The effect of web structure on wet web runnability

Markku Ora

The effect of web structure on wet web runnability

Julkaisun otsikon käännös: Rainan rakenteen vaikutus märän rainan ajettavuuteen

Markku Ora

Tutkimustuotos: Doctoral Thesis › Monograph

Abstrakti

Työssä tutkittiin paperin rakenteen vaikutusta märän rainan lujuuksiin ajamalla uudelleen kostutettuja tehdasvalmisteisia paperirullia ajettavuuspilotissa. Tutkimusta varten kehitettiin uusi kostutusmenetelmä, jolla päästiin paperikoneen puristin- ja alkukuivatusosan kuiva-ainepitoisuuksiin. Lisäksi yksi koesarja ajettiin tasoviiratyyppisellä pilotpaperikoneella, jossa märän rainan lujuus mitattiin suoraan puristinosalla. Laboratoriomittaisiin menetelmiin verrattuna käytetyt menetelmät tarjoavat realistisemman ympäristön lujuusmittauksille. Tulosten mukaan formaation ollessa hyvä, kuten se tyypillisesti on moderneilla paperikoneilla, formaation edelleen parantaminen ei paranna märän rainan lujuusominaisuuksia. Vain jos formaatio on huono, kuten se voi olla tasoviiratyyppisillä koneilla, formaation parantaminen lisää märän paperin vetolujuutta ja vetojäykkyyttä. Kuituorientaatiolla on sitä vastoin voimakas vaikutus edellä mainittuihin ominaisuuksiin. Mielenkiintoinen havainto oli se, että orientaatioprofiililla z-suunnassa ei ole vaikutusta märän rainan lujuusominaisuuksiin, jos keskimääräinen kuituorientaatio pysyy vakiona. Tästävoidaan päätellä, että märän rainan lujuuden kannalta ei ole väliä ajetaanko paperikonetta ali- vai yliperällä. Formaatio vaikuttaa märkien ja kuivien papereiden vetolujuusvaihteluun. Vaikutus riippuu formaation mittakaavasta ja paperin kuiva-ainepitoisuudesta. Märissä papereissa suurimittakaavaisella formaatiolla on voimakkain vaikutus ja kuivissa papereissa pienimittakaavaisella. Lisäksi näyttää siltä, että mitä huonompi formaatio on sitä alemmassa kuiva-ainepitoisuudessa lujuusvaihtelu formaation vaikutuksesta alkaa. Sitä vastoin kuituorientaatiolla ei ole vaikutusta vetolujuusvaihteluun. Kuivan paperin lujuutta voidaan kuvata ääriarvojakaumalla, kuten esimerkiksi kaksiparametrisella Weibull-jakaumalla. Sitä vastoin märän paperin vetolujuus on normaalijakautunut, joten märällä paperilla ei ole "weak-link" -ominaisuutta (katkeaminen heikoimmasta kohdasta) eikä "weak-link scaling" -ominaisuutta (pienen näytekappaleen lujuus on suurempi kuin suuremman näytteen). Lisäksi suuretkaan viat eivät haittaa märän rainan ajettavuutta puristin- ja alkukuivatusosalla, ainakaan jos viat eivät ole aivan radan reunassa.

Julkaisun otsikon käännös	Rainan rakenteen vaikutus märän rainan ajettavuuteen
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Maloney, Thaddeus, Vastuuprofessori Paulapuro, Hannu, Ohjaaja Kajanto, Isko, Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-4568-9
Sähköinen ISBN	978-952-60-4569-6
Tila	Julkaistu - 2012
OKM-julkaisutyyppi	G4 Monografiaväitöskirja

Tutkimusalat

ajettavuus
formaatio
lujuusjakauma
lujuusominaisuudet
märkä raina
orientaatio
paperikone
rakenne

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-4569-6

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title = "The effect of web structure on wet web runnability",

abstract = "The effect of paper structure on wet web strength properties was studied by running the re-wetted mill-made paper reels on a pilot runnability device at the dry solids contents (DSC) typical to the press section and the first part of the drying section. In order to run those reels with low DSC, a new re-wetting procedure was developed. In addition, one trial was conducted with measuring the wet web strength in situ on the press section of a pilot Fourdrinier. The benefit of these approaches is the ability to measure the strength properties in more realistic conditions compared with standard laboratory methods. According to the results, if formation is good - as it presumably is on modern paper machines - further formation improvement does not improve average wet strength properties. Only when formation is poor - as it can be on a Fourdrinier-type machine - does improved formation result in improved average wet tensile strength and tensile stiffness. Instead, the fibre orientation had a strong effect on these strength properties. Interestingly, the orientation profile in the z-direction did not affect the wet strength properties if the average orientation remained constant. This suggests that it does not matter whether the machine runs the jet-wire-ratio in the rush or drag side. Formation has an influence on the tensile strength variation of wet and dry papers. In addition, the effect depends on the scale of formation and dry solids content. In wet papers, large scale formation has the strongest effect on the strength variation. Conversely, in dry papers the strength variation is controlled by small scale formation. In addition, it is suggested that the poorer the formation the lower the DSC at which the variability due to the effect of formation appears. Contrary to formation, fibre orientation does not affect the strength variation. The strength distribution of dry paper can be described by an extreme value model, such as the 2-parameter Weibull. Instead, the strength distribution of wet webs appears Gaussian, meaning that the wet papers do not show either weak-link behaviour or weak-link scaling. In addition, even large defects do not impair wet web runnability on the press section or in the first part of the drying section, at least if the defects are not located just at the edge of the web.",

keywords = "formation, orientation, paper machine, runnability, strength distribution, strength properties, structure, wet web, ajettavuus, formaatio, lujuusjakauma, lujuusominaisuudet, m{\"a}rk{\"a} raina, orientaatio, paperikone, rakenne, formation, orientation, paper machine, runnability, strength distribution, strength properties, structure, wet web",

author = "Markku Ora",

year = "2012",

language = "English",

isbn = "978-952-60-4568-9",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "38",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - The effect of web structure on wet web runnability

AU - Ora, Markku

PY - 2012

Y1 - 2012

N2 - The effect of paper structure on wet web strength properties was studied by running the re-wetted mill-made paper reels on a pilot runnability device at the dry solids contents (DSC) typical to the press section and the first part of the drying section. In order to run those reels with low DSC, a new re-wetting procedure was developed. In addition, one trial was conducted with measuring the wet web strength in situ on the press section of a pilot Fourdrinier. The benefit of these approaches is the ability to measure the strength properties in more realistic conditions compared with standard laboratory methods. According to the results, if formation is good - as it presumably is on modern paper machines - further formation improvement does not improve average wet strength properties. Only when formation is poor - as it can be on a Fourdrinier-type machine - does improved formation result in improved average wet tensile strength and tensile stiffness. Instead, the fibre orientation had a strong effect on these strength properties. Interestingly, the orientation profile in the z-direction did not affect the wet strength properties if the average orientation remained constant. This suggests that it does not matter whether the machine runs the jet-wire-ratio in the rush or drag side. Formation has an influence on the tensile strength variation of wet and dry papers. In addition, the effect depends on the scale of formation and dry solids content. In wet papers, large scale formation has the strongest effect on the strength variation. Conversely, in dry papers the strength variation is controlled by small scale formation. In addition, it is suggested that the poorer the formation the lower the DSC at which the variability due to the effect of formation appears. Contrary to formation, fibre orientation does not affect the strength variation. The strength distribution of dry paper can be described by an extreme value model, such as the 2-parameter Weibull. Instead, the strength distribution of wet webs appears Gaussian, meaning that the wet papers do not show either weak-link behaviour or weak-link scaling. In addition, even large defects do not impair wet web runnability on the press section or in the first part of the drying section, at least if the defects are not located just at the edge of the web.

AB - The effect of paper structure on wet web strength properties was studied by running the re-wetted mill-made paper reels on a pilot runnability device at the dry solids contents (DSC) typical to the press section and the first part of the drying section. In order to run those reels with low DSC, a new re-wetting procedure was developed. In addition, one trial was conducted with measuring the wet web strength in situ on the press section of a pilot Fourdrinier. The benefit of these approaches is the ability to measure the strength properties in more realistic conditions compared with standard laboratory methods. According to the results, if formation is good - as it presumably is on modern paper machines - further formation improvement does not improve average wet strength properties. Only when formation is poor - as it can be on a Fourdrinier-type machine - does improved formation result in improved average wet tensile strength and tensile stiffness. Instead, the fibre orientation had a strong effect on these strength properties. Interestingly, the orientation profile in the z-direction did not affect the wet strength properties if the average orientation remained constant. This suggests that it does not matter whether the machine runs the jet-wire-ratio in the rush or drag side. Formation has an influence on the tensile strength variation of wet and dry papers. In addition, the effect depends on the scale of formation and dry solids content. In wet papers, large scale formation has the strongest effect on the strength variation. Conversely, in dry papers the strength variation is controlled by small scale formation. In addition, it is suggested that the poorer the formation the lower the DSC at which the variability due to the effect of formation appears. Contrary to formation, fibre orientation does not affect the strength variation. The strength distribution of dry paper can be described by an extreme value model, such as the 2-parameter Weibull. Instead, the strength distribution of wet webs appears Gaussian, meaning that the wet papers do not show either weak-link behaviour or weak-link scaling. In addition, even large defects do not impair wet web runnability on the press section or in the first part of the drying section, at least if the defects are not located just at the edge of the web.

KW - formation

KW - orientation

KW - paper machine

KW - runnability

KW - strength distribution

KW - strength properties

KW - structure

KW - wet web

KW - ajettavuus

KW - formaatio

KW - lujuusjakauma

KW - lujuusominaisuudet

KW - märkä raina

KW - orientaatio

KW - paperikone

KW - rakenne

KW - formation

KW - orientation

KW - paper machine

KW - runnability

KW - strength distribution

KW - strength properties

KW - structure

KW - wet web

M3 - Doctoral Thesis

SN - 978-952-60-4568-9

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

The effect of web structure on wet web runnability

Abstrakti

Tutkimusalat

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