Sandvik Construction 1 A world leader in Construction Module 2a How material factors affecting crusher performance

2 Protective Equipment Assembly Point Emergency Exit Emergency Number Alarm 2 Safety is our top priority Safety first Sandvik Construction

3  What are the major influences?  From material factors?  From equipment/mechanical factors? Crushing concepts Raw materials What do we really know about crushing?

The major influences on crusher performance.  material factors such as 1.toughness, 2.bulk density/particle size distribution 3.reduction ratio 4.not discussed here –but abrasivity has a long term effect. Sandvik Construction 4 Crushing concepts Raw materials What are we about to examine?

 Rock is crushed when the strength of the rock particle cannot absorb the strain energy applied by the crusher and the rock deforms beyond it’s plastic limit to ultimate failure.  Rock needs to be breakable!!!!!  Plastic fines in the chamber will become compacted and absorb energy without deformation and failure. Sandvik Construction 5 Crushing concepts Raw materials Why do we need to know about the material properties?

 The toughness of the rock is one factor affecting the performance of the crusher.  it will determine the power drawn by the crusher from the motor or engine and therefore will determine the minimum setting at which the crusher will operate and give satisfactory mechanical reliability.  all crushers have a maximum mechanical design limit related to the maximum power they are permitted to absorb.  it will determine the capacity.  The abrasivity of the rock will affect the liner life and the performance of the crusher over a period of time.  The grain structure will influence the way in which the rock fractures and therefore the cubicity of the end product. Sandvik Construction 6 Crushing concepts Raw materials Why do we need to know about the material properties?

 Igneous  molten rock becomes solid  Sedimentary  weathered rock deposited in water  makes up 75% of he Earth’s surface  Metamorphic  existing rock changed by heat and pressure Volcanic rocks: Basalt, Andesite, Obsidian Intrusive: Diabase, Porphyry, Porphyrite Deep: Granite, Diorite, Gabbro Medium grained: Sandstone Fine grained: Limestone, Greywacke Limestone Marble Quartz sandstone Quartzite Granite Gneiss Sandvik Construction 7 Crushing concepts Raw materials

Impact Work Index (WI) Description of the Crushability < 10Very soft 10 – 14Soft 14 – 18Medium 18 – 22Tough 22 – 26Very tough > 26Extremely tough Abrasion Index (AI)Description of the Wear < 0.1Very low wear 0.1 – 0.2Low wear 0.2 – 0.4Intermediate wear 0.4 – 0.6Normal medium wear 0.6 – 0.8High wear > 0.8Extremely high wear Sandvik Construction 8 Crushing concepts Raw materials Work Indices Abrasion Indices

MaterialWIAICompressive strength (Mpa) Amphibolites Andesite Basalt Diabase Dolomite12< Diorite Gabbro Greywacke MaterialWIAICompressive strength (Mpa) Gneiss Granite Limestone11< – 180 Marble12< Quartzite Sandstone Iron ore (Hematite) Iron ore (Magnetite) Sandvik Construction 9 Crushing concepts Materials Average values

From raw material shotpile to product stockpile requires reduction Sandvik Construction 10 Crushing concepts Raw materials Reduction

Sandvik Construction 11 Crushing concepts Raw materials Particle size distribution

Sandvik Construction 12 Crushing concepts Raw materials Particle size distribution

Size (mm) % passing Max sieve size = 90mm/100mm for practical laboratory screening Above 90mm by estimation/photo analysis Sandvik Construction 13 Crushing concepts Raw materials Particle size distribution

Sandvik Construction 14 Crushing concepts Raw materials Particle size distribution

40  Fine Blasted Rock  F80  13% less than 40mm Sandvik Construction 15 Crushing concepts Raw materials Particle size distribution 13

70mm 350mm Reduction Ratio: F80/P80 350/70=5.0 70mm Reduction ratio A ratio recognising the reduction in size of a material when passed through a crusher. F80: the size at which 80% of the feed will pass P80: the size at which 80% of the product will pass Sandvik Construction 16 Crushing concepts Raw materials Reduction

Normal reduction: Jaw crusher 2-3 Gyratory crusher 3-4 Cone crusher 3-5 Impact crusher (VSI) (F50/ P50) 4-6 Impact crusher (HSI) 7-10 Sandvik Construction 17 Crushing concepts Raw materials Reduction

F 80 Feed: 400 mm P 80 Products: 16 mm Min. required plant reduction ratio: Using reduction ratio to predict required no. of crushing stages  2-stage Impact Plant: 10x7=70 OK, Only for Ai <0.3  2-stage Jaw/cone Plant: 3x4=12 NOT OK  3- stage Jaw/cone Plant 3x3x4=36 OK Sandvik Construction 18 Crushing concepts Raw materials Reduction

Sandvik Construction  Increased crushing force and power draw  Coarser product size  Lower capacity Tougher rock Increased moisture content 0 0,2 0,4 0,6 0,8 1 1, Moisture content (%) Capacity Jaw crusher, CSS 100 mm Jaw crusher, CSS 50 mm Cone crusher, CSS 20 mm Cone crusher, CSS 10 mm  Lower capacity 19 Crushing concepts Raw materials What happens if other properties change?

Sandvik Construction Smaller feed size Capacity up Finer product Better shape Bulk density increases Capacity increases but a higher risk of packing due to compression limit Packing 20 Crushing concepts Raw materials What happens if other properties change?

Sandvik Construction %passing size (mm) Two particle size distribution curves with the same specific gravity. Both curves can be described as 28 x 0mm. Curve 1 has approx. 48% < 10mm. Curve 2 has approx. 24% < 10mm. Curve 1 has the higher bulk density since there are less voids. Curve 2 Curve Crushing concepts Raw materials Compression limit

1,9 1,8 1,7 1,6 1,5 1, mm 4-32 mm 8-32 mm mm mm 0-11,2 mm 4-11,2 mm 8-11,2 mm Bulk density (t/m 3 ) 2,65 t/m3 specific gravity Bulk density increases - higher risk of packing as feed becomes finer. Bulk density- a combination of Specific gravity & particle size distribution Specific gravity increases from 2.65 to capacity increases by 20.75% Sandvik Construction 22 Crushing concepts Raw materials Compression limit

23  Packing in the chamber is caused when there are no voids for the newly crushed fines to move into. This results in the crusher trying to compress the material back together again.  The result of packing is extreme crushing pressure surges which will require the setting to open and allow the pack material to leave the chamber. Cone crusher’s are measured on both power and pressure. Any major spike in either will result in the opening of the chamber to relieve the overload. Sandvik Construction Crushing concepts Raw materials Compression limit Packing

Sandvik Construction More cubical shape Rounder shape Faster flowHigher capacity Improved feed particle shape 24 Crushing concepts Raw materials What happens if other properties change?

 Toughness.  Feed size.  Particle size distribution and specific gravity.  Bulk density.  Feed shape.  Volume crushed.  Moisture  Clay content Sandvik Construction 25 Crushing concepts Raw materials Summary

Machinery factors such as 1.setting 2.throw 3.chamber volume 4.speed Sandvik Construction 26 Work done(energy)=volume x toughness x reduction ratio Crushing concepts Raw materials Cone crushers Summary Work done Material factors such as 1. toughness. 2. feed size---product size. 3. particle size distribution and specific gravity---bulk density---volume crushed. 4.feed shape---moisture---clay content--- flowability.

All crushers have a volumetric and a mechanical limit Toughness of material, feed material particle size analysis, volume and reduction ratio all play their part in the ability of the crusher to perform the duty over an acceptable lifecycle. If any combination of these factors overstress the mechanical capability of the crusher (demands too much energy from the motor) it will be necessary to reduce the influence of another. Eg. The demand for greater throughput at the expense of reduction. Work done(energy)=volume x toughness x reduction ratio Sandvik Construction 27 Crushing concepts Raw materials Take home message

Sandvik Construction 28 Sandvik Construction A world leader in Construction