Paper Technology Journal 19 - Voith

3 4
Our reference list includes high and low
speed lines for graphical grades such as
newsprint, SC and LWC as well as numerous
machines for specialty grades
like decorative papers, photographic papers
and also board and packaging paper
machines.
As shown in Fig. 2, various process conditions
are analyzed at the same time, using
a common procedure with comparable
instrumentation:
● Hydraulic stability from machine chest
to headbox; simultaneous recording
of up to 32 pressure signals in the
0-1000 Hz range
● Stock consistency variations;
simultaneous recording of up to 3 flow
streams in the 0-10 Hz range
● Vibration measurements in all relevant
points to establish interference
potential; simultaneous recording on
up to 48 channels
Fig. 3: Tapio analyzer.
Fig. 4: Measuring location.
● Speeds and speed variations of mixers,
pumps, screens and fans
● Free and dissolved gas content in
stock suspension
● pH and conductivity values for all
stock and water loops
● Mixing conditions based on stock
consistency and ash content
measurements in each flow stream.
Apart from data delivered by the Voith
measuring systems specially developed
for Wet End Process Analysis, settings
and readings are also taken over from the
process control system and directly from
the wet end machines. These include operating
speed, chest levels, flow rates,
valve and headbox settings, vacuum settings,
etc. Also included in the documentation
and evaluation are process-relevant
data such as furnish characteristics
and additives, as well as productionrelated
data like shift reports and sheet
break records.
Wet End Process Analysis
evaluation and assessment
methods
51
An intensive Wet End Process Analysis,
generally completed in 2 to 3 days by a
experienced Voith team of experts, delivers
an enormous amount of data and
readings. Generally, the analysis covers
settings for more than one grade or production
rate.
A well-structured analysis and evaluation
methodology is imperative for efficient
goal attainment.
The paper quality characteristics on-site
are determined by direct transmission
sensors and complemented with data
from the other measurement parameters.
This procedure enables targeted measures
to be taken already at the measurement
stage, particularly for troubleshooting, so
that the causes of paper defects or markings
can be pinpointed and eliminated.
Another benefit is that it reveals the curious
effect that the negative influence on
paper quality can be caused by vacuum
pumps, refiners, chemical dosing equipment,
shakers or fans well away from the
stock and water loops.
A Wet End Process Analysis is therefore
a universal tool in the decision making
process for optimization measures in the
Wet End.
19/05