Environmental Engineering Reference
In-Depth Information
3
ChaPTer
hydrauliC
MaChines: PuMPs
A hydraulic machine, or pump, is a device that raises, compresses, or
transfers fluids.
3.1 inTroduCTion
“Few engineered artifacts are as essential as pumps in the devel-
opment of the culture which our western civilization enjoys” (Garay,
1990). This statement is germane to any discussion about pumps sim-
ply because humans have always needed to move water from one place
to another against the forces of nature. As the need for potable water
increases, the need to pump the water from distant locations to where it
is most needed is also increasing.
Initially, humans relied on one of the primary forces of nature—
gravity—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 far-
ther. 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 capac-
ity, and (2) it is a high energy consumer. It was not until the 19th cen-
tury that pumping technology took a leap forward from its rudimentary
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