Page 27 - Fluid Power Engineering

4 Cha pte r O n e

FIGURE 1.4 Power transmission in an electrical power system.

or by using a drum and wire. However, holding the load position
requires a special braking system.

1.2.3 Pneumatic Power Systems
Pneumatic systems are power systems using compressed air as a work-
ing medium for the power transmission. Their principle of operation is
similar to that of electric power systems. The air compressor converts
the mechanical energy of the prime mover into mainly pressure energy
of compressed air. This transformation facilitates the transmission and
control of power. An air preparation process is needed to prepare the
compressed air for use. The air preparation includes filtration, drying,
and the adding of lubricating oil mist. The compressed air is stored in
the compressed air reservoirs and transmitted through rigid and/or
flexible lines. The pneumatic power is controlled by means of a set of
pressure, flow, and directional control valves. Then, it is converted to
the required mechanical power by means of pneumatic cylinders and
motors (expanders). Figure 1.5 illustrates the process of power trans-
mission in pneumatic systems.

FIGURE 1.5 Power transmission in a pneumatic power system.