Ensuring reliable energy supply in harsh environments

During the mining and subsequent storage of bauxite, a
sedimentary rock for the production of aluminium oxide, a lot of dust is
produced, which is a major challenge especially for the moving machine parts of
conveyor units. For this reason, the Aluminum Oxid Stade GmbH (AOS), a major
German alumina producer decided to use energy chains from motion plastics
specialist igus. For several years now, they have reliably supplied conveyor
units and stockpiling equipment with energy, data and media.

Aluminum oxide and hydroxide are basic materials used
in the manufacture of a wide variety of aluminium products needed throughout
the world. The production of these substances requires bauxite, a reddish
sedimentary rock that is mined mainly in Australia, China and South America.
From there, it is shipped to Germany, to the Aluminum Oxide Stade GmbH (AOS),
one of the major alumina producers in Germany. The company processes around two
million tonnes of bauxite every year, from which around one million tonnes of
alumina can be extracted.

A single ship delivers up to 70,000 tonnes of raw
material to the AOS port. After unloading by the ship-to-shore crane, it is
transported via an enclosed conveyor belt system for intermediate storage
before being taken for processing. Both when loading and unloading ships as
well as during storage, AOS relies on reliable energy supply systems from igus
for the conveyor units. The heavy dust arising during the movement of bauxite
is an enormous stress, especially for moving machine components. “In the
past, we used motor cable drums for the energy supply,” recalls Fabian
Wilhelm, Head of Electrical Engineering at AOS. “Here we had the problem
time and again that the cables were not properly wound on the drum, which
ultimately caused machine failure due to cable damage.”

Different
applications, same challenges

Since the previously used energy supply systems were
very maintenance-intensive and always caused problems, Fabian Wilhelm decided
to use an energy chain system from igus for the first time in 2012. “At
that time, Mr Bšhm from igus introduced me to the principle of energy
chains,” he explains. “At first I was sceptical about the operation
of the chains in this environment. However, after looking at a seaport and an
aerated concrete plant as reference applications and having the opportunity to
talk to other customers and users, we decided in favour of igus.” As with
AOS, the visited references were all applications with travels over 100 metres,
or applications in coarse dust and dirt. In particular, the stress of the
abrasive salt dust in the seaport on the systems is very high.

First
joint project – extreme stress under the hall roof

The first joint project of AOS and igus was the
so-called ‘loop car’. When it comes to very dusty bauxite, it is not stored in
a heap in the open, but in a large hall to reduce the dust released into the
environment. In this hall, the loop car moves back and forth over a distance of
almost 140 metres under the hall roof to different points to discharge the
bauxite. While temperatures up to 60 degrees Celsius prevail in summer, the
environmental conditions in winter are even more difficult. “When warmer
bauxite is transported from a height of 20 metres to the cold heap, the
temperature difference causes condensation,” reports Fabian Wilhelm.
“This rises and becomes liquid again at the roof of the hall, causing it
to start to rain inside the hall. Moisture coupled with the bauxite dust
results in a stubborn tough material that sticks everywhere and also affects
the path of the energy supply.” This is where the igus energy chain system
brings another benefit, as all applications at AOS also have built-in
electronic push/pull force monitoring systems. “If the run of the chain is
hampered too much by dust and dirt, the push/pull monitoring system will shut
down the system before any damage occurs,” Fabian Wilhelm explains.
“The fact that igus was the only provider to offer such an electronic
surveillance system then was one of the main reasons in favour of igus. If the
monitoring shuts down the system today, we know that it is time again to clean
the travel of the chain. Then the system will run again without any
problems.” The potential to carry not only data and energy but also
compressed air was another plus point in its favour.

Second
joint project – general overhaul of the dumping equipment

Just a short time after the first successful
conversion, AOS again opted for an energy chain system from igus in the course
of a major overhaul of the dumping unit. The bauxite that does not have to be
stored in the hall lands here, in the open. In this project as well, AOS relied
on the support of the igus assembly service, which undertakes the complete
installation of the chain and the trough system in which the chain is moved.
“The special feature of all the projects in this regard has always been
the good cooperation between AOS and igus,” explains Markus Bšhm,
Technical Sales Consultant in charge at igus. “The work was very well
dovetailed and it worked very well together even when mutual support was
required in the assembly work.”

The dumping unit will now be supplied by the longest
e-chain in use at AOS. A roller energy chain of type 5050RHDAX moves along a
travel of 330 metres. “The rolling in the chain links causes the push/pull
forces to drop enormously over long travel distances when the upper run of the
chain lies on the lower run,” explains Markus Bšhm from igus. “Because
of the lower coefficients of friction, up to 57 percent of the energy required
to drive the energy chain system can be saved.” The ‘AX’ in the product
name stands for ‘external stop-dogs’. Since the stop-dogs are not situated
inside between the chain links, as usual, the dust cannot get into the
stop-dogs very much.

In addition to various energy and data supply cables,
which were also produced by igus and specifically developed for use in
e-chains, a water hose with a diameter of 48 millimetres for sprinkling the
bauxite is also located in the chain on the dumping equipment. Furthermore, as
with the other applications, a floating moving end ensures lateral tolerance compensation
and undisturbed movement. This is necessary especially on long travels in order
to save drive energy on the one hand, and to compensate for possible
parallelism errors between running rail and guide trough on the other hand.

Third
joint project – loading and unloading of ship

In the most recent joint project of AOS and igus,
which was implemented in 2017, two energy chains move on a travel of 218 metres
reverse in a common trough. They supply the two cranes that deliver the bauxite
and then remove the produced alumina again. Here, among others, medium-voltage
motor cables of the CFCRANE series are routed, as well as fibre optic cables of
the CFLG series. “This is a real advantage for us,” affirms Fabian
Wilhelm. “Earlier, in the event of crane failures or maintenance, we
always had to first climb 40 metres onto the crane with a laptop to read the
data. Today, thanks to the fibre optic cable connection, this is done directly
from the desk. This enormously improves the maintenance effort.”

Motorised cable drums were also used in these two
applications in the past. However, these always caused problems here because
torque motors had to be operated, which always kept the cables of the motorised
cable drum under tension. “Here in the past, the starting resistors on the
motors rusted time and again and had to be replaced,” recalls Fabian
Wilhelm from AOS. “This meant a ten-day shutdown. And we only had one
unloading crane that can handle around 50 ships a year. Therefore, a failure naturally
weighs very heavily and must be avoided at all costs. Today, of course, the
energy chain systems from igus give us a longer service life and significantly
less maintenance.”

Maintenance at AOS is also handled by igus experts.
“Once a year, we check all the chains according to the igus maintenance
manual and carry out visual inspections,” explains Markus Bšhm. “The
first chain on the loop car has been in use for over five years now. Here at
the last inspection we did not notice any significant signs of wear despite the
very difficult conditions under the hall roof.” This also applies to the
other systems from igus that are in use at AOS. In addition, Fabian Wilhelm
from AOS sums up: “Less maintenance effort, higher availability, the
possibility of running all different cables and hoses in one system, electronic
push/pull force monitoring … all these advantages have completely convinced
us of the igus products. I would always use igus energy chains!”

The igus products are available from Treotham
Automation in Australia. Contact Treotham today to find out how igus energy
chains can improve your application.

For more information, please visit the Treotham
Automation website www.treotham.com.au or call 1300 65 75 64.

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