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A sand conveyor is any device that moves sand from one place to another. Generally, there are two different types of systems that are commonly called sand conveyors: screw conveyors and bucket conveyors. Both types of conveyance systems are used in a wide range of industries to move things other than sand, but they can also move the fine particles without suffering clogs or adverse wear. A third type of specialized belt system is also used as a sand conveyor, but this is a much less common device.
The most common sand conveyor uses a giant screw inside a tube. One end of the tube is inside the sand that needs to move. As the screw turns, it pulls sand up from the pile and traps it between its teeth. This causes more sand to fall into the position of the moved material so the screw can just pull it up again. This eventually results in the screw containing a continuous coil of sand.
The major drawback for using a screw as a sand conveyor is finding a reasonable angle. The closer the screw can get to perpendicular to the ground, the more efficient it operates. A tube that is straight up operates at almost double the efficiency of one on its side. This means that the screw is only practical if the situation works with it.
Bucket conveyors are the second major variety of sand conveyor. This style has a huge amount of variation in appearance, but the principle behind all the different types is the same. A continuous system, typically a belt or chain, is connected to a series of individual scoops. Each of these scoops will travel from one end of the conveyor to the other and then back to the beginning. The scoops might be nothing more than dimples in a flexible belt or can be as complex as self-contained and sealable containers.
There are two common drawbacks to bucket conveyors. In order to keep material in the bucket, the conveyor must operate at a set angle. Most of these systems have only a few degrees of variation in their setup. The other major problem is the return step. A small bucket is easy to send back to the start, but a larger bucket takes up a great deal of space on the return leg.
Occasionally, a specialized belt system will operate as a sand conveyor. This device has a belt similar to the conveyors seen in airports and supermarkets, but it is covered in hair-like rubber strings. These will capture the sand and keep it from sliding off the belt. These systems can work at any incline provided the hairs are long enough to keep the sand from sliding. Their biggest drawback is their specialization; while the other conveyor types can move other materials, these belts cannot.