BENDIX MC-12 MODULATOR CONTROLLER ASSY Instrukcja Naprawy Pobierz pdf (Strona 55)

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The Fundamentals of Compressed Air

Compressed air is air which has been forced into

a smaller space than that which it would ordinarily

occupy in its free or atmospheric state.

Free air which we breathe – or atmosphere – is

normally always under pressure because of the weight

of the air above it. This pressure amounts to 14.7

pounds per square inch at sea level, and it decreases

as the altitude increases.

The normal atmospheric pressure of 14.7 pounds per

square inch is usually ignored and the atmosphere

is considered as being free air under no pressure.

Thus, the pressure of compressed air is commonly

indicated by stating the amount the pressure, in

pounds per square inch, is above the atmosphere.

This is the reason air pressure gauges register zero

when connected only to atmosphere.

FREE SPRING – FREE AIR

The energy of compressed air is best compared

to the energy of a coiled spring. Figure 8 shows a

coiled spring in its free position and air in its free or

atmospheric state.

COMPRESSED SPRING – COMPRESSED AIR

When the spring is compressed, as shown in Figure

9, energy is stored in it. Similarly when free air is

compressed, energy is stored in the air. This energy

can be used to do work, and due to the ﬂ exibility of air

such energy can be stored in a relatively small space.

See Figure 10. If two reservoirs are connected and

one contains air above atmospheric pressure and the

other contains air at only atmospheric pressure, air

will ﬂ ow from the reservoir with the higher pressure

until the pressures in both reservoirs equalize or until

the ﬂ ow is interrupted by some outside force, such as

the closing of a valve in the connecting line. This is

similar to the action of liquids, except that pressure is

the controlling medium, whereas, the force of gravity

would ordinarily be the controlling medium in the case

of liquids.

FIGURE 8 - FREE SPRING / FREE AIR

FIGURE 9 - COMPRESSED SPRING / COMPRESSED AIR

FIGURE 10 - FREE SPRING / FREE AIR

FIGURE 11 - FREE SPRING / FREE AIR

Properties of Compressed Air

1 2 ... 50 51 52 53 54 55 56 57 58 59 60 ... 69 70

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