Simulation of a rapid nip pressure strike and its effect on press felt samples

• Autorzy: Hakala T. , Harlin A.
• Języki publikacji: EN

Abstrakty

EN

Special technical textiles are used in papermaking to support, transfer, and dewater the paper web. These textiles, paper machine cloths, have many essential functions connected to their position on the paper or board machine. Mechanical wet pressing uses press felts, whose porosity and resiliency are important for effective dewatering. Water is squeezed out by two overlapping paper machine rolls, which form a nip. After squeezing, the porous felt should be void and return to its original thickness to ensure efficient dewatering. Friction forces are also present at the nip, since abrasive interfaces occur between the cloths and the rolls by pressure, heat, and movement. Thus in time, the harsh papermaking process wears out the press felt, deteriorating its quality. At high machine speed, defects in press felts, rolls, or other parts of the nip environment can cause runnability problems such as noisy run, that is, vibration in the pressing section, decreasing paper quality and output capacity. This study sought for a new way to simulate the ambiguous nip phenomenon on laboratory scale and to find out a way to predict this noisy run problem. A dynamic test method, the Hopkinson Split Bar, was used to define the ease with which strike energy passed through from the upper roll to the lower roll and the damping of strikes by new and worn felt samples. In our study, the elasticity of the press felt was strongly linked with the ageing time. Decreased elasticity lets a nip impulse more easily through the press felt.

Słowa kluczowe

EN

paper machine cloths; nip; resiliency; vibration; runnability; Hopkinson Split Bar

PL

ubranie; maszyny papiernicze; sprężystość; wibracja; płynność ruchowa

• Wydawca: Lodz University of Technology, Faculty of Material Technologies and Textile Design
• Czasopismo: Autex Research Journal
• Rocznik: 2008
• Tom: Vol. 8, no. 3
• Strony: 84--91
• Opis fizyczny: Bibliogr. 12 poz.

Twórcy

autor

Hakala T.

• Fibre Materials Science, Tampere University of Technology, P.O. Box 589, FIN-33101 Tampere, Finland Tel. [phone], Fax [phone]

autor

Harlin A.

• VTT Technical Research Centre of Finland, FIN-02044 VTT, Finland

Bibliografia

• 1. Adanur, S. Papermachine Clothing. Asten 1997, CRC Press. 395 p.
• 2. Apostol, M. Strain Rate and Temperature Dependence of the Compression Behavior of FCC and BCC Metals. Dissertation. Tampere 2007. Tampere University of Technology. Publication 649. 112 p.
• 3. Chen, W., Lu, F., Zhou, B. A Quartz-crystal-embedded Split Hopkinson Pressure Bar for Soft Materials. Experimental Mechanics 40(2000)1, pp. 1-6.
• 4. Hakala, T., Wilenius, T., Harlin, A. Laboratory ageing Test Device for Press-Felt Clothes of Paper Machine. Autex Research Journal. 7(2007) 1, pp. 71-79.
• 5. Hopkinson Split Bar (HSB). 2007. Institute of Material Science, TUT. [WWW]. [Cited 03.04.2007]. Available at: http://www.tut.fi/umits/mol/materiaalioppi/ehopkinson.html.
• 6. Paulapuro, H. (edit.). Papermaking Part 1. Stock Preparation and Wet End. Book 8. TAPPI 2000, Fapet. 461 p.
• 7. Paulapuro, H. Wet Pressing – Present Understanding and Future Challenges. Presented at the 12th Fundamental Research Symposium, Keble Collage, Oxford, UK, September 17th-21st, 2001. FRC, pp. 639-678.
• 8. Resnyansky, A. D. The Impact Response of Composite Materials Involved in Helicopter Vulnerability Assessment: Literature Review – Part 1. April 2006. Defence Science and Technology Organisation.DSTO-TR-1842 Part 1. 84 p.
• 9. Szikla, Z. On the Basic Mechanisms of Wet Pressing. Dissertation. Espoo 1992. KCL Paper Science Center. 219 p.
• 10. Szikla, Z., Paulapuro, H. Z-directional Distribution of Fines and Filler Material in the Paper Web Under Wet Pressing Conditions. Helsinki 1986. The Finnish Pulp and Paper Research Institute. Report 583, pp. 654-664.
• 11. Technology solutions for every need. Paper Machine Press Sections. 2006. Brochure of Metso Paper, Inc. 16 p.
• 12. Vomhoff, H., Gullbrand, J. New Insights in the Mechanisms of Rewetting. Das Papier 2004-T194, ipw 11/2004, pp. 40-43.