Techniques for nip impressions

Paper machine technology has resulted in faster running paper machines with ever increasing operating pressures in the press and other sections of the paper machine. It is now more important than ever that the operating pressure between two or more rolls be evenly distributed across the face of the nipped rolls to ensure product quality and roll cover integrity. One way to ascertain if a uniform pressure distribution is being applied is to take nip impressions. This Technical Information Paper reviews the need for nip impressions, the various media available to perform the work and general instructions for taking the impressions. In addition, measurement analysis is addressed, and a crown correction equation based on nip impression measurements is discussed.