Screw conveyor design handbook pdf

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Water is pumped by turning a screw-shaped surface inside a pipe. Archimedes’s lifetime by unknown screw conveyor design handbook pdf. This mechanism quickly replaced the ancient practice of working the pipe by treading.

The screw is usually turned by windmill, manual labor, cattle, or by modern means, such as a motor. As the shaft turns the bottom end scoops up a volume of water. The contact surface between the screw and the pipe does not need to be perfectly watertight, as long as the amount of water being scooped with each turn is large compared to the amount of water leaking out of each section of the screw per turn. If water from one section leaks into the next lower one, it will be transferred upwards by the next segment of the screw.

In some designs, the screw is fused to the casing and they both rotate together, instead of the screw turning within a stationary casing. A screw could be sealed with pitch resin or other adhesive to its casing, or cast as a single piece in bronze. A cylinder was built around the helices using long, narrow boards fastened to their periphery and waterproofed with pitch. The screw was used predominately for the transport of water to irrigation systems and for dewatering mines or other low-lying areas. The principle is also found in pescalators, which are Archimedes screws designed to lift fish safely from ponds and transport them to another location. This technology is used primarily at fish hatcheries, where it is desirable to minimize the physical handling of fish.