Felt Cleaning - City Computing Limited

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Felt Conditioning Technology
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Impact of Felt Problems on
Performance
Compaction
Filling
Sizing
Wear
Fiber damage
900
850
800
ml/minute
•
•
•
•
•
CD Felt Permeability
750
700
650
600
550
500
CD Position
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Philosophy of Felt Conditioning
• Condition press felts to keep them in their
original, “broken in” condition throughout their
useful lives
• Slow down the process of felt filling and
deposit formation
• Remove built-up contaminants with the
proper cleaning chemistry
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Felt Permeability over Time vs.
Felt Treatment
ml/minute
“Broken in” permeability
Ideal performance
Batch cleaning only
Conditioning only
Untreated
Days
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Which Treatment?
•
•
•
•
•
Survey the machine
Identify root causes
Correct mechanical problems
Determine customer goals
Prepare treatment options
– Different programs have different costs and results
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Felt Cleaning
• Type of contaminant
• Feed schedule
– Down batch
– Batch-on-the-fly (BOTF)
• Shower location
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Contaminants and Cleaning Agents
Solvent Extractable
Amide
Asphalt
Latex, Grease
Polyethylene
Oil, Wax
Abietic Acid
Rosin Size
Fatty Acid
Fatty Ester
Starch
Alkaline
Dry Strength
Extractable Biological Slime
Lignin
Glue
Fatty Acid Salt
Abietic Acid Salts
Wet Strength
Alkaline
Size
Aluminum
Hydroxide
Calcium
Carbonate
Clay, Talc, TiO2
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Ash
Acid
Extractable
Down Batch vs. BOTF
Cleaning
Down Batch
• Advantages
– Intensive cleaning
– Not regulated regarding
food contact, etc.
– Easy to keep personnel out
of the press section
• Disadvantages
– Requires machine
downtime
– Not performed until felts
become significantly dirty
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BOTF
• Advantages
– Milder cleaning than down
batch
– No machine downtime
required
– Felts only become a little
dirty before performing
• Disadvantages
– May surprise personnelmust warn operators, etc.
before performing
– Regulated regarding food
contact, etc.
Amazon Felt Cleaners
• AmiClean AP2048 (Down Batch/ BOTF)
– Non-solvent
– Good for Tissue & wet strength
• AmiClean AP1850 (Down Batch/ BOTF)
– Water-soluble solvent
– Good for latex
• AmiClean AP1894 (Down Batch)
– Heavy solvent
– High odor
– Good for stickies
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Chemical Action: CleanerDown Batch/BOTF
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Chemical Shower Location: Down
Batch
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Chemical Shower Location: BOTF
Light weight
grades
Heavy weight
grades
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Felt Conditioning
• Type of contaminant/grade of paper
• Three basic approaches
– Surfactants
– Passivation
– Solvents (acid/alkali/hydrocarbon)
• Shower location
• Percentage of product by felt position
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Chemical Action: Surfactant
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Commonly Used Surfactants
Dispersants
• Anionic
• Effective on charged
materials
– Pitch
– Coated broke
– Filler
_ _ __
_
_
_
Non-ionic surfactants
• Charge neutral
• Emulsifiers and penetrants
• Effective on non-charged
materials
– Size
– Oils
– Antifoams
_
_
Contaminant
_
_
_
_ _ _
_
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Contaminant
Chemical Shower Location: Surfactants
If overspray or
dripping is a
concern
If overspray or
dripping is not a
concern
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Chemical Action:
Passivation
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Passivation: Surface Energy
Modification
Contaminant spreads and becomes
well attached
 Contaminant < Surface
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Contaminant does not spread
and is removed easily
 Contaminant > Surface
Chemical Shower Location:
Passivation
Good choice for
surface contaminationmust minimize shower
volume
Good general
purpose choice
Usually 1st
choice for
internal filling
control
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Choosing the Right Felt
Conditioner
• Passivation
– Especially effective on
stickies
– Product feed rate is
independent of application
shower volume
– Must have at least -30
µeq/liter charge in headbox
– Must use fresh water in
application shower
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• Surfactants
– Can use clarified white
water in the application
shower
– May cause foam
– Product feed rate is
dependent on application
shower volume
• Solvents
– Potential environmental
and safety concerns
– Product feed rate is
dependent on application
shower volume
Amazon Felt Conditioners
• Passivation
– AmiSpray AP8683
– AmiSpray AP8694
• Surfactant-based
– AmiClean AP2048
– AmiSpray AP8705
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Felt Conditioner Feed Rates
by Felt Position
• Feed according to need
• More water removed by the felt means more
contaminants in the felt
• Pickup felts need extra attention
• Mechanical cleaning affects felt conditioning
needs
– Needle shower pressure
– Oscillation rate
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Conditioner Distribution by Felt
Position
2nd top: 20%
Pickup: 50%
Transbelt
1st bottom: 30%
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Commonly Monitored
Variables
Indirect Monitoring
Direct Monitoring
• Uhle box vacuum
• Production
• Uhle box water flow
• Machine speed
• Uhle box air flow
• Felt life
• Felt permeability
• Sheet breaks
• Felt moisture
• Sheet defects
• Sheet moisture profile
• Dryer section steam
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• Downtime for cleaning
Uhle Box Vacuum
• Oldest indicator of felt performance
• Increase in vacuum level can indicate filling,
compaction, or higher water content in felt
• Decrease in vacuum level can indicate felt
wear or partial vacuum loss
– Uhle box deposits
– Misplaced deckle strips
• Only indicates average performance across
the felt width
• Not useful with a Turbo blower or shared
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vacuum source
Huyck Smith Porosity Tester
• Portable vacuum source and gauge
• Can be used to measure percent loss of
porosity over the life of the felt
• Gives readings across the width of the felt
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Uhle Box Water Flow over Time
Liters/minute
800
0
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Days
Microwave Moisture Meter
• Measures the water content of the felt
• Gives a detailed profile of the felt across its
width
• Excellent tool for troubleshooting and checking
press loading and roll crown problems
• Strongly influenced by press section shower
volumes
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Felt Permeability Tester
• Measures the ability of the felt to accept water
• Gives a very precise profile in the cross machine
direction
• Can be used to troubleshoot, like the microwave
moisture meter
• Can detect felt sizing
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High Pressure Shower
Recommendations
• Nozzles
– 6” or 12” (15 or 30 cm)
center to center
– 0.040” (0.1 cm) diameter
orifice
– 0.59 gpm (2.2 l/min)
• Oscillator stroke: 12” (30
cm)
• Pressure: 150-350 psi
(10-24 bar)- depends on
felt structure and
contaminant load
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• Position
– Sheet side
– 15-45o angled against felt
run
– 4-8” (10-20 cm) from felt
• Operation
–
–
–
–
Continuous
Pressure regulation
Warm water
Proper oscillation rate
Illustration of High Pressure Shower
Cleaning Jet
10 cm
10-20 cm
>20 cm
.2 cm
2400 Kpa
HP Cleaning Summary
Phase Distance
Comments
I
0-4” / 10 cm
.040” (.1 cm) cleaning;>tendency for felt damage/wear
II
4-8” / 10-20 cm .080” (.2 CM) cleaning;>velocity - max cleaning action
through
IIIDelivering
overValue
8” / >20
cmPeople Chemistry
Jet velocity breakup; jet expands and entrains air - little cleaning
Correct Shower Oscillation Rate
S: Running Speed (m/min) N: Rev. per Min (rpm)
R: Stroke Rate (cm/min)
L: Loop Length (m)
t: Width cleaned per Nozzle (cm)
Oscillation Rate = R = S * t/L
EXAMPLE: S = 1100 m/min, L = 21 m Felt, C = 5.75 m for a 1.8 m dia roll and
t = .1 for a .1 cm orifice nozzle
Felt Complete Coverage Stroke Rate:Complete Coverage Cleaning Incorrect Oscillator Rate
S·t
1100 * 0.1
R= L =
21
= 5.2 cm/min
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Uhle Box Shower
Recommendations
• Nozzles
– 6-8” (15 -20 cm) center to center
– 0.03 - 0.07 gpm/inch (0.045-0.075 l/min-cm)
• Pressure: 20-30 psi (1.4-2.1 bar)
• Position
– Angled into Uhle box nip
• Operation
– Continuous
– Pressure regulation
– Warm water
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Chemical Shower
Recommendations
• Nozzles
– 6-8” (15 -20 cm) center to
center
– 0.08-0.15 gpm/inch (0.120.23 l/min-cm)
• Pressure: 40-50 psi
(2.75-3.4 bar)
• Position
– Conditioning application:
inside with dwell time
– Passivation application:
sheet side
– BOTF: Uhle box lube
shower
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• Operation
– Continuous (BOTF is
intermittent)
– Pressure regulation
– Warm water (fresh water
for passivation)
– Even coverage
Uhle Box
Recommendations
• Vacuum: 10” Hg (35 kPa) - 15” Hg (50 kPa)
• Dwell Time: 3-5 milliseconds
• Air Flow Rate:
– Slots: 12-15 cfm/in2 (3.2-4.0 m3/h-cm2, or 8.8-11 m/sec)
– Herringbone: 12 cfm/in2
• Square cover edges on uhle boxes (doctoring effect)
• Separate vacuum source for each felt
• Control
atmospheric
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People Chemistry (breaker) valve
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