Mining in focus
Weighbridges play a huge role in
controlling production and costs,
writes Leon Louw.
Weighing the transport trucks with product
in the bin before it leaves to its destination,
where it will have to be weighed again.
E
nsuring that every single ton of extracted ore arrives
safely at its destination has been a headache for as
long as bulk mining operations exist. As theft and
corruption become more prevalent, and as new ways of
defrauding mines are devised every day, mining companies
are focused on developing methods and systems to prevent
excessive losses. But the fact remains: once the trucks load
ore from the stockpiles, there are no solid guarantees that
the same tonnages that leave the gate will arrive at the
siding or port.
The most effective method is the tried and tested
weighbridge; therefore, it is important to ensure that
the best weighbridges are installed and maintained
to manage and control stock and tonnages. When
developing new mines, factors like mining methods,
strip ratios, mine design, and all sorts of different
ratios demand all the attention, with functions like
stockpile, transport, and weight control being relegated
to secondary functions that do not need immediate
attention. Yet, it should be top of mind, as it is essential
for a mine or quarry to know exactly what sort of
tonnages enter and exit its gates and to monitor how
much ore actually arrives at the destination.
According to independent mining consultant Nicolaas
C Steenkamp, weighbridges are an essential part of most
mine and quarry operations that rely on road transport
of their product to their market. “The primary use of
weighbridges is as a control measure — keeping track
of the mass of product leaving the mine or quarry versus
the mass of material delivered to the market or to the
port. In Africa, this is essential, as there are cases of load
skimming, substitution, and theft that occur between
the mine or quarry gate and the port of market-delivery
load-off points,” says Steenkamp.
At the stockpiles, the loading of the trucks can be done
by front-end loaders or load-out stations. The benefit of
load-out stations is that there is better control over the
volume of material being loaded and the shape of the
loaded material. A good loading shape results in more
accurate weighbridge measurements.
Steenkamp says that weighbridges can also be used as
a high-level indicator of the moisture content or quality
control of the mined material by a skilled operator. Some
products, such as soils, clays, and sand, absorb water,
increasing the mass per volume. “It is common practice
at most quarries to measure the moisture content of
the material