First Mining Drc-Zambia July/Aug 2019 First Mining DRC-ZAMBIA July-August 2019 digital | Page 10

NEWS
Zest WEG
provides fast-track solution for
tailings project
demonstrates the engineering flexibility
that WEG Transformers Africa can
offer customers in meeting specific
operating parameters,” Stuart Brown,
sales team leader at WEG Transformers
Africa, says. “It is not a distribution
transformer as such, but rather a VSD-
type transformer.”
Cooling capacity had to be increased
to accommodate the harmonics, and
flux density is also reduced. The WEG
transformers are built to SANS 780
specification, which stipulates losses
even lower than the global IEC standard.
Brown explains that this will translate
over time into energy savings for the
customer and is an important advantage.
Fabrication of all MCCs and the
adaptations to the container were
undertaken by WEG Automation
Africa at its facilities in Robertsham,
Johannesburg and Heidelberg, further
adding to the high local content on
this project. This local manufacturing
capability is an integral part of Zest
WEG Group’s status as a B-BBEE Level
1 contributor.
W
EG Automation Africa and
WEG Transformers Africa,
part of the Zest WEG Group,
assisted with the commissioning of a
containerized substation and control
room solution at DRDGOLD’s new Far
West Gold Recoveries Project’s Phase
1 tailings site. The container was mounted on a
concrete plinth with 2.5 m pillars
elevating the structure to allow optimal
visibility from the control room. Heat
losses were factored into the design
to ensure the substation remained
cool and the installation is fitted with a
comprehensive fire detection system.
The tailings recovery project will see 500
000 tons per month of material pumped
from the Driefontein 5 dam through a
new 2 km pipeline to the Driefontein 2
plant. Business development manager
for projects and contracts at WEG
Automation Africa, Tyrone Willemse
highlights the tight timelines in which
work had to be conducted. Willemse says that an important
consideration was to reduce the footprint
of the substation, and using free-
standing VSDs allowed this. “Had the
VDS configuration been a conventional
design these units would have been
incorporated in panels and we would
have needed an additional container,”
he says. The VSDs are placed against
the container wall and are completely
isolated from any exposed conductors.
The development of Phase 1 began in
August 2018 with first commissioning
beginning just four months later, in
December 2018. In an unusual step for
such a project, the electrical portion
was supplied ahead of the mechanical
aspects to expedite the contract.
“At the tailings facility, the customer
required a medium voltage (MV)
substation, a low voltage (LV) substation
and a control room,” Willemse says. “This
was accommodated within a double-
container structure, which also included
a room to house all the free-standing
variable speed drives (VSDs) and
uninterruptible power supplies (UPSs).”
Motor Control Centres (MMCs) were
also provided for the modifications to
the Driefontein 2 plant. The MCC for
the thickener is fed by two 1 600 kVA
transformers and the tailings MCC is fed
by one 1 600 kVA transformer; both were
manufactured at WEG Transformers
Africa’s Wadeville facility. These WEG
transformers have a local content of
95 %, well over the required 90 %
specification.
“For this project, the transformers
are designed to incorporate the VSD
component of the load, and this
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Particular care was taken with on-site
modifications at the plant itself.At the
milling and classification MCC extension,
WEG Automation Africa was required to
connect to DRDGOLD’s existing MCCs.
The use of joggle chambers on either
side of the existing board made for
best practice and greater safety. On
the return water MCC, a raised plinth
was added for easier cable access.
Top entry cables for the slurry receiving
and tailings MCC was facilitated by
innovative board design.
The MCCs incorporate an extensive
range of WEG LV products including
WEG air circuit breakers (ACBs) to
facilitate a 50 kA fault level, WEG
moulded case circuit breakers (MCCBs),
WEG contactors, WEG fast-acting high
rapid fuses, and WEG motor protection
relays.
WEG W22 LV electric motors were
selected to drive the tailings facility
pumps,
ensuring
lower
energy
consumption through the design of these
units, which have an optimal cooling fin
design. Ingress protection is to IP66
ensuring effective sealing against liquid
and dust.
WEG Automation Africa, formerly known
as Shaw Controls, recently changed
its name to align with parent company,
Brazil-based WEG’s global strategy.
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