Machinery for metalliferous mines : a practical treatise for mining engineers, metallurgists and managers of mines by Davies E. Henry (Edward Henry)

Author:Davies, E. Henry (Edward Henry)
Language: eng
Format: epub, pdf
Tags: Mining machinery
Publisher: London : Crosby Lockwood ; New York : Van Nostrand
Published: 1902-03-25T05:00:00+00:00

THE WORKING OF JIGGERS.

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to time by the removal of a plug in the bottom. The compartment in which the pistons work is covered with a board (0) to prevent the violent splashing of the water, and is lined with thin boards, which take up the wear, and save the permanent sides of the machine. In the ordinary Hartz jigger the hutch or jigger box is 3 ft. 6 in. deep, and the size of the sieves 2 ft. 4 in. x i ft. 6 in.

The Working of Jiggers.—The object in dividing the jigger into a number of compartments is in order to obtain two or more products, as, for instance, when the ore contains both galena and blende the same jigger will effect their separation from each other, and the sterile gangue giving also a mixed product containing both the minerals, which must be sent back to be recrushed. The stroke of the piston of each compartment is regulated according to the work to be done; and for the same reason the composition of the " bed " of the jigger varies on each of the sieves. The speed also of each machine is varied according to the size of the material, the rule being the coarser the mineral the slower the speed, so that the speed will vary from 60 strokes per minute for 10 mm. stuff up to 300 strokes for the jiggers treating the fine sands from the classifiers. The speed at which the jigger is to run is decided upon when the mill is designed, but the stroke is adjusted by the foreman dresser or manager, according to the

mineral under treatment, and the amount of enrichment which it is desired to give to the ore. As a general rule, the length of the stroke must be sufficient to lift the ore through a height equal to the diameter of the grains, and the time between the strokes must be sufficient to allow the grains to settle. The end sought after is a stroke which will be just sufficient to lift up and open the bed of the jigger, and allow the rich grains of mineral to pass through ; while, at the same time, it drives off the lighter and poorer mineral into the next compartment.

If the stroke is too great it drives the rich ore over, and the steriles contain too high a percentage of metal; on the other hand, if it is not enough, the poor stuff falls through with the rich, and the percentage of metal in the concentrates goes down.

The following table will give an approximate idea of the length ol stroke and speed appropriate to jiggers treating ore from 10 mm. down to 3- mm. diameter. These figures, however, give only general dimensions, for practice with the kind of ore under treatment is the only

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