Paper Technology Journal - Voith

It is exactly this wealth of variation and
the adaptability within the Janus Concept
which offers a particular opportunity to
upgrade existing calenders using the
potential of the Janus Technology.
Two recent examples can be used to provide
food for thought for others running
existing plants.
In a Finnish paper mill for uncoated
gravure paper it was decided to modify
the more than 25 years old Eck supercalenders
to such a state that, together with
modernisation measures to the paper
machine itself, natural gravure paper
could be produced which would satisfy
the highest quality standards applicable
in today’s industry.
The elements, which are necessary to
convert this customer’s supercalender
into a Janus, are illustrated in colour in
Fig. 2. Compensation of the overhanging
loads form the basis for this, creating a
geometrically straight nip.
This means, that the previously sliding
calender bearing housings are now
mounted on swivel levers, which are fitted
with hydraulic cylinders and used to
eliminate the detrimental effect from the
overhanging loads.
The existing antifriction bearings and
bearing housings of the supercalender
are re-used.
The extremely complicated mechanical
and electric/electronic means that were
necessary when changing filled rolls with
different diameters have become obsolete
now. This facility provides the basis for
Finishing
Fig. 1: Different Janus calender lay-outs,
1 x 6 rolls, 2 x 5 rolls, 2 x 7 rolls, 1 x 11 rolls.
Fig. 2: Modifications to a Janus calender with a
heating roll surface temperature of 100°C.
Fig. 3: Quality target values.
2 3
New
■ Lever position with OLC cylinders
■ Marun air stream rolls with JanuTec
coating
■ Water heating/cooling system
■ Rotary joints for heating rolls
■ MicroFlow steam moisturizers
■ Bearing housing for top and bottom
S roll
■ Bottom hydraulic cylinder
■ Auxiliary drives for guide rolls
Gloss Tappi 75° Hunter ✞ 50%
Roughness PPS-10 S ✜ 1,0❍m
Blackening index ✜ 45
Loss of luminescence (ISO) ✜ 4,5%
Opacity reduction ✜ 3,5%
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replacing the filled rolls with plastic rolls.
The filled roll shafts, however, will be
converted into a MARUN roll provided
with a JANUTec cover and continue to be
used.
So as to provide the necessary process
heat within the Janus Technology, the
next logical step must be pursued on the
heating side. In this particular case,
extensive laboratory tests in conjunction
with the paper makers and calender manufacturers
enabled a process to be
worked out where 100°C of surface temperature
of the heating roll proved to be
sufficient.
In this project the restriction of surface
temperature to 100°C has the advantage
that the old heating rolls of the supercalender
need not be changed, leaving only
the procurement of a more effective and
new heating installation.
The surface moistening necessary for
natural paper by means of steam is being
modified to the latest state-of-the-art as
well as to future use by the addition of
new micro-steam moisturizers. The result
of this is illustrated in Fig. 3. As can be