A scraper flight / drag conveyor consist of a series of metal. Wood, or plastic flights attached at uniform intervals to one or two strands of endless chain which moves the flight along in a trough, the chain or chains passing around sprocket at the end of the trough. The flights push or slide the material along, therefore abrasive materials should not be handled by this type of conveyor, unless the speed of conveyor is very low, Material can be discharged at any point along the trough through gates or at the end of the trough. In a drag conveyor the chain itself act as a scraper.
There are many variations of flight conveyors handling bulk materials such as coal, dry sewage sludge, dry wood chips, and other nonabrasive, free flowing and fairly dry materials. Every cannery uses a form of scraper flight conveyor for moving to refuse bin or boiler such materials as string beans, ears of corn before husking and mush waste. Sugar producer plants use a double strand of roller chain with steel flight to remove bagasse from mill to furnace.
Material such as coal is pushed along the trough by the flight which actually bottoms itself in the trough ( scrapes in the bottom of trough).
Single Strand flight conveyor, Double strand flight conveyor with roller suspended flights.