STEEL + TECHNOLOGY 01/2020 EXTRACT

46 | STEEL TECHNOLOGY
of nitrogen
in the
future, adding
the width adjustment
will be without impact,
simple, quick and inexpensive.
X-JET is rated to produce the following
low coating weights at high line speeds
(coating weight is indicated as the total of
both sides):
• 50 g/m² (0.164 oz/ft²) at 140 m/min
(459 ft/min)
• 70 g/m² (0.229 oz/ft²) at 175 m/min
(574 ft/min)
• 78 g/m² (0.256 oz/ft²) at 180 m/min
(590 ft/min)
• 100 g/m² (0.328 oz/ft²) at 200 m/min
(656 ft/min)
Main achievements and results
attributed to the X-JET
A recent revamp of a continuous galvanizing
line (CGL) in South America involved
supplying Danieli Kohler X-JET technology
in order to change the product mix to thinner
strip with light coating weight while
increasing the line speed to maintain the
overall production rate. The following
goals have been reliably achieved:
Figure 5. X-JET system during operation
(Picture: Danieli)
Figure 4. Design scheme of the X-JET air knife rig (Picture: Danieli)
• increase of the speed
from 150 m/min to 180 m/min for
producing Z80,
• operation at 9.5 mm “knife-to-strip”
distance (actual) instead of theoretical
7 mm (from the mathematical model),
providing further performance potential,
• decrease of production rejects due to
wiping-related defects by almost 70%.
Another X-JET revamp of a CGL in
South-Eastern Asia targeting increased
strip quality to serve the export market has
given following results:
• decrease of coating (zinc) consumption
by 5%, thanks to overcoating deviation
reduction,
• improvement of surface appearance,
such that the product is now accepted
in all export markets.
Two X-JET revamping projects in Turkey
showed that upgrade to X-JET technology
allowed a payback time of only 4
months. This result is based only on a
projected production increase of approximately
10%. The calculation does not
account for the reduction in zinc consumption
or further benefits (i.e., in both
lines the wiping equipment revamping
routinely produces Z80 at 180 m/min
and the average coating weight of the
products is now less than 100 g/m²,
therefore the customer has expanded its
product range towards low coating
weight).
Development of the Compact
X-JET
Despite the proven advantages of the
X-JET design for revamping projects,
crowded pot areas and space constraints
often are limiting factors. Lead-time and
cost are increased by the need to modify
or replace existing equipment. In extreme
cases, it might not be practical to fit into
an existing pot area at all. To overcome this
limitation, Danieli returned to the same
team that was so successful in its initial
efforts. The new goal was to achieve the
same performance in a substantially more
compact envelope.
The further development of air knives
resulted in the Compact X-JET (CXJ) air
knife, designed to be even more easily
integrated in already operating galvanizing
lines. The critical dimension perpendicular
to the strip is significantly reduced for the
Compact X-JET (CXJ). It is now possible
to fit into extremely crowded pot areas
(with minimal disruption to surrounding
equipment).
Features of Danieli Kohler X-JET
and CXJ air-knife wiping
equipment
Product quality. The new X-JET nozzle
design technology, along with precise and
durable lips and precise pressure control,
makes it possible to process the strip at
high speed with very low coating weight,
while obtaining great surface appearance,
visual defect reduction and zinc consumption
savings (by means of uniform zinc
coating distribution and minimum deviation
from target weight).
Modular design allows installation of an
electromagnetic strip stabilizer. The method
of installation maintains easy equipment
handling and process observation.
The possibility to change standard rolls
with coated surface rolls further improves
performances for automotive or other
high-quality applications.
Wiping efficiency. The elevator/positioners
with high-precision horizontal (including
skew) and vertical positioning of airknife/edge
baffle rigs, the stiff and proven
design of automatic lip cleaner, the automatic
non-contact edge baffles with precise
positioning mechanism and sensors,
plus the optional nozzle width-adjustment
mechanisms ensure the highest efficiency
in coating process management.
Advanced automation for precise, repeatable
positioning control with optional
closed-loop coating weight control.
Equipment lifetime and maintenance.
Quick-release bushing housings provide
the fastest turnaround on roll changes.
Roll scrapers are available on demand for
high-quality production and extended
campaign time, especially for Al55%-Zn
STEEL + TECHNOLOGY 2 (2020) No. 1