WORLD PROSPECTS
Scalping screens engineered for tonnage
“Large scalping screens are part of our technological
heritage,” Kim Schoepflin, CEO of South Africa-
based vibrating equipment OEM Kwatani, says. “We
have been producing vibrating screens that are
engineered for tonnage for more than four decades
and recognise the demanding conditions under
which scalping screens are placed in the mining
environment and designs accordingly.”
First and foremost, scalping screens must deliver
tonnage throughput, she says; this means a detailed
understanding of the extreme forces at play that
need to be accommodated by the design and
manufacture of equipment.
In a recent project, Kwatani developed and
commissioned a large secondary scalper for a South
Africa iron ore operation where material ranging
from fines to 0.5 m in size was falling 1.5-2.5 m from
a conveyor. The large scalping screen, weighing 54 t,
3.7 m wide and over 10 m long, was specially
designed to perform under these conditions.
Schoepflin says the result was a throughput
improvement of 1,500 t/h over the previous capacity
to 7,500 t/h.
To achieve this goal, Kwatani worked in
collaboration with the mine on extensive research
and development. It applied its depth of design
expertise not only to the screen and exciter drives,
but to the deck screening panels themselves, the
company said.
“This ensured that the scalping screen could deal
Weir Minerals solves ‘dirty water’ problem
A
s mine dewatering needs become a
bigger industry issue, Weir Minerals is
stressing the importance of using a fit-
for-purpose pump in these applications that can
handle “dirty water”.
While the market offers specialised slurry
pumps to handle thick and abrasive slurries, as
well as submersible and sump pumps for
pumping clean water, neither of these options
provide an effective solution for pumping dirty
mine water, Weir Minerals says.
The company has leveraged its extensive
knowledge of pumping slurries and developed
the Warman ® DWU (Dirty Water Unit) pump,
designed to handle both increased suspended
solids in dirty water while operating at high
discharge head pressures.
“The introduction of, and subsequent
clogging from, suspended solids is one of the
most common causes of premature failure in a
dewatering pump,” Weir Minerals says. “‘Upset’
conditions during the underground mining
process are the general cause of increased
suspended solids levels entering the mine’s
dewatering discharge water.”
The Warman DWU pump combats both these
challenges, transporting the dirty mine water to
its designated discharge point via single (140
m), multi-stage (480 m) portable, or permanent
pumping solutions, the company says.
‘Dirty water’ is the name given to water with
too high a percentage of suspended solids to be
considered ‘clean’ but too low of a percentage to
be classed as slurry, Weir Minerals says. “Dirty
water becomes a problem on site when the
solids concentrate inside a dewatering pump
collects around the motor frame, overheating
the pump and causing the motor to fail.”
The Warman DWU pump is, Weir Minerals
says, specifically designed to handle dirty water
from onsite ponds and open pits with specific
gravity of up to 1.05. Where a pump built to
handle clean water will fail once dirty particles
are introduced, the DWU pump will not,
according to Weir. “That is because the DWU
6 International Mining | APRIL 2020
was designed using computational fluid
dynamics and utilises Weir Minerals’ advanced
material technology, allowing the DWU pump to
process the fluid efficiently and minimise pump
maintenance in the long run,” the company
said.
Marnus Koorts, Product Manager for Pumps
at Weir Minerals Africa, said: “In most
circumstances, high-head clean water pumps
will fail when they are required to process even
a minute amount of particles. Once you have
greater than 1% of particles, a site’s only other
option is to install slurry pumps.”
Slurry pumps are commonly used to address
the dirty water problem, but this solution is
costly and inefficient, according to Weir
Minerals.
“Without a specialised dirty water pump like
the Warman DWU, up to three slurry pumps
need to be sourced, installed, and maintained
just to pump the dirty water as far as a single
Warman DWU pump can,” the company said.
“The pump utilises a new high-pressure casing
to withstand pressures up to 7,000 kPa,
enabling it to operate at maximum speed and
achieve a head of 140 m at the best efficiency
point.”
Koorts summarises: “This results in a lower
The Warman DWU pump is designed to handle
both increased suspended solids in dirty water
while operating at high discharge head
pressures
with the demanding conditions including surge
loading from the conveyor, while still providing
regular feed to the gyratory crusher,” Schoepflin
said.
“As with this application, scalping screens are
frequently a critical element of mine productivity.
Their position in a single-line, run-of-mine
application requires a high level of reliability and
availability.” www.kwatani.co.za
total ownership cost and reduced downtime for
the customer while providing them with
increased efficiency and energy savings over
using slurry pumps in the same application.”
The Warman DWU pump provides a solution
to a fluid transfer problem that can quickly
affect an entire operation, according to Weir
Minerals. “By making use of the latest Warman
WBH ® mechanical end design, customers
benefit from 90% common component
interchangeability, allowing them to reduce
stockholding of spares,” the company said. “In
addition, the Warman DWU pump is available
with either an electric or diesel motor, and can
be mounted on either a pontoon, skid, or trailer,
which provides sites with the flexibility to move
the pump around to where it’s needed.”
Koorts said: “Pontoon mounting an electric
DWU pump allows for series pumping at base
level or stage pumping out of an open pit. With
Weir Minerals’ dewatering expertise, we’re able
to engineer a complete solution that places the
suction end of the pumps into the water, while
the pump and motor are mounted at an angle
above the water line. This keeps the suction end
of the pump submerged and eliminates suction
problems. With a diesel driven pump, we install
a vacuum assisted priming system that reprimes
the pump when needed.
“Essentially, customers can set and forget.”
The Warman DWU pump provides a flexible
dewatering solution to sites, not
only in the portability around site,
but in the range of fluids the pump
is built to handle, Weir Minerals
says. “In the nine years the pump
has been on the market, Weir
Minerals engineers have continued
to improve the DWU’s
capabilities.”
Although designed to handle
dirty water, the Warman DWU
pump is also able to process clean
water with 78% efficiency, and the
addition of a stainless-steel casing means the
DWU pump is now suitable for highly acidic
applications (pH >2), according to Weir
Minerals. www.global.weir/industries/mining/