STEEL + TECHNOLOGY 04/2019 EXTRACT

56 | STEEL TECHNOLOGY
Figure 3. Spout cleaning manipulator in working position (Picture: BSE)
• 25% of cooled area (lower part)
designed in copper pipes, fin-type;
remaining upper area designed with
steel pipes.
For overall safety, each individual water
return outlet is equipped with temperature
measurement with permanent recording
and visualization, as well as alarm generation
through the integrated automation
system.
To leave it by highlighting these single
examples of connection between design
and safety aspects of EAF operation the
following conclusion can be made.
The right design set-up of the EAF is an
essential pre-condition not only for working
safety. Or the other way around, the
right design of an EAF with reliable engineering
solutions is also a good investment
in overall safety.
To have the EAF with the “right
design set-up” in place and ready for
production, unfortunately is only “half of
the battle”. To apply the operational
standards can be seen as even more
important. Due to the fact, that also the
operational standards linked and influenced
by almost numberless factors,
the following chapter will be constrained
by a number of typical examples and a
general conclusion.
Operational standards (safety
degree 2)
To set up operational standards, certain
pre-conditions have to be fulfilled, such as:
• skilled technical plant management
with “management on the spot”
approach,
• educated, trained and experienced
workforce,
• set-up of plant organization (operation,
maintenance, safety, etc.).
This aspect is of high importance to reach
permanently high efficiency and productivity,
as well as a high level of safety in the
whole production route of a mini mill.
A first example of an operational standard
for an EAF is the set-up of the charge
mix. By looking on the set-up of the charge
mix with scrap charge, the following main
aspects have to be taken into account:
• charge composition regarding product
requirements,
• availability of different scrap types,
• set-up of layout, equipment and organization
for execution, as well as scrap
control.
At the end, the right practical standards have
to be established. One example is bucket
loading practice such as different scrap layers
in the bucket, with lime and carbon in
the bottom and layering of heavy pieces in
lower layers and for example turnings in
between to be compressed with denser
scrap on top. A really important aspect of
operational standard in the scrap handling
area regarding safety is scrap control. Hollow
bodies or even explosive devices in the
scrap can be only identified by applied
standards of all involved operators to avoid
damages and unsafe situations by preventing
such things charged into the EAF.
Another example of applied operational
standard at BSW is the tap hole preparation
of the EAF. In the past, tap hole breakthroughs,
caused by remaining slag in the tap
hole channel before filled with tap hole refractory.
To overcome these frequent breakthroughs
with the related delays, the cleaning
of the tapping channel with manual oxygen
lance in combination with visual inspection
before re-filling was set as a standard operation
for each heat. The result was, that these
events of tap hole breakthroughs nowadays
do not happen anymore.
Furthermore, standard operating profiles
for electrical as well as chemical power input
are essential for consecutive EAF operation.
As far as possible these standard profiles
shall be established within the EAF automation
system. Automated EAF operation with
the right set-up lead also to reliable and stable
operating conditions and therefore minimized
delay-rates of the production route.
An integrated EAF automation system
(e.g. EAF Level 1 with HMI) is furthermore
the best base for the implementation of
additional equipment and systems dedicated
for working and process safety.
Dedicated automation and safety
equipment (safety degree 3)
For stable and consecutive EAF operation
certain actions and activities must be executed
to ensure productivity and quality.
Due to the fact, that these actions are carried
out mainly in dangerous areas, special
safety equipment is required to ensure
operator safety and further improve the
overall process performance. The following
examples show latest technological
developments in the field of automation
and safety equipment around the EAF.
Robots. The implementation and use of
industrial robots in the steel processing
industry opens a wider range of applications
for automation of actions to avoid more and
more that operators are exposed to dangerous
situations. A good example for multi-function
robot application is the MultiROB
installation at BSW at the EAF #2 (figure 1).
The MultiROB is installed in front of the EAF
to execute the following functions:
• taking of steel sample during power-on
in the EAF,
• temperature measurement of liquid
steel during power-on in the EAF before
tapping,
• EAF shell inspection after tapping by
taking a thermo-scan via thermo-camera
(figure 2).
The multi-functioning of the MultiROB is
given by the application of a tool-changing
system that enables the MultiROB to
change automatically (during tapping) its
STEEL + TECHNOLOGY 1 (2019) No. 4