HYDRAULIC MACHINES: PUMPS
Initially, humans relied on one of the primary forces of naturegravity-to move water from one place to another. Gravity only works, of course, if the water is moving downhill on a sloping grade. It was soon discovered that the pressure built up by accumulating water behind the water source (e.g., behind a barricade, levy, or dam) moved the water farther. But, when pressure is dissipated by various losses (e.g., friction loss) or when water in low-lying areas is needed in higher areas, the energy needed to move that water must be created. Simply, some type of pump is needed. In 287 B.C., Archimedes, a Greek mathematician, physicist, and mathematician, invented the screw pump (see Figure 3.1). It is believed that around 100 A.D. the Roman emperor Nero developed the piston pump. The piston pump displaces volume after volume of water with each stroke. The piston pump has two basic problems: (1) its size limits capacity, and (2) it is a high energy consumer. It was not until the 19th century that pumping technology took a leap forward from its rudimentary
beginnings. The first fully functional centrifugal pumps were developed in the 1800s. Centrifugal pumps can move great quantities of water with much smaller units compared to earlier versions of pumps.