b'DRYER SECTION INNOVATIONSOn-Site Dryer Services: Longer service life and higher productivity through attention to detail By Carl Taylor, Global Product Manager Drying, Division Fabric & Roll Systems, VoithHEIDENHEIM, Germany. Quality problems and web breaks in paper production are often the result of inadequate roll coatings in the dryer section. When recoating existing cylinders, Voiths On-Site Dryer Services attach great importance to ensuring a homogeneous surface. In the long term, thorough preparation and attention to detail by an experienced team pays off for paper manufacturers through reduced wear, improved paper quality and higher productivity. Various practical examples show that the work of Voiths service teams makes it possible to significantly extend the runtimes of components. Figure 1. Chatter marks on a dryer cylinder caused by uneven grinding.LONGER RUNTIMES REDUCE LIFE CYCLE COSTS CAREFUL GRINDING REDUCES VIBRATIONS evidence of chatter marks will ensure Downtime on paper machines isThe temptation can often be to grindan optimum particle bonding of the always associated with costs and asoff the cylinder surface quickly to savecoating. A case of unwanted chatter such is kept as short as possible.time, for example, in steps of 0.04marks caused by too coarse grinding is The metalizing and grinding of dryermm by using high grinding pressures.shown in Figure 1. cylinders is a high investment item forVoiths experience proves that a the paper manufacturer. It requiresgradual removal of thinner layers,Grinding is often required to remove downtime and, if not done correctly,for example 0.02 mm, reduces thedamages or corrosion in the cylindermetalizing can be very expensive in terms ofrisk of vibration, producing a moresurface. It is critical to ensure theand grinding further downtime and lost production.homogeneous cylinder surface. Theproblem area is removed beforeof dryer There are too many cases in thesubsequent blasting process removesmetalizing the cylinder. Figure 2 showscylinders, paper industry where service suppliersall grease residues. This ensures thathow corrosion should be removedif not done cut corners, resulting in furtherthe new coating bonds better to thethrough grinding. If grinding iscorrectly, unnecessary lost production for thesurface. stopped too soon and some evidencecan be very papermaker.of corrosion remains, this will notexpensive As with most things in life, time thatbe apparent once metalized but willin terms Voith shows how attention to detail onis spent in preparation will often payshow through at a later stage. Voithof further each process step when metalizing adividends when applying subsequentensures that all problem areas are fullydowntime dryer cylinder can provide long-termprocesses. For example, time spentremoved before metalizing the cylinder,and lost payback for the paper manufacturer.preparing the cylinder to remove anyresulting in a longer service life. production.86 WORLD PULP&PAPER'