Paper Technology Journal 17 - Voith

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Specialists visited the mill and examined
all current threading processes thoroughly.
They discussed the threading difficulties
with personnel at the mill and developed
a detailed optimization plan based
on their findings.
The first problematic threading section
was Dryer 52 to the last Coater ropes
section. Originally, the tail was transferred
into the rope nip by air nozzles located
under a mini doctor blade. This
system did not operate properly and required
operator involvement when blowing
the tail into the rope nip. The new solution
from Voith TTG included a multiple
VTT Turbo conveyor system to stabilize
the tail, eliminate the double tail and to
provide a reliable, controlled transfer into
the rope nip. The VTT Turbo conveyors
are built with internal turbines that generate
a large amount of vacuum. These
conveyors also include an internal Drum
Drive for efficient operation and space
savings. This section was rebuilt during
the summer of 2002, approximately eight
weeks before the main shut, allowing a
smooth and efficient take-over for the operators.
This contributed to a good startup
after the main rebuild as the operators
were already familiar with the new
threading technology.
The second optimized section was the
Dryer to Size Press section. Again, the
original system used air nozzles to blow
the tail into the ropes. This manual sys-
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Finishing
tem was very unreliable and compromised
operator safety. The optimized solution
included a multiple VTT Turbo conveyor
section with a Flip Tray transfer device
and a Tail Ripper. The Flip Tray was
mounted directly on the dryer cylinder
doctor to allow for the movement of the
scanners and other equipment. The purpose
of the Flip Tray was to stabilize the
tail during the transfer. The Tail Ripper
was used to efficiently eliminate the double
tail.
The third section to be optimized was
Dryer 2R to the 1st Coater Ropes section.
Again, air nozzles were used in the original
transfer. As the air nozzles were located
under the doctor blade, the system
didn’t operate properly and required operator
involvement. The new solution included
VTT Turbo conveyors, a Flip Tray
and a Tail Ripper. In this section, the Flip
Tray moves the tail onto the conveyor
where the tail is kept under control and
transferred into the rope nip. The rope
nip was also relocated to allow for a better
tail transfer into the coater ropes.
The results of the optimization process
were exceptional. Right after the system
start-up, threading was successful 85%
on the first attempt and 100% within
three attempts. Threading times were
also significantly reduced allowing for increased
machine efficiency and production.
Other benefits from the optimization
included elimination of double tail, no
Min
30
25
20
15
10
5
0
20
Fig. 2: VTT Turbo conveyor
installed at Condat.
Fig. 3: Dryer to size press
drawing; optimized threading
at Condat.
Fig. 4: Threading times before
and after optimization.
Before optimization
After optimization
10
15
5
30
15
Coater 1 Coater 2 Film Press
Sections
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manual intervention, improved operator
safety, limited maintenance requirements
and space savings. Voith TTG took full
ownership of the threading process during
start-up resulting in a significant
threading improvement.
Within six months of the start-up, total
time losses at the coater sections had
been reduced by 35%. The optimization
resulted in a significant 65% reduction in
threading downtime. The mill and operators
are also impressed with the reliability
of the threading system and the effect
the system has had on operator safety.
The ultimate result of this optimization is
a 4% increase in total machine efficiency.
In a very short time, less than seven
months, this installation has proven to be
very successful. The co-operation between
Voith and the customer Condat
made it possible to reach all the deadlines
and make this installation a true
success.
17/04
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