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Powerscreen develop density separator

The MDS 4 mobile density separator is the latest addition to Powerscreen’s range of screening, washing and recycling machines.

Capable of treating all types of materials through its vibratory feed trough and four-stage process, the MDS 4 is designed to produce more saleable products from recyclable waste. It is suitable for existing operators of trommels for cleaning up after fines separation; for three-way-split screen plant owners for cleaning after or before crushing and prior to sizing; and for the separation of glass and plastic from compost. The density separator is also targeted at waste-transfer and sorting stations where it can replace manual picking.

The MDS 4 uses a completely dry process to separate heavy and light material. The four stages of the treatment process begin with the waste being agitated to free agglomerated materials and to spread the waste evenly across the feeder tray.


Stage two is a fluidizing process where the material passes over a short perforated screen which causes lightweight material to rise to the top, the heavier material remaining in contact with the vibrating trough.

Stage three sees the material being passed across an air knife, immediately after the fluidization section, which produces a high-velocity low-pressure air stream. This air stream is angled to blow the lighter material across a ‘drop-out’ gap while the heavier material carries on down the discharge chute.

Stage four provides a secondary separation process where the marginal material passes over the chute gap and is caught on an adjustable sloping plate which causes the heavier material to fall back and the lighter particles to be conveyed forward for discharge and stockpiling.

The MDS 4 has an operating weight of 8.5 tonnes and transport dimensions of 6.59m long x 2.75m wide x 4m high. The power unit is diesel/hydraulic with a Deutz F4L1011F diesel engine developing 44kW.

The screen unit and fan consists of an input target area of 0.95m x 1.52m. The hydraulic direct-force vibratory separator drive rotates at 960 rev/min and comprises two 238 eccentric contra-rotating shafts. The impeller-type fan rotates at 2,960 rev/min and produces an air volume of 10,500ft3/min. The discharge conveyor, which can be mounted either side of the machine, is 650mm wide and fitted with a three-ply chevron belt and a direct-drive system. Stockpile height is 2.35m, providing a volume of up to 19.33m3.

For road transportation, the single axle has 235/75 R17.5 dual wheels, leaf-spring suspension and air brakes. Once on site the MDS 4 can be set up and operational in under 5min.


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