Cover Image
close this book Tools for Mining
close this folder Technical Chapter 13: Classification
View the document 13.1 Set of rigid screens
View the document 13.2 Screen riddle, vibrating screen
View the document 13.3 Cantilever grizzly
View the document 13.4 Sizing drum, classifying drum
View the document 13.5 Cone classifier
View the document 13.6 Countercurrent hydraulic classifier
View the document 13.7 Hydro-cyclone
View the document 13.8 Log washer, spiral classifier
View the document 13.9 Rake classifier
View the document 13.10 Sluice, sluice box, washing sluice

13.9 Rake classifier

Deep Mining General

Beneficiation, Classification

germ.:

Rechenklassierer

span.:

clasificador transportador a rastrillo

Manufacturer:

Volcan, Eq. Ind. Astecnia, IAA, COMESA, FAHENA, MAENSA, FAMESA

TECHNICAL DATA:

Dimensions:

1.2 x 3.5 x 1.0 m HWD for a small rake classifier, working frequency 10 - 30 min-1, minimum angle of inclination 12 Weight: approx. 600 kg

Extent of Mechanization:

ully mechanized

Power:

1.5 PS

Form of Driving Energy:

mechanical via electric motor, internal combustion engine, turbine

Mode of Operation:

continuous

Throughput/Capacity:

0.5-1 t/h

Operating Materials:

 

Type:

water

ECONOMIC DATA:

Investment Costs:

minimum of 10.000 DM when locally produced

Operating Costs:

low, primarily energy costs

CONDITIONS OF APPLICATION:

Operating Expenditures:

low |————|————| high

Maintenance Expenditures:

low |————|————|high

Location Requirements:

none, except water

Grain Size of Feed:

high proportion of fine grains (0.1 - 0.5 mm) necessary to guarantee stability of the suspension. Only under these conditions can a rake classifier separate with high precision.

Special Feed Requirements:

30 - 50 % by vol. solids in the slurry

Output:

the classifying is regulated by controlling the slurry density

Replaces other Equipment:

spiral classifier

Regional Distribution:

very rare

Operating Experience:

very good |————|————| bad

Environmental Impact:

low |————|————| very high

Suitability for Local Production:

very good |————|————| bad

Under What Conditions:

national machinery manufacturers

Lifespan:

very long |————|————| very short

Bibliography, Source: Gerth

OPERATING PRINCIPLE:

In a declined trough, the coarse material is scraped upwards by a rake. At the return point, the rake is lifted, moved back down to the initial position and lowered onto the bottom of the trough. The fine material remains suspended and flows out over a weir at the lower end of the trough. The slurry-feed intake is located about a third of the way up from the lower end of the trough.

AREAS OF APPLICATION:

For intermediary classification of milled material in a closed grinding circuit.

REMARKS:

Very low wear, limited to the rake.

The rake has a very long lifespan due to the possibility to adjust its height. For lead-zinc ore, Gerth estimates a rake lifespan of approx. 30.000 t throughput (rake height worn from 60 down to 20 mm).

SUITABILITY FOR SMALL-SCALE MINING:

Rake classifiers are characterized by their simple construction and low wear' and are suitable for small scale mining if they can be nationally manufactured.


Fig.: Schematic diagram of a rake classifier. Source: Schmiedchen.


Fig.: Simplified elevation drawing of a rake classifier. Source: Schmiedchen.