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Introduction to Wear in
Solids Handling SystemsFundamentals: Controlling: Predicting
Dr Pablo García-Triñanes
Wolfson Centre for Bulk Solids Handling Technology
Faculty of Engineering and Science
University of Greenwich, UK
Wear in Solids Handling Plant
Principal effects:
• Unplanned maintenance
• Process downtime
• Iron in product
• Mess from spillage
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Types of Wear
Two distinct types in solids handling plants:
• Erosion (erosive wear)
– From particles hitting a surface
• Abrasion (abrasive wear)
– From a bed of particles sliding along a surface
• May occur together
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Wear in Solids Handling Plant
Erosion:
• Impact of particles on surface from a stream of bulk
solid, for example in:-
– Pneumatic conveyors
– Transfer points between belt conveyors
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Wear in Solids Handling Plant
Abrasion:
• Sliding of a body of particles against a surface, for
example
• Hoppers (Silos/bins/bunkers)
• Chutes
• Screw and drag chain conveyors.
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion Example - Pipeline Wear
• Usually most severe
at bends
Puncture point
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Bend wear
in pneumatic
conveying
With erosive products:
• Hard
• Angular
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Impact erosion of solids handling equipment
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Effect of Velocity
Erosion = k . (particle velocity)n
where
k = a constant
n = a power; 2.2 to 2.8 for most materials
Example: +25% velocity
leads to + 60% to +90% wear!
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Other Variables
Solids concentration - e.g. dilute versus dense phase
Number of changes of direction - bends, transfer points
Geometry of impact - e.g. radius, shape of bends or
impact zone
Material properties - impact zone and particles
Quality of pipe fitting
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Dilute phase conveying
Particles suspended in air flow
(typical air velocity 15-20 m/s)The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Particle Properties
Increased erosion results from:
• Harder particles
• More angular particles
• Larger particles - up to about 200 microns
• Abrasive inclusions in soft particles
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Material Properties
• Hardness of surface not a good guide
• Different materials respond differently to angle of
impact
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Effect of Angle
• Brittle response
– ceramics
– glass
– rock
Erosion
rate
Angle of attack, alpha 90
(Normal
impact)alpha
0
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Effect of Angle
• Ductile response
– steel
– most metals
Erosion
rate
Angle of attack, alpha 90
(Normal
impact)alpha
0 30
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Effect of angle
• Elastomers
– rubbers
– polyethylene
Erosion
rate
Angle of attack, alpha 90
(Normal
impact)alpha
0
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Prediction of wear rate
• Laboratory scale erosion test
– Samples of bulk solid and surface material
– Velocity, angle, concentration comparable to
real system
• E.g. rotating disc tester
• Scale material loss to real system
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
EROSION - Centrifugal erosion tester
• Kleis (Tallinn)
• Soderberg (Trondheim)
• Burnett, Deng (Greenwich)
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Impact wear
tester
Centrifugal feed of material to impact
targets
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Protection techniques I
Minimise impact velocity
– For example, with velocity exponent of 2.6
– Reduce velocity
from 18 to
12 m/s (33%)
– Erosion reduced
by 65%! 0
0 10 20 30
Ero
sio
n r
ate
Impact velocity m/s
E=k.v2.6
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Protection techniques II
Select “wear resistant” material carefully
• Elastomers for high angle impact
– Rubber
– Polyethylene
• As an impact zone liner
• Or as a hanging curtain
– Weight important
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Protection techniques III
• Ceramics for low angle impact
– Fused alumina
– Cast basalt
• Erosion tests!
– To identify most cost-effective material
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Protection techniques III
Retain particles in impact zones
– “Dirt box” in transfer point
– Can compromise flow
– “Blind tee” bend in
pneumatic conveyor
– Gives high pressure drop
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Erosion - Protection techniques IV
Sacrificial protection
– Expendable liner
• Simple shape
• Cheap to make
• Easily changed
• Must check it regularly!
– Choose steel carefully
• Hardness not a guide
• Erosion test needed
– Extra thickness “wear back” locally
• Erosion test to identify thickness
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Abrasion
• Sliding of bulk solid against surface
• Abrasion rate
A = k.p.v
• Found in
– Silos
– Chutes
– Mechanical conveyors
– “Hood and spoon” transfers
Velocity v
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Abrasion - Prediction of Wear Rate
• Laboratory abrasion testers
– Press bulk solid against surface at controlled
pressure
– Sliding at known velocity
• Scaling for velocity and pressure is reliable
– Can test at accelerated abrasion rate
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Abrasion - Laboratory testers
• Linear Abrasive Wear Tester
– Roberts (Newcastle), Mengistu (Greenwich)
• Test at increased velocity and scale down
• Many other types
Force applied
by dead load
Test material
Velocity v
Bulk solid in
feed hopper
Conveyor belt
Bed of bulk solid
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Sliding Abrasion Wear Test
Rotating annulus of test material and wear sample
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Abrasion - Protection I
• Difference in hardness a key factor
– if Hsurface > 1.2 x Hbulk solid, no wear
– if Hbulk solid > 1.2 x Hsurface, significant wear
– Greater difference, greater wear
– More angular particles - greater wear
• Select surface harder than bulk solid
– Hard steel (for some bulk solids)
– Hard-faced steel (but care with surface finish and high friction)
– Ceramics e.g. alumina, basalt
– Hard materials difficult to work!
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Material options for abrasive wear resistance
• Austenitic Stainless– 304 or 316
– Significantly better than carbon steel against corrosion-erosion (eg damp conditions)
– Limited abrasion resistance
– Can bend and fabricate easily
• Maternsitic stainless– Significantly harder, so better abrasion resistance
– Hard to bend and fabricate
– Air-hardening (e.g. 420) cracks when welded
– Quench-hardening softens when welded
• Low alloy/high carbon– Harder, but susceptible to corrosion
– Poor under wet abrasion conditions
– Softened by welding
Material options for abrasive wear resistance II
• Clad plate– Mild steel with surface of chromium-carbide hard facing
welded on
– Mild steel backing can be welded
– Hard facing not much softened by welding
– Cannot be bent much
– Surface not smooth – high wall friction
• Alumina ceramics– Very hard
– Brittle
– Not impact resistant
– Stick-on tiles
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Abrasion - Protection II
• Lubrication reduces wear
– Wet abrasion usually less
– Not if corrosion can result (corrosion and abrasion
have synergistic effect!)
• Sacrificial protection
– Cheap replaceable liner (Check regularly!)
– Additional wear allowance determined from test
• “Dirt box” technique (retained particles)
– Cheap
– Can compromise flow
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Wear in Solids Handling Plant
SUMMARY
• Two main phenomena
– Impact EROSION
– Sliding ABRASION
• Rates of wear depend on
– Bulk solid properties (hardness, angularity)
– Surface properties (toughness, hardness, elasticity)
– Conditions of interaction (impact angle, velocity,
concentration, contact pressure)
The content of this presentation is proprietary and confidential information of the Wolfson Centre for Bulk Solids Handling Technology (University of
Greenwich, UK). It is not intended to be distributed to any third party without the written consent of Wolfson Centre for Bulk Solids Handling Technology
(University of Greenwich, UK)
Wear In Solids Handling Plant
SUMMARY (cont’d)
• Protection
– Choice of material at impact site
• Many factors to consider
• Wear testing an essential guide
– Sacrificial protection
• Wear allowance, replaceable liner
– Geometry
• Optimise angle for material in use
• Retain particles
www.bulksolids.com
For further questions contact:
Dr Pablo García-Triñanes
Wolfson Centre for Bulk Solids Handling Technology
Faculty of Engineering and Science
University of Greenwich, UK