Paper Machine Drying Department Is Not Simple

- Mar 18, 2012-

The control of the drying part on the sheet shrinkage
It is an important method to control the tension of the paper sheet and the tensile force of the drying section.
When traction is large, the longitudinal contraction is limited or even elongated. The longitudinal elongation will result in the further longitudinal arrangement of the fiber, so the transverse contraction will be increased.
When the dry cloth tension increases, the paper page is pressed on the cylinder surface, thereby binding the paper page transverse contraction, but in turn, will limit the fiber in the paper page in the tension under the action of the row, so conducive to longitudinal contraction.
When the dry cloth tension and traction hours, longitudinal contraction of the largest, but the smallest horizontal contraction, conversely, when the dry cloth tension is small, traction is large, in the longitudinal contraction of the most intense areas, the smallest contraction, while the transverse contraction is the largest. This fits perfectly with the rules.
Therefore, according to this rule, we can use these two factors effectively to adjust the nature of paper. For example, when the production of translucent paper, should give greater traction and dry cloth tension, so that the paper page both vertical and horizontal can not fully shrink, so that the shrinkage of water loss will occur in the thickness of the paper page direction, so that the paper page thinning, conducive to improving transparency.
For the ground drawings, color printing paper, also requires the drying department to control the paper shrink, in order to reduce the paper expansion deformation. To this end, in the drying department should also be appropriate tensioning dry cloth, and the appropriate increase in traction to reduce wet paper in the dry longitudinal and transverse contraction. Alternatively, the curved rollers can be used to flatten the page to reduce transverse shrinkage.
For paper-bag paper, it is more important to increase longitudinal elongation and toughness to increase its rupture power than to increase its resistance to tension. Therefore, as far as possible to allow wet paper in the absence of external constraints in the state of drying, so that the paper longitudinal and transverse can be fully contracted.
This can be done by drying the dryer of the cylinder:
A, in the paper dry degree more than 58% of a group of baking cylinder, dry cloth should be adjusted as far as possible relaxation some, traction tension smaller, allowing the longitudinal and transverse paper in the dryer can have a certain degree of contraction.
In the paper dry degree of less than 58% and more than 58% of the dryer, when the contraction effect is not significant, the dry cloth should be tightened some, on the one hand to increase the heat efficiency of the baking cylinder on the paper, on the other hand, not because of dry Butaison caused by the paper page warping and wrinkling;
B, as long as the dryer has enough drying capacity, in the wet paper shrinkage rate of the largest number of drying cylinder above can not blanket, so that the paper can be free to shrink;
C, drying capacity is not enough, can be in a few of the drying cylinder on top of the installation of high-speed hot air cover, neither affect the paper contraction, but also increase drying capacity;
D, the paper shrinkage rate of the largest part of the baking cylinder, the number of groups, each group of smaller number of baking cylinder to adjust the speed between the various sets of dryer to meet the longitudinal paper more contraction.