desserrage

CONT: The jigging cycle for coal may be represented as a sine wave ... in which water velocity is plotted against time. Starting from rest, the water commences to rise through the closely packed bed of coal with increasing velocity. Dilation of this bed begins with the loosening of the uppermost stratum. (In jigging coal it is possible to apply water so as to toss the whole bed solidly upward and then to allow it to open out upward and downward, but this is not feasible with heavy minerals.) As the water column attains a rising velocity of 100 mm./sec., the upper part of the coal bed opens and begins to teeter. Velocity continues to increase, and layer after layer opens until the whole bed is dilated and teetering. Then, as the pulsion stroke passes its peak, the velocity of the water lessens and the suction stroke begins.
CONT: Expansion of a jig bed.