nonwoven how to form a glass fiber mat?design considerations leo bos nonwoven tappi fiberglass...
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HOW TO FORM A
GLASS FIBER MAT?DESIGN CONSIDERATIONS
LEO BOS
NONWOVEN
TAPPI FIBERGLASS COMMITTEE MEETING SEPTEMBER 2019
• Control the fiber formation
• Having the right fiber consistency and water
flow
• Finding the ideal fan pump configuration
• Keep the fibers well dispersed up to the former
• Laying fibers with the right fiber orientation
and well distributed on the wire
• Keep the web forming process stabile
when creating a fiber mat
CHALLENGES
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01 FORMATION
CHAPTER OVERVIEW
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02 CONSISTENCY
03 DISPERSING
04
05 CONTACT
07
08
09
10
06
WETLAID FORMING OF A WEB WITH FIBERS
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White water loop of a inclined wire former
What is good formation?
WETLAID FORMING OF A WEB WITH FIBERS
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• Most fibers in water have a tendency
to agglomerate and build up flocs
• Small flocs are necessary to form a
sheet on the wire
• Larger flocs appears as clouds in the
formed web
How good the formation highly depends
on the product requirements
+
Quality Level should not fluctuate
Three design points are essential
1. Give the fibers enough room to move freely around in the water-fiber suspension
2. Bring enough turbulence in the water-fiber suspension. Keep the fibers moving.
3. Lay the fibers in the best fiber orientation and good distributed on the wire
Chemicals can be added to slow down the floc building
• Viscosity modifiers: more resistance from the fluid and slow down agglomeration to flocs
=> Consequence: More dispersing energy is needed
• Surfactants: Reduction of force by which the fibers agglomerate
=> Consequence: To be minimized due to associated foam formation!
Wet end design of a fiber glass mat wetlaid line has a significant impact on the forming process.
Applying best design can limit the dependency on white water viscosity and surfactant chemicals.
WETLAID FORMING OF A WEB WITH FIBERS
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How can formation be influenced?
01 HOW TO INFLUENCE FORMATION
CHAPTER OVERVIEW
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02 CONSISTENCY
03 DISPERSING
04
05 CONTACT
07
08
09
10
06
• Consistency = weight-% of solids in
the fiber slurry, AKA “solids”
• The longer the fiber, the lower the
consistency need to be
• The lower the consistency, the higher
the flow in the white water loop at a
constant line throughput
• The capacity of the former and fan
pump will be defined by: consistency,
line speed, base weight and forming
width
• The former & the fan pump should be
able to handle the large flow!
The required flow defines the former design and fan pump choice
GIVE THE FIBERS ROOM - CONSISTENCY
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0,0000%
0,0500%
0,1000%
0,1500%
0,2000%
0,2500%
0 5 10 15 20 25 30 35
Consit
ency
Fiber length
Fiber 1, normal formation
Fiber 1, good formation
Fiber 2, normal formation
Fiber 2, good formation
Key figures for a centrifugal pump: Head
GIVE THE FIBERS ROOM - FAN PUMP
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Static
head
Fan pump
• (Total) Head: The pressure difference between the
discharge and suction side of the pump
• It consists of:
• Static head (height difference between level on
suction side and discharge side)
• Vacuum in the white water return tank
• Friction head (friction losses, caused by the
flow of the fluid)
Friction head is based on assumptions because of the
operating range diversity of a line, chemicals usage and
associated complex calculations.
The range of real total head value of an inclined
wire former requires design slack
The Q-H curve (Q=Flow; H=Head)
GIVE THE FIBERS ROOM - PUMP CURVES
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Underload
area
Overload area
Optimal
operation
window
Lines of constant
efficiency
Lines of constant
rpm
Flow (Q)
Design operating points
• NPSHa: Net Positive Suction Head available (at
the suction flange of the pump) is the Absolute
Pressure head minus the Vapor Pressure of
the liquid.
• NPSAa is the result of a process design. An
important influencers is the level above the
suction flange.
• NPSHr: NPSA required and is directly linked to
the pump design.
• Cavitation occurs if NPSHa < NPSHr. Under
low pressure conditions, the liquid turns in
vapor bubbles. The bubbles implode when the
pressure increases. Those implosions cause
damage to the suction side of the impeller.
Key figures for a centrifugal pump: NPSH
GIVE THE FIBERS ROOM - FAN PUMP
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NPSHa
Fan pump
The NPSHr curve
GIVE THE FIBERS ROOM - PUMP CURVES
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• The NPSHr curves are giving the NPSHr for each
constant RPM line
• Optimal operating points for NPSHr are in the most
horizontal part of the curve
Uncertainties in the head calculations can lead to NPSH problems
GIVE THE FIBERS ROOM - COMPARE 2 PUMPS
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Pump 1
• Seems to be the right choice.
There is even room for future
flow increase.
Pump 1 Pump 2
Design point
with “safety”
in head
Real
operating
point
Design point
with “safety”
in head and
future flow
Real
operating
point future
flow
NPSHr < NPSHa but
already on inclining
part of curve
NPSHr > NPSHa
Pump runs in
cavitation!
Design point
with “safety”
in head
Design point
with “safety”
in head and
future flow
Real
operating
point
Real
operating
point future
flow
NPSHr <
NPSHa
NPSHr <
NPSHa
• But if in reality the head is
significant lower, the pump is
already running close to overload
area and there is no room for
future flow increase.
Pump 2
• Is running in underload at the
original design point, but can be
used.
• If the real head is lower, the pump
is running in the preferred
operating window, the future flow
will be the optimum
Low pulse - double suction – split case pumps
GIVE THE FIBERS ROOM - FAN PUMP
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Take away:
For a reliable and long-term fan pump
choice ensure Design Slack: pump shall
be able to handle theoretical and future
head and flow:
Is the position of the pump low enough
to ensure NPSHa > NPSHr?
Too small pumps and shallow basement
are suspicious!
01 HOW TO INFLUENCE FORMATION
CHAPTER OVERVIEW
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02
03 DISPERSING
04
05 CONTACT
07
08
09
10
06
Mixing fibers in white water: Flocs but no clumps…
DISPERSING – KEEP THE FIBERS MOVING
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Mixing glass fibers in white water is:
• Depending of the fiber length and diameter
• Depending of the fiber finish
• Depending of the white water chemicals
• Depending of the residence time in the mix and store chests
Testing of glass fiber dispersing in specialized technology centers is highly recommended
before choosing the type of mixers and stock prep configuration!
• For most glass fibers, dosing fibers in one step to the final thick stock consistency is not the
optimal solution
• Beside suboptimal dispersing, there is no possibility to adjust fiber dosing fluctuations/errors
Dilution water in steps
DISPERSING – KEEP THE FIBERS MOVING
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0,00%
0,10%
0,20%
0,30%
0,40%
0,50%
0,60%
0 50 100 150 200 250 300
Consis
tency
Time
Consitency mix tank in
Consitency mix tank out
Consitency machine tank out
• Mixing on higher consistency. This is very often more efficient.
• Extra dilution step can reduce consequences of fiber feed dosing errors.
Controlled second dilution step
DISPERSING – KEEP THE FIBERS MOVING
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0,00%
0,20%
0,40%
0,60%
0,80%
1,00%
1,20%
1,40%
0 50 100 150 200 250 300
Consis
tency
Time
Consitency mix tank in
Consitency mix tank out
Consitency machine tank out
Double diffusor
DISPERSING – KEEP THE FIBERS MOVING
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Pre diffusor
Decoupling of functions
• Pre diffusor for changing flow in header from cross machine direction in machine direction
• Main diffusor optimized for optimal turbulence: Defloccing
Main diffusor
DISPERSING – KEEP THE FIBERS MOVING
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1 2 3 4 5 6 7 8 9 10 11
Speed
Pos
Fluid speeds double diffusor
Double diffusor => More DISPERSING ENERGY
1 2 3 4 5 6 7 8
Sp
ee
d
Pos
Fluid speeds single diffusor
Two peaks
One peak
1. MF IN
2. MF OUT
3. HDF IN
4. HDF OUT
5. DUS IN
6. DUS OUT0
20
40
60
80
100
double
diffusor
single
diffusor
Dip
sers
ing e
nerg
y
(%)
01 HOW TO INFLUENCE FORMATION
CHAPTER OVERVIEW
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02
03
04 FIBER ORIENTATION
05 CONTACT
07
08
09
10
06
Guiding of the slurry flow to the wire
FORMING THE WEB – GOOD FIBER LAYING
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Control factors for forming process
FORMING THE WEB – GOOD FIBER LAYING
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Wire speed
Gap 1
Speed of the slurry
Gap 2 HB Pressure Flow
Flow control valves
Flow transmitters
To fan pump
Vacuum
Overflow
Even dewatering in Machine Direction and Cross Machine Direction
FORMING THE WEB– GOOD FIBER LAYING
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A combination between the materials , the process and the machine
FORMING THE WEB– GOOD FIBER LAYING
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An optimized machine and process
design:
• Reduce the dependency of excipients
as viscosity modifier and dispersants
• Reduce operating costs
• Improve formation Quality
01 HOW TO INFLUENCE FORMATION
CHAPTER OVERVIEW
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02
03
04
05 CONTACT
07
08
09
10
06
Our team is at your disposal
WE LOOK FORWARD
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Leo Bos
Business Development Manager Wetlaid
ANDRITZ Küsters GmbH
Eduard-Küsters-Strasse 1
47805 Krefeld, Germany
p: +49 2151 34 1436
m: +31 6 5472 5045