Transcript Pneumatic Principles - MACCRAY High School

Pneumatic Principles
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Introduction
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A pneumatic system uses air or some other
gas to transmit and control power to perform
work.
Properties of a pneumatic system often make
it the best choice for industry
History
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Man has used air to do work for centuries
and today, pneumatic devices are a common
Early man learned to attach sails to boats
Windmills were used to pump water and
grind grain in the 12th century
Helping solve part of today's energy
problems
History
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Scientists in 17th century began to study the
properties of gases and the effects of pressure,
temperature, and flow
Efficient methods of compressing air were
developed
Man learned to use compressed air to do work
which had been done manually
History
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Since WW II the advantages of pneumatics
has been fully utilized
Use of pneumatic devices has been
expanding rapidly because:
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low cost, small size, high power-to-weight ratio,
flexibility of use, long service life and ease of
service
Properties of Air
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Air is a mixture of gases, mostly nitrogen
and oxygen, making up the earths
atmosphere
At the surface of earth air naturally exists
under pressure due to the weight of the
atmosphere
The pressure is equal to approximately 14.7
#/in2 at sea level
This pressure exerts force on all of the
surfaces it touches
Properties of Air
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Since this pressure is constant it is not
noticeable
Air has no size or shape of its own
It always takes the shape of its container and
completely fills it
If air is placed in a closed container, the
pressure of the air will be equal force against
all the surfaces within that container
Properties of Air
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Air pressure is measured in pounds per
square inch
Reflects the amount of force a given air
pressure exerts on each square inch of
surface it contacts
As air is compressed it releases heat
In most compressed air systems a cooler is
used to absorb this heat
Properties of Air
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As the compressed air is released to
atmosphere it expands and absorbs heat.
This is the reason air-operated devices
become cool while running.
Air has the ability to hold water vapor.
This ability is affected by both the
temperature and the pressure of the air.
Properties of Air
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As air is compressed, its ability to hold
moisture is reduced
This causes water to condense and fall out
of the air
This why water collects in a compressed air
system and must be drained periodically
Properties of Air
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Air is considered a fluid
It always flows from the area of highest pressure
to the area of lowest pressure
As a fluid begins to flow begins to lose pressure
The faster it flows the lower its pressure will
become
Using Air To Transmit Force
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A pneumatic system can use air to transmit
mechanical force from one place to another.
To do this mechanical force is first converted
into a fluid pressure.
The pressure is created by the compression
of the air and is equal to the amount of force
being applied against it.
Using Air To Transmit Force
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A pressure of 100 pounds per square in is
being applied to the surface of a piston which
has a surface area of 12 square inches.
This produces 1200 pounds of thrust.
Advantages Of Using Pneumatic
System
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Spark-Resistance
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Air operated products generally are not likely to produce
sparks, which makes then suitable for use in hazardous
environment.
Control
Pneumatic systems provide a fine degree of control,
allowing force to be applied where it’s needed, when it’s
needed, and in the amounts needed.
– Remote or automatic control of pneumatic equipment
allows the machine operator to be removed from the
14 immediate area of the machine.
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Advantages Of Using Pneumatic
System
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Light/Compact
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Pneumatic products are very light and compact
for the amount of power they produce.
Used with less operator fatigue and allows
stationary units to be mounted in confined
spaces.
Advantages Of Using Pneumatic
System
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Instant Reversibility
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Most pneumatic devices can be instantly reversed
without damage
Speeds up production
Advantages Of Using Pneumatic
System
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No overheating/Burnout
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Equipment can be used indefinitely under heavy
load or stall conditions without becoming hot or
damaging itself.
Usually the more a pneumatic device runs, the
cooler it becomes
Advantages Of Using Pneumatic
System
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Safety
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Pneumatic equipment has no chance of shock
and usually operates at low pressures
Advantages Of Using Pneumatic
System
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Cost
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Operating costs are low when considering service
life, serviceability, increased production, reduced
operator fatigue
Lower operating cost results in increased
profitability