Gravel-washing Machine

a machine for washing gravel or ballast to remove impurities (such as clay and organic inclusions). Gravel-washing machines are divided into drum and trough (cam) types.

Drum gravel-washing machines are for washing gravel with pieces up to 150 mm in size; the drum is driven by an electric motor. The inner surface of the drum has directing blades; at one end there is a feed hole for the material and at the other a discharging hole, through which tubes supply water and washed material is discharged. The running water carries the impurities through the charging hole. The output of drum gravel-washing machines is 40–200 cu m/hr, with a drum diameter of up to 2,500 mm. In some designs, gravel washing-machine drums are fitted with additional sorting devices with perforated surfaces on which the material is fractionated.

Trough, or cam, gravel-washing machines are used to wash heavily contaminated materials with piece sizes up to 100 mm; these machines consist of rectangular inclined troughs with blade-equipped shafts rotating in them to mix the material; water flowing against the movement of the material carries off the impurities. The output of trough gravel-washing machines depends on the size and running conditions and is 10 to 125 tons/hr.