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TECHNOLOGY
stirrers between furnaces 24/7 for 365 days a year, the design and
equipment choice becomes very important in order to ensure continuous
and reliable operation. It is very important to consider the design
of the movement mechanisms and the cooling feed mechanisms so
as to minimise future maintenance or operational issues. The Altek
design and engineering team have many years of experience of supplying
electrical induction equipment to aluminium casthouses (and
steel plants), and have spent a lot of time in designing their turnkey
solutions to ensure a reliable system.
By using air-cooling we have removed the need for mobile water
hoses/couplings and the associated maintenance problems which can
occur, such as movement cycling under the aluminium furnaces. Altek
also believe a turnkey supply responsibility is important for the
stirrers and for their associated movement mechanisms, and for this
reason we undertake the full supply not just of the stirrer and control
system but also of the scissor lift / hydraulic trolley and movement
systems.
The movement systems that we have applied in the market are very
robust and efficient, giving repeatable operation. Each system undertakes
full factory acceptance testing (FAT) as indicated in Fig. 6.
For an Altek stirrer that will serve a melting furnace pair the installation
is designed to be controlled from the operator pulpit through
the furnace master control, so as to allow movement between the
two furnaces by an electrically driven trolley. Local control is also
available.
The cooling air fan can be either towed behind the stirrer or remain
fixed in position on it with a unique connection adaptor. Automatic
and hydraulically operated latches will secure the trolley under
the furnace once the correct position for operation has been detected
by the proximity detectors. This is important to ensure the
stirrer cannot move once it starts operating.
Fig. 7 shows the new Altek type 700 stirrer in its basement position on a
multiple furnace operation
The stirrer rises on its hydraulically operated scissor lift to the designated
position under the stainless steel plate (leaving a 10 mm air
gap) in the furnace hearth, and then to start the stirring action.
The speed of stirring (frequency), direction of stirring (forward or
reverse), power of stirring (current) are all controlled from the furnace
control PLC supplied by the furnace supplier. This sends instructions
to the stirrer controls system via Ethernet link.
This multiple furnace system has been in operation at other facilities
in Europe (Hydro) and it works very effectively. We are currently
supplying a similar multi-furnace system (to serve 4 furnaces with
2 inductor systems) to CSAC, Taiwan, and also to Carcano, Italy.
Performance results
Melt rate and energy savings: The Altek side mounted stirrer shown
in Fig. 4 earlier (as presented at TMS 2011) achieved a very good
ALUMINIUM · 3/2013