Roll Covers

Roll cover technology is a key factor in improving sheet release, reducing draw, improving dewatering performance, ensuring consistent coating and sizing, and excellent calendering results. The various applications on the paper machine require a variety of roll cover designs and coating materials.

The materials used range from ceramic coatings to very soft elastomeric covers and have surface profiles ranging from plain polished to high open surfaces, as well as complex cross-machine direction crown designs.

Depending on specific applications, roll covers or coatings have to fulfill various functions on the paper machine. Effective but web-gentle dewatering in the press section asks for engineered surface designs and customized roll cover materials. The release or adhesion of the paper sheet is influenced by the cover surface and its self-cleaning or dirt-repellent properties. The same is true with demands for uniform coating or sizing. Calender applications require simultaneous elasticity and high stress resistance, while winder drums demand a surface design that results in faultless winding.

Apart from these special demands in the various machine sections, roll covers generally need to provide shock and vibration absorption and chemical resistance, as well as support the paper sheet drive throughout the whole machine.

The choice for the right cover or coating for the specific application is a scientific decision that requires experience and knowledge of the complete paper making process. Temperature, chemical application, speed and produced paper quality are just some of the factors that need to be taken into account. Nip impression measurements and water balance calculation have to be considered as well.