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Productivity improvements of a newsprint paper machine by reduction of web breaks
2009 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

A frequent problem when producing newsprint are web breaks, which result in down-time and wear on machine parts and hence a decreased yield. The purpose of this thesis is to identify production parameters that correlate to web breaks on paper machine 5 (PM5) at Ortviken paper mill in Sundsvall. The focus is on findings from previous studies that have been considered to be important for the occurrence of web breaks. These are: • Variations of release angle at the open draw from press to dryer • The impact of skew paper web profiles on web breaks • Multivariate analysis of production parameters • Velocity fluctuations of the driver dryer rolls in the dryer • The impact of defects in the paper web on web breaks The thesis authors have applied the D.M.A.I.C method in the problem solving process. This method is applied within the Six Sigma improving program. The analysis of the profiles showed skewness in the machine. This skewness results in web feeding problems along with an increased risk of web breaks due to a skew web tension profile. Suggested improvements to solve this problem consisted of different calibrations and adjustments of the head box (distributes the pulp on the wire cloth), press, dryer and moisture profiles. No approximation of cost savings where measured. The velocity study of the dryer rolls in the dryer revealed a slack in the web break signal. This resulted in extra downtime and additional web breaks caused by debris swirling around in the machine. Machine components were also damaged due to this delay. The yearly cost savings of these problems was approximated to 400 000 SEK. A solution to this problem is under development as this thesis is being finalized and will be implemented during the spring of 2009. No correlations between defects in the paper and web breaks could be found. However, the analysis showed a higher density of defects at the edges of the paper web. High variations of edge actuators in the steam box, causing moisture variations at the edges, might generate these defects at the edges causing web breaks. It was also found that most web breaks started from the front side (FS) of the machine (facing the operators). Several of these web breaks could be explained by a non satisfactory solution for cutting the paper edges. Skew TSO and TSI profiles indicating a higher web tension on the front side, could also contribute to more web breaks on that side.

Place, publisher, year, edition, pages
2009.
Keyword [en]
Social Behaviour Law, six sigma, DMAIC, paper machine, web breaks
Keyword [sv]
Samhälls-, beteendevetenskap, juridik
Identifiers
URN: urn:nbn:se:ltu:diva-56964ISRN: LTU-EX--09/043--SELocal ID: db021507-b072-4d83-bf09-ca45883ac438OAI: oai:DiVA.org:ltu-56964DiVA: diva2:1030351
Subject / course
Student thesis, at least 30 credits
Educational program
Industrial and Management Engineering, master's level
Examiners
Note
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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