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Higher productivity and less downtime?

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Higher productivity and less downtime?

September 18, 2013 - 23:54

Higher productivity and less downtime? New roll coatings can help move papermakers one step closer to this target. Newly developed coatings for cylinders, guide and vacuum rolls in the dryer group minimize dirt deposits, improve corrosion and wear resistance. In addition, these new coatings can be applied directly inside the paper machine.Dirt, stickies, slime deposits and chemical fall out can have a negative effect on machine efficiency from within the dryer section. Contamination of rolls and dryer fabrics continually harm the roll surfaces during operation. Rising demands in productivity, higher machine speeds, a larger variety of chemical additives and lower quality of raw material require improved roll surfaces. Cleaning devices can also have a strong influence on the corrosion of rolls. The move towards shorter first dryer groups, use of harder particles such as sand in the pulp, necessitates the need for better wear resistance of the roll surface.

BRUSSELS, BELGIUM, Sept. 19, 2013 (PPI Magazine) -Repellent and Resistant

Voith's coating researchers have developed this new generation of coatings for guide rolls and drying cylinders. Their work has focused on evaluating all the influencing variables to combine properties such as dirt repellence, wear resistance and corrosion protection into the correct ratio. Each coating characteristic has to be adapted to the respective requirements of the dryer fabrics and cleaning systems. Together with external scientific support, Voith Paper has developed a method for investigating the interaction between roll surfaces and stickies, dirt, dust, glue and starch. In contrast to other materials and methods, the new coatings can then be tailored to the special requirements of the paper industry. On completion of the development stages, preliminary field trials were introduced on demanding applications with selected customers. The results achieved higher levels of coating performance than in laboratory tests. The interaction between release forces and surface energy clearly shows that an improved "anti-stick" performance can be achieved compared to existing products on the market. In addition, the successful trials demonstrated that a higher wear resistance could be realized with the unique Voith coating system.

Roll Coating Inside the Paper Machine

Another main target was to apply the coatings directly inside the paper machine since the disassembly of dryer cylinders and the associated downtime normally incurs enormous costs and loss in production. The new coatings can be applied on-site by a service team to significantly reduce the time needed for a machine shut ("Express" in product name). To achieve this goal the method of application has been upgraded to avoid a high temperature treatment in an expensive oven and so coatings can be applied at lower temperatures without affecting its performance. Those machines having temperature sensitive materials, such as carbon fiber re-enforced roll bodies, can also benefit from this new method of coating. PPI