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Electrolytic Cleaning Line
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High Current Density Electrolytic Cleaning Lines (ECL)
Cold rolled coils processed in cold rolling mills have a thin film of residual rolling
oil on the surface after rolling. The alkaline cleaning of cold rolled coils by the
use of high current density (HCD) ensures totally clean surface of the strip
before annealing. This electro-chemical cleaning process is called Electrolytic
Cleaning and the processing line the Electrolytic
Cleaning Line.
These
techniques are more effective in cleaning cold rolled steel than
conventional cleaning processes used on high speed electro tinning and
alkaline-cleaning lines.
A cleaning of 92% was achieved by Essar Indonesia using Dassnagar's high-current-density Electrolytic Cleaning lines.
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The Technology
An ECL
line cleans the strip surface of oil and dirt by chemical action, using an
alkaline solution. The strip passes between electrodes which are immersed in
tanks containing the electrolyte. This technique is more effective in
cleaning cold rolled steel than conventional cleaning processes used on high
speed electro tinning and alkaline-cleaning lines.
Classification
They are categorized into two types :
- High Current Density (HCD) Electrolytic cleaning lines
- Low Current Density (LCD) Electrolytic cleaning lines
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The Dilemma !
A "Low Current density" Electrolytic
cleaning line with multiple mechanical brushing
units remove about 80% of the black Carbon
patches, resulting on cracking of rolling mill lubricants during the
annealing phase. These sheets are not acceptable in sectors where aesthetics
("Look and Feel" after painting) is desired. But being a cheaper
solution often used by processors who look for economy.
On the other hand a "High current density"
Electrolytic cleaning line with multi brushing
roll units can clean cold rolled annealed strips often upto 98%
purity. But lines with two sets of Brushing units are too expensive
and thus not recommended.
A compromise can be made by using Dassnagar's
high-current-density electrolytic cleaning lines, encapsulating a single
brushing unit. A cleanliness of 92% has
been achieved at a continuous line speed of 250
MPM. Higher speeds can be achieved based on system design. The
chemical technology is based on Nippon Steel-Japan,
pioneers of chemical cleaning technology. Low current density lines are
also available on request.
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Fact sheet
Following figures have been achieved :
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Contaminants
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Incoming Strip
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Outgoing Clean Strip
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| Oil and Dirt |
800 mg / sq. meter |
20 mg / sq. meter
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| Iron Fines |
200 mg / sq. meter |
Cleanliness : 95%
Cleaning solution used :
Na4SiO4
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Salient Features
- wide processing range 0.40 mm to 4.6
mm,
- productivity > 300,000 tpa, line speed
350 mpm,
- cold rolled annealed strip cleaning upto
95%,
- electrodes below strip have sufficient clearance to allow sag
between sink rolls,
- gauge measuring system after breaker unit,
- strip lead & tail end joining - A•D•S Indexing, double
row strip stitcher,
- auto tail out function ensures that the coil is processed till
its tail,
- bridle roll units provides tension to avoid sagging,
- uncoiling tension - by DC motor - drag
generator principle,
- side trimming or slitting
possible online
- automation - level 1, 2 or 3
- in house manufacturing of all equipment
to maintain quality,
- servicing within 48 hrs in any corner of the world,
- readily shippable spare parts
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