Improving Sheet Quality: Rolls and Press Felts Working Together, PaperCon 2010 Conference

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The press section plays a major role in building a high quality sheet. While engineered nip designers are often initially limited to changing line loads, they have freedom to vary roll cover and press felt parameters. Optimum designs can only be achieved through synergistic solutions that maximize the interactions among the roll covers and press felts. This paper provides background on the engineered nip concept and demonstrates that judicious combinations of roll covers and press felts can work together to improve sheet quality while simultaneously reducing production costs.

We argue that the pressure profile can only be estimated by including both the influences of the roll cover properties and the press felt properties. The roll covers and press felts are chosen together to reach peak pressure targets for each nip. The pressure progression from nip to nip is adjusted to maximize water removal, maintain bulk, minimize sheet two-sidedness, reduce excessive stratification, and to produce smooth surfaces.