consideration during the engineering
phase of the truck body. The data is
scrutinised with protractors, measuring
the angle of the material and
calculating the angle(s) of repose.
The data is used to create a
simulated, 3-D load profile of how the
material will look after it settles inside
a body. During the simulation, the load
is put into a virtual bed and moved
around to achieve optimal distribution
of weight and centre of gravity.
Engineers make further refinements to
the body design from this simulation,
supporting load-bearing areas and
minimising steel in areas that do not
require the support. This helps create
an effective truck body best suited to
the specific material being hauled at
that specific site. With the predictive
load modelling system, the body
manufacturer accurately determines
what the mine will achieve out of the
body before it even hits the production
line.
This scientific and
engineering‑based approach ensures
maximum productivity, essentially
translating to more material hauled per
cycle, completing additional cycles due
to the decreased loading time and
fixing the mine’s costs, while growing
production. Because this approach is
specific to each mine and the materials
it hauls, it is truly a custom approach
where the truck body is a
purpose‑built, one-of-a-kind solution
for the mine’s specific needs.
While a custom design can mean a
slightly higher investment, in the
current economy where mines are
being pressed to cut costs further and
further, they are finding that investing
more in the right equipment, saves
them a significant amount of money
over the long haul. The typical cost of
owning a 200 t to 400 t payload truck
is US$12 000 – US$16 000/short t of
hauling capacity. The hourly owning
operation cost is approximately
US$220/hr for a 200 t capacity truck
and approximately US$380/hr for a
400 t capacity truck. Considering these
costs, it is important that each truck
hauls as much material as possible for
each and every hour of operation. It is
not uncommon for generic truck bodies
to underhaul by 10 to 15%, or more. In
the context of a 200 t truck, it would
underhaul 20 to 30 short t per cycle,
which adds up to significant shortfalls
and further increasing the material’s
transportation costs.
Weighted decision‑making
Angles of repose are not the only
characteristic affecting the design of the
truck body. Weight is a critical factor in
any hauling operation – and that
concern for weight goes beyond the
rated capacity of the truck. Weights of
materials vary greatly. Even within
coal, certain regions of the world have
very clean coal and thus the product is
lighter in weight. Other areas have thin
coal seams that can contain a large
amount of impurities, requiring a
significant amount of cleaning. This
type of coal naturally weighs more
per yd
3
. To maximise productivity, the
truck body must be designed to
achieve the optimal volumetric
capacity, carrying enough material to
reach as close as possible without
exceeding the truck’s maximum gross
vehicle weight.
With a lightweight material like
coal, trucks need to have a large body
to accommodate the way coal heaps
and the fact that more material is
needed to reach a truck’s capacity.
Some manufacturers simply tried to
achieve extra volume by extending the
truck body’s sidewall height. This
might work, in theory, but it makes it
much more difficult for both the truck
driver and loader operator.
Increased sidewalls and a narrow
truck body pose a number of
challenges and safety hazards. First,
the high walls prevent a good site line
to the body of the truck, which makes
material loading difficult and time
consuming. The loader or shovel
operator must carefully position the
bucket to ensure he or she will not hit
the sidewall of the truck when
dumping. This often results in loading
more material to the far side of the
truck, placing uneven strain on the
truck’s axles, chassis and tyres. Over
time, this can lead to premature tyre
failure and significant damage to the
truck chassis. In addition, uneven truck
loading creates a safety hazard on the
narrow, sloped roads inherent in mines,
risking a shift of weight that could
result in a roll.
The truck driver also suffers the
effects of the difficult loading. Due to
the tall side walls, there is a small
loading target that is hard for the
operator to see. This means he or she
has to drop the load from a higher
distance, resulting in more impact on
the truck bed and harsh vibrations that
impact the driver in the cab. Load after
load, day after day, these vibrations can
add up to serious damage to the
structural integrity of the truck bed and
potentially health issues for the
operator.
High-performance coal bodies are wider and match up with the loading equipment
shovel, allowing for a larger loading target.
June 2015
|
World Coal
|
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