Sizing & Coating Challenges/ Solutions

There are many challenges when it comes to the processes of coating and sizing. Foremost among these are issues related to coat weight variation and sizer nip load profile.

Coat weight variations can be difficult to detect and their root causes hard to identify. It is important to solve them because they may cause unexplained problems elsewhere. With sizer nip load profile issues the cause-and-effect relationship is typically easier to detect, but many times difficult to solve. Root causes are identified and explained in this paper, as is a new novel technology for online load and profile measurement.

Consumables at the coater and sizer areas play an important role in maintaining product end quality and improving machine performance. Hard-coated blades deliver the best possible surface and longer lifetimes for high-quality paper and board grades. Insert rod beds for sizers bring savings and better runnability. Case studies are provided.

Machine-direction coat weight variation can be harmful in many ways. Oftentimes it is difficult to see with typical scanning methods and shows as a disturbance in the cross-direction (CD) coat weight profile.

Furthermore MD-variation can cause coating color waste as the coated quality is often optimized and adjusted in the worst case according to the poorest spot or, as in most cases, according to the average coat weight level. Similarly drying is optimized to the average coat weight level which might leave savings potential if the variation was reduced. Also the less coated areas may be over-dried leading to reduced strength properties