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

Tomi Hakala, Ali Harlin

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

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.
Original languageEnglish
Pages (from-to)84-91
Number of pages8
JournalAutex Research Journal
Volume8
Issue number3
Publication statusPublished - 2008
MoE publication typeA1 Journal article-refereed

Fingerprint

Felts
Papermaking
Dewatering
Elasticity
Textiles
Rolls (machine components)
Abrasives
Porosity
Damping
Aging of materials
Wear of materials
Friction
Defects
Water
Hot Temperature

Keywords

  • Hopkinson split bar
  • nip
  • paper machine cloths
  • resiliency
  • runnability
  • vibration
  • paper machine clothing
  • paper machines

Cite this

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title = "Simulation of a rapid nip pressure strike and its effect on press felt samples",
abstract = "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.",
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Simulation of a rapid nip pressure strike and its effect on press felt samples. / Hakala, Tomi; Harlin, Ali.

In: Autex Research Journal, Vol. 8, No. 3, 2008, p. 84-91.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Simulation of a rapid nip pressure strike and its effect on press felt samples

AU - Hakala, Tomi

AU - Harlin, Ali

PY - 2008

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N2 - 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.

AB - 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.

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