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Module 2bHow machinery factors affecting crusher performance

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The major machinery influences on crusher performance, which are

1. setting

2. throw

3. chamber volume

4. speed

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Crushing concepts Machinery factorsWhat are we about to examine

Jaws Cone HSI VSI

Chamber Limited by plate

profile

Various & many Limited by position of

curtains and setting

on bottom curtain.

Different depth rotors

Throw Limited Various & many X X

Speed Limited Yes Yes Yes

Setting Yes Yes Yes X

Other Nip Angle Automation X Bi-Flow operation

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Crushing concepts Machinery factorsControl features

Nip Angle

Width

Gape

Flywheel speed

What features can be changed?

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Crushing concepts Machinery factorsJaw crushers Control features

What machine factors can be used to adjust the performance of a jaw crusher?

Closed side setting (C.S.S.)

Jaw plate tooth profiles

Speed

Stroke

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Crushing concepts Machinery factorsJaw crushers Control features

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All other parts in the crusher are ”only” there to hold the chamber in place or to create movement of the mantle.

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Crushing concepts Machinery factorsCone crushers Chambers

All crushing starts

with the chamber!

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Crushing concepts Machinery factorsCone crushers Why so many chambers?

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Which loaded EC chamber will produce the best performance

Should both feeds be fed to the same chamber?

Consider volumetric capacity

Consider mechanical advantage

Consider wear profiles

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Crushing concepts Machinery factorsCone crushers Why so many chambers

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C.S.S. reduction

Smaller volume in the crushing chamber

Risk of packingLower capacityHigher pressure

Higher energy consumption

Improved shape

Finer product

Higher net capacity

More power

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Crushing concepts Machinery factorsCone crushers CSS Consequence map

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Eccentricity Eccentricity

Increasing the eccentric throw-more energy to the material-more capacity-more nett product

MainshaftEccentric bush

Eccentric

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Crushing concepts Machinery factorsCone crushers Throw Altering the eccentric throw

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Small throw

Eccentric throw

Increased average chamber volume Large throw

Increased throw resulting in increased chamber volume results in• higher capacity• more stones in the chamber to compress

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Crushing concepts Machinery factorsCone crushers Increased throw Larger avarage volume

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Throw increased

More crushingstone-against-stone

Packing riskHigher capacity More power needed

Higher powerconsumption

Improved shapeHigher net capacity

Largeraverage setting

Higher flow Higher torqueIncreased

compression

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Crushing concepts Machinery factorsCone crushers Throw alteration Consequence map

1. Best results are achieved when the optimum chamber is fitted to the crusher.

2. The optimum throw has a major influence on obtaining best results

1&2 are volumetric issues and may well determine the utilisation of the crusher ---remember all crushers work best when continuously choke fed

3. The crusher setting has an effect on both volume and reduction.

4. Is the feed condition correct—have you removed the risk of packing

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Crushing concepts Machinery factorsCone crushers Take home message

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

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Crushing concepts Machinery factorsTake home message