Page 24 - Fluid Power Engineering

CHAPTER 1

Introduction to

Hydraulic Power

Systems

1.1 Introduction
God created the first and most wonderful hydraulic system. It
includes a double pump delivering a fluid flow rate of about 10 L/min
at 0.16 bar maximum pressure. This pump feeds a piping network
stretching more than 100,000 km. That’s nearly two and a half times
around the Earth. It operates continuously for a very long time, mostly
maintenance free. It is the human blood circulatory system. By the age
of 50 years, the hearts of 10 men should have pumped a volume of
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blood equaling that of the great Egyptian pyramid (2,600,000 m ).
As for the hydraulic power systems developed by man, their his-
tory started practically 350 years ago. In 1647, Blaise Pascal published
the fundamental law of hydrostatics: “Pressure in a fluid at rest is trans-
mitted in all directions.” In 1738, Bernoulli published his book Hydro-
dynamica, which included his kinetic-molecular theory of gases, the
principle of jet propulsion, and the law of the conservation of energy.
By the middle of the nineteenth century, fluid power started playing an
important role in both the industrial and civil fields. In England, for
example, many cities had central industrial hydraulic distribution net-
works, supplied by pumps driven by steam engines.
Before the universal adoption of electricity, hydraulic power was
a sizable competitor to other energy sources in London. The London
Hydraulic Power Company generated hydraulic power for every-
thing from dock cranes and bridges to lifts in private households
in Kensington and Mayfair. In the 1930s, during the glory days of
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hydraulic power, a 12 m /min average flow rate of water was
pumped beneath the streets of London, raising and lowering almost
anything that needed to be moved up and down. As a power source,

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