An examination of two hybrid top-wire former configurations for producing newsprint.

Application: Mill engineers can use the results of this study as guidelines for evaluating top wire units.

This paper examines the design of roll and blade top-wire forming units from a fundamental drainage standpoint. The conversion of a newsprint machine from a top-wire roll former to a top-wire blade unit afforded the opportunity for the direct comparison of these competitive designs. Both units were located an identical distance from the headbox and used the same furnish. The roll-type top unit provided constant pressure forming, with high drainage velocity under low shear rate. By contrast, the bladed type former imparted variable, increasing pressure pulses at locations on the former, subjecting the wet web to multiple shear conditions. This study explores the effects of the different drainage mechanisms on final sheet properties. It also compares measurements on paper samples taken before and after conversion of the newsprint machine to theory.

Wildfong is group leader and design engineer with Johnson Foils, 40 Progress Avenue, Springfield, MA 01104; Genco is professor in the Department of Chemical Engineering, University of Maine, 205 Jenness Hall, Orono, ME 04469. Email Genco at [e-mail].