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For conveyors used to move cement or aggregate in a concrete plant, divisions of conveyors are usually based on how the conveyor operates and what type of material it handles best. These three types of conveyors include belt, screw, and pneumatic, or air, conveyors. Belt conveyors are open systems that carry materials to a mixing bin. Belt conveyors best handle aggregates such as gravel, sand or stone. On the other hand, screw conveyors mainly handle fine, powdery materials such as cement or fly-ash. Flanges push the material inside pipes. Pneumatic, or air, conveyors are similar to screw conveyors in the materials they handle. However, rather than pushing materials, pneumatic conveyors use a low-pressure, high-volume air stream to blow the materials. Look for certain qualities to ensure that you are purchasing an efficient, reliable conveyor. Proper equipment and quality construction should be integral in any conveyor you purchase. Conveyor breakdowns must be kept to a minimum. Maintenance for conveyors includes greasing and checking parts and belts. Safety is a big concern when using conveyors. All conveyors should be equipped with emergency shut-off switches, start/stop warning horns and pinch point nip guards. Other safety features should include: well-marked, non-slip stairs; adequate lighting; guards on screw conveyors; easily accessible controls; and employee training seminars.