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Potlatch Brainerd Wet End Training 3
- 1. 01/30/15 Copyright © 2001 Bill Frawley
Potlatch Brainerd
Wet End Training
March 2001
By
Bill Frawley
- 2. 01/30/15 Copyright © 2001 Bill Frawley
Introduction
Understanding the paper forming
process, equipment and chemistry
Bill Frawley and Joe Osfar
Training Consultants
- 3. 01/30/15 Copyright © 2001 Bill Frawley
Topics of Discussion
Looking at machine as relates to
fiber mat formation.
How each area impacts fiber mat
Entry zone
Forming zone
Dewatering zone
Consolidation zone
Pressing
- 5. 01/30/15 Copyright © 2001 Bill Frawley
The Five Zones of the
Forming Table
Entry Phase
Forming Zone
Dewatering Zone
Transition Zone
Consolidation Zone
- 7. 01/30/15 Copyright © 2001 Bill Frawley
1 Entry Phase
Headbox
Slice and Jet
Pressure Forming Vs Velocity
Forming
Impingement point
Forming board
Structuring of filtering mat
- 8. 01/30/15 Copyright © 2001 Bill Frawley
Headbox Approach System
Approach system
Fan pump
Attenuator
Tube bundle
- 9. 01/30/15 Copyright © 2001 Bill Frawley
Headbox Components
Headbox Components
Diffuser block
Distributor rolls (holy rolls)
Nozzle
Slice
- 10. 01/30/15 Copyright © 2001 Bill Frawley
Rectifier Roll
Agitates dilute
stock so flocks can
not form in headbox
Velocity through
center of hole
greater than outside
do to boundary
effect
Designed for fixed
flow range
- 11. 01/30/15 Copyright © 2001 Bill Frawley
Rectifier Roll Pattern in Sheet
If roll capacity is
exceeded streaks
will flow through
nozzle
Forming board will
set pattern in
filtering mat
- 17. 01/30/15 Copyright © 2001 Bill Frawley
Rushing the Jet
Jet velocity greater
than wire speed
CD fiber orientation
Sheet has less MD
strength.
- 18. 01/30/15 Copyright © 2001 Bill Frawley
Dragging the Jet
Jet velocity less
than wire speed
MD fiber orientation
Sheet has more MD
strength.
- 19. 01/30/15 Copyright © 2001 Bill Frawley
Pressure Vs Velocity
Forming
Pressure Forming
Rapid development
of fiber mat
Low first pass
retention
Sheet sealing
Tissue applications
- 20. 01/30/15 Copyright © 2001 Bill Frawley
Velocity Vs Pressure
Forming
Velocity Forming
Better filtering mat
Carry lower
consistency in to
forming zone
Higher first pass
retention
Flat grades
- 21. 01/30/15 Copyright © 2001 Bill Frawley
How The Filtering Mat
Develops
Filtering mat
developed on the
forming board
- 22. 01/30/15 Copyright © 2001 Bill Frawley
Sheet Consistency Development
Formation is over when stock
consistency reaches 1.2 – 1.4%
Excessive activity past this point
will degrade sheet properties!
- 23. 01/30/15 Copyright © 2001 Bill Frawley
2 Forming Zone
Breast Roll Shake
How foils & table rolls work
Harmonics
1. Machine speed
2. Foil spacing
3. Box spacing
Amplitude - Function of angle
All over when stock reaches 1.2-
1.4% consistency Sheet set point
- 24. 01/30/15 Copyright © 2001 Bill Frawley
How The Forming Zone
Develops Fiber Mat
Forming zone
works fibers &
fillers in upper
part of
suspension
- 25. 01/30/15 Copyright © 2001 Bill Frawley
Table Rolls
High activity at low
speeds
Positive and
negative pressure
Ever increasing nip
Work up to 1200
fpm
Higher
maintenance
- 28. 01/30/15 Copyright © 2001 Bill Frawley
How Foils Work
Nose: Skives water off
bottom of wire
Flat: Seals fabric so
vacuum can happen
Angle: Creates gravity
vacuum
- 29. 01/30/15 Copyright © 2001 Bill Frawley
Nose:
Skives water off
bottom of wire
Creates speed bump
If the nose is too
sharp fibers will staple
over and cause
streaks (like a rock in
a river)
Foil Nose
- 30. 01/30/15 Copyright © 2001 Bill Frawley
Foil Flat
Flat seals fabric to
bottom of wire so
vacuum can happen
This can tell us how
foils is wearing or
aligned
Wear should be from
nose back
If wear starts on back
of flat t-slot is wrong
or tilted
- 31. 01/30/15 Copyright © 2001 Bill Frawley
Foil Angle
Foils won’t work under 400
FPM
Angle draws water through
filtering mat as nip moves
away from wire
Vacuum brakes when water
can’t fill nip
Wire is pulled down with
water
When vacuum brakes, wire
snaps back causing activity
- 32. 01/30/15 Copyright © 2001 Bill Frawley
Harmonics
Speed ÷ Spacing ÷ 5 = CPS
1500 fpm ÷ 5 = 300 ÷ 5 = 60 CPS
Sweet spot for formation is
around 80 Cycles per second
If activity stops for an instant
flocculation will occur
- 33. 01/30/15 Copyright © 2001 Bill Frawley
Foil Box Spacing
Box spacing has to be set to the blade
spacing of the proceeding box
Example: Foils are spaced 5” center to
center the next box has to set 5” 10”
or 15” from the tip of the last foil to the
tip of the first foil on the next box
- 34. 01/30/15 Copyright © 2001 Bill Frawley
3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00 5.25 5.50 5.75 6.00
ft/min in /sec
500.00 100.00 33.33 30.77 28.57 26.67 25.00 23.53 22.22 21.05 20.00 19.05 18.18 17.39 16.67
600.00 120.00 40.00 36.92 34.29 32.00 30.00 28.24 26.67 25.26 24.00 22.86 21.82 20.87 20.00
700.00 140.00 46.67 43.08 40.00 37.33 35.00 32.94 31.11 29.47 28.00 26.67 25.45 24.35 23.33
800.00 160.00 53.33 49.23 45.71 42.67 40.00 37.65 35.56 33.68 32.00 30.48 29.09 27.83 26.67
900.00 180.00 60.00 55.38 51.43 48.00 45.00 42.35 40.00 37.89 36.00 34.29 32.73 31.30 30.00
1000.00 200.00 66.67 61.54 57.14 53.33 50.00 47.06 44.44 42.11 40.00 38.10 36.36 34.78 33.33
1100.00 220.00 73.33 67.69 62.86 58.67 55.00 51.76 48.89 46.32 44.00 41.90 40.00 38.26 36.67
1200.00 240.00 80.00 73.85 68.57 64.00 60.00 56.47 53.33 50.53 48.00 45.71 43.64 41.74 40.00
1300.00 260.00 86.67 80.00 74.29 69.33 65.00 61.18 57.78 54.74 52.00 49.52 47.27 45.22 43.33
1400.00 280.00 93.33 86.15 80.00 74.67 70.00 65.88 62.22 58.95 56.00 53.33 50.91 48.70 46.67
1500.00 300.00 100.00 92.31 85.71 80.00 75.00 70.59 66.67 63.16 60.00 57.14 54.55 52.17 50.00
1600.00 320.00 106.67 98.46 91.43 85.33 80.00 75.29 71.11 67.37 64.00 60.95 58.18 55.65 53.33
1700.00 340.00 113.33 104.62 97.14 90.67 85.00 80.00 75.56 71.58 68.00 64.76 61.82 59.13 56.67
1800.00 360.00 120.00 110.77 102.86 96.00 90.00 84.71 80.00 75.79 72.00 68.57 65.45 62.61 60.00
1900.00 380.00 126.67 116.92 108.57 101.33 95.00 89.41 84.44 80.00 76.00 72.38 69.09 66.09 63.33
2000.00 400.00 133.33 123.08 114.29 106.67 100.00 94.12 88.89 84.21 80.00 76.19 72.73 69.57 66.67
2100.00 420.00 140.00 129.23 120.00 112.00 105.00 98.82 93.33 88.42 84.00 80.00 76.36 73.04 70.00
2200.00 440.00 146.67 135.38 125.71 117.33 110.00 103.53 97.78 92.63 88.00 83.81 80.00 76.52 73.33
2300.00 460.00 153.33 141.54 131.43 122.67 115.00 108.24 102.22 96.84 92.00 87.62 83.64 80.00 76.67
2400.00 480.00 160.00 147.69 137.14 128.00 120.00 112.94 106.67 101.05 96.00 91.43 87.27 83.48 80.00
2500.00 500.00 166.67 153.85 142.86 133.33 125.00 117.65 111.11 105.26 100.00 95.24 90.91 86.96 83.33
2600.00 520.00 173.33 160.00 148.57 138.67 130.00 122.35 115.56 109.47 104.00 99.05 94.55 90.43 86.67
2700.00 540.00 180.00 166.15 154.29 144.00 135.00 127.06 120.00 113.68 108.00 102.86 98.18 93.91 90.00
Foil Frequency Chart
- 35. 01/30/15 Copyright © 2001 Bill Frawley
Foil Amplitude
Function of wire speed and foil
angle
Lower angle lower pulse
Higher angle higher pulse
4-5 Degree foils maximum
Turbulence making foils
- 36. 01/30/15 Copyright © 2001 Bill Frawley
Activity
Rating
Chart
1. Flat Clam
2. Calm
3. Ripples
4. Small Waves
5. Small Waves
6. Wave action
7. Micro
turbulence
8. Micro
turbulence
9. Necking
10. Stock Jump
- 37. 01/30/15 Copyright © 2001 Bill Frawley
Calm to Small Waves
No shear in stock
suspension
Flocculation
Mat can get so
dense that it will
retard drainage
- 38. 01/30/15 Copyright © 2001 Bill Frawley
Wave Action
Shear starts to
begin
Fibers in upper
suspension
move
Filtering mat
stays open
Formation can
improve
- 39. 01/30/15 Copyright © 2001 Bill Frawley
Micro Turbulence
Shear occurs
Flock size is
significantly
smaller and more
uniform
Fibers in upper
suspension move
Filtering mat
stays open
Formation
improves
- 41. 01/30/15 Copyright © 2001 Bill Frawley
Stock Jump
Filtering mat is
destroyed
Retention drops
Droplets can
rain on your
parade (rings in
sheet)
Chunks of
filtering mat
could cause
large flocks
- 42. 01/30/15 Copyright © 2001 Bill Frawley
Dewatering Zone
Gravity Foils
Vacuum Foils
Top Wire Units
- 43. 01/30/15 Copyright © 2001 Bill Frawley
Thickening The Stock
Add a little flour
and stir over low
heat
- 44. 01/30/15 Copyright © 2001 Bill Frawley
Thickening The Stock
Keep mat open
Remove water
Graduate low
vacuum levels
to prevent sheet
sealing
Finish top side
of sheet
Consistency
levels form 1.4 –
13%
- 45. 01/30/15 Copyright © 2001 Bill Frawley
Gravity Foils
In the dewatering zone
angles should be a
compromise between
water removal and
stock activity
Need to keep mat open
for drainage
Need to carry
harmonic activity to
last gravity unit
- 47. 01/30/15 Copyright © 2001 Bill Frawley
Low Vacuum Foils
Low vacuum foils are
need to remove water
when the filtering mat
has thickened to a point
where gravity foils
become inefficient
Control consistency
coming in to top wire
unit 1.8 – 2.1%
- 48. 01/30/15 Copyright © 2001 Bill Frawley
Low Vacuum Foils
Vacuum measured in
inches of water
Blower supplies
negative pressure
Water on top of fiber
mat creates air tight
seal
Open area = dwell time
Ramp up vacuum
To much vacuum to
soon will seal sheet
- 49. 01/30/15 Copyright © 2001 Bill Frawley
Controlling Low Vacuum Foils
Ramp vacuum
Drop leg seals
bottom and
determines how
much vacuum is
possible
It is better to use
narrow 0º blades
and adjust t-bar
spacing for open
area (less drag)
- 51. 01/30/15 Copyright © 2001 Bill Frawley
Bel Bond Advantages
Fiber mat is sandwiched
between two forming fabrics
Dewaters up
Finishes top of sheet
Structures mat uniformly
Less two sidedness
Increases consistency of sheet
from 2 – 11%
- 53. 01/30/15 Copyright © 2001 Bill Frawley
Lead-in Box
Four adjustments for
controlling H2O
1. Height of roll
2. Raise or lower
trailing edge of lead-
in box
3. Raise or lower
vacuum of lead-in
box
4. Raise or lower
vacuum of lovac box
- 54. 01/30/15 Copyright © 2001 Bill Frawley
Impingement Point of Two Wires
Water is forced up through
top wire on lead-in box
Water is vacuumed down
in to lead-in box up to 25”
H2O vacuum
Curvature of lead-in box
helps force water up
Adjusting height of trailing
edge of lead-in box has
affect on formation
Lead-in roll has biggest
impact on dewatering
- 56. 01/30/15 Copyright © 2001 Bill Frawley
Auto Slice
Vacuums free water and air from
inside of top wire 20-25” H2O vac
Roof is adjustable by hand
Setting is determined by closing
roof until slice rejects some water
then opened back up a smidge so
all water is removed
Roof regulates only amount of air
removed NOT amount of water
- 57. 01/30/15 Copyright © 2001 Bill Frawley
1st
Vacuum Chamber
15 two inch ceramic
blade vacuum zone
under auto slice box
Vacuum level shifts
to 3 – 5” Hg
Connected to a
vacuum pump
Water is move up
channel to a weir
- 58. 01/30/15 Copyright © 2001 Bill Frawley
2nd
Vacuum Chamber
14 two inch ceramic
blade vacuum zone
under auto slice box
Vacuum level shifts
to 4 – 6” Hg
Connected to a
vacuum pump
Water is move up
channel to a weir
- 59. 01/30/15 Copyright © 2001 Bill Frawley
Transfer Box
Transfer box keep
the sheet on the
bottom wire
Wires separate on
curved surface
Begins sheet
consolidation zone
8 slots pulling 4-6
inches of mercury
- 60. 01/30/15 Copyright © 2001 Bill Frawley
Suction Boxes
Ramp up vacuum
from 4-10” of mercury
Boxes have
adjustable deckles
Dries sheet from
about 12-17%
consistency
Vacuum supplied by
Nash vacuum pump
- 62. 01/30/15 Copyright © 2001 Bill Frawley
Function of Suction Couch Roll
End of consolidation zone
Dries sheet to 18-22%
Helps drive forming fabric
At speeds over 1200 FPM
water never penetrates shell
Liquid ring seal
Highest vacuum element on
machine
- 63. 01/30/15 Copyright © 2001 Bill Frawley
Forming Section Review
Stock delivery system
Forming zone
Dewatering zone
Top wire unit
High Vacuum
Couch
Sheet development
- 65. 01/30/15 Copyright © 2001 Bill Frawley
Press Section Functions
To remove water by squeezing
or wringing sheet against a felt
Felts act like a sponge
Pressing make sheet denser
Press nips squeeze sheet and
felt or just sheet to remove
water or to smooth sheet
Overloading can crush and mark
- 67. 01/30/15 Copyright © 2001 Bill Frawley
4 Phases of Press Roll Nip
Phase 1: Felt and sheet
compresses sheet becomes
saturated
Phase 2: Water is squeezed
from sheet to felt
Phase 3: Felt expands faster
pulling more water from
sheet
Phase 4: Sheet rewets as it
partially expands
- 68. 01/30/15 Copyright © 2001 Bill Frawley
PLI Vs PSI
Pli is used measure
force of mating rolls
Pli is the number used
for press loading
Psi is used when
discussing force of nip
on sheet or felt &
sheet
- 69. 01/30/15 Copyright © 2001 Bill Frawley
Why Press are Crowned
Crown is needed
to
Even out pressure
under nip loading
Compensate for
Sag & deflection
- 70. 01/30/15 Copyright © 2001 Bill Frawley
Press Loading
1st
Press 450 PLI
2nd
Press 600 PLI
Smoothing 450-500 PLI
Excessive pressure will crush or
shadow mark sheet
- 71. 01/30/15 Copyright © 2001 Bill Frawley
Combi-Roll
The Combi roll is a pickup &
suction first press roll in
one
Low vacuum area lifts sheet
off wire and holds it on the
felt until the high vacuum
zone under first press nip
Low vac area doesn’t
remove water
High vac holds water in felt
until sheet can get away
- 72. 01/30/15 Copyright © 2001 Bill Frawley
Combi-Roll Operation
Vacuum must be off to move
into wire
Low vacuum is set about 8” Hg
Low vac zone doesn't remove
water
High vacuum is set at 20” Hg And
holds water in felt until sheet is
clear of nip
Box alignment critical
1st
press loaded to 450 Pli
- 73. 01/30/15 Copyright © 2001 Bill Frawley
Suction Felt Roll
Acts like an anti-blow
box
Sucks sheet tight to
felt to prevent flutter
entering 2nd
press
Doesn't remove water
from sheet only air
Stabilizes sheet after
open draw from
pickup felt
- 74. 01/30/15 Copyright © 2001 Bill Frawley
2nd
Press
2nd
press uses a venta-
nip grooved bottom roll
Grooves in rubber cover
act like tread on your
car tires
Water is squeezed from
sheet through felt and in
to voids of grooves
Too much pressure can
cause shadow marking
and crush sheet
- 75. 01/30/15 Copyright © 2001 Bill Frawley
Smoothing Press
Smoothing press as
it’s name says
smoothes the sheet
for better drying
No water is removed
so nip load has to be
lower that 2nd
press
Both rolls are hard
- 76. 01/30/15 Copyright © 2001 Bill Frawley
Press Roll Showers
Showers in
suction rolls are
invisible
Venta-nip shower
keeps grooves
clean and open
- 77. 01/30/15 Copyright © 2001 Bill Frawley
Press Felts
Act as a blotter or sponge
Absorb water +
dirt, fines, pitch ash, minerals…
at nip
Cleaned with showers &
chemicals (batch wash)
Dried on uhle boxes
Trade line needs to run square
Change when filled and worn
- 78. 01/30/15 Copyright © 2001 Bill Frawley
Press Section Felt Showers
Each felt has
Batch chemical and
flushing shower
High pressure
cleaning shower
Uhle box lube
shower
- 79. 01/30/15 Copyright © 2001 Bill Frawley
Uhle Boxes
Shop-vac for felts
4 milliseconds dwell minimum to
dry and clean
Be careful of edges outside
sheet they will dry out first
Adjust deckles to sheet width
Vacuum will start around 10” Hg
when felt is new and increase to
15-17” when felt is filled
- 80. 01/30/15 Copyright © 2001 Bill Frawley
Press Section Review
To remove water by squeezing
sheet against an a felt
Felts act like a sponge
Uhle boxes & showers clean and
dry felts
Pressing make sheet denser
Press nips squeeze sheet and
felt or just sheet to remove
water or to smooth sheet
Overloading can crush and mark
Notas do Editor
- Pay Attention to graph line under the wire return, regarding stock consistency per machine section.