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Paper machines and pulp lines

In the construction of the paper machine map seven features were used: wire width, wire trim width, speed, minimum and maximum grammages, present technical production capacity and the year the machine was (re)built. For the pulp lines five features were used: bleaching type, fibre type, main pulp grade type, market capacity as a percentage of the total pulp production and the total pulp production capacity itself. The units, ranges and mean deviations of the components are given in table 5.1. The different types of bleaching, fibre and main pulp grade are listed in table 5.2.


Component value range M.D. tex2html_wrap_inline3522
Paper machine data
Wire width (mm) 0 - 10160 1200 420
Wire trim width (mm) 0 - 9450 1200 400
Speed (m/min) 0 - 2800 310 130
Grammage, min ( tex2html_wrap_inline3530 ) 0 - 999 50 28
Grammage, max ( tex2html_wrap_inline3530 ) 0 - 9999 180 120
Capacity ( tex2html_wrap_inline3534 ) 0.1 - 525 36 13
(Re)built (year) 1863 - 1996 14 7.1
Pulp line data
Bleaching code 1,2,3 0.97 0.24
Fibre code 1,2,3,4 0.94 0.16
Main pulp grade code 1,2,3,4,5 1.3 0.28
Market pulp capacity (%) 0 - 100 26 5.7
Total capacity ( tex2html_wrap_inline3534 ) 1 - 1075 73 35
Table: Paper machine feature vector components (top) and pulp line feature vector components (bottom). The second column gives the range of values of the component. The third column gives the mean deviation from component average (M.D.). It is provided for comparison with the value in the fourth column, the mean component deviation of data projections. Both deviations are given with the precision of two meaningful digits.


Code Value Meaning
BL 1 bleached
SBL 2 semibleached
UNBL 3 unbleached
WO 1 wood
OV 2 other virgin fibre
RA 3 rags
WA 4 waste paper
Main pulp grade
C 1 chemical
M 2 mechanical
CM 3 chemimechanical
SC 4 semichemical
PW 5 process waste paper
Table: The bleaching, fibre and pulp grade types of the pulp line data.

Three different-sized 1-dimensional SOMs were trained for both the paper machine and pulp line data and their quality was measured using four different quality measures. The results are depicted in table 5.3. It can be seen that as the size of the map increases the quantization error measure ( tex2html_wrap_inline3144 , equation 3.4) decreases, as does the energy function (E, equation 2.5). This is a natural consequence of having more neurons available for quantization. On the other hand the topographic error ( tex2html_wrap_inline3148 , equation 3.2) does not follow this trend, but is smallest for the smallest map (paper machines) or the second smallest (pulp lines). The topograhic quantization error ( tex2html_wrap_inline3142 , equation 3.5) combines these errors.

From the errors it is apparent that the pulp line data can be expressed much better with the 1-dimensional map than the paper machine data. The biggest paper machine map folds to make better use of its neurons, and the two criterias (topology preservation and resolution) become contradictory goals, as in figure 2.4. The best paper machine map was the one with 20 neurons. Both to use equal sized low level maps and since the 20x1-sized pulp line map was relatively good, the 20x1-sized maps were selected for further analysis.


Map size tex2html_wrap_inline3144 E tex2html_wrap_inline3148 tex2html_wrap_inline3142
Paper machine maps
10x1 1.10 2.41 0.0479 2.02
20x1 0.928 1.72 0.0912 1.89
30x1 0.798 1.28 0.134 1.96
Pulp line maps
10x1 0.961 1.27 0.0225 1.78
20x1 0.663 0.783 0.0094 1.26
30x1 0.555 0.592 0.0097 0.963
Table: The different sized maps trained with the paper machine (top) and pulp line (bottom) data sets. Four quality measures were calculated from each map: the average quantization error ( tex2html_wrap_inline3144 ), the average energy value per sample (E), the topographic error ( tex2html_wrap_inline3148 ) and the topological quantization error ( tex2html_wrap_inline3142 ).

The vector component values in the map units can be seen from the component plane representations in figure 5.2. By visual inspection of the paper machine map the three first components wire width, wire trim width and speed, have a strong correlation, as do the next two components minimum and maximum grammage. In the pulp line map none such global correlations can be seen. The mean deviations of vector components with respect to the values in their best-matching weight vectors are listed in the fourth column of table 5.1.

Figure 5.2: The component planes of the paper machine (a) and pulp line (b) maps. The name of the component on the right and the corresponding values in the map units from 1 to 20 in the middle. All components are presented with a grayscale with black representing the maximum value and white the minimum.

The clustering of the maps was based on visual inspection of the u-matrixes shown in figure 5.3 supplemented by the knowledge of the distribution of component values. From the paper machine map 6 clusters were extracted corresponding to different types of machines. The clusters and their descriptions are shown in table 5.4. The first cluster correspondes to new, high capacity machines with high speed and high value for wire width. The second cluster includes slightly older big or average sized machines. The fourth cluster resembled the second with the difference that the machines are a bit smaller and about 5 years older. The third cluster consists of machines with big paper weight. The two last clusters got the largest number of hits. They correspond to smallest and oldest paper machines. Based on the properties of the clusters, the paper machines can be divided into three different types:

  1. The new machines with highest capacity and speed and widest wire (cluster 1).
  2. The paper machines with big paper weight (cluster 3).
  3. The majority of the paper machines belong to the third type the capacity and size of which decrease steadily with increasing age (clusters 2, 4-6).

The pulp line map can be divided into five clusters listed in table 5.4. The pulp lines in the first cluster make bleached pulp and use waste paper for fibre. The second cluster corresponds to pulp lines making unbleached pulp with varying fibre and main grade types. The third cluster has pulp lines which produce bleached pulp mostly from wood or other virgin fibres with chemical main grade. The fourth cluster consists of pulp lines with high capacity and an average market ratio. The pulp was bleached, fibre mostly wood and grade mostly chemical. The last cluster consisted of pulp lines with high market ratio. All in all, there are three major pulp line types:

  1. Those using waste paper for pulp.
  2. Those making unbleached pulp, further divided into three subtypes:
    1. wood fibre and semichemical pulp grade
    2. wood fibre and either chemical or mechanical pulp grade
    3. other virgin fibers with chemical pulp grade
  3. Those using chemical pulp grade to produce mainly bleached pulp from wood fibre. This type could further be divided into three subtypes: those with small capacity, those with high capacity and those with a high market ratio of production.

Figure: The u-matrix presentations as of the paper machine (a) and pulp line (b) maps, with the map unit on the x-axis and the value of u-matrix on y-axis. Clusters on map are separated by peaks in the u-matrix. Clusters are listed in table 5.4.


Cluster Units Hits Description
Paper machine map
1 1,2 454 Wide wire and high speed, small paper weight, high capacity, new machines.
2 3-6 1024 Average sized machines, over ten years old on the average.
3 7-9 467 Narrow wire, slow speed, big paper weight, small capacity.
4 10-12 1033 Average wire width and speed, over 15 years old on the average.
5 13-16 2648 Small machines, over 15 years old on the average.
6 17-20 3139 Small and old machines.
Pulp line map
1 1-4 557 Pulp made from waste paper.
2 5-11 993 Unbleached pulp, both fibre and grade vary.
3 12-15 762 Bleached pulp, wood or other virgin fibres, chemical main grade.
4 16-18 303 Bleached pulp, mostly wood fibre and chemical main grade, average market ratio, high capacity.
5 19,20 364 Big market ratio, mostly wood fibre and chemical main grade.
Table: Clusters of the paper machine map (top) and pulp line map (bottom). The second column gives the units that belong to a certain cluster. The third column gives the number of samples that were projected to the cluster. See also figures 5.2 and 5.3.

next up previous contents
Next: Mill techonology Up: Pulp and paper technology Previous: Pulp and paper technology

Juha Vesanto
Tue May 27 12:40:37 EET DST 1997