Web defects in newsprint production - a mill case study

Fouling of wet end operations is known to adversely affect the production efficiency of a paper machine. Runnability issues manifested as web breaks can often be directly linked to the formation of defects such as holes and ragged web edges. Identification and elimination of defect sources may lead to considerable savings in production losses and unwarranted down time. In this paper we present a mill case study, in which a number of plausible causes associated with an excess rate of web breakage were studied on a newsprint line. Results showed that many runnability issues could be traced back to the accumulation of contaminants on short circulation, the deposition of agglomerated pitch and bacterial biofilms, and the precipitation of carbonate and other additives due to the instability in the chemical process. Specific causes behind the web defect formation and a proven 'hands on' approach to enhance the process efficiency are also discussed.