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Last Update: 01.2003/by:MK19.1
19-ScrewElements.gb ...
Chapter: 19Screw Elements: Types, Function, IdentificationBasics on screw elements
Conveying elements
Kneading elements
Neutral elements
Installation of the screw elements
Numbering of the screw elements
Principle of operation of the screw elements
CWP Customer Training Seminar
Last Update: 01.2003/by:MK19.2
19-ScrewElements.gb ...
CWP Customer Training Seminar
• The Erdmenger patent "conditions of the sealing profile must be met"
Along the screw connection there must be the same cross-section at all points
Both shafts must have the same screw profile.
Last Update: 01.2003/by:MK19.3
19-ScrewElements.gb ...
Do = Outer screw diameter
Di = Inner screw diameter
a = Axle distance
Diameter ratio:
Da / Di
(indicates available volume)
Specific capacity:
Md / a3
(Indicates torque)
Da
Di
a
Do
Di
a
Characteristic Dimensions
Last Update: 01.2003/by:MK19.4
19-ScrewElements.gb ...
Da
Pit
ch (
mm
)
x Da High pitch Low pitch
Conveying Elements
Last Update: 01.2003/by:MK19.5
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Extruder
Rightflighted Elements Leftflighted Elements
Conveying direction
direction of the extruder flow
against the inConveying direction
direction of the extruder flow
Conveying Elements Right and Left-Hand Pitch
Last Update: 01.2003/by:MK19.6
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Conveying Elements, Conveying,
Last Update: 01.2003/by:MK19.7
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1
2
3
4
(5)
Stagger angle
1
2
3
4
Spacer ring
Kneading disc
5
Wide kneading discs
Narrow kneading discs
Kneading Blocks
Last Update: 01.2003/by:MK19.8
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Kneading Blocks
• Kneading blocks comprise several kneading discs arranged behind one another.
• The staggering angle by standard is 45 or 90°
• The number and the width of the individual kneading discs is variable.
• The position of the kneading discs at the beginning and the end should be identical, for compatibility with other kneading blocks (i.e. to keep the modular concept).
Last Update: 01.2003/by:MK19.9
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Kneading Elements
Last Update: 01.2003/by:MK19.10
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Element
own conveying
without
Extruder
Rightflighted Elements Leftflighted ElementsNeutral elements
Conveying direction
of extruder flow
in the direction against direction Conveying direction
of extruder flow
Kneading Elements
Last Update: 01.2003/by:MK19.11
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Conveying and Kneading Elements, Left-Hand Pitch
Last Update: 01.2003/by:MK19.12
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Quiz
Q: Which connection between the screw element and the screw shaft is shown?
A: Refer 18.1 ff
Last Update: 01.2003/by:MK19.13
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Installation of Screw Elements
Last Update: 01.2003/by:MK19.14
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Installation of Screw Set Elements
Last Update: 01.2003/by:MK19.15
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1-flight elements 2- flight elements 3- flight elements
Faces always parallelly
Faces always offset by 90°
Installation of Screw Set Elements
Faces always parallelly
Last Update: 01.2003/by:MK19.16
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Profile Transitions
Profile A Profile B
Transition piece required- for profile joint (profile A to B- if the faces of identical profiles
are offset (kneading block)
Profile A Profile B
Risk of breakage
Last Update: 01.2003/by:MK19.17
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Transition Elements
• For technical fluidic reasons, but also to prevent mutual contact of the screws, a transition piece is necessary between different profile cross-sections, similar to that required for kneading blocks.
• Spacer rings, with the same outside diameter as the inside diameter of the screw elements, can be used instead of transition elements in some cases.
Last Update: 01.2003/by:MK19.18
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Part Numbers on the Screw Elements
No. of flights, direction1
2
3
4
5
6
9
1-channel, right
Special version
2-channel, right
3-channel, right
1-channel, left
2-channel, left
3-channel, left
3
4
6
9
30°
45°
60°
90°
Kn.block : 4 0 5
No. of discs
Offset angle
Pitch of conveying elements
-/- 0 6 01.-8 0 4 0 0 6 020 0 2 4
Connection Screw Elemnet/Shaft
00, 01, 02
66, 67, 68
24, 25, 34
Feather key (0°)
6-key
Involute SC
Other numbers available for special geometries.
34 MEGA-Compounder
Profile1
2
6
Screw element with sealing profile
Screw element with sealing profile
Kneading block
Element lengthScrew diameter
Material00
05
68
15
25
Nitriding steel
Cr steel
CPR-HSS steel
Wear and/or corrosion protected elements ofcomposite materials
37 CPR - composite material
Last Update: 01.2003/by:MK19.19
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Recognising Screw Element Materials
Corrosion and wear-resistantHIP - composite
25
15Standardwear protectionHIP - composite
Nitriding steelnitrified
Material no.
0005
Material Specif.
Last Update: 01.2003/by:MK19.20
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Recognising Screw Element Materials
10
28
Former standardwear protectionHIP - composite
Soft martensitichardened Cr-Nisteel with applied crest welding
Material no. Material Specif.
Last Update: 01.2003/by:MK19.21
19-ScrewElements.gb ...
Kneading (dispersing)
elementsKneading-
Mixing(homogenising)
elementsMixing
Conveyingelements
Conveying Pressure Barrier
Process Section
elementsLeft-handed
Principle of Operation of the Screw Elements
Last Update: 01.2003/by:MK19.22
19-ScrewElements.gb ...
Conveying Mechanism
1-flight elements
Reduced product flow from one screw tothe other. => improved transport capacity
2-flight elements
Main portion of the product flows from one screw to the other.=> lower transport capacity
Last Update: 01.2003/by:MK19.23
19-ScrewElements.gb ...
Principle of Operation of the Conveying Elements
Type of element Free cross-section
Conveying efficiency
1-channel elements
Standardelements
"Undercut" elements
Last Update: 01.2003/by:MK19.24
19-ScrewElements.gb ...
Filling Level of Conveying Elements
With decreasing pitch the free volume in the screw channel decreases, i.e. the filling level increases.
Last Update: 01.2003/by:MK19.25
19-ScrewElements.gb ...
Filling Level of Conveying Elements
• Normally conveying elements with a high pitch are installed below the feed inlet.
• The bulk material is compressed by the reduction in pitch in a downstream direction, i.e. as a result of reduction of the channel volume.
Last Update: 01.2003/by:MK19.26
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Type of element
Mixing effect
Conveyingeffect
Kneadingeffect(shearing)
neutral
standard
X°
X°
Type ofelement
Mixing effect
Conveyingeffect
Kneadingeffect(shearing)
wide vs. narrow: standard vs. neutral:
Merit comparison for different Kneading Blocks
Last Update: 01.2003/by:MK19.27
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Left-Handed Elements
product flow
p [bar] p [bar]
Last Update: 01.2003/by:MK19.28
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Left-Handed Elements
Last Update: 01.2003/by:MK19.29
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Principle of Operation of the Left-Handed Elements
Type of element Build-up effect
Right-handed screw elementwith low pitch
Neutral kneader block
Left-handed kneader block
Left-handed screw element
Last Update: 01.2003/by:MK19.30
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1re li re li re li re li re li
3
2
Residence Time
Time (sec)
Tra
cer
0 50 100 150
1
3
2with left and righthand KB
with righthand kneading block
without kneading block
Last Update: 01.2003/by:MK19.31
19-ScrewElements.gb ...
Recognising Screw Element Materials
Q: Which features can be used to recognise
the material of a screw element if the material
code on the faces of the screw elements has
become illegible with cleaning?
A: refer Chapter 19, slide 18ff