HAUL ROADS
Keep those
wagons rolling
Paul Moore reviews some
advice on haul road
management and reasons
for poor roads such as truck
overloading, as well as
looking at the effect on costs
from phenomena such as
rolling resistance
verloading is a problem in the mining
industry, not least for the detrimental
effects it can have on haul roads that
may already be in a poor state. Over the years,
the approach to mining truck payloads has
moved between overloading in order to increase
production versus the desire to optimise costs
and performance with load management. Now,
today with miners eager to increase production
with fewer trucks, it is swinging back towards
overloading.
John Ingle, Performance Manager for Larger
Mining Trucks at Caterpillar told IM: “Purported
advancements in loading tool payload monitors
are promising the next step in improved load
distributions and enhanced abilities for
achieving truck target payloads with fewer
under loads. However, while the mining industry
has good acceptance of the ‘not to exceed’
payload limit for trucks as 120% of rated
capacity for safety, there is a perception by
some that reducing payload distributions can
allow an increase in the average payload. This is
based on the misconception that the average
payload on trucks can be increased without
durability consequences as long as loads do not
exceed the 120% mark. But frame and drivetrain
component life are a function of stress and the
number of cycles. Thus, life is more related to
the median than the mean or ‘average’ of
stresses. For structures, a massive overload is
not offset by an extremely low under load. Now,
all that said, the top truck manufactures design
for good life in severe applications, so lower
O
72 International Mining | AUGUST 2017
stress applications will see even longer life.
Many Cat large mining trucks have accumulated
more than 150,000 work hours, and those trucks
are still earning their living in production
haulage. There are also Cat mining customers
who operate at higher than rated payloads
because of their application and their good
management of truck stress through Cat Road
Analysis Control (RAC) and their own tools and
processes. The result is exceptionally good
value and long life from their Cat trucks.”
The point of this discussion is off-highway
truck manufacturers need to do a better job of
explaining that structures and drivetrain
components are optimised to a target payload.
Truck design is optimised around tyres, weight,
horsepower, operating cost, safety/regulatory
standards and production. Ingle adds: “This is
true for any brand of large mining truck. Moving
payload targets up to overload in the long term
causes manufacturers to increase structures and
requires stronger drive components that in turn
leads to a heavier truck that gets fitted with
larger tyres. The result is a truck that has been
upsized and optimised for the new higher
payload. The other key consideration is tyres.
Trucks are designed as a system with tyres and
rims, and while truck designers are not directly
responsible for tyre performance, the truck rated
payloads are set to match the nominal tyre
capacity loads provided by tyre suppliers. While
tyres are designed to deal with the occasional
excessive overload, they also have nominal
stress versus life limitations and optimum
Mine operators are increasingly turning to
geosynthetic materials that can create a
mechanically stabilised layer (MSL) within weak
roadway subgrades
performance ratings. Caterpillar remains
confident in the concept of an optimum rated
target payload distribution and a maximum
design limit payload.”
HAULSIM 2.5 haulage network
optimisation
RPMGlobal (RPM) has recently announced the
release of HAULSIM 2.5 – “mining’s digital twin
for mine haulage network optimisation, truly
revolutionising haulage outcomes. The new
release of HAULSIM brings functionality that is
not available in any other mine haulage
software for mining – Fleet Planner and
Cornering Speed optimisation.”
Fleet Planner allows users to configure their
fleet and productivity levels for the next shift. It
does this through the analysis of the haul cycle
while balancing productivity requirements. The
number of haulers for each configuration can be
automatically calculated. For each configuration
there are over 300 results available for analysis,
including detailed analysis of the haul cycle,
cost and productivity information. The number
of haulers in the fleet planner can be changed
on the fly, allowing the users to immediately see
the impact on any of the results.
Michael Baldwin, EGM Product Strategy, said
“Fleet Planner provides our customers with the
level of certainty and agility needed to