A powder conveyor is a specialized material transport mechanism that is designed specifically to move fine powdered materials within manufacturing, storage or dispatch installations. Although powdered loads can be — and often are — transported with conventional belt-type conveyors, realities such as potential contamination of loads or the environment, dust generation and explosion hazards usually dictate that specialized conveyors are used for these materials. Some of the more common powder conveyor types include pneumatic, aeromechanical and screw-type systems. Disc chain and bucket elevator systems are also often used to move powdered materials. Although most of these systems differ considerably from one another, they do share some similarities, such as sealed transport chambers and relatively low transport speeds.
Powered materials usually are challenging to transport within manufacturing, storage and distribution facilities. This is particularly true of very fine aggregates, food stuffs and hazardous materials. Loads might become contaminated or cause contamination of the environment through spillage, and dust generation from open powdered loads is always an issue. In fact, even the dust from apparently inert materials, such as flour, can pose serious risks to operators' respiratory health and, under certain circumstances, might explode if it is inadvertently ignited. For these reasons, conventional belt conveyors are seldom used to transport finely powdered materials because there are specialized powder conveyor systems that reduce all the risks inherent to the transport of powders.
There are many types of powder conveyor on the market, all specifically designed to transport fine materials safely and efficiently. One of the most common of these is the screw conveyor. Based on the Archimedean screw design, these powder conveyors are ideal for transporting these materials over fairly short, straight routes, particularly on steep gradients. Consisting of a coarse screw thread designed element that rotates in a sealed cylinder, the screw powder conveyor is also one of the more simple and reliable types. As the screw element rotates any material, including fluids, placed in the tube, it is moved forward to the discharge point in the advancing spaces between the individual threads.
Another common type of powder conveyor is the pneumatic conveyor. Air is pumped out of a sealed transport tube, creating a vacuum that draws any material placed in it along its length. Aeromechanical conveyors work on a similar principle and consist of a series of discs strung along a cable, and the discs travel at high speed in a sealed tube. As the discs move through the tube, they create an airflow that transports the powder along the tube. Both of these types feature fairly high transport feed rates.
Disc chain powder conveyors closely resemble the aeromechanical conveyor with a string of discs on a centrally located chain in a sealed tube. Unlike aeromechanical conveyors, however, they mechanically lift the material in the spaces between the discs and carry it along the tube to the discharge point. Another fairly common powder transport method used to lift fine material vertically is the bucket elevator. These systems feature a series of closely spaced bucket containers on a endless, rotating vertical belt. As the belt rotates around the lower pulley, the buckets pass through the powder store at the bottom of the system, filling them and carrying them to the top of the assembly, where they are discharged as the belt travels over the top pulley.