Examination of Two Hybrid Top-Wire Former Configurations for Producing Newsprint, 2002 Technology Summit Proceedings

V. Wildfong & J. M. Genco

This paper examines two top-wire forming units from a fundamental standpoint. One is a roll type top unit while the second is a bladed top unit. Both units are located an identical distance from the headbox and use the same furnish. The fundamental dewatering mechanisms are examined for both the roll type and blade type formers. Both configurations are numerically modeled to evaluate differences in the pressure fields, estimated pressure gradients, and shear between the wires.

The roll type top unit demonstrates constant pressure forming and the characteristics of high drainage velocity under low shear. By contrast, the bladed type former demonstrates web forming brought about by variable, increasing pressure pulses at locations on the former where the wet web is subjected to multiple shear conditions. The effect of these different mechanisms is explored relative to final sheet properties that were measured on representative paper samples taken before and after conversion of the newsprint machine from the top-wire roll to the top-wire blade unit.