An evaluation of a forming section rebuild on the fluid mechanics and sheet structure of a bladed style top former producing board grades

摘要

The rebuild of a fourdrinier with a vintage blade style top forming configuration is examined for papermachines producing board grades. Limitations of the pre-rebuild design are discussed from a fundamental standpoint. The fluid mechanics of the vintage and rebuilt twin wire forming sections are examined. Design challenges and solutions to mitigate the limitations of the pre-rebuild former are discussed. The rebuild is engineered for the specific furnish and application based upon end product needs. A majority of the existing forming section remains intact minimizing installed cost and papermachine down time for installation. Three rebuilds are reported on, two on linerboard grades and one on a woodfree uncoated grade. Performance is characterized before and after each rebuild with regards to operating capacity and a variety of sheet properties, depending on the grade of paper being produced. Significant improvements in capacity, formation, smoothness, and mechanical strength properties were realized after the rebuilds.