Basics ofPneumatics

Eng. / Alaa E. Omar

Rev.0,12/2009

Fluid Power“ The transmission and control of power

by means of fluid under pressure”

History

From the earliest recorded times, man has used the

air around him to drive his sailing ships and turn the blades of his windmills.

Sailors and shipbuilders knew through countless years of trial and error how to cut and set a sail for maximum

efficiency. Why the pressure and flow of air made one shape better than another was of little interest to them.

The air was then made to "magically open and close" temple doors to the wonderments of the assembled rulers and common people. Here again the why was no practical

value in the eyes of these people, and therefore did not particularly interest them.

Early Egyptian writings tell of Priests using simple bellows to compress air.

It wasn't until the early to mid 17th century that man started to recognize the importance of the world around

him. At this time his knowledge of the air around him began to increase significantly.

History

HistoryThe Flemish Alchemist, Van Helmont,

suspected from his study from the vapors given off by fermenting fruit juices that the air

was not composed of a single element, but that it might be a compound or mixture of

substances.

Henry Cavendish, was among the first to establish that air was indeed a mixture of at

least 4 chemically different gases. In the process, he discovered hydrogen.

HistoryRobert Boyle, an English physicist in the later

half of the 17th century, discovered the laws governing the relationship between air

pressure to volume

The great Frensh chemist, Antoine Lavoisier was set the proportions of oxygen to nitrogen in air, and proved that the oxygen

content was essential to animal life.

Alexandre Charles discovered the laws governing the relationship of air pressure and temperature.

History

Evangelista Torricelli in about 1630 discovered the principle of the barometer by being the first to measure the weight of the atmosphere. In an elegant experiment, he

found it to be equivalent to a column of mercury 30 inches high. 

HistoryAir, when compressed, represents a

potential energy that can be used in a tremendous variety of ways.

Man began to compress air and apply it to a widespread and diverse uses about

100 years ago.

Early compressors were steam driven, but in other respects were essentially the same as today's models, differing only

in refinement of materials and tolerances.

History

Compressed air is demonstrably one of the oldest forms of energy known to man

and applied to enhance his physical capability

KTESIBIOS; Greek man, more than 2000 years ago built a compressed air impulse catapult.

History

One of the first books concerning the application of compressed air as energy

originated in the 1st century A.D. and describes devices which were driven by

warm air.

What’s fluid?What’s fluid power?What are methods of power transmission and control?What are the advantages and disadvantages of fluid power?What are the differences between hydraulic and pneumatic?

FluidFluid is a substance in which the molecules can

move about with freedom.A fluid is defined as a substance that continually

deforms (flows) under an applied shear stress.Fluids are a subset of the phases of matter and

include liquids, and gases.

Fluid

Fluid

A diagram of how the configuration of molecules/atoms differs for the solid, liquid, and gas phases.

A typical phase diagram. The dotted line gives the anomalous behaviour of water. The green lines show how the freezing point can vary with pressure, and the blue line shows how the boiling point can vary with pressure. The red line shows the boundary where sublimation or deposition can occur.

Fluid

Gas: Is a fluid which will

expand to completely fill the available space; its density varies considerably with its temperature and pressure.

Liquid: Is a fluid which will flow

under gravity to take up the shape of the containing vessel in such a way that it reduces its potential energy to a minimum; its density changes only very slightly with changes in temperature and pressure.

Fluid

Gas:

Liquid:

Fluid

LiquidLiquid is one of the principal states of matter. A

liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material. The surface is a free surface where the liquid is not constrained by a container.

GasIn physics, a gas is a state of matter,

consisting of a collection of particles (molecules, atoms, ions, electrons, etc.) without a definite shape or volume that are in more or less random motion.

A gas also exhibits the following characteristics: Relatively low density and viscosity compared to the

solid and liquid states of matter. Will expand and contract greatly with changes in

temperature or pressure, thus the term "compressible". Will diffuse readily, spreading apart in order to

homogeneously distribute itself throughout any container.

Fluid dynamicIn physics, fluid dynamics is a sub-discipline

of fluid mechanics that deals with fluid flow—the natural science of fluids (liquids and gases) in motion. It has several sub disciplines itself, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion).

Fluid Movers

Fluid

Fluid powerFluid power is the technology of exploiting

the properties of fluids to generate, control, and transmit power as a result of the pressurization of fluids.

As the term fluid refers either to gases or to liquids, fluid power is also subdivided into the categories of hydraulics and pneumatics. The differences being that with hydraulics the medium used is a liquid (i.e. mineral oil or water) and for pneumatics it is a gas (i.e. air or another inert gas).

PneumaticPneumaticUse compressed air as a

fluid.Generally used when

relatively low forces (up to 10KN=1Ton) and fast cycling speeds are wanted.

HydraulicHydraulicUse oils and other

liquidsAre used when high

forces, precision speed control and high power/weight are needed.

Fluid Power

PneumaticPneumatic

“Pneuma”

HydraulicHydraulic

“Hydrau”

Fluid Power

Expression derived from the ancient Greak, and meant breath or wind.

Expression derived from the ancient Greak, and meant water.

PneumaticPneumatic HydraulicHydraulic

Fluid Power

Hydro-pneumaticHydro-pneumatic

Is a combined system; utilizing both hydraulic fluids in some parts of the system and air in other parts.

Hydraulic machineryHydraulic machinery are machines and

tools which use fluid power to do work. Heavy equipment is a common example.

In this type of machine, high-pressure liquid — called hydraulic fluid — is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders. The fluid is controlled directly or automatically by control valves and distributed through hoses and tubes.

The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and wide array of actuators that can make use of this power.

Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering medium. Pneumatics, on the other side, is based on the use of a gas as the medium for power transmission, generation and control.

Methods of Power transmission: Mechanical ( gears, belts, shafts,

… )Electrical (Motor, steeper

motor,..)Electronic (Transmitter, … ) Pneumatic ( Air operated )Hydraulic ( Liquid operated )

Hydraulic System

PumpPumpPrime Mover Control devices Actuator Machine

Electrical or Thermal Energy

Mechanical Energy

Hydraulic Energy

Mechanical Energy

28

Air Production System Air Consumption System