Water Pump
The Mesopotamians invented the first pump about 3000 B.C.; they had previously used buckets alone to water their crops in the Nile River valley. Their shaduf, or swipe, was a long wooden lever that pivoted on two upright posts situated on the riverbank. A pole with a bucket attached to it was suspended from one end of the lever, with a counterweight fixed to the other end. To operate the water pump, the user pushed the pole down so that the bucket filled with water; the counterweight then helped to raise the bucket, which was emptied into a trough that led to the irrigation ditch constructed between the river and the fields. The shaduf became popular throughout the Middle East, and was the only form of water pump used in that region for the next two thousand years.
Around 500 B.C., three new water-lifting devices came into use. The saqiya, or waterwheel, which had pots attached around its circumference, was mounted over the water so that the lowest pots filled. As the wheel turned, the filled pots would rise to the top and dump their water into a chute that led to the irrigation ditch. Eventually the pots were replaced by troughs. Both the saqiya and the tympanum--a wheel comprised of radiating, watertight compartments with openings to allow water in and out--were mentioned by the Roman engineer Vetruvius in his writings from the first century B.C.
Another ancient water pump was the bucket chain, a continuous loop of buckets that passed over a pulley-wheel, thought to have been used to irrigate the Hanging Gardens of Babylon around the year 600 B.C. Perhaps the most famous of early water pumps was the Archimedean screw. The Greek Archimedes (287-212 B.C.) was a famous mathematician and inventor who, in about 250 B.C., devised a pump made of a metal pipe in a corkscrew or helix shape that drew water upward as it revolved. This device proved particularly useful for removing water from the hold of a ship. (Although the invention of the screw-type pump is usually attributed to Archimedes, many researchers believe he merely popularized an invention he had seen in Egypt.) The modern screw pump features helices rotating in open, inclined troughs; it is particularly well-suited to pumping sewage in wastewater treatment plants, because its design allows debris to pass without clogging.
The ancestor of the modern force pump—which features a cylinder with a plunger or piston at the top that creates a vacuum and draws water upward through valves at the bottom--was reputedly designed by Ctesibus of Alexandria, Egypt. Vetruvius mentioned this device, as he did the saqiya, in his first century B.C. chronicles. Remains of this pump, which was usually made of bronze, have been found in many buildings dating from the days of the Roman Empire. The valves and plungers were particularly valuable inventions that were incorporated into other kinds of machinery, including military equipment. The Romans, for instance, used this kind of pump to hurl flammable liquids at invading Arabs.
One of the most common water pumps in use today is the centrifugal pump, comprising a motor-driven, propeller-like impeller contained in a housing--when turned, the impeller creates suction that draws a continuous flow of fluid. The positive displacement pump, on the other hand, traps individual portions of fluid in an enclosed area, then moves them along. French inventor Denis Papin invented the centrifugal pump in the late 1600s. His impeller had straight vanes, whereas that developed by the British inventor, John G. Appold, in 1851 had the curved vanes still preferred today.
Other modern pumps include axial-flow pumps used as compressors in jet engines since the 1940s; jet pumps, which send a jet of steam or water through the fluid to be moved and which are used to raise water from wells deeper than 200 feet (60 m); and electromagnetic pumps, used in nuclear reactors.
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