basics in mineral processing-wear in operation

8/8/2019 Basics in Mineral Processing-wear in Operation

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Product Handbook 9:1

Wear in operation

Wearin

operation

BASICS IN MINERAL PROCESSING

Introduction

Mineral processing activities unavoidably result in wear. And wear costs money.Often lots of money. This is related to the structure of rock, ore or minerals, beingcrystals normally both hard and abrasive.

Why wear at all?

Wear is caused by the normal rock stress forces Compression (1)

Impaction (2)

Shearing (3)

Attrition (4)

in combination with mineral hardness and energy!

Wear in operation

COMPRESSION

protected by

METALS

ManganeseSteel

SLIDINGIMPACTIONLOW VELOCITY 7m/s

Ni hardNi-Cr white iron

High CromeCr white iron

Polymers

Rubber

Polyurethane

CERAMICS

1 2

3 4

caused by


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COMPRESSION

Metals

ManganeseSteel




Wear by Compression

Applications:

Crushers

Gyratory

Cone

Jaw

Metals and compression

Manganese steel: The first option for compressionwear is manganese steel. This alloy has a very specialproperty, being self hardening and self healing whenexposed to large amounts of compression and impactenergy.Normal standard is a 14% Mn alloy which is firstoption in most crushing applications.18 % Mn alloy is a harder but also a more brittle alloyused in applications where the rock is softer (limitedself hardening) but very abrasive.

Restrictions:When installed in applications without work hardeningservice life will be poor!

The alloys of cast white iron type (High-chrome andNi- hard) shall be avoided in crushers submitted toheavy compression.

}

COMPRESSION

Metals

Manganese

Steel




Applications:

Impactors

Grinding Mills

Slurry Pumps

HSI

VSI

Metals and impaction

The metals can be classified as:

Manganese: Needs high impaction for selfhardening. If impaction is getting lower andsliding is increasing Manganese is not suitable.High Chrome: Opposite to manganese, cantake heavy sliding but is more fragile andtherefore limited against impaction.Ni-hard: Somewhere between the two materialsabove.Cr-Mo: Used in grinding when High Crome is toobrittle

Note! The use of chrome steel (less brittle thanchrome iron) is increasing for liners, curtainsand hammers.

}

Wear by Impaction (high)


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COMPRESSION

Metals

Rubber


Polyurethane

CERAMICS

Wear by Impaction (low)

Applications:Dump Trucks, Feeder hoppers,Transfer points, Grinding MillsSlurry pumps

Rubber and impaction

For low velocity impaction (material speedless than 7 m/s) SBR, styrene butadienerubber (60 ShA) is always the first choiceand will give the best cost effectiveness.The material is also very tolerant tomaterial size and is excellent for use ingrinding mills, dump trucks and primaryhoppers.

Restrictions:

Look out for aromatic and fuel oils.Impact angles have to be considered, see9:4.

COMPRESSION

Polymers

Rubber

SLIDINGIMPACTION

LOW VELOCITY 7m/s

Polyurethane

CERAMICS

Wear by Sliding

Applications:

Chutes, Spouts

Rubber and slidingNatural rubber is an outstanding option for thesliding abrasion of small, hard and sharpparticles. Also for wet conditions.

Restrictions:If sliding speed is exceeding 7 m/s (dry appli-cations) temperature can start to rise andcause damage. Besides temperature oil isalways a threat.

Polyurethane and slidingBest option for tough sliding applications whenparticle size is lower than 50 mm. Excellent inwet applications. Tolerant to chemicals and oil.

Restrictions:Large sizes and high velocity might cause problems.

Ceramics and slidingThe natural choice when mission is too hard for the options above. Hardness,

resistance to temperature and corrosion plus low weight gives a masterpiece forsliding.Al203 (Aluminium oxide) is the most cost-effective material.

Restrictions:Impaction is dangerous for ceramics (cracking) and must be avoided. Combinationceramics + rubber is an option. Composition and quality can vary from supplier tosupplier.


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Wear Protection Wear Products

Modules

Rubber modulePolyurethanemodule

Ceramicmodule

Sheets, elements and profiles

Customized lining systems

>1000 >500 >100 >80 64 32 22 16 11 8 4 0 Size mm

100 micron

HEAVY IMPACT

IMPACT & SLIDING

SLIDING & IMPACT

SLIDING/ BUILD UP

Elements Rubber

Square Modules Rubber Polyurethane Ceramic

Sheeting Rubber Polyurethane

Low Friction

Wear products applications


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100 micron

Heavy Impact Selection

Truck Box

Primary FeederHopper

Thickness

Rubber 60 Sh

Steel Backing

Size / Weight

Drop Height

=

&

Impact and Sliding Selection (modules)

>1000 >500 >100 >80 64 32 22 16 11 8 4 0 Size mm

100 micron

>1000 >500 >100 >80 64 32 22 16 11 8 4 0 Size mm

Impact angle

Capacity

Size / Weight

Drop Height

&

&

&

Ru

Pu

Ceram


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Impact and sliding Selection (sheeting)

>1000 >500 >100 >80 64 32 22 16 11 8 4 0 Size mm

100 micron

Impact angle

Capacity

Size / Weight

Drop Height

&

&

&

=

Sliding and build up selection

>1000 >500 >100 >80 64 32 22 16 11 8 4 0 Size mm

100 micron

Thickness

MATERIAL THICKNESS

mm mm


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Wear Protection Wear Parts

Wear parts Screening

Self supportingrubber panels

Rubber & polyurethanetension mats

Rubber & polyurethanebolt down panels

Antiblindingrubber mats

Rubber / polyurethanemodular systems

Rubber linings Poly-Met TMlinings OrebedTMlinings

Steel linings Discharge systems Trommel screens

Wear parts Grinding


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Tumbling mill lining components

Lining life time Standard Liningsball park figures

Type of mill Months

AG 12 24

SAG 3 12

Rod 6 24

Ball 6 36

Pebble 12 48

1. 2. 3. 4. 5.

6. 7. 8. 9. 10.

Lifter bars rubber and compound

Autoge

nousandSemi-autogenousMills

PrimaryBallMills

RodMills

Seconda

ryBallMills

R

egrindandPebbleMills

Rubber Poly-MetHiCr HB 700

Poly-MetHiCr HB 700

OwerflowBall

andRodMills

AutogenousM

ills

Poly-MetMartensitic steelHB 500

SemiAutogenousMills

higherspeeds

lowerspeeds

higherspeeds

lowerspeeds

= mill rotation


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AG and SAG mills Rod mills

Dry: Metal (white iron700 Br)

Wet: Metal (white iron700 Br)or Poly Met (700 Br)

Dry: Metal (Cr-Mo350 Br)

Wet: Metal (Cr-Mo350 Br)or Poly Met

(500 Br)

Dry: Metal (white iron 700 Br)Wet: Metal (white iron 700 Br)

Rubber and Poly Met,(Poly Met at mill ends)

Dry: Metal (or rubber if temperaturenot critical)

Wet: Rubber (Secondary and re-grind) Poly Met (700 Br)

Dry-rod: Metal

Dry-ball: Metal (or rubber iftemperature not critical)

Wet-rod: Metal

Wet-ball: Rubber

Tumbling mill liners material

Ball and Pebble mills SRR mills

VERTIMILL Liners

Screw metal with Nihard linersChamber Orebed magnetic liner


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Wear parts Slurry Pumps

Although the size of solids in a slurry is smaller than the feed size to a crusher ora grinding mill, wear represents a high operation cost for slurry pumping. This isnaturally related to the high dynamic energy input in the form of high tip speed ofthe pump impeller causing both sliding and impaction wear.

Wear material vs size

Wear parts pumps metal

High chrome iron (600Br) can be used at Ph down to 2.5. Standard wear materialfor most pump ranges.

Ni hard with hardness exceeding 600 Bn used mainly as casing material forpumps in grinding circuits or dredging.

High density frozen Ni-hard with hardness up to 900 Bn used as casing materialin primary grinding circuits.

Manganese steel with hardness up to 350 Bn used for dredging applications.

Size 1m 1 dm 1 cm 1 mm 100 micron 10 micron 1 micron

LIMITFORHYDRAULICTRANSPORT

HIGH CHROME

LIMITFORHARDIRONS

LIMITFORRUBBERLINERS

LIM

ITFORRUBBERIMPELLERS

MANGANESESTEEL


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Material Physical Chemical Thermal

properties properties properties

Max. Wear Hot water, Strong and Oils, Highest service

Impeller Tip resistance diluted acids oxidising hydro temp.(oC)

Speed acids carbons Contin. Occasion.(m/s)

Elasta family 27 Very good Excellent Fair Bad (-50) to 65 100

(Natural rubber)

MeroPrene 452 27 Good Excellent Fair Good 90 120

(Chloroprene type)

MeroLen 016 30 Good Excellent Good Bad 100 130

(EPDM type)

MeroTyle 30 Fair Excellent Good Bad 100 130

(Butyl type)MeroThane 30 Very good Fair Bad Good 45-50 65

Polyurethane

Wear parts pumps elastomers

Something About Ceramic Liners

Although ceramics have high resistance against wear, temperature and mostchemicals, they have never really been accepted as day-to-day standards inSlurry Pumping.

Being both brittle and expensive to manufacture.

Development work on ceramics continue in an attempt to improve the possibleacceptance.


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Wear in Slurry Pipelines

It is not easy to compare wear rates for different materials in a slurry pipelinedepending on variations in duty. As a guide the figures below can be used (BritishSteel Corporation test report).

Average wear rates given as loss of material in mm per hour at a given speedand slurry composition.

Material Average Relative wear ratewear rate (months)

Polyurethane 0,024 19,0

Rubber 0,033 13,8

Stainless steel 0,056 8,1

Alumina (97.5%Al2O3) 0,070 6,5

Cast iron

(2.8% C, 2.0%Cr, 3.8%Ni) 0,287 1,6

Polyethylene 0,353 1,3

API steel 0,396 1,2

Mild steel 0,456 1,0

PVC 0,880 0,5

basics in mineral processing-wear in operation

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