Sludge thickeners, either bridge supported or pier supported will typically include pickets and dropped (hung) flights.

The RS Thickener mechanism consists of two fabricated steel arms supported from a central rotating drive cage. The cage is suspended from an enclosed spur gear drive turntable unit which, in turn, is supported on the center pier. The driving unit consists of a special primary double reduction worm gear unit driven through a steel roller chain connected to a gear motor with all-weather construction.

For greater flows and the resultant larger basins, higher torque capacities, a spur gear driven pier-supported collector is best applied. Walker Process pier-supported collectors are built around a center pier which supports the entire rotating portion of the machine plus half of the access bridge load. In addition to providing support, the pier resists the torque developed by the collector's sludge plowing action.

Bridge-supported collectors have as their basic support a bridge that spans the entire clarifier basin diameter.  The entire rotating mechanism is supported mid-span by the bridge that must be designed to limit deflection to less than ½ inch to prevent the scraper arms from contacting the floor.

Bridge supported collector mechanisms may be designed with Segmented Plow type scrapers, Spiral Rakes, Tapered Suction Headers, or SightWell type sludge removal arrangements.