By Mauricio
Acuna
The Tasmanian forest industry has been put on notice by
Workplace Standards Tasmania (following a coroner’s report)
to eliminate the practice of motor-manual felling of trees (in
which harvesters fell trees using chainsaws), particularly in
forests in which the trees are of small-to-medium diameter. This is
a response to recent accidents and fatalities, but aims to provide
a safer working environment for forest workers. The most obvious
way to improve worker safety and still maintain timber production
is to replace motor-manual tree felling with mechanical tree
felling, in which the worker is enclosed in a protective cabin
while felling trees.
Factors limiting implementation of mechanical felling
However, some known factors limit effectively implementing
mechanical felling systems in Tasmanian native forests. Native
forests in Tasmania are characterised by steep slopes, with rocky,
rough and uneven terrain. They typically have very large diameter
older trees interspersed among relatively uniform-sized even-aged
regrowth trees of small-to-medium diameter. Introducing mechanical
tree felling in such forests will require changing work methods,
introducing new machines and/or combinations of machines, and will
have implications for productivity, safety and associated
costs.
Study details
To investigate the factors affecting the productivity and costs
of mechanical (feller buncher) and manual felling systems, a
detailed time and motion study was conducted on two different sites
in southern Tasmania. Ground conditions on each site were assessed
with a terrain classification system defined by the CRC for
Forestry. Before collecting data, all trees within each plot were
identified according to their diameter class with a painted colour
code. Over a period of one or two weeks, the operation and work
elements of each machine were recorded using a camcorder and timing
software. Complementary information, such as operating delays,
painted colour code, species, branchiness, number of logs per stem,
and terrain classification assessment were recorded on data
collection forms.
Preliminary results
The data is still being analysed, but preliminary results
indicate that in hard conditions (rough and rocky ground, and big
trees) the productivity of mechanised (feller buncher) systems is
about 60% higher than motor-manual systems but comes at a
considerably higher hourly cost. It was also noted during the study
that there were areas that simply could not be accessed by the
mechanical system and discussions with contractors and operators
confirmed that the selection of felling system is dictated mainly
by the presence of rocks and the ground conditions, and less by the
tree. The results of this study will be published soon in an
industry bulletin and will be used to propose recommendations to
improve the productivity as well as the safety of the operations
under those conditions.
The project is being undertaken by research fellows Mauricio Acuna,
Damian
Walsh and Mohammad
Ghaffariyan in collaboration with Gunns Ltd and harvesting
companies Eastern Tiers and Howell’s Logging.
