Thickeners traction drives

Design Features There are three classes of thickeners, each differentiated by its drive mechanism (1) bridge-supported, (2) center-column supported, and (3) traction drives. The diameter of the tank will range from 2 to 150 m (6.5 to 492 ft), and the support structure often is related to the size required. These classes are described in detail in the subsection Components and Accessories for Sedimentation Units. ... 

Drive-Support Structures There are three basic drive mechanisms. These are (1) the bridge-supported mechanism, (2) the center-column-supported mechanism, and (3) the traction-drive thickener containing a center-column-supported mechanism with the driving arm attached to a motorized carriage at the tank periphery. 

Thickeners may vary from a few metres to several hundred metres in diameter. Small ones are made of wood or metal and the rakes rotate at about 0.02 Hz (1 rpm). Very large thickeners generally consist of large concrete tanks, and the stirrers and rakes are driven by means of traction motors which drive on a rail running round the whole circumference the speed of rotation may be as low as 0.002 Hz (0.1 rpm). 

The last common configuration of the conventional thickener is the traction thickener. The movement of the rake mechanism is provided here by a single long arm, pivoted round the centre column and driven by a drive trolley which travels on a peripheral rail around the basin. Such units exist from 60 to 130 m in diameter. 

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