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TAPPI Paper Machine Operations Course
Press Fabric Design for Modern Paper Machines
Ellen Gibbs
TAPPI Paper Machine Operations Course
TOPICS• Pressing
• Press Fabric Function• Roll Types• Press Section Arrangements
• Press Fabric Properties• Press Fabric Structure & Nomenclature• Review Press Fabric Design• Conditioning• Moisture Equilibrium• Returned Fabric Analysis• Troubleshooting
TAPPI Paper Machine Operations Course
Functions of a Press Fabric
• Accept water from the sheet• Sheet Solids 12-20% 40-50%
• Consolidate the fiber to increase strength• Transport the sheet through the press• Impart desired sheet finish• Power transmission• Uniform pressure distribution
TAPPI Paper Machine Operations Course
Forming Section5,947 gpm
Press Section124 gpm
Dryer Section72 gpm
Water Removal
TAPPI Paper Machine Operations Course
Cost of Water Removal
0%10%20%30%40%50%60%70%80%
% o
f Tot
al Co
st
FormingSection
PressSection
DryingSection
TAPPI Paper Machine Operations Course
Press Rolls
Sheet
Simple Press Section
Felt
Felt Rolls
Guide Roll
Tension Roll
TAPPI Paper Machine Operations Course
Water Removal
@ 4000 fpm water removal occurs in 0.002 seconds
0.0
200.0
400.0
600.0
800.0
1000.0
1200.0
1400.0
-0.50 -0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50
Position (inches)
Stre
ss (p
si)
TAPPI Paper Machine Operations Course
Sheet Dewatering
• Pressure• Time• Temperature
TAPPI Paper Machine Operations Course
Roll Types• Plain • Suction • Grooved• Blind Drilled • Granite
TAPPI Paper Machine Operations Course
Plain Press
Slow speed 1000 fpm (305 mpm) and below Latter nips Addition of paper roll after nip to separate sheet
from felt
TAPPI Paper Machine Operations Course
Suction Press
Typically used in PU, Top, Bottom, Transfer Postions
Usually driven roll 15-30% open area
TAPPI Paper Machine Operations Course
Grooved Press
Vented roll to enhance water removal Centrifugal force on outgoing nip slings water out Usually harder than 12 P&J; open area ~16%
TAPPI Paper Machine Operations Course
Blind Drilled Press
Cheaper than a suction roll Can use smaller holes than suction rolls- less
tendency for shadow mark compared to suction Can be as soft as 50 P&J (softer than grooved rolls)
less tendency to close;open area ~20% More Void Volume than a grooved roll
TAPPI Paper Machine Operations Course
Double Felted Press
TAPPI Paper Machine Operations Course
Wahlstrom Model
Peak MidNip Pressure (PP)
PP = Pms + Ph
TAPPI Paper Machine Operations Course
TAPPI Paper Machine Operations Course
• As the paper web is compressed, water is removed from the space between the fibers and the walls of the fibers
• The water escapes into the press fabric and the press roll• Two situations can occur depending on whether the web can be
compressed further – Pressure or Flow controlled
TAPPI Paper Machine Operations Course
Sheet Dewatering
• Pressure Controlled• Lighter sheets• Free draining furnishes• Dryness is a function of peak pressure
• Flow Controlled
TAPPI Paper Machine Operations Course
Sheet Dewatering
• Pressure Controlled• Flow Controlled (time dependant)
• Typical of heavy sheets, or low freeness
• Early presses of light sheets
TAPPI Paper Machine Operations Course
Sheet Dewatering
• Flow Controlled• Linerboard• Corrugating Medium• Food Board
• Pressure Controlled• LWC• Newsprint• SC Grades• Directory
TAPPI Paper Machine Operations Course
Sheet Dewatering
• Flow Controlled• Long Dwell Time• Large Roll
Diameters• Soft Covers• Double Felting• Shoe Press
• Pressure Controlled• High Peak Pressure• Small Roll Diameters• Hard Roll Covers• Single Felted
TAPPI Paper Machine Operations Course
Pressing - Mechanical
• Lineal Load• Roll Diameter• Cover Hardness• Cover Material• Cover Thickness • % Open Area
TAPPI Paper Machine Operations Course
Hydraulic• P (Hyd) Adds to Peak Pressure• Need Sufficient P(Hyd) for Best Drying• Excessive P(Hyd) Results In:
o Sheet Crushingo Sheet Blowingo Batt Fiber Damageo Roll Cover Wear
TAPPI Paper Machine Operations Course
HydraulicInsufficient P (Hydraulic) for a Specific Combination of Fabric Structure and Operating EnvironmentWill Result in
Slow Startup
Poor Drying
TAPPI Paper Machine Operations Course
Press Theory Wahlstrom model Single felted nip
Hydraulic pressure on felt side < plain roll side Differential in hydraulic pressure – water removal
Amount of sheet dewatering Force Time Flow resistance of sheet Propotional to Nip Impulse
Nip Impulse (Pa.s ; lb.s/in) ave nip pressure x dwell time nip load/machine speed
TAPPI Paper Machine Operations Course
Effect of cover hardness & fabrics on nip
P&J KN/m (pli) felt Peak pressure MPa
7 70 (400) Single 4
7 92 (525) Double 4
37 130 (740) Single 4
37 144 (820) Double 4
TAPPI Paper Machine Operations Course
Granite Roll
Smoothness Good release properties Manmade rubber, resin &
ceramic
TAPPI Paper Machine Operations Course
Press Section Arrangements
Open Draw Press Transfer Press Inclined Press Combination Pickup Press No-Draw Press Arrangements Shoe Press
Others...
TAPPI Paper Machine Operations Course
Open Draw Press SectionStraight through pressUp to 2000 fpm (610 mpm)
Suction PressGroove Press
Open Draw
Felt
TAPPI Paper Machine Operations Course
Water Removal by Position
0%
10%
20%
30%
40%
50%
60%
70%
1st Press 2nd Press 3rd Press 4th Press
TAPPI Paper Machine Operations Course
Reverse Press SectionReduce two-sidedness Max 1200 fpm (365 mpm)
Suction PressGroove Press
Open Draw
Felt
TAPPI Paper Machine Operations Course
Transfer Press SectionTransfers sheet from top felt to bottom feltTwo presses before the 1st open draw – 2nd press somewhat inefficientUp to 4000 fpm (1220 mpm)
Suction PressGroove PressSuction Pickup
Open Draw
Felt
TAPPI Paper Machine Operations Course
Inclined Press Section - TwinverHigher loadings in the 1st and 2nd pressTwo efficient presses before open drawEven sided dewateringDrop offs on heavyweights
Suction Press
Groove PressSuction Pickup
Open Draw
Felt
TAPPI Paper Machine Operations Course
Combination Pickup Press SectionMinimum two-sidednessEliminated drop-offs on heavy weight machinesOpen draw limited speed
Groove PressSuction PickupSuction Press
Felt
TAPPI Paper Machine Operations Course
No-Draw Press Sections – TrinipSpeeds in excess of 3400 fpm (1036 mpm)Uneven dewateringHigher loadsPotential shadow mark/two sidedness
Groove Press
Suction Pickup
Open Draw
Groove Press
Felt
TAPPI Paper Machine Operations Course
Trinip w/ 4th Press4th press to “even” dewatering & reduce sheet two-sidednessSmall increase in sheet dryness
Groove Press
Suction Pickup
Open DrawGroove Press
Groove Press
TAPPI Paper Machine Operations Course
Trivent w/ 4th pressEliminate the suction roll mark from trinip configuration
Groove Press
Suction Pickup
Groove Press
Groove Press Groove PressFelt
TAPPI Paper Machine Operations Course
Shoe Press Assembly, Support
Beam,Static Shoe Press
Assembly
Shoe Press Belt, acts as flexible roll cover.
Counter Roll RotatesDriven (Drives belt)
Oil Film
Shoe Press Design
Stationary, HydraulicallyLoaded Shoe
TAPPI Paper Machine Operations Course
Shoe Press• First developed in 1980• Uses a metal plate to squeeze water out of
sheet• Shoe belt rotates during running• Belt is grooved – works like a tire on a wet
road• Oil is supplied inside to provide lubrication,
thermal protection and loads the shoe• Sheet dryness in press section goes from
21-22% up to 50-52%
TAPPI Paper Machine Operations Course
Shoe press operating conditions
Shoe
Shoe Belt
Top press felt
Paper
Bottom press felt
Counter roll
• Shoe presses are used to make all grades
• Operating loads are between 300 – 1500 kN/m
• Most shoe presses operate at 1000 kN/m or lower (6000pli)
• Machine speed can be from 150 - 2000 m/min
• Machine speed decided by paper grade
• The shoe can be in the top or bottom position
TAPPI Paper Machine Operations Course
Shoe press market usage
TAPPI Paper Machine Operations Course
Shoe press dewatering
MPa• Nip width is longer• Higher pressure can be
applied• Shoe belt allows venting of nip
TAPPI Paper Machine Operations Course
Uhle box vs. nip dewatering
MD
Uhle box dewatering:• Felt removes water
from sheet• Uhle box is a vacuum
box to remove water from felt
• Restricts machine speed – need min dwell time
TAPPI Paper Machine Operations Course
Uhle box vs. nip dewatering
MDNip dewatering:• Water removed via
belt grooves• Spray enters save-all
pan and is taken away• Allows higher
machine speeds to be reached
TAPPI Paper Machine Operations Course
Why use a shoe press?• Longer dwell time in the
press• Increase dewatering
Extend nip length
• Increase machine speed• Better sheet strength –
less breaksIncrease sheet
dryness
• Better sheet stiffness• Use less fiber to make
the same paper
Increase sheet bulk
Increased profit
TAPPI Paper Machine Operations Course
Common machine configurations – one shoe press
• Shoe press in 2nd press• Good option for machine
rebuilds
• Shoe press in 3rd press• Enables high speed
manufacture
TAPPI Paper Machine Operations Course
Shoe Press – BoardNo open draw
Shoe
Shoe BeltFelt
TAPPI Paper Machine Operations Course
Single Shoe Press
• Grooved bottom roll• Grooved belt
TAPPI Paper Machine Operations Course
Single nip shoe press
Benefits 46-48% dryness Less expensive to install Less space required Lower operating cost
Press fabrics Energy consumption –
drives and vacuum
Press fabric design Fine surface to overcome
roughness Fine enough base to not
strike through Shorter felt life – fine
webs
TAPPI Paper Machine Operations Course
Common machine configurations – two shoe presses
• Shoe press in 1st & 2nd
position
TAPPI Paper Machine Operations Course
Process belts are polyurethane covered fabrics used on a shoe press to dewater
TAPPI Paper Machine Operations Course
Felt – belt interaction
• Dewatering in the shoe press relies on both felt and belt
• If felt and belt don’t match we can see:
• Marking • Poor dewatering• Wear
• The felt/belt combination can help create either uhle box or nip dewatering
TAPPI Paper Machine Operations Course
Felt – belt interaction example
Total 750cm3/m2
450cm3/m2
450cm3/m2
300cm3/m2
300cm3/m2
Total 750cm3/m2
The ratio of press fabric to belt void volume can be altered while maintaining the same overall void volume in the press nip. Choosing the correct void volume configuration can optimise the dewatering of both products.
TAPPI Paper Machine Operations Course
Shoe belt product requirements
Crack resistance Abrasion resistance Modulus
Impact resistance Dewatering
TAPPI Paper Machine Operations Course
Shoe belt construction
Functional Layer: Long lifetime and excellentdewatering on the felt side.
Base fabric: Excellent dimensional stability, reinforces belt structure to allow optimum high speed operation.
Shoe side: Slides across shoe oil film, acting like a sliding bearing.
TAPPI Paper Machine Operations Course
Shoe belt groove styles
GL
D
C
GL
D
C
g
U grooves E grooves
• Standard grooves• Proven technology• Good for HSPG manufacture
• Developed from U grooves • Manufactured for a long
time• Good for highly loaded
presses
TAPPI Paper Machine Operations Course
Grooved Belt Parameters
PARAMETER RANGE THICKNESS (mm) 4.8 TO 5.3
HARDNESS (Shore C) 68 TO 73
LAND WIDTH (mm) 1.8 TO 2.5
GROOVE DEPTH (mm) TO 1.5 mm
GROOVE WIDTH (mm) 0.64, 0.72, 0.79, 0.95
VOID VOLUME (cc/sqm) 200 TO 365
TAPPI Paper Machine Operations Course
Impacts of wrong application – shadow marking
Shadow marking is a felt belt interaction issue
TAPPI Paper Machine Operations Course
How does marking occur?Caused by a combination of groove width and press fabric design
1. Press fabric too thin
2. Groove too wide
Shadow Marking
Groove Opening > 1.0mm
Paper SheetThicker Press Fabric
Narrower Grooves
Groove Opening > 1.0mm
Paper Sheet
Paper Sheet
Groove Opening < 1.0mm
2 possible solutions
TAPPI Paper Machine Operations Course
How does groove closure occur?
Loading
u – grooves flex under load
Groove edge fatigue
Loss of performance & life time
Groove closure
Poor dewatering
Uncompressed Compressed @ 10MPa
TAPPI Paper Machine Operations Course
Nip Pressure Profiles
0
200
400
600
800
1000
1200
1400
Position (inches)
Stre
ss (p
si)
Roll Press Shoe Press
Press Type Roll dia. M (in) Nip width mm (in)Conventional 1.1 (45 ) 40 (1.57)LDR 1.8 (72) 100 (4.0)Shoe Press 250 (10)
TAPPI Paper Machine Operations Course
Other Press Sections
n Board Gradesn Tissue / Towel Machines
TAPPI Paper Machine Operations Course
Double Felted LDR – BoardHeavy weight board grades, high volume of waterHeavy loadsDouble felted – two sideded dewatering
Felt
TAPPI Paper Machine Operations Course
Long Bottom – Forming & Pressing Suction Drum “Long” Top or Top – most have been eliminated 2nd Main Press
Cylinder Machine
TAPPI Paper Machine Operations Course
Tissue Requirements
n Delicate sheetn Small amount of water removaln High speeds
TAPPI Paper Machine Operations Course
Two Felt Tissue Machine (“flat” tissue)
Suction Pressure Roll
Suction Press
Felt
TAPPI Paper Machine Operations Course
Single Felt Tissue Machine
Felt
Suction Pressure Roll
TAPPI Paper Machine Operations Course
Press Nip Profile ComparisonNewsprint Tissue-
PM 1Tissue-
PM 2Top Roll 45”/
0 P&J144”/0 P&J
180”/ 0 P&J
Bot Roll 42”/0 P&J
32”/40 P&J
30”/36 P&J
Lineal Load (pli)
500 500 500
Speed (fpm)
4000 2800 6000
TAPPI Paper Machine Operations Course
Nip Comparisons
00.5
11.5
22.5
33.5
4
Nip Width (in) Dwell Time (msec)
NewsTis 1Tis 2
Slower speed
TAPPI Paper Machine Operations Course
Nip Comparisons
0200400600800
1000120014001600
Peak Pressure (psi) Ave Pressure (psi)
NewsTis 1Tis 2
TAPPI Paper Machine Operations Course
General Nip Profile Comparison
0.0
200.0
400.0
600.0
800.0
1000.0
1200.0
1400.0
1600.0
-1.50 -1.00 -0.50 0.00 0.50 1.00 1.50
Position (inches)
Stre
ss (p
si)
Tissue Nip
SS Newsprint Nip
TAPPI Paper Machine Operations Course
Press Fabric Properties
TAPPI Paper Machine Operations Course
Key Properties of Press Fabrics Mass Caliper Air Permeability
Void Volume Compressibility /
Resiliency Flow Resistance Pressure Uniformity
TAPPI Paper Machine Operations Course
Dynamic Character of Press Fabrics
Properties change around press loopCompressed State in nipUncompressed State at Uhle Box
Properties change over cyclesRelationship around press loop changes over time
TAPPI Paper Machine Operations Course
Void Volume
TAPPI Paper Machine Operations Course
Void Volume Amount of water a fabric will hold under a given
load Equivalent to the “empty space” in the fabric Increasing load decreases volume Reduces with fabric age
TAPPI Paper Machine Operations Course
Seamed fabrics
2 layer larger yarn
4 layer single seam
3 layer laminated
2 layer multi-axial
2-layer stdyarn
TAPPI Paper Machine Operations Course
Press Fabric Structure -Compressibility
MEDIUMMEDIUM
FINEFINE
Base
COARSE
Batt
MEDIUMMEDIUM
FINEFINE
Base
COARSE
Batt
Under Load, in the Nip –
LITTLE OR NO CHANGE
MEDIUMMEDIUM
FINEFINE
Base
COARSEBatt
Under Load, in the Nip –
SIGNIFICANT CHANGE
CALIPER UNDER LOAD IS KEY
TAPPI Paper Machine Operations Course
Performance Characteristics Compressibility / Resiliency
Change in fabric caliper from out-of-nip to in-nip
Ability of fabric to revert to out-of-nip caliper.
Flow Resistance Rate at which water can enter and exit
fabric Low flow resistance allows water to move
easily into and out of fabric
TAPPI Paper Machine Operations Course
Pressure Uniformity
How evenly is pressure transferred from loaded rolls to paper sheet
Impacts sheet quality and dryness Large scale related to mesh count and
yarn size Small scale related to batt structure
TAPPI Paper Machine Operations Course
Pressure Distribution
TAPPI Paper Machine Operations Course
“One Size Does Not Fit All”
Physical Dimensions Paper Grade Differences Press Nip Differences Position Differences - Incoming Dryness Failure Mode Differences
TAPPI Paper Machine Operations Course
Failure Modes Wear Compaction Filling Marking Poor Water
Removal (slow speed)
Water carrying / slinging
Instability (wrinkling / rippling)
Sheet breaks Sheet handling
(following / drop-offs)
Vibration Moisture Profile
TAPPI Paper Machine Operations Course
Press Fabric Structure & Nomenclature
TAPPI Paper Machine Operations Course
Finish
LifeWater Removal
Press Fabric Design
TAPPI Paper Machine Operations Course
Press Fabric Structure
Batt -Nonwoven
Base -Woven
COARSEMEDIUMMEDIUM
FINEFINE
COARSE Batt
TAPPI Paper Machine Operations Course
Needling
Fiber
Preparing
Webmaking
Yarns
Dressing
Winding
Weaving
Burling
Heatsetting
TAPPI Paper Machine Operations Course
Needling Trade Line
Wet/Dry Finishing ShippingInspection
TAPPI Paper Machine Operations Course
WEAVING(endless weaving)
MD
TAPPI Paper Machine Operations Course
HARNESSES
REED
WIDTH
LENGTHSHUTTLESHUTE(Mach. direction)
DONUTS
WARP(Cross-Mach. Direction)
WEAVING(endless weaving)
TAPPI Paper Machine Operations Course
ENDLESS WEAVING
DOUBLE ENDLESS WEAVING
HARNESS
REED
WIDTH
LENGTH
ENDLESS BASE WEAVINGSHUTTLE
PIRN
DONUT
WARP
HARNESS
HEDDLES
WARP YARNS
EYELETS
TAPPI Paper Machine Operations Course
WEAVING(endless weaving)
TAPPI Paper Machine Operations Course
WEAVING(Flat weaving)
MD
TAPPI Paper Machine Operations Course
FIBERPREPARATION
TAPPI Paper Machine Operations Course
WEB MAKING(CARDING)
TAPPI Paper Machine Operations Course
NEEDLINGPROCESS
NEEDLE
BASEFABRIC
WEBS
WEB
TAPPI Paper Machine Operations Course
MANUFACTURE OF
PRESS FABRICS
TAPPI Paper Machine Operations Course
MATERIALS USED� NYLON (POLYAMIDE)
� EXCELLENT TENSILE STRENGTH � ABRASION RESISTANCE� RESISTANT TO ALKALIES
TAPPI Paper Machine Operations Course
Press Fabric YarnsSpun Plied
MultifilamentMonofilament Plied
Monofilament
TAPPI Paper Machine Operations Course
Batt Fiber Fineness-Surface, Void Volume, Flow Resistance –Larger Fibers in Use – 66 (90), 110 (100) dtex (almost like a monofilament)
~ .01”
Tissue
Pulp
Fibers/gm79K 39K 20K 12K 8K 5K 3K
3 6 10 15 24 401.5
20 28 35 43 55 7016
Denier
Diameter
How do we make a structure “closer”?
How do we make a structure “more open”? What is best for cleanability?
What is best for drying? What is best for sheet pickup?Decitex is mass in grams per 10,000 mDenier is mass in grams per 9,000 m
TAPPI Paper Machine Operations Course
Batt Fiber
Base Fabric
Press Fabric Anatomy
TAPPI Paper Machine Operations Course
Press Fabric Structure Compression Properties Vary With:MD / CD Yarn Type and Count# of Base LayersBase Fabric Weave Pattern / TypeBatt Fiber DirectionalityChemical Treatment
TAPPI Paper Machine Operations Course
Number of Base Layers
1-Layer
2-Layer
3-Layer
CD
TAPPI Paper Machine Operations Course
Press Fabric Structure Weave Pattern / TypeIntegrally Woven
Stacked Staggered Stratified
LaminatedSeamedMultiaxialCrossless
TAPPI Paper Machine Operations Course
Weave Patterns (3-Layer)
Stacked
Staggered
Stratified
CD
TAPPI Paper Machine Operations Course
Batt-on-Mesh
Cross Machine Direction
Benefits•Easy To Install-Some Styles•Good Pressure Uniformity•Good Sheet Moisture Profile
TAPPI Paper Machine Operations Course
Laminated Base FabricsTop Base
Main Base
Batt Fiber
Cross Machine Direction
Attributes•More Open Under Load•Improved Pressure Uniformity
Benefits•Better Sheet Contact•Easier to Keep Clean•Uniform Sheet Moisture Profile
TAPPI Paper Machine Operations Course
Seam Fabrics
Machine Direction
Attributes•Seamed Press Fabric•Single, Multiple Layer, or Laminated Bases•Choice of Yarn Structures•Durable Seam Design
Benefits•Safety•Shorter installation time•Excellent compaction resistance•Enhanced water handling•More Open Under Load •High Void Volume**•Easier to Keep Clean•Holds Caliper - Long Life
TAPPI Paper Machine Operations Course
Multiaxial PressFabrics
Attributes•Multiaxial Press Fabric•Yarn Systems in 4 directions•Yarn Systems Do Not Nest Under Load•Uniform Surface Topography
Benefits•Stable•More Open Under Load•Better Moisture Profile•Easier to Keep Clean•Holds Caliper - Long Life•Uniform Pressure Distribution
TAPPI Paper Machine Operations Course
Advanced /Crossless
TAPPI Paper Machine Operations Course
Crossless100 % non-woven
TAPPI Paper Machine Operations Course
Advanced/Crossless MaterialsAttributes
• Planar Structure • No Loom Edges• Maximum
Pressure Uniformity
• Outstanding Caliper Recovery (Advanced)
• Highly Compressible
Benefits• Uniform Pressure
Distribution• Dampens Press
Section Vibration (Advanced)
• Sheet Smoothness• Improved Sheet
Solids• Improved Sheet
Finish • Steady State
Pressing
TAPPI Paper Machine Operations Course
Review Press Fabric Design1. What is the name of the press section arrangement?2. Which position removes the least amount of water?3. Which position requires the most void volume?4. If you had a drop – off problem with the pickup felt what could
you change in the design?5. If the 4th press felt contained a multifilament and had short life
because of caliper loss, what might you do to extend life?6. What design would you use for an easy installation?7. We noticed a felt filling problem on the plied mono design on the
Bottom felt- what could we do to improve it?8. To maximize sheet smoothness what kind of felts could we use?9. What are the three types of press base weaving & describe
each?
TAPPI Paper Machine Operations Course
Groove Press
Suction Pickup
Groove Press
Groove Press Groove PressFelt
TAPPI Paper Machine Operations Course
CONDITIONING
TAPPI Paper Machine Operations Course
Benefits of Proper Cleaning & Conditioning
Steady state operation
Improved profile
Improved clothing life
Negative Impact of Press Fabric Filling
Reduced Water Removal Sheet breaks Higher sheet draws Increased Steam
Consumption Overall Runnability
Poor sheet profile Sheet Stealing Sheet Drop off Crushing
TAPPI Paper Machine Operations Course
Press fabrics fill up on each pass
Showers and vacuum must clean on each pass
Remaining materials can cure and grow via reaction within fabric Depends on grade and additives
Shower water quality should be known
Conditioning Strategy
TAPPI Paper Machine Operations Course
Particle Size
A clean press fabric will filter out 100% of particles greater than 50 microns 95% of particles greater than 25 microns Particles below 10 microns will pass thru the
press fabric with water
TAPPI Paper Machine Operations Course
Cleaning & Conditioning Axioms Use right volume at right location Use an acceptable minimum volume Excess volume will transfer to nip Deliver uniformly onto fabric Clean before the First Faceside Felt Roll
(if possible)
TAPPI Paper Machine Operations Course
Press Fabric Conditioning Equipment High Pressure Showers (1- needle 2-fan) (Mechanical)
Prior to 1st Uhle Box to loosen contaminants- face side WARNING : “That which cleans also destroys”
Flooded Nip Showers (4) Inside of press fabric, ahead of the roll, away from uhle box
Wet up aide during start-up Flush contaminants from the inside Good location for continuous or batch chemicals
UB Lube Showers (3) Lubricate the leading edge of the uhle box; reduce drag Adequate seal for maximum volume
Chemical Showers (5) (Chemical cleaning) After press nip Sheet or face, far from uhle
TAPPI Paper Machine Operations Course
3 3 2 1
4 or 5
5
1 2 3 3
4 or 5
1 2 3 3
4 or 5
123
4
3 3 2 13 3 2 1
4 or 5
5
1 2 3 3
4 or 5
1 2 3 3
4 or 5
123
4
TAPPI Paper Machine Operations Course
Cleaning & Conditioning� Fan Showers� Needle Jet Showers� Uhle Boxes
TAPPI Paper Machine Operations Course
Showers� Shower types
� Fan jet� Flushing action� Apply chemicals
� Needle jet� Apply energy
� Single needle jet� Streak Control
TAPPI Paper Machine Operations Course
Press Fabric Conditioning Equipment Uhle Boxes
Cover PU or ceramic Monitor for wear Lubricate to minimize wear
Style Straight slot Herringbone
Alignment Dwell time
3-5 ms Dwell Time (ms) =
[Slot width (in) x5000]/Machine Speed (fpm)
TAPPI Paper Machine Operations Course
Uhle Box Covers
TAPPI Paper Machine Operations Course
3 3 2 1
4 or 5
5
1 2 3 3
4 or 5
1 2 3 3
4 or 5
123
4
3 3 2 13 3 2 1
4 or 5
5
1 2 3 3
4 or 5
1 2 3 3
4 or 5
123
4
TAPPI Paper Machine Operations Course
1 2 3 4 5Shower Type H.P. Needle Jet H.P.Fan Lube Flooded Nip ChemicalLocation Sheet side Sheet side Sheet side Non sheet side aft er press
nip before inner roll.After press nip before inner roll
100 - 300 mm 75 - 150 mm 100 – 300 mm 75 - 150 mm 150 – 300 mm
4 – 12 in 3 – 6 in 4 - 12 in 3 - 6 in 6 - 8 in75 – 200 mm 150 – 200 mm 150 – 200 mm 200 – 300 mm 80 – 200 mm3 – 8 in 6 – 8 in 6 - 8 in 6 – 8 in 3 – 8 in
Trave rse Distan ce T wice the spacing dist ance
T wice the spacing dist ance
T wice the spacing dist ance
T wice the spacing dist ance
T wice the spacing dist ance
S pe e d of Trave rse W idth of nozzle per rev. of fabric
W idth of nozzle per rev. of fabric
An gle 90 degrees or with the fabric run
90 degree Contact fabric and uhle box leading edge
90 degrees 90 degrees
.7 – 1.5 Mpa 1.0 – 1.72 Mpa .15 - .2 Mpa 0.30 – 0.40 Mpa .15 - 0.4 Mpa100 – 200 psi 150-250 psi 20 – 30 psi 40 – 60 psi 20 – 60 psi.7 – 1.0 mm .7 – 1.0 mm0.02 – 0.04 in 0.02 – 0.04 in
O sci l lation Yes Yes Opt ional Opt ional Opt ionalW ate r Te m p. Stock T emp. Stock T emp. Stock T emp. Stock T emp.
Distan ce
Noz z le S pacin g
Pre ssu re s
Noz z le S iz e
TAPPI Paper Machine Operations Course
Steam Box/Steam Shower
TAPPI Paper Machine Operations Course
� Improve dryness� Increase speed� Net energy
savings� Improve
moisture profile� Fabrics run
cleaner
TAPPI Paper Machine Operations Course
TAPPI Paper Machine Operations Course
Steam shower under transfer roll- stickies transferred to cold last press fabrics
Temp on lightweight coated linerboard using 100% recycled furnish steam box off.
TAPPI Paper Machine Operations Course
Non-turbulent steam shower over top fabric uhle box; also installed over bottom fabric uhle box
TAPPI Paper Machine Operations Course
Increased production to 1 ton/hrIncreased uhle box dewatering last presses Longer life of fabrics
TAPPI Paper Machine Operations Course
PU fabric kept more open and eliminated batch washes – extra week of life!
TAPPI Paper Machine Operations Course
Moisture Equilibrium
TAPPI Paper Machine Operations Course
Paper grade Machine speed Sheet dryness exiting forming section Shower volume applied in press section Press fabric compression properties Individual Machine
Moisture EquilibriumWater is Accepted By and Released From a Press Fabric On Every Fabric Revolution
TAPPI Paper Machine Operations Course
Purpose of Moisture Equilibrium Balance
“Spot Checks”, MD & CD, for uniformity
Determine mechanism, direction and location of H2O movement
Monitor Individual Machine Performance
TAPPI Paper Machine Operations Course
CD Moisture Scan1 PM CD SCAN
Date Time Mean Range StDev Weight Machine Position1/11/2 09:18 735.4 76.0 18.85 225.0 1 PM VOITH-97592/28/2 09:15 770.8 111.0 25.14 218.0 1 PM ALBANY-317449
Distance - inches
0 20 40 60 80 100
Moisture Level
gsm
1000949899848797747696645594544493
TAPPI Paper Machine Operations Course
CD Moisture Scan2 PM CD SCAN
Date Time Mean Range StDev Weight Machine Position6/11/1 14:15 994.8 160.0 38.41 401.0 3 TM WEAVEXX-6/25/1 10:06 885.7 116.0 27.20 401.0 2 TM WEAVEXX
Distance - inches
0 20 40 60 80 100
Moisture Level
gsm
1200
1150
1100
1050
1000
950
900
850
800
TAPPI Paper Machine Operations Course
CD Moisture Scan2 PM CD SCAN
Date Time Mean Range StDev Weight Machine Position1/24/2 16:41 1047.4 94.0 24.05 417.0 2 PM ALBANY-3163432/11/2 13:29 849.6 69.0 16.49 395.0 2 PM ALBANY-317583
Distance - inches
0 20 40 60 80 100
Moisture Level
gsm
12001150110010501000950900850800750700650600
TAPPI Paper Machine Operations Course
Returned Fabric Analysis
TAPPI Paper Machine Operations Course
CD Scans – Loading, Showering/Conditioning, Filling
TAPPI Paper Machine Operations Course
Historical CD Scans – Last 5 fabrics
TAPPI Paper Machine Operations Course
TAPPI Paper Machine Operations Course
Contaminants
Inorganic OrganicSilicates, clay, talc PitchTiO2 Hot meltsCaCO3 Size chemicalsFeOx LatexMgCO3 Oil
DefoamersWet & dry strength resins
TAPPI Paper Machine Operations Course
Troubleshooting
TAPPI Paper Machine Operations Course
Trouble Picking up the Sheet
Press Fabric Surface is too “rough”
Fabric is too “open”
Adjust tension – only some styles
Machine Stock change Condition of the forming
fabric Suction pickup roll
operation – plugging; deckles
Improper fabric conditioning equipment –trim squirts
TAPPI Paper Machine Operations Course
Sheet Stealing – where does the sheet go?
Press Fabric Poor Pickup Bottom
Surface too “smooth” Carrying too much water-
too much void volume Design related Wear related
Fabric is filled
Machine Press geometry
Change the wrap of the felt, roll, or sheet
Roll cover material Modify vacuum and
showering
TAPPI Paper Machine Operations Course
Slow Start-up
Press Fabric Too much void volume
under load Increase “precompaction” More compressible and/or
lower void volume base Increase “fineness” of web
Machine Modify water load via
showering & vacuum
TAPPI Paper Machine Operations Course
Crushing
Press Fabric Press fabric cannot
handle the water Filled Not enough void volume Adjust felt tension – only
some styles
Machine Non-uniform pressure in
the nip If streaky, non-uniform
cleaning Check conditioning
equipment
Sheet is too wet Plugged press pan Check Suction box if
suction roll Plugged grooves
TAPPI Paper Machine Operations Course
Loss of speed at the end of life Press fabric is worn
Examine surface condition Shaggy Shower streaks
Modify batt/needling Improve bonding
Modify batt/needling/base Easier to clean
TAPPI Paper Machine Operations Course
Wear – Design, Mechanical, Chemical & HydraulicPress Fabric Too much hydraulic
pressure Modify base/web for less
resistance to flow.
Chemical cleaning and/or residual bleaching agents Add chemical resistant
treatment
Machine Press rolls
Crowns Bearing Misalignment Rough surfaces
Fabric Conditioning Worn suction box covers, XS shower pressure Lube shower coverage
Abrasives in the furnish, Ca CO3
TAPPI Paper Machine Operations Course
Blowing – air between sheet & fabric ahead of the nipPress Fabric Dirty or plugged felt Fabric too open
Machine Geometry “Blow” box ahead of the
nip
TAPPI Paper Machine Operations Course
Sheet Marks Press Fabric Drainage too fast Insufficient web
Design Wear
Base too coarse
Machine Non-Uniform Pressure in
the nip Felt conditioning
equipment Suction press filling up Check for water dropping
on the press Sheet too wet entering
press section Rounded edges in drill
pattern of roll
TAPPI Paper Machine Operations Course
Performance Review1. Why should press fabrics be conditioned?2. Should we clean before or after the first faceside felt roll?3. What is the high pressure shower warning?4. Why take moisture profiles?5. Why would a moisture scan show less water at the end of
life?6. What does returned fabric analysis tell us?7. What surface will the sheet follow in the press section?8. What can we do to improve a slow start-up?9. The sheet is crushing. If we determine it is from the felt,
does the press fabric have too much or too little void volume?
10. What kinds of wear are present in press fabrics?
TAPPI Paper Machine Operations Course
Thank you for your Time
Any Questions?