP
branches and 71.9% of DC branches (Fig. 6c). However, no statistically significant differences arise for
HIu5 (Table 2). A large part of the wounds were sealed,
and HIo5 was almost 1 (Fig. 6b).
DB showed a more symmetrical healing process,
followed by BP, but not significant differences (p = 0.09)
were observed (Table 2). A symmetrical healing process could mean that the cambium worked well on
both sides and this could lead to shorter sealing times.
The distance between the cutting section of the
branch and the underbarked stem perimeter (SC) was
higher in the knots obtained by DB and BP than in DC
knots (Table 2), i.e. BP and DB resulted in shorter sealing times.
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Effects of Cutting Patterns of Shears on Occlusion Processes in Pruning ... (295–304)
Fig. 6 Distribution of healing process index (HI) classes (%) – 3 shears: double blade (DB), bypass (BP) and draw cut (DC) – Quercus robur L. – a)
HI1: healing index assessed fifteen months after pruning; b) HIo5: healing index assessed overbark five years after pruning; c) HIu5: healing index
assessed underbark five years after pruning
Slika 6. Distribucija po razredima indeksa procesa zarašćivanja (HI) – 3 tipa škara: s dvostrukim sječivom (DB), s mimoilaznim sječivom (BP) i s
jednostrukim sječivom (DC) – Quercus robur L. – a) HI1: indeks zarašćivanja ustanovljen petnaest mjeseci nakon orezivanja; b) HIo5: indeks zarašćivanja ustanovljen na kori pet godina nakon orezivanja; c) HIu5: indeks zarašćivanja ustanovljen nakon uklanjanja kore pet godina nakon orezivanja
DWI differed significantly between DB and DC
(Table 2). DWI of DB and DC showed that 29% and
54% of the new wood, respectively, was damaged by
entrapped cork layer. DB showed the shortest time for
sealing the pruned branch (HT) while DC and BP did
not differ. The healing time (HT) increased with increasing branch diameter for the three cutting patterns
(Figure 8).
Finally a linear regression with dummy variable
was performed to test the relation between years to
complete the healing process, type of pruning tool and
branch diameter (at 2006). The regression was statistically significant (p < 0.001; R2adjusted = 0.27; SE = 1.13;
MAE = 0.85) and the result is shown in Equation (1)
and Fig. 8:
y = 3.96 – (0.76 × t) + (0.05 × D)
(1)
Where y is the number of years needed for sealing, t
the pruning tool pattern (dummy variable; DC=1,
BP=2, DB=3), and D the branch diameter at cutting
Table 2 HIu5, healing index assessed under bark; HSI, healing symmetry index; SC, distance between cutting section of a branch when pruned
and underbarked stem perimeter; DWI, damaged woundwood index; HT, healing time five years after pruning by double blade (DB), bypass (BP)
and draw cut (DC) shears (S.E. and N). Different letters show significant differences among values in a column (Kruskal-Wallis test, p < 0.05)
Tablica 2. HIu5, indeks zarašćivanja ustanovljen nakon uklanjanja kore; HSI, indeks simetrije zarašćivanja; SC, udaljenost između mjesta reza
grane pri orezivanju i plašta debla bez kore; DWI, indeks oštećenja drva rane; HT, vrijeme zarašćivanja pet godina nakon orezivanja škarama s
dvostrukim sječivom (DB), s mimoilaznim sječivom (BP) i s jednostrukim sječivom (DC) (S.E. i N). Različita slova označuju signifikantne razlike
među vrijednostima u stupcu (Kruskal-Wallisov test, p < 0.05)
Tool – Oruđe
DB
BP
DC
p
HIu5
HSI
SC, cm
a
1.00
0.81
18.0
(na N = 21)
(0.04 N = 17)
(1.4 N = 19)
a
0.99
0.78
18.4
(0.01 N = 32)
(0.04 N = 28)
(1.1 N = 30)
b
DWI
0.29
HT, years – HT, godine
a
2.4 a
(0.04 N = 19)
0.42
ab
3.6 b
(0.05 N = 30)
0.54
(0.1 N = 19)
b
(0.2 N = 30)
4.0 b
0.95
0.65
12.1
(0.02 N = 36)
(0.05 N = 27)
(0.6 N = 32)
(0.06 N = 32)
(0.2 N = 32)
ns
ns
< 0.001
< 0.03
< 0.001
na: not available because all the wounds were completely healed, i.e. HIu5 = 1 – na: nije dostupno zbog toga što su sve rane potpuno zarasle, odnosno HIu5 = 1
ns: not significant – ns: nije signifikantno
300
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Fig. 7 Examples of a cutting section after pruning (above) and 15 months later (below). a – Double blade shear; b – Draw cut shear; c –
Bypass shear. Quercus robur L.
Slika 7. Primjeri mjesta reza nakon orezivanja (gore) i 15 mjeseci poslije (dolje.); a – dvostruko sječivo; b – jednostruko sječivo; c – mimoilazno
sječivo. Quercus robur L.
4. Discussion and conclusion – Rasprava
i zaključak
Fig. 8 Healing Time (HT in years) versus branch diameter per each
cutting pattern
Slika 8. Ovisnost vremena zarašćivanja (HT u godinama) o promjeru grane za pojedini način rezanja
time. Only 27% of the variability of the healing time
was explained by the independent variables considered.
Croat. j. for. eng. 34(2013)2
The analysis of damage caused by the different
tools over time showed contrasting results. The injuries measured immediately after pruning showed that
BP was the worst cutting pattern. Fifteen months later,
no significant differences between DC and BP were
recorded, suggesting that the injury caused by DC was
underestimated when recorded immediately after
pruning. Therefore, damage estimation by measuring
the angle included in the arc of the injured section perimeter cannot be recommended for Q. robur immediately after pruning. This may be due to the higher
patch area of the DC anvil relative to the BP hook
which, together with the elevated Q. robur bark thickness, may have minimized the evidence of cambium
compression during macroscopic analysis. In the long
term (5 years), such a compression resulted in a decline of radial growth so that the distance between the
cutting section and the underbark stem perimeter (SC)
was lower for DC than for the other two tools. It may
be interesting to apply the same method of pruning
damage analysis to trees with a thinner and softer
bark.
The healing index HI1 applied one year after the
pruning turned out to be a better parameter for early
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Effects of Cutting Patterns of Shears on Occlusion Processes in Pruning ... (295–304)
damage assessment. HI1 is in fact a non destructive
method, whose results were confirmed by the assessment of the healing time HT. HT was destructively
applied five years after the pruning when most of the
cuttings were sealed, which resulted in non significant
differences in HI5.
The woundwood analysis showed a minimum
DWI value of 0.29 for the DB tool and a maximum
value of 0.54 for DC. This means that the portion of
stem core with knots or wood with defects will increase by 0.58 cm for DB and 1.08 cm for DC relative
to the tree diameter at pruning time. Double-blade
shears are, therefore, to be recommended for increasing the quality of timber. The time necessary to complete the healing process (HT) was less when DB was
used, suggesting that double-blade shears maximize
the quantity of high-quality timber. HT for BP and DC
were 1.5 and 1.7 times higher than for DB, respectively. These figures may even be underestimated because
the unhealed knots were given a further one-year period to complete the healing process. The hypothesis
that a symmetrical healing process implied an optimal
woundwood growth on both sides and thus shorter
sealing times was not confirmed. In fact, the healing
symmetry index (HSI) did not significantly depend on
the pruning tool. The hypothesis that the larger the
pruned branch diameter, the longer the time to seal
(Joyce et al. 1998, Nicolescu and Kruch 2009) was confirmed, thus suggesting that early pruning (diameter
< 3 cm) should be carried out.
The double-blade cutting pattern caused the least
mechanical injury. We postulate that this is because
both blades penetrate the wood and cut the bark tissues clean off. By contrast, the hook and the anvil of
the other cutting patterns oppose the cutting force necessary for the blade to cut the tissue, but cause evident
injury at the point of contact between the hook or the
anvil and the bark. In DC the anvil patch area involves
both the cut branch and branch collar causing bark
injury close to the stem. In BP the hook patch area
should involve only the cut branch but the lack of contact between the hook and the blade in the terminal
phase of a cut causes injury. When the cutting parts of
a by-pass tool come in touch with each other, and the
branch starts bending downwards, the hook tends to
slip, thus damaging the bark close to the stem.
Ultimately the DB tool showed the best pruning
performance and is to be recommended as short healing processes may avoid pathogen attacks which cause
a reduction of timber quality and value.
In conclusion, the effect of pruning tool used in
branch removal on wound occlusion process is not
negligible, suggesting that a higher attention to the
302
pruning tool is recommended for improving research
on the pruning methods and on the subsequent physiological response of trees.
Acknowledgement – Zahvala
Authors would like to thank Claudio Bidini for the
execution of the pruning operations.
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14(4): 349–352.
Pearce, R. B., 2000: Decay development and its restriction
in trees. Journal of Arboriculture 26(1): 1–11.
E. Marchi et al.
Petruncio, M., Briggs, D., Barbour, R. J., 1997: Predicting
pruned branch stub occlusion in young, coastal Douglasfir. Canadian Journal of Forestry Research 27(7): 1074–1082.
Picchio, R., Maesano, M., Savelli, S., Marchi, E., 2009: Productivity and energy balance in conversion of a Quercus
cerris L. coppice stand into high forest in Central Italy.
Croatian Journal of Forest Engineering 30(1): 15–26.
Roth, E. R., 1948: Healing and defects following oak pruning. Journal of Forestry 46(7): 500–504.
Schatz, U., Kannisto, K., Rantatalo, M., 2008: Influence of
saw and secateur pruning on stem discolouration, wound
cicatrisation and diameter growth of Betula pendula. Silva
Fennica 42: 295–305.
Shigo, A. L., Marx, H. G., 1977: Compartmentalization of
decay in trees. Agriculture Information Bulletin No. 495. 73
p.
Shigo, A. L., 1984: Tree decay and pruning. Journal of Arboriculture 8: 1–12.
Skilling, D. D., 1958: Wound healing and defects following
northern hardwood pruning. Journal of Forestry 56 (1):
19–22.
Smith, K., 2006: Compartmentalization today. Arboricultural Journal 29: 173–184.
Sprent, P., Smeeton, N. C., 2001: Applied Nonparametric
Statistical Methods. 3rd edn. Chapman & Hall/CRC, London, 461 p.
Springmann, S., Rogers, R., Spiecker, H., 2011: Impact of
artificial pruning on growth and secondary shoot development of wild cherry (Prunus avium L.). Forest Ecology and
Management 261(1): 764–769.
Sažetak
Utjecaji načina rezanja škara na zarašćivanje pri orezivanju stabala
u plantažama za proizvodnju drva visoke kakvoće
Stabla se u plantažama orezuju radi proizvodnje visokokvalitetnoga drva. Da bi se odredili tip i opseg mehaničkih
ozljeda koje orezivanje uzrokuje kambiju stabla te utjecaj na zarašćivanje, odabrani su različiti tipovi škara (s dvostrukim sječivom – DB, s jednostrukim sječivom – DC i s mimoilaznim sječivom BP) kojima je orezana osmogodišnja
plantaža hrasta lužnjaka. Količina uklonjene, odvojene i nagnječene kore ustanovljena je analizom snimaka neposredno nakon orezivanja. Petnaest mjeseci nakon orezivanja mjerenjem zarasle površine orezane grane istraživan je utjecaj
različitih načina rezanja na zarašćivanje. Na temelju zarasle i ukupne površine prereza određen je indeks procesa
zarašćivanja (HI1). Pet godina nakon orezivanja jednaka je analiza provedena mjerenjem na kori (HIo5) i nakon uklanjanja kore (HIu5). Osim toga ustanovljeni su i ostali parametri radi određivanja količine i kakvoće (simetrije)
zarašćivanja te vremena zarašćivanja. Utvrđeno je da utjecaj oruđa za orezivanje ovisi o načinu rezanja i promjeru
grane. S povećanjem promjera grane raste i vrijeme zarašćivanja. Uporaba oruđa s dvostrukim sječivom uzrokovala
Croat. j. for. eng. 34(2013)2
303
E. Marchi et al.
Effects of Cutting Patterns of Shears on Occlusion Processes in Pruning ... (295–304)
je manje ozljede i brži process zarašćivanja. Stoga se radi poboljšanja kakvoće drva pri orezivanju plantaža preporučuje
uporaba oruđa s dvostukim sječivom. Također se preporučuje primjena indeksa procesa zarašćivanja (HI1) za rano
određivanje štete uzrokovane orezivanjem.
Ključne riječi: hrast lužnjak, oruđa za orezivanje, agrošumarstvo, kakvoća drva, zarašćivanje
Authors’ address – Adresa autorâ:
Assoc. Prof. Enrico Marchi, PhD.
e-mail: [email protected]
Francesco Neri, PhD.
e-mail: [email protected]
Marco Fioravanti, PhD.
e-mail: [email protected]
Giacomo Goli, PhD.*
e-mail: [email protected]
Giuseppina Di Giulio
University of Firenze,
Department of Agricultural, Food and Forestry
Systems (GESAAF)
Via S. Bonaventura 13
50145 Firenze
ITALY
Received (Primljeno): January 11, 2013
Accepted (Prihvaćeno): July 20, 2013
304
Rodolfo Picchio, PhD.
e-mail: [email protected]
University of Tuscia,
Department of Agriculture, Forests, Nature
and Energy (DAFNE)
Via S. Camillo de Lellis
01100 Viterbo
ITALY
*Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Preliminary note – Prethodno priopćenje
Possibility of Determination of Daily
Exposure to Vibration of Skidder Drivers
Using Fleet Manager System
Zdravko Pandur, Dubravko Horvat, Marijan Šušnjar, Marko Zorić
Abstract – Nacrtak
This paper describes an indirect method of determining exposure to vibration of skidder drivers using the Fleet Manager System. The hand-arm exposure of workers to vibration is expressed as energy equivalent A(8), which is determined by the procedure clearly described in
the international standards ISO 5349-1-2001 and ISO 2631-1-1997. A(8) is a value that
depends not only on the vibration level in certain operating procedures, but also on the duration of exposure (duration of each skidder working procedure).
Research was done on the skidder Ecotrac 120V equipped with the Fleet Manager System (FMS).
The role of the FMS is to measure engine speed and duration of a certain engine speed during
the working day. The analysis of the working days was performed in the aim to connect skidder
working elements (driving, winching, pulling out of winch rope, etc.) with engine speeds.
Vibration on the steering wheel and seat of the skidder Ecotrac 120V was measured by vibrometer with triaxial accelerometer (Brüel and Kjaer 4447) at different engine rotational speeds.
The exposure to vibration of a skidder driver on a daily basis A(8) was calculated using data
of the summarized durations at certain skidder engine rotational speeds measured by the FMS
and the measured level of vibrations at specific engine rotational speeds.
Keywords: vibrations, A(8), engine rotational speed, Fleet Manager System, skidder
1. Introduction – Uvod
Field scientific research, such as the research of some
exploitation characteristics of forest vehicles during
extraction of different forest products, the impact of
extraction on some soil characteristics aimed at determining the environmental viability and its impact on
ergonomic conditions in the operator’s cabin, requires
a lot of time spent in the field and is hence very expensive. The Fleet Manager System (hereinafter FMS) is a
system of remote monitoring and control of the vehicle
operation, which enables gathering of data without
disturbing the vehicle operation, i.e. it provides the
possibility to research in almost uncontrollable exploitation conditions. The FMS is a very useful tool for the
control and organization of the complex system of
production and supply of wood chips from the place
of chipping to the buyer (Holzleitner et al. 2013.) as
well as during the time study.
Croat. j. for. eng. 34(2013)2
The use of FMS as the tool in the process of data
gathering from the vehicle aimed at measuring and determining some ergonomic parameters such as vibrations transmitted through the steering wheel on the
hands and through the seat to the whole body of the
operator, is not known in the literature. Goglia et al.
(2012) consider that, with the methodology of determining 8-hour energy equivalent of the total value of the
estimated accelerations A(8), an accurate picture of the
working day should first be made and whole day shooting of the operator’s work with the film camera is one
of the ways to get such a picture. The same authors state
that, in practice, it is practically impossible to measure
the levels of vibrations for each activity and for this reason it is necessary to make initial measurements in the
test polygon under controlled conditions.
Measuring vibrations on chain saws, Rottensteiner
et al. (2012) conclude that the level of vibrations is con-
305
Z. Pandur et al.
Possibility of Determination of Daily Exposure to Vibration of Skidder Drivers ... (305–310)
siderably affected by wood density and that it should,
therefore, be one of the basic parameters in calculating
the worker’s daily exposure to vibrations A(8).
Goglia et al. (2003) measure vibrations on the steering wheel of the small farming tractor while idling
and under full load, and then they calculate the daily
exposure to vibrations A(8), which amounts to
14.28 m/s2. According to ISO 5349-1-2001, it means that
in less than two years adverse effects of vibrations can
be expected with 10% of tractor drivers.
Dewangan and Tewari (2009) measure vibrations
on steering handles of one-axle farming tractor during
driving and soil processing at three tractor speeds. The
highest vibrations were measured at the lowest tractor
speed and during soil processing, and actually higher
vibrations were measured during soil processing.
Poje (2011) concluded that the worker`s exposure
to whole-body vibration were the highest during the
skidding operations and for operations where a cable
skidder was moving with no load (1.31 m/s2) and
ramping (1.22 m/s2), and the lowest with the full load
(0.91 m/s2).
The A(8) value does not only depend on the vibration level in certain operating procedures, but also on
the duration of exposure, i.e. on the duration of each
skidder operating procedure. Therefore the FMS, as
the system for monitoring and control of the vehicle
operation, is highly suitable for determining the A(8)
values, because the analysis of data gathered from the
vehicle (time, engine rotational speed, winch/crane
operation, position/moving, vehicle speed, etc.) can
easily show the duration of individual operations at
specific engine rotational speed. By subsequent measurement of vibrations (ahv) at characteristic engine
speeds, the A(8) value can be simply calculated, as
specified by the standard ISO 5349-1-2001.
2
2
2
ahv = ahwx
+ ahwy
+ ahwz
1
A(8) =
T0
N
∑a
i =1
2
hvi
⋅ Ti
(1)
(2)
Where:
T0 = available time of 8 h or 28 800 s,
ahvi = total exposure to vibrations for i operation,
Ti = duration of this operation,
N = the total number of operations.
Sherwin et al. (2004) state that with harvesters the
vibration level is affected by the characteristics of the
vehicle (engine rotational speed, engine fitted with
shock-absorbers), terrain characteristics (surface obstacles), methods of wood processing (processing of
306
trees), seat characteristics, physical condition and sitting position of the operator and soil characteristics
(dry, frozen, wet soil). The same authors conclude that
the air pressure in tires has a considerable impact on
the level of vibrations that are transmitted through the
seat to the whole body of the operator while the harvester is moving on uneven terrain. Kumar (2004) concludes that the vehicle speed and the type of terrain
on which it moves highly affect the level of vibrations
that are transmitted through the seat to the whole
body of the operator.
The Directive 2002/44/EC defines the minimum
health and protection requirements for the workers
exposed to vibrations that are transmitted to the handarm system (HAV – Hand-Arm Vibrations) and to the
whole body of the operator (WBV – Whole Body Vibrations). According to this Directive, the upper limit
of the worker’s daily exposure to hand-arm vibrations
is 5 m/s2, while the daily warning value is 2.5 m/s2. The
worker’s exposure through hand-arm system is measured in accordance with the specifications described
in the standard ISO 5349-2:2002.
According to the Directive 2002/44/EC, the upper
limit of the worker’s daily exposure to vibrations that
are transmitted to the whole body is 1.15 m/s2, while
the daily warning value is 0.5 m/s2 (8-hour working
time). Scarlett et al. (2002) agree that these limit values
could be exceeded with a large number of modern
farming tractors. Workers’ exposure to vibrations that
are transmitted to the whole body is measured by the
method specified by the standard ISO 2631-1:1997.
2. Material and Methods – Materijal
i metode
Engine rotational speed obtained by the use of the
FMS was divided into classes of 100 min–1, ranging
between 800 and 2 100 min–1. As in the FMS report the
engine rotational speed is shown in the dependence
of time, the duration of engine operation at specific
engine rotational speed was determined by further
analysis.
Subsequent measurement of vibrations at the same
engine rotational speed classes was performed with
the help of vibrometer Brüel & Kjaer, type 4447 and
triaxial accelerometer, type 4520-002, on the steering
wheel and triaxial accelerometer, type 4524-B, fitted in
the rubber protective cover on the seat and seatback
of the researched skidder.
The measurements were carried out on the skidder
Ecotrac 120V whose mass is approximately 7.5 tons.
The researched skidder is powered by a 6-cylinder airCroat. j. for. eng. 34(2013)2
Possibility of Determination of Daily Exposure to Vibration of Skidder Drivers ... (305–310)
Fig. 1 Measuring of vibrations on the steering wheel
Slika 1. Mjerenje vibracija na kolu upravljača
Fig. 2 Measuring of vibrations on the seat
Slika 2. Mjerenje vibracija na sjedištu
Table 1 Time consumption per classes of engine rotational speed
Tablica 1. Prikaz utrošenoga vremena prema razredima brzine vrtnje
pogonskoga motora
Revolution per minute, rpm
Duration
Duration – Ti
Broj okretaja u minuti
Trajanje
Trajanje – Ti
min–1
hh:mm:ss
s
850 (800–899)
00:07:27
447
950 (900–999)
00:01:03
63
1050 (1000–1099)
00:03:05
185
1150 (1100–1199)
00:26:39
1599
1250 (1200–1299)
02:39:06
9366
1350 (1300–1399)
02:19:23
8363
1450 (1400–1499)
02:22:56
8576
1550 (1500–1599)
00:44:17
2657
1650 (1600–1699)
00:32:40
1960
1750 (1700–1799)
00:31:41
1901
1850 (1800–1899)
00:28:52
1732
1950 (1900–1999)
00:29:02
1742
2050 (2000–2099)
00:12:17
737
10:58:28
39328
Total time – T0
Ukupno vrijeme – T0
cooled engine of the nominal power of 86 kW. The
skidder is fitted with an air suspension seat whose
sensitivity can be regulated manually.
Croat. j. for. eng. 34(2013)2
Z. Pandur et al.
3. Results – Rezultati
Based on the analysis of the working day of vehicles through the engine rotational speeds and their
duration obtained by the use of the FMS and subsequent measurement of the total exposure to vibrations
(the resulting vector) ahvi on the steering wheel (Fig. 1),
seat (Fig. 2) and seatback of the skidder Ecotrac 120V,
the operator’s daily exposure to vibrations A(8) was
calculated.
Total working time, obtained by the use of the FMS
and by subsequent analysis of the engine speed,
amounted to 10:58:28 hours (39 328 s), meaning that
the work was organized in two-shifts with two operators. The highest share of time (more than two hours)
was measured in three rotational classes: 1 250, 1 350
and 1 450 min–1 (Table 1).
The diagram in Fig. 4 shows that the highest values
of the total exposure to vibrations ahv at all three measuring points were measured when the engine was
idling, and in the engine rotational speed class of
850 min–1. According to the presented curves, the highest vibrations were measured on the steering wheel,
somewhat lower on the seatback, and the lowest vibrations were measured on the seat in the whole range of
the engine rotational speeds.
According to the diagram in Fig. 5, with the skidder in question the daily exposure to vibrations A(8)
through the steering wheel on the hand-arm system is
2.12 m/s2. According to the Directive 2002/44/EC this
is below the daily warning value of 2.5 m/s2.
The daily exposure to vibrations A(8) calculated for
the seat exceeds the daily warning value for the allowed vibrations that are transmitted to the whole
307
Z. Pandur et al.
Possibility of Determination of Daily Exposure to Vibration of Skidder Drivers ... (305–310)
Fig. 3 Position of the researched skidder on the map with the diagram showing engine rotational speeds during a working day
Slika 3. Položaj istraživanoga skidera na karti s dijagramom prikaza brzine vrtnje motora tokom jednoga radnoga dana
body (0.5 m/s2) amounting to 0.99 m/s2, while A(8) calculated on the seatback exceeds the upper limit value
of the worker’s daily exposure to vibrations (1.15 m/s2)
amounting to 1.73 m/s2.
4. Discussion – Rasprava
The FMS proved to be a highly suitable system for
gathering data on engine rotational speed aimed at
determining the worker’s daily exposure to vibra-
308
tions A(8). It is very easy to deduct the duration of
engine operation in individual classes of rotational
speed from the report generated by the FMS control
center.
The measured values ahv on the steering wheel as
well as on the seat and seatback show that the highest
vibrations occur when the engine is idling. Regarding
these results, it should be noted that all measured
values ahv are mostly below 1 m/s2, which is very satisfying.
Croat. j. for. eng. 34(2013)2
Possibility of Determination of Daily Exposure to Vibration of Skidder Drivers ... (305–310)
Z. Pandur et al.
Fig. 4 Evaluated vibration accelerations ahv according to the engine
rotational speed for all three measuring points on the skidder
Ecotrac 120V
Slika 4. Prikaz vrednovanih ubrzanja vibracija ahv prema brzini vrtnje motora za tri mjerna mjesta na skideru Ecotrac 120V
Fig. 5 Daily exposure to vibrations A(8) for all three research points
Slika 5. Dnevna izloženost vibracijama A(8) za sva tri istraživana
mjesta
The calculated value of the worker’s daily exposure
to vibrations A(8) for the recorded working time of
10:58:28 hours in accordance with the Directive
2002/44/EC shows that on the steering wheel it does
not exceed the daily warning value of 2.5 m/s2 for the
arm-hand system. The calculated A(8) value on the
seat exceeds the warning value of 0.5 m/s2, while the
calculated A(8) value on the seatback exceeds the upper limit value of the daily exposure to vibrations of
1.15 m/s2. Since the work was organized in two shifts
with two operators in one working day, the exposure
to vibrations A(8) of one worker was in fact half of the
calculated values, and according to the Directive
2002/44/EC, the A(8) value exceeds the daily warning
value of 0.5 m/s2 only on the seatback.
The aim of further research is to divide the skidder
working day not only by engine rotational speed but
also by operating procedures and by vehicle speed,
and based on these parameters, obtained with the help
of the FMS, to calculate the worker’s daily exposure to
vibrations A(8).
The further research will also include the impact of
terrain characteristics (surface obstacles), methods of
tree processing, seat characteristics, physical condition
and sitting position of the operator and also soil characteristics for determining the worker’s daily exposure
to vibrations A(8).
5. References – Literatura
Croat. j. for. eng. 34(2013)2
Dewangan, K. N., Tewari, V. K., 2009: Characteristics of
hand-transmitted vibration of a hand tractor used in three
operational modes. International Journal of Industrial Ergonomics 39: 239–245.
Directive 2002/44/EC Of European Parliament and of the
Council: The minimum health requirement regarding to exposure of workers to the risks arising from physicla agents
(vibration). Offical Journal of the European Communities
177: 13–19.
Goglia, V., Gospodarić, Z., Košutić, S., Filipović, D., 2003:
Hand-transmitted vibration from the steering wheel to drivers of a small four-wheel drive tractor. Applied Ergonomics
34: 45–49.
Goglia, V., Suchomel, J., Žgela, J., Đukić, I., 2012: Izloženost
vibracijama šumarskih radnika u svjetlu Directive 2002/44/
EC. Šumarski list 126(5–6): 283–289.
Holzleitner, F., Kanzian, C., Höller, N., 2013: Monitoring the
chipping and transportation of wood fuels with a fleet management system. Silva Fennica 47(1): 1–11.
ISO 2631-1-1997. Mechanical Vibration and Shock – Evaluation of Human Exposure to whole-body Vibration – Part 1:
General requirements. International Standard Organization,
Geneva.
ISO 5349-1-2001. Mechanical vibration – Measurement and
evaluation of human exposure to hand transmitted vibra-
309
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Possibility of Determination of Daily Exposure to Vibration of Skidder Drivers ... (305–310)
tion. Part 1: General requirements. International Standard
Organization, Geneva.
Dokt. disertacija. Ljubljana, Univ. v Lj., Biotehniška fakulteta, Oddelek za gozdarstvo in gozdne vire, 1–232.
ISO 5349-2-2001. Mechanical vibration – Measurement and
evaluation of human exposure to hand transmitted vibration. Part 2: Practical Guidance for Measurement at the
Workplace. International Standard Organization, Geneva.
Rottensteiner, C., Tsioras, P., Stampfer, K., 2012: Wood Density Impact on Hand-Arm Vibration. Croatian Journal of
Forest Engineering 33(2): 303–312.
Kumar, S., 2004: Vibration in operating heavy haul trucks in
overburden mining. Applied Ergonomics 35: 509–520.
Poje, A., 2011: Vplivi delovnega okolja na obremenitev in
težavnost dela sekača pri različnih organizacijskih oblikah.
Scarlett, A. J., Price, J. S., Stayner, R. M., 2002: Whole-body
vibration: Initial evaluation of emissions originating from
modern agricultural tractors. Health and Safety Executive
Books, 1–26.
Sažetak
Mogućnost određivanja dnevne izloženosti vibracijama vozača skidera
upotrebom sustava Fleet Manager
U radu je opisana indirektna metoda određivanja izloženosti vibracijama vozača skidera upotrebom sustava daljinskoga praćenja vozila (Fleet Manager System ili FMS). Izloženost radnika vibracijama iskazuje se kao energijski
ekvivalent A(8), koji je određen i jasno opisan u međunarodnim standardima ISO 5349-1-2001 i ISO 2631-1-1997.
A(8) je vrijednost koja ne ovisi samo o razini vibracija pri određenom radu nego i o vremenskom trajanju vibracija
(trajanje svakoga radnoga zahvata skidera).
Istraživanje je provedeno na skideru Ecotrac 120V opremljenim sustavom za daljinsko praćenje vozila (FMS).
Zadaća je FMS-a bila mjerenje brzine vrtnje motora te vremensko trajanje pojedinih brzina vrtnje tokom radnoga
dana. Napravljena je analiza radnoga dana skidera po pojedinim radnim elementima (vožnja, privitlavanje, izvlačenje užeta itd.) kako bi se određeni radni element mogao povezati sa specifičnom brzinom vrtnje motora.
Vibracije na kolu upravljača i sjedištu skidera Ecotrac 120V mjerene su vibrometrom s troosnim akcelerometrom
(Brüel and Kjaer 4447) pri različitim brzinama vrtnje. Dnevna izloženost vibracijama A(8) vozača skidera izračunata je na temelju podataka o ukupnom trajanju brzine vrtnje motora u pojedinim razredima brzine vrtnje izmjerenih pomoću FMS-a te pomoću vrijednosti vibracija pri istim razredima.
Ključne riječi: vibracije, A(8), brzina vrtnje motora, sustav Fleet Manager, skider
Authors’ address – Adresa autorâ:
Received (Primljeno): June 4, 2013
Accepted (Prihvaćeno): September 5, 2013
310
Zdravko Pandur, MSc.*
e-mail: [email protected]
Prof. Dubravko Horvat, PhD.
e-mail: [email protected]
Asocc. prof. Marijan Šušnjar, PhD.
e-mail: [email protected]
Marko Zorić, MSc.
e-mail: [email protected]
Department of Forestry Engineering
Faculty of Forestry
University of Zagreb
Svetošimunska 25, 10000 Zagreb
CROATIA
*Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Preliminary note – Prethodno priopćenje
Analysis of Work Accidents in Selected
Activities in Slovakia, Czech Republic
and Austria
Jozef Suchomel, Katarína Belanová, Mária Vlčková
Abstract – Nacrtak
The aim of this article was to analyze the development and rate of work accidents in the Slovak
Republic (SR) and to compare the results with the status in the Czech Republic and Austria.
The occurrence of fatal accidents in the forestry of SR was also studied, as well as the share of
these accidents in the main activities of agriculture, forestry and fishing. Information about
accidents was stored in a database system. Data were entered and edited using an original
form. The absolutely highest rate of fatal work injuries was recorded in Austria in the sector
of agriculture, forestry and fishing. In SR, agriculture, forestry and fishing was evaluated as
the second most hazardous industry with 12 accidents per 109 791 workers. The share of fatal
work accidents in the forestry of SR in the total amount of fatal work accidents in SR reached
more than 10% in the year: 2001, 2003, 2005 and 2006.
Keywords: work accidents, activities, forestry, cause, source
1. Introduction and issues – Uvod
i problematika istraživanja
Due to social changes after 1989, business structure
in various sectors of the national economy has changed
considerably. Traditionally strong sectors such as engineering, heavy industry, mining and forestry were
definitely weakened. At the same time, the structure
of traditional business has also changed significantly
so that small and medium enterprises were established and entrepreneurship was encouraged.
These changes also caused the collapse of the workers’ safety and health at work – an effective care system
until that time.
The aim of any successful company is to achieve
maximum profit at minimum costs. As it is difficult to
minimize the costs of components such as raw material needed for production, energy, labor and resources, everybody (companies, employers, self-employed
persons and traders) often try to »save« costs at the
expense of their own health or the health of their workers. They use machinery and equipment after their life
expectancy, buy personal protective equipment of inCroat. j. for. eng. 34(2013)2
ferior quality, fail to provide the mandatory breaks
(mode of work and rest) and reconditioning stays, and
last but not least, neglect regular preventive medical
examinations, which can prevent illnesses or professional diseases. Therefore, the health and safety at
work have now become one of the most important and
most highly developed aspects of EU employment and
social affairs.
The primary objective of the Community Strategy
for the period 2007–2012 is to reduce the overall rate
of workplace injuries by 25–27% in 2012 in EU by improving safety and health of workers, which will significantly contribute to the success of strategy for
growth and employment. To achieve this ambitious
goal, the Community proposes to:
Þ ensure proper implementation of EU legislation,
Þ support small and medium enterprises in im-
plementing the existing legislation, adapt the
legal framework to changes in the workplace
and simplify it, especially with regard to small
and medium enterprises,
311
J. Suchomel et al.
Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
Þ support the development and implementation
of national strategies,
Þ support changes in the behavior of workers and
health-focused approaches of employers, develop methods for identifying and evaluating
new potential risks,
Þ improve the monitoring of progress,
Þ promote health and safety worldwide.
In order to improve workers safety and health at
the national level, it is first necessary to establish connections between national prevention strategy and a
common strategy of the European Union. The European Union is focused on objectives set for the strategy
2007–2012 on supporting small and medium enterprises. However, it is necessary to pay attention to
these objectives especially at the state level.
In the forestry sector, changes in structure and
number of employees in state enterprises were mainly
influenced by the process of forest re-privatization and
the fact that the main activities in state-owned enterprises were performed by contractors. A vast majority
of employees left the state forests, and consequently
the share of forestry activities performed by self-employed (freelancers) and small and medium enterprises significantly increased. These changes and changes
in social and health insurance, as well as in health and
safety legislation and registration of work injuries
caused the decrease of accidents in this sector. In reality, the share of work accidents is significantly higher
than indicated by official statistics and records. The
issue of the trend of work accidents (2000–2007) and
occupational diseases (2000–2010) in Slovakian forestry was comprehensively assessed by Suchomel et
al. (2008) and Suchomel et al. (2011). In connection
with the development of biomass use for energy purposes, new occupational diseases occur in forest management. Suchomel and Belanová (2012) found interesting results by analyzing the selected risks in the
processing of forest biomass for energy purposes.
2. Methodology – Materijal i metode
This paper evaluates the development and rate of
work accidents in Slovakia and compares the results
with the status in Czech Republic and Austria. It also
presents the occurrence of fatal accidents in the forestry of SR, as well as the share of these accidents in
the main activities of agriculture, forestry and fishing.
Data about fatal work accidents and work accidents in
the Czech Republic and Austria have been sourced
from the Report of Occupational Accidents in 2008
(latest available) issued by the organization EUROGIP
312
(EUROGIP 2009, 2010). The rate of fatalities in the
Czech Republic was calculated based on 100 000 insured workers, and the rate of accidents with sick
leave (SL) of more than 3 days based on 100 insured
workers. In Austria, the rate of accidents was calculated based on the total number of workers, not only
insured workers. Information about the number of accidents in Slovakia for 2008 was extracted from the
data of the National Labor Inspectorate (Backstuberová 2010). For purposes of calculating the rate of fatalities, data on the number of workers in various sectors, available at the website of the Statistical Office of
the Slovak Republic (www.statistics.sk), were used.
The main activities of NACE Rev. 2 are as follows:
A Agriculture, forestry and fishing;
B Mining and quarrying;
C Manufacturing;
D Electricity, gas, steam and air conditioning supply;
E Water supply, sewerage, waste management and
remediation activities;
F Construction;
G Wholesale and retail trade; repair of motor
vehicles and motorcycles;
H Accommodation and food service activities;
I Transportation and storage;
J Information and communication;
K Financial and insurance activities;
L Real estate activities;
M Professional, scientific and technical activities;
N Administrative and support service activities;
O Public administration and defense; compulsory
social security;
P Education;
Q Human health and social work activities;
R Arts, entertainment and recreation;
S Other service activities;
T Activities of households as employers; undifferentiated goods- and services-producing activities
of households for own use;
U Activities of extraterritorial organizations and
bodies.
The analysis of fatal accidents in the forestry of SR
was prepared based on data (years 2000–2011) obtained from the National Labor Inspectorate. Data
about accidents were stored in a database system. Data
were entered and edited using an original form. The
evaluation criteria in the database were the information about accidents in accordance with the ESAW
(European Statistics on Accidents at Work) and information needed for a detailed analysis of causes and
sources of fatal work accidents.
Croat. j. for. eng. 34(2013)2
Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
3. Results – Rezultati
Fig. 1 graphically shows the comparison of the number of accidents in Slovakia, Czech Republic and Austria. The frequency of accidents with SL of more than 3
days in Slovakia has a downward trend until 2004. After
this year, there is a modest increase in the number of
accidents until 2008, when accidents begin to decrease.
The incidence of fatal work accidents is fluctuating. The
trend of the fatal work accidents (FWA) in SR is almost
the same as FWA in Austria. The development of work
accidents (SL more than 3 days) in the Czech Republic
in this period has a downward trend. The incidence of
fatal work accidents in 2006 also falls, but in 2007 there
is an evident increase of the number of accidents. This
fact is confirmed by the calculated rate of workplace
accidents. Incidental trend in Austria is rather unstable.
In the last reporting year (2008), the number of accidents
with SL more than 3 days increased, as well as the number of fatal accidents.
The rate of work accidents in various industrial sectors of the selected countries is shown in Fig. 2. The
absolutely highest rate of fatal work injuries was recorded in Austria in the sector of agriculture, forestry
and fishing. In this sector, the maximum frequency of
J. Suchomel et al.
fatal accidents was recorded in 2008 with 63 deaths per
100 000 employees. Transportation and storage is the
second sector with the highest risk of fatal accidents
in this country and the sector of construction is the
third. Based on the calculated rate of FWA in Slovakia,
it can be concluded that the highest risk was recorded
in the sector of water supply, sewerage, waste management and remediation activities. The sector of agriculture, forestry and fishing is ranked second with 12
accidents per 109 791 workers, while the sector of construction is again third. In the Czech Republic, construction has been assessed as the sector with the highest risk of fatal work accidents, and then followed by
mining and quarrying, water supply, treatment and
discharge of waste water, waste management and remediation activities. The sector of agriculture, forestry
and fishing, with FWA of 15 per 4 313 employees, is
ranked fourth.
The rate of accidents with SL of more than 3 days
per 100 employees was clearly highest in Austria in the
sector of mining and quarrying (12.66), followed by
agriculture, forestry and fishing (9.58), and the sector
of construction, where the injury rate was 9.34. In the
Czech Republic, the highest level of risk with SL of
more than 3 days (2.98) was found in the sector of
Fig. 1 Trend of work accidents in selected countries
Slika 1. Ozljede na radu u Slovačkoj, Češkoj i Austriji
Croat. j. for. eng. 34(2013)2
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Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
Fig. 2 The rate of fatal accidents per 100 000 workers
Slika 2. Smrtonosne ozljede na radu (uzorak od 100 000 radnika) prema skupinama djelatnosti
Fig. 3 The rate of work accidents per 100 workers
Slika 3. Ozljede na radu na 100 radnika, prema skupinama djelatnosti
agriculture, forestry and fishing, followed by manufacturing (2.51) and water supply, sewerage, waste
management and remediation activities (2.35). In Slovakia, the highest calculated rate of accidents with SL
of more than three days was recorded in the sector of
manufacturing (1.09), followed by water supply, sewerage, waste management and remediation activities
(0.89) and agriculture, forestry and fishing (0.67).
314
The survey of work accidents in different sectors is
shown in the following two graphs. Fig. 4 shows that
most accidents with SL of more than three days were
recorded in industrial production in all the three countries. In the Czech Republic, 32 595 work accidents
were recorded in this sector, which is still about 4 183
cases more than in Austria. In Slovakia, 5 782 work
accidents with sick leave of three days and more was
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Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
J. Suchomel et al.
Fig. 4 Survey of work accidents with SL of more than 3 days in selected sectors
Slika 4. Bolovanja u trajanju duljem od tri dana (izazvana ozljedom na radu) u određenim skupinama djelatnosti
recorded in production. In SR and CR, wholesale and
retail trade, repair of motor vehicles and motorcycles
(SR – 1 256, CR – 7 523) were ranked second. In Austria,
construction was ranked second with 23 161 cases.
Construction accidents were ranked third with 916
cases in Slovakia and 5 537 in the Czech Republic. In
Austria, the sector of administrative and support services was ranked third with 9 831 work accidents.
Based on the evaluation of work accidents with SL of
more than three days, the sector which includes forestry (agriculture, forestry and fishing) was ranked
fifth in CR (4 313 cases) and Slovakia (739 cases), and
in Austria, it was ranked twelfth with 1 663 cases.
The analysis of fatal accidents in two countries –
Austria and Slovakia, showed that they prevailed in
construction industry, as the total number of accidents
in Austria and in SR was 29 and 18, respectively. In the
Czech Republic, accidents prevailed in the manufacturing sector with 48 fatal work accidents. The second
riskiest sectors were again construction in CR (46 FWA)
and manufacturing in Austria and Slovakia with 19
and 15 work accidents, respectively. The third highest
number of FWA was established in the Czech Republic and Austria in the sector of transport and storage
(CR – 21 cases, Austria – 18 cases). In Slovakia, the
third highest risk was assessed in the sector of agriculture, forestry and fishing, with 12 accidents. In the
Czech Republic, 15 fatal work accidents were recorded
(4th highest risk) in agriculture, forestry and fishing
and in Austria 11 FWA (5th highest risk).
Croat. j. for. eng. 34(2013)2
The number of fatal work accidents in Slovakia
during the evaluated period ranged from 76 to 100 WA
per year. The figure below shows the number of fatalities recorded in the forestry of SR. The share of fatal work accidents in the forestry of SR in the total
amount of fatal work accidents in Slovakia reached
more than 10% in the year: 2001, 2003, 2005 and 2006.
Taking into consideration that the forestry sector goes
along with agriculture and fishing, this share is not
negligible. Most fatal work accidents were recorded in
2001, followed by a fluctuating further development
of accidents. In 2007, there was a rapid decline from
10 cases per year to 4. Downward trend continued until 2011, when there was only one fatal work accident.
Fig. 7 presents the distribution of fatalities recorded
in the forestry of SR, according to sources of work accidents in the period 2000–2011. Most fatal work accidents were caused by source group V – Material, loads,
subjects (51%), source group V.a (including injuries
caused by falls of soil, rocks, stones, and pieces of bulk
material or by objects, products or equipment) caused
31% of FWA and source group V.b (including injuries
caused by locomotion or otherwise manipulated objects, by sharp edges or by fragments) caused 20% of
FWA. Source group I – Vehicles accounted for 22% of
FWA. Source group III – Machinery – driving, ancillary
and working accounted for a considerable share of 11%.
Source group II - Hoists and elevators, lifting and transport equipment and source group IV – Work or traffic
road places as sources of workers falls accounted for 5%
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J. Suchomel et al.
Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
Fig. 5 Survey of fatal work accidents in selected sectors
Slika 5. Smrtonosne ozljede na radu po određenim skupinama djelatnosti
Fig. 6 Trend of fatal work accidents in forestry of SR
Slika 6. Smrtonosne ozljede na radu u slovačkom šumarstvu
of FWA. Source group VII – Industrial pollutants, hot
substances and objects, fire and explosives, source
group X – People, animals and natural forces and source
group XI – Other sources accounted for 1.5%.
Fig. 8 presents the distribution of fatalities recorded in the forestry of SR, sorted by causes of accidents.
Cause 8 (use of hazardous work practices or methods,
including work without authorization, against orders,
316
prohibitions and directions, staying in hazard area)
was determined in 42% of fatal work accidents. 20%
of fatal work accidents were the result of cause 12 (the
lack of individual prerequisites for proper job performance – for example lack of physical prowess, sensory deficiencies, negative personal qualities and immediate psycho-physiological statuses). Improper
organization of work (cause 6) caused 11% of FWA,
hazard by other persons, e.g. distraction at work, joking, arguing, other incorrect and dangerous actions
(cause 11) prompted 9% of FWA. Failing to provide
safe work conditions and lack of necessary skills
(cause 7) resulted in 3% of fatal work accidents. 6% of
FWA were caused by unidentified reasons. 1.5% of
FWA were caused by wrong or bad status of accident
source (cause 1), lack of protective equipment or inadequate protective equipment and security (cause 2),
non-use or misuse of prescribed and assigned personal protective equipment (cause 10), hazard from
animals and natural causes (cause 13).
4. Discussion – Rasprava
The aim of this article was to analyze the development and rate of work accidents in the Slovak Republic (SR) and to compare the results with the status in
the Czech Republic and Austria, neighboring countries of Slovakia. The obtained results are similar to the
results obtained by Croatian researchers. The number
of fatalities among professional forest workers in Croatia increased by more than twice in the two 5-year
Croat. j. for. eng. 34(2013)2
Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
Fig. 7 Distribution of fatal work accidents in forestry of SR by source
groups
Slika 7. Smrtonosne ozljede na radu u slovačkom šumarstvu po
uzrocima ozljeda
Fig. 8 Distribution of fatal work accidents in forestry of SR by
causes of accidents
Slika 8. Smrtonosne ozljede na radu u slovačkom šumarstvu prema
razlozima ozljeda
monitored periods (1995–1999, 2000–2004) (Klun and
Medved 2007).
The absolutely highest rate of fatal work injuries
was recorded in Austria in the sector of agriculture,
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J. Suchomel et al.
forestry and fishing. In this sector, the maximum frequency of fatal accidents was recorded in 2008 with 63
deaths per 100 000 employees. In Slovakia, the sector
of agriculture, forestry and fishing is ranked second
with 12 accidents per 109 791 workers.
According to the classification of business activities
in the National Classification of Activities, agriculture,
forestry and fishery together account for 3.43% of all
injuries recorded in 2009, which places them in the
lower part of the annual review. Comparing the number of injuries in Croatian forests with the number of
employees in 2009, an exceptionally high ratio is obtained of 29.40 injuries per 1 000 employees, the highest index among the above said industry sectors
(Martinić et al. 2011).
The use of hazardous work practices or methods,
including work without authorization, against orders,
prohibitions and directions, and staying in hazard area
was determined in 42% of fatal work accidents recorded in the forestry of SR. Most fatal work accidents were
caused by source group V – Material, loads, subjects
(51%), source group V.a (including injuries caused by
falls of soil, rocks, stones, and pieces of bulk material or
by objects, products or equipment) caused 31% of FWA
and source group V.b (including injuries caused by locomotion or otherwise manipulated objects, by sharp
edges or by fragments) caused 20% of FWA.
In the structure of injury causes, two thirds of all
injuries in Croatian forestry are caused by falls during
movement, or by unsafe practices and disregard of
work safety rules (Martinić and Radočaj 2006).
World and European trends in the field of work
accidents and development of occupational diseases
confirm changes. The change in the nature of work,
level of technology and automation that affect the nature of work changes, has a decisive influence on these
changes. Stress and lifestyle also have a decisive impact on the quality of life, especially on work, as confirmed by the findings of Martinić et al. (2006) and
Landekić et al. (2011).
The number of fatalities is an important indicator
of mastering the risks and shows the effectiveness as
well as integrity of measures taken by individual
countries in their attempts to provide safety in forest
work (Klun and Medved 2007).
5. Conclusion – Zaključak
The results of the analysis of fatal work accidents
can be used in prevention, control and organizational
activities in forestry entities in Slovakia.
Data and information from the analysis can be applied in specifying risks for various harvesting opera-
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Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
tions – transport technologies, in assessing the risks of
work accidents and quantifying their impact on the
economy of individual companies and entities, and
they can also be used for insurance purposes. Improving safety and health protection of workers can minimize the number of work accidents. It is especially
important to focus attention on self-employed persons, who often underestimate the risk of work accidents in an effort to maximize the profit. It is important
to use tools and equipment in accordance with health
and safety requirements, as well effective personal
protective equipment at work and to provide mandatory breaks. Working techniques of workers directly
employed in forest operations play a key role in
achieving a satisfactory degree of safety and efficiency
in forestry work (Martinić et al. 2011). Applying these
principles would be highly motivating and in contrast
their breaching would be highly discouraging.
Acknowledgements – Zahvala
This work was supported by the Slovak Research
and Development Agency based on the contract. No.
LPP-0420-09 »Analysis of Safety, Health and Hygiene
Risks in the Processing of Forest Biomass for Energy
Purposes« and the COST Action FP 0902 Development
and harmonization of new operational research and
assessment procedures for sustainable forest biomass
supply.
EUROGIP, 2009: Statistical Review of Occupational Injuries
– AUSTRIA 2008. Ref. Eurogip – 46/E, December 2009, 20 p.,
<http://www.eurogip.fr/fr/>
EUROGIP, 2010: Statistical Review of Occupational Injuries
– CZECH REPUBLIC 2008. Ref. Eurogip – 51/ET, June 2010:
19 p., <http://www.eurogip.fr/fr/>
Klun, J., Medved, M, 2007: Fatal injuries in forestry in some
European countries. Croatian Journal of Forest Engineering
28(1): 55–62.
Landekić, M., Martinić, I., Lovrić, M., Šporčić, M., 2011: Assessment of Stress Level of Forestry Experts with Academic
Education. Collegium antropologicum 35(4): 1185–1192.
Martinić, I., Landekić, M., Šporčić, M., Lovrić, M., 2011: Forestry at the EU’s Doorstep – How Much are We Ready in the
Area of Occupational Safety in Forestry? Croatian Journal of
Forest Engineering 32(1): 431–441.
Martinić, I., Radočaj, B., 2006: What are the current characteristics of safety and quality of forest work in Croatia? Nova
mehanizacija šumarstva 27(3): 25–31.
Martinić, I., Šegotić, K., Risović, S., Goglia, V., 2006: The effect
of body mass on physiological indicators in the performance
of forestry workers. Collegium antropologicum, Vol. 30(2):
305 – 311.
SLOVSTAT, 2012: Priemerný počet zamestnaných osôb
podľa ekonomických činností (SK NACE Rev. 2) v osobách
(2007Q1-2011Q4) <http://www.statistics.sk/pls/elisw/objekt.
send?uic=2787&m_sso=2&m_so=15&ic =39>
Suchomel, J., Belanová, K., Vlčková, M., Ivan, L., Holécy, J.,
Radocha, M., 2008: Analýza pracovných úrazov v Lesoch SR,
š.p. Zvolen. Technická univerzita vo Zvolene. ISBN 978-80228-1979-4, 135 pp.
6. References – Literatura
Suchomel, J., Belanová, K., 2012: Analýza vybraných rizík
pri spracovaní biomasy na energetické účely. Technická univerzita vo Zvolene. ISBN 978-80-228-2400-2, 107 pp.
Backstuberová, V., 2010: Pracovná úrazovosť v organizáciách
v pôsobnosti dozoru Národného inšpektorátu práce za roky
2007 až 2009. Bezpečná práca 41(2): 10–18.
Suchomel, J., Belanová, K., Vlčková, M., 2011: Analýza
výskytu chorôb z povolania v lesníctve Slovenska. Technická
univerzita vo Zvolene. ISBN 978-80-228-2206-0, 109 pp.
318
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J. Suchomel et al.
Sažetak
Ozljede na radu u Slovačkoj, Češkoj i Austriji u pojedinim
djelatnostima
Autori istražuju ozljede i smrtonosne ozljede na radu u Slovačkoj, Češkoj i Austriji. Podaci za Slovačku djelomice
su dobiveni iz autorovih istraživanja, a djelomice iz baze podataka slovačkoga Državnoga zavoda za statistiku (www.
statistics.sk), dok su podaci za Češku i Austriju preuzeti iz EUROGRIP-ova izvješća o ozljedama na radu za 2008.
godinu. Ozljede i smrtonosne ozljede na radu, za sve tri zemlje u vremenu od 2000. do 2008. godine, prikazane su
na slici 1. Broj smrtonosnih ozljeda na radu u Republici Češkoj izračunat je na temelju uzorka od 100 000 zdravstveno osigurnih radnika, a broj radnika koji su bili na bolovanju dužem od tri dana (zbog ozljede na radu) na temelju
uzorka od 100 zdravstveno osiguranih radnika. Broj ozljeda na radu u Republici Austriji temelji se na ukupnom
broju radnika (nevezano uz zdravstveno osiguranje). Broj ozljeda i smrtonosnih ozljeda na radu prema pojedinim
skupinama zanimanja prikazan je na slikama 2 i 3. Skupine su zanimanja:
A Poljoprivreda, šumarstvo i ribarstvo;
B Rudarstvo i kamenolom;
C Proizvodnja;
D Klimatizacija i opskrba strujom, plinom i parom;
E Opskrba vodom, upravljanje otpadom, sanacija i odvodnja;
F Građevinske djelatnosti;
G Maloprodaja i veleprodaja, servis motornih vozila;
H Uslužne djelatnosti (smještaj i hrana);
I Prijevoz i skladištenje roba;
J IT;
K Financije i osiguranje;
L Djelatnosti vezane uz zemljišta i nekretnine;
M Znanstvene i tehnološke djelatnosti;
N Administrativne djelatnosti;
O Javna administracija i obrana, socijalno osiguranje;
P Obrazovanje;
Q Zdravstvo i socijalni rad;
R Umjetnost, zabava i sport;
S Ostalo;
T Djelatnosti kućanstava kao poslodavaca; nediferencirana roba i usluge kao djelatnosti kućanstava za
vlastitu uporabu;
U Djelatnosti izvanteritorijalnih organizacija i tijela.
Udjeli bolovanja radnika u trajanju duljem od tri dana (izazvana ozljedom na radu) te smrtonosne ozljede na
radu po skupinama djelatnosti za sve tri zemlje prikazani su na slici 4 i 5. Smrtonosne ozljede na radu u šumarskoj
djelatnosti Republike Slovačke prikazane su na slikama 6, 7 i 8. Slika 6 prikazuje broj smrtonosnih ozljeda na radu
kod muškaraca i žena zabilježenih od 2000. do 2011. godine. Slika 7 prikazuje broj smrtonosnih ozljeda na radu
ovisno o uzrocima ozljeda (I – upravljanje vozilima; II – upravljanje dizalicama, dizalima i podiznim uređajima i
vozilima; III – upravljanje strojevima; IV – radovi na prometnicama; Va – odroni zemlje, kamenja i stijena, udari
materijala, proizvoda ili opreme u proizvodnji; Vb – udari zbog rada strojeva, alata i opreme; VII – industrijsko
onečišćenje, vruće tvari i predmeti, požari i eksplozije; X – ljudski i životinjski čimbenici, sile prirode; XI – ostalo).
Slika 8 prikazuje broj smrtonosnih ozljeda na radu ovisno o razlozima ozljeda (1 – nepovoljan izvor ozljede; 2 – nepostojanje ili neprikladna zaštitna oprema za rad; 6 – pogrešna organizacija rada; 7 – nepridržavanje uputa o zaštiti
na radu ili neobrazovano radno osoblje; 8 – opasni radni postupci ili metode, uključujući i rad bez odobrenja, protivno uputama i zabranama; 10 – nekorištenje ili pogrešno korištenje propisane i dodijeljene osobne zaštitne opreme;
11 – rastresenost, svađanje, šaljenje i slične radnje koje odvlače pozornost; 12 – nedostatak pojedinih preduvjeta za
pravilno obavljanje poslova (u smislu općega zdravstvenoga stanja); 13 – životinje i prirodne sile).
Croat. j. for. eng. 34(2013)2
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Analysis of Work Accidents in Selected Activities in Slovakia, Czech Republic and Austria (311–320)
Poboljšanje sigurnosti i zaštite na radu može smanjiti broj ozljeda te očuvati zdravlje radnika. Važno je upotrebljavati alat i opremu u skladu sa zdravstvenim i sigurnosnim zahtjevima te voditi računa o uporabi osobne zaštitne
opreme. Radnike bi trebalo primjereno pozitivno poticati na pravilan i siguran rad, a one koji ne rade u skladu s
uputama treba ukoriti i primjereno kazniti.
Ključne riječi: ozljede na radu, radne djelatnosti, šumarstvo, uzrok, razlog
Authors’ address – Adresa autorâ:
Assoc. Prof. Jozef Suchomel, PhD.*
e-mail: [email protected]
Mária Vlčková, MSc.
e-mail: [email protected]
Department of Forest Harvesting and Mechanisation
Faculty of Forestry
Technical University in Zvolen
Masarykova 24
96053 Zvolen
SLOVAKIA
Received (Primljeno): July 9, 2013
Accepted (Prihvaćeno): August 11, 2013
320
Katarína Belanová, PhD.
e-mail: [email protected]
Vojenské lesy a majetky SR, s.e.
Lesnícka 23
96263 Pliešovce
SLOVAKIA
*Corresponding author – Glavni autor
Croat. j. for. eng. 34(2013)2
Comment – Osvrt
International Scientific Symposium
FORMEC 2013, Stralsund, Germany,
September 30 – October 2, 2013
Međunarodno znanstveno savjetovanje
FORMEC 2013. Stralsund, Njemačka,
30. rujna – 2. listopada 2013.
The 46th International Symposium on Forestry
Mechanisation (FORMEC) with the motto »Techniques for sustainable management« was held in Stralsund/Germany, on September 30 – October 2, 2013. A
tough programme of nearly 45 presentations and a
field trip to KWF – Focus Days, practical demonstrations of environmentally sound management of wet
forest sites, was challenging and suspenseful. Nevertheless the symposium was also a good possibility for
networking and discussions about innovations in forest engineering. In this way FORMEC has again demonstrated to be one of the most important scientific
meetings in forest engineering. The meeting was organised by TU Dresden (Germany).
The key aspects of presentations of this year’s
meeting focused on forest harvesting systems, wood
transportation, forest road network planning and con-
struction, environmental effects of forest operations,
and forest work sciences. One session was organised
in conjunction with INFRES, an EU research project
with the focus on new innovative solutions to forest
biomass supply in the EU.
This year 105 participants from 20 different countries attended the symposium. There is already a keen
interest for further meetings in Gerardmer/France on
September 23 – 26, 2014, and Linz/Austria on October
4 – 8, 2015.
Links
FORMEC
http://formec.boku.ac.at/
5th Forest Engineering Conference
http://fec2014.fcba.fr/
Fig. 1 Head of organising committee Prof. Jörn Erler (l.) and Portal harvester presented during KWF – Focus Days(II.). Photo: Christian Kanzian (BOKU)
Slika 1. Predsjednik organizacijskog odbora savjetovanja Prof. dr. sc. Jörn Erler (prvi dan savjetovanja) i portalni harvester prezentiran tijekom KWF-a
(drugi dan savjetovanja). Snimio: Christian Kanzian (BOKU)
Karl Stampfer, Martin Kühmaier
Croat. j. for. eng. 34(2013)2
321
Comment – Osvrt
International Scientific Symposium FORMEC 2014
and 5th Forest Engineering Conference,
Gerardmer – France, 23–26 September 2014
Međunarodno znanstveno savjetovanje FORMEC 2014.
i 5. savjetovanje šumarskog inženjerstva,
Gerardmer – Francuska, 23. – 26. rujna 2014.
FCBA, the French technology institute for forestry,
cellulose, wood construction and furniture, will host
the 5th Forest Engineering Conference (FEC) together
with the 47th International Symposium on Forestry
Mechanisation (FORMEC).
The conference will take place on September 23–26,
2014 in Gerardmer (France) under the general theme
»Forest engineering: propelling the forest value chain«.
Two days of in-doors technical sessions will be
completed with a full day of field demonstrations in
the local mixed sub-mountainous forests.
Topics for presentations and posters
The conference themes have been defined by the
technical committee in close cooperation with the Precision Forestry Committee, so that both up-coming
events will complete each other, in 2014.
1. Managing interactions between logging operations and forest ecosystems services
2. Answering specific challenges in harvesting
technologies and working methods
3. Being innovative in transportation solutions and
logistics
4. Better working conditions and educational programs
Croat. j. for. eng. 34(2013)2
5. Organisational innovations and other strategies
for a better planning and monitoring of forest
operations in specific contexts
6. Implementing Precision Forestry concepts for
improved wood-supply-chains
Selection and publication of the presentations
Both scientists and practitioners, as well as students, are invited to submit abstracts in connection to
the themes of the conference before December 31th,
2013. Selection will be done by the FEC-FORMEC 2014
technical committee.
Three types of publications are encouraged, all to
be gathered in final proceedings:
1. Peer-reviewed scientific papers, also to be published either in the Croatian Journal of Forest
Engineering (CROJFE) or in the International
Journal of Forest Engineering (IJFE);
2. Full manuscripts, for papers with scientific content;
3. Extended abstracts, for posters, practitioners’
testimonials on specific experiences or products,
or impacts of past research results successfully
transfered to field operations.
323
Maryse Bigot et al.
Comment – Osvrt
5th Forest Engineering Conference
Important dates
Authors should pay attention to the following deadlines:
Abstracts submission
Feedback from technical
committee
Full paper submission
December 31st, 2013
February 15th, 2014
May 15th, 2014
NB : Registration to the conference will be open from
October 2013 until July 31st 2014 and ealy birds rates
will apply until March 15th 2014.
FEC-FORMEC 2014 technical committee
Maryse Bigot, ONF, France.
Karl Stampfer, BOKU, Austria
Pierre Ackerman, Stellenbosch Univ., South Africa
Jean-Francois Gingras, FP Innovations, Canada
Hans Heinimann, ETHZ, Switzerland
Raffaele Cavalli, University of Padova, Italia
Mark Brown, USC and AFORA, Australia
Ola Lindroos, SLU, Sweden
Bruce Talbo, Skgoglandskap, Norway
Antti Asikainen, METLA, Finland
Jori Uusitalo, METLA, Finland
Bo Dahlin, University of Helsinki, Finland
Magnus Thor, Skogforsk, Sweden
Rien Visser, Canterbury University, New-Zealand
Loren Kellogg, Oregon State University, USA
Woodam Chung, University of Montana, USA
Fernando Seixas, ESALQ, Brazil
Contacts:
FCBA
Morgan Vuillermoz
& Emmanuel Cacot
10, avenue de Saint Mandé
F-75012 Paris
FRANCE
Tel +33(0)1 40 19 49 19
Fax +33(0)1 40 19 48 91
[email protected]
Web: fec2014.fcba.fr
The conference is organised in partnership with the
International Union of Forest Research Organisations
(IUFRO) and its Division 3 (Forest Operations Engineering and Management).
Maryse Bigot, Morgan Vuillermoz, Emmanuel Cacot
ISSN 1845-5719
9 771845 571000

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