MOTORS AND DRIVES_proof 26/10/2016 09:43 Page 2
MOTORS AND DRIVES
eliminating a conveyor’s gearbox reduces
maintenance costs while increasing reliability.
Other benefits are lower energy consumption
and noise levels.”
An ABB example illustrated how the GCD
reduces operational costs. In a conveyor line of
four flights with 12 drives in total and power of
1,000 kW/1,340 hp handling 8,800 t/h, the
energy cost was 10 ct/kWh and gearbox
efficiency 96% with annual operation time of
6,900 hours. A commercial trade off was
simulated for the conveyor system. Major cost
factors are electric energy, system maintenance,
repair and loss of production. After 15 years, a
mine would have saved about $12 million by
using GCD. A return on investment can be
expected after less than one year.
Torque limiting in crushing
When crushing mined rock and materials,
uncrushable objects constitute a severe risk for
the production process as well as the installed
equipment. In order to limit torque load without
disrupting operation, Voith recently designed its
SlipSet coupling to temporarily slip in the event
of an overload situation and thus act as a shock
absorber. The company’s Coupling Monitoring
System (CMS 310) offers further benefits by
providing real time status information as well as
performance analyses; displayed in a particular
web interface, on a HMI panel or integrated in
an already existing supervision system.
“When getting stuck in the crushing chamber
or between the rollers, too hard materials or too
huge pieces cause the system to stop running.
As the motor and the momentum of the driveline
still deliver torque, the resulting overload
overheats the motor or leads to the collapse of
the driveline. To avoid cost-intensive repair
works or downtime, belt drives can be replaced
with direct drives protected by an integrated
torque limiting coupling.”
Voith SlipSet couplings consist of a twinwalled hollow sleeve with friction generated by
pressurised hydraulic oil. In case of a torque
peak which exceeds the preset torque limit, it
will instantly slip and
protect the
equipment from
high stresses. If
the blockage
persists, the
coupling
slips until
the
rotational
energy is
completely
absorbed and the drive
can be stopped to enable the
blockage to be cleared. On a scale of
1 to 20,000 kNm the trigger point for slipping
can be set at 50 to 100% of the maximum load.
Due to its compact design, the SlipSet coupling
is easily installed at the optimum position in the
driveline.
“As it separates the input torque from the
output torque of the driveline, the slipping
feature of the SlipSet coupling paves the way for
a detailed monitoring of the coupling and the
occurring forces around it. In order to increase
product intelligence and enable nonstop
performance supervision, Voith developed the
PLC based Coupling Monitoring System CMS
310. It is based on the calculation of the torque
limiting coupling input and output rotational
positions. The measurements are made by
inductive sensors mounted on each side. If the
coupling slips, there will be a pulse difference
between the sensors. The difference in relative
position is recorded and recalculated to a slip
angle in real time.”
Once a slip occurs, the CMS informs the
operator about the incident via a web interface
or an optional HMI panel for closed systems.
Dependi ng on the respective information, the
operator can either adapt the power input,
material feed or initiate a controlled shut down.
This ensures the maximum output of the crusher
since it helps the operator to align the motor
power with the full capacity of the machine.
The used Profinet communication standard
Voith SlipSet couplings consist of a twin-walled
hollow sleeve with friction generated by
pressurised hydraulic oil
makes it easy to individually integrate
relevant data from the Voith CMS
into existing supervision systems.
WEG continues success in
Middle East
Specialised in providing solutions to
the main market segments by
supplying premium quality products and
systems, the traditional global motor
player WEG has been appointed the
single supplier of all low and medium
voltage induction motors for a new alumina
refinery under construction in the UAE. This is
the second WEG achievement in the Middle East
aluminum industry after the successful supply
and commissioning of all electric motors to
Ma’aden Aluminum in Saudi Arabia, where again
WEG was the sole supplier.
Located in the aluminium cluster under
development at the Khalifa Industrial Zone Abu
Dhabi (KIZAD), the new refinery is being
developed by Emirates Global Aluminium (EGA)
and will be operated by its subsidiary, Al
Taweelah Alumina. Phase I of the project will
have a nameplate capacity of 2 Mt/y. EGA plans
to double the capacity of Al Taweelah Alumina in
Phase II. The refinery will extract aluminum
oxide from mined bauxite. WEG has been
selected as the single supplier of all low and
medium voltage induction motors for the project
for its engineering and project management
expertise.
EGA, which is jointly owned in equal shares
by Mubadala Development Company of Abu
Dhabi and Investment Corporation of Dubai, is
one of the world’s five largest primary aluminium
producers and also owns upstream assets.
Power distribution safety
Power management company Eaton displayed
an expanded range of electrical, hydraulic,
pneumatic and mechanical power management
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54 International Mining | NOVEMBER 2016