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The Lumwana trommel complete and ready for dispatch. |
Local Company Builds
Largest Trommel Ever For U.S. Customer Multotec Manufacturing has completed the
largest trommel it has ever built, an order it received from
FFE Minerals. “This is probably the largest trommel ever
built in southern Africa,” remarks Anthony Yell, product
manager – screening, Multotec Manufacturing.
The trommel has an internal diameter of 5.1 metres and is
5.4 metres in length, with a mass of 25 tons. After the
steelwork was completed, the trommel was taken by road to
DCD-DORBYL in Vereeniging for stress-relieving, whereafter
the frame was shotblast and prepared for rubber lining. The
trommel flange was machined and rubber lining completed
before the screen panels were installed.
The trommel was despatched to Lumwana Copper Mine in Zambia,
and will be attached to a 11.6 metre diameter by 5.5 metre
long SAG mill supplied by FFE Minerals. The SAG mill will
have a 3 600 tph capacity, and will be driven by an 18 MW
motor. |
The trommel incorporates hand-cast
polyurethane panels, each measuring 785 mm wide by 1 350 mm
long x 44 mm thick with 12 mm x 38 mm slotted apertures. Multotec’s toolroom had to
make up a special mould to cast these panels. After casting,
the panels were trimmed and then rolled to the correct
radius of the trommel.
Yell says Multotec Manufacturing, a company in the Multotec
Group, can rightfully claim to be one of the largest
suppliers of trommel screens to the mining industry.
Trommel screens are still considered a wear component in
smaller mills. However, technological advances over the past
decade have resulted in frames designed to last for many
years. The structure is rubber-lined to prevent erosion of
the steelwork, while the surfaces are now equipped with
replaceable screen media.
Flanges are machined to ensure seamless contact with the
mill trunnion flange to prevent undue stress in the joint.
In actual fact, trommel screens are complex steel structures
that have to cater for uneven loads discharged from mills
and scrubbers.
As the units rotate, the product discharges through an arc
of no more than 25° of the circumference, creating a
preferential load-bearing zone, and keeping the frame under
constant stress.
Over the years, Multotec has developed methods of designing
trommels in-house to cater for these requirements with the
assistance of finite element analysis.
The company is ISO 9001 listed, and uses extensive quality
assurance procedures in the manufacture of trommel screens
to ensure a high-quality product is produced.
With the advent of large SAG and ball milling processes,
trommel screens have become more prominent in processing
plants. Mills have increased in size to cater for higher
throughputs, significantly increasing the size and
complexity of trommel screens as well. |
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