Pre-Screeners GS 425 V, GS 500, GS 500 V, GS 850 The coarse screen units GS 425 V, GS 500, GS 500 V and GS 850 are used primarily as pre-screener units in combined large-scale de-sanding plants on tunneling and cutter diaphragm wall projects. The entire volume of the slurry intake is pre-screened by a coarse screen. The V-type coarse screen is adjustable in increments from a 25° downward to a 0° horizontal incline. The incline of the coarse screen is dependent on the type of soil material to be treated. The pre-treated slurry is then distributed equally via a flow controller unit to two standard de-sanding plants BE 250, BE 275 or BE 425 f or further treatment. The coarse screen units can also be deployed as stand-alone units for coarse screening (e.g. 5 mm mesh size).