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MODERN MINING
June 2016
MINING News
Marthinusen & Coutts, a division of Actom,
has again demonstrated its ability to
undertake challenging work on rotating
machinery. The division was recently called
upon to assist Gold Fields’ South Deep
Twin Shafts when the mine experienced
a failure on one of the stators on its main
winder installation.
Marthinusen & Coutts rewinds South Deep stator
Pictured with the stator are (from left) Richard Botton, Divisional CEO at Marthinusen & Coutts, Michael Olivier,
Engineering Manager at South Deep, Chris van Heeswijk, electrical consultant to South Deep, and Rob Melaia,
Engineering Executive at Marthinusen & Coutts.
Rob Melaia, Engineering and Technical
Executive at Marthinusen & Coutts,
explains that the sheer physical size of the
stator alone is quite unique – especially in
terms of the challenges of rewinding such
a large unit.
“The 65-ton stator mass driving a squir-
rel cage induction motor very probably
makes this the largest motor of its type in
the world,” he says. “While there are many
larger synchronous motors, it is highly
unlikely that there are larger squirrel cage
rotor machines.”
He says that the 6 MW, 3,3 Hz, eight-
pole design of the stator makes it greater
than a 90 MW, 50 Hz, 750 RPM equivalent,
and that when one adds in the fact that
these are driven by cycloconverters, the
uniqueness of the installation is apparent.
Following a thorough assessment by
Marthinusen & Coutts, it was ascertained
that the stator insulation had failed prema-
turely after approximately eight years, when
one would normally expect a 30-year ser-
vice life from this machine. This failure was
unusual in that there was no physical exter-
nal damage and no signs of overheating.
Furthermore, with two parallel connected
motors one would expect both to fail if a
severe external transient was the root cause.
The prevailing root cause remained cyclical
stresses on the stator insulation due to ther-
mal expansion and contraction cycles.
Gold projects in Tanzania to be amalgamated
Kibo Mining, listed on AIM, has signed a
Memorandum of Understanding (MOU)
with Lake Victoria Gold to amalgamate
the companies’ respective Imweru and
Imwelo gold projects into a new com-
pany (NEWCO). The board of NEWCO will
comprise a mix of Kibo and Lake Victoria
management combining significant
experience across exploration and mine
development.
T h e p r o j e c t s h a v e c omb i n e d
JORC-compliant stated resources of
approximately 755 300 ounces. Based on
upside potential identified in the exist-
ing Imweru CPR, the combined project
will provide NEWCO with the potential to
achieve a plus 1 million ounce resource in
a relatively short time frame.
The two companies have a production
target of 50 000 oz of gold per annum
within 12 to 18 months of forming NEWCO,
targeting 100 000 oz per annum within 24
to 30 months.
“The past two years’ steady work on
the Imweru DFS advanced the Imweru
project to a level where we could come to
an arrangement with Lake Victoria Gold,
which will see the amalgamation of the
respective projects on a like for like basis,
to create a project with critical mass and a
clear path to near-term production,” com-
ments Louis Coetzee, CEO of Kibo.
The Imweru and Imwelo projects are
located in the Lake Victoria goldfield of
northern Tanzania, approximately 35 km
west of AngloGold Ashanti’s Geita mine
and within a similar geological setting,
prospective for Archaean age ‘greenstone’
hosted gold mineralisation.
After acquiring the Imweru project in
2013, Kibo carried out additional resource
drilling in late 2013 leading to the publica-
tion of a new mineral resource statement
of 16,48 Mt at 1,14 g/t (550 000 oz) in
February 2014. Kibo announced the com-
mencement of a Definitive Feasibility
Study (DFS) on the project in October 2014.
Since then it has completed a Preliminary
Economic Assessment and commenced
a Prefeasibility Study which together will
comprise the first stage of the DFS.
Lake Victoria Gold’s Imwelo gold project
is located along strike and contiguous with
the Imweru project. It effectively forms an
extension of Kibo’s Imweru East Mineralised
Zone and has a published JORC mineral
resource of 205 200 oz at a grade of 2,3 g/t
(of which 90 800 oz is in the measured and
indicated categories). Lake Victoria was
granted a mining licence over the project
in January 2015 which should enable mine
development to progress rapidly.