Pneumatic Power
Pneumatic Power
•Pneumatic power
•Pneumatics vs.
hydraulics
•Early pneumatic uses
•Properties of gases
•Pascal’s Law
•Perfect gas laws
•Boyle’s Law
•Charles’ Law
•Gay-Lussac’s Law
•Common pneumatic
system components
•Compressor types
•Future pneumatic
possibilities
Pneumatic Power
Pneumatics
The use of a gas flowing under pressure
to transmit power from one location to
another
Gas in a pneumatic system behaves like
a spring since it is compressible.
Pneumatics vs. Hydraulics
Pneumatic Systems . . .
Use a compressible gas
Possess a quicker, jumpier motion
Are not as precise
Require a lubricant
Are generally cleaner
Often operate at pressures around 100 psi
Generally produce less power
Early Pneumatic Uses
Bellows
Tool used by
blacksmiths and
smelters for
working iron and
other metals
Early Pneumatic Uses
Otto von Guericke
• Showed that a
vacuum can be
created
• Created hemispheres
held together by
atmospheric pressure
Early Pneumatic Uses
America’s First Subway
•
•
•
•
Designed by Alfred Beach
Built in New York City
Completed in 1870
312 feet long, 8 feet in
diameter
• Closed in 1873
Properties of Gases
Gases are affected by 3 variables
– Temperature (T)
– Pressure (p)
– Volume (V)
Gases have no definite volume
Gases are highly compressible
Gases are lighter than liquids
Properties of Gases
Absolute Pressure
Gauge Pressure: Pressure on a gauge
does not account for atmospheric pressure
on all sides of the system
Absolute Pressure: Atmospheric pressure
plus gauge pressure
Gauge Pressure + Atmospheric Pressure = Absolute Pressure
Properties of Gases
Absolute Pressure
Pressure (p) is measured in pounds per square inch
(lb/in.2 or psi)
Standard atmospheric pressure equals 14.7 lb/in.2
If a gauge reads 120.0 psi, what is the absolute
pressure?
120.0 lb/in.2 + 14.7 lb/in.2 = 134.7 lb/in.2
Properties of Gases
Absolute Temperature
0°F does not represent a true 0°
Absolute Zero = -460.°F
Absolute Temperature is measured in degrees
Rankine (°R)
°R = °F + 460.
If the temperature of the air in a system is 65
°F, what is the absolute temperature?
Answer:
65 °F + 460. = 525 °R
Pascal’s Law
Pressure exerted by a confined fluid acts
undiminished equally in all directions.
Pressure: The force per unit area exerted
by a fluid against a surface
p 
Symbol
Definition
Example Unit
F
p
Pressure
lb/in.2
A
F
Force
lb
A
Area
in.2
Pascal’s Law Example
How much pressure can be
produced with a 3 in.
diameter (d) cylinder and 50
lb of force?
F o rm u la
A  r
2
d = 3 in.
F = 50 lb
F o rm u la
p 
2
S u b / S o lve A  (1 .5 )
F in a l
A  7 .1 in.
2
S u b / S o lve
F in a l
p 
p=?
A=?
F
A
5 0 lb
7 .1 in.
p  7 .0
2
lb
in.
2
Perfect Gas Laws
The perfect gas laws describe the behavior
of pneumatic systems
Boyle’s Law
Charles’ Law
Gay-Lussac’s Law
Boyle’s Law
The volume of a gas at
constant temperature
varies inversely with the
pressure exerted on it.
NASA
p1 (V1) = p2 (V2)
Symbol
Definition
Example Unit
V
Volume
in.3
Boyle’s Law Example
A cylinder is filled with 40. in.3 of air at a pressure of 60. psi.
The cylinder is compressed to 10. in.3. What is the resulting
absolute pressure?
p1 = 60. lb/in.2
V1 = 40. in.3
p2 = ?
V2 = 10. in.3
Convert p1 to absolute pressure.
p1 = 60. lb/in.2 + 14.7 lb/in.2 = 74.7 lb/in.2
F o rm u la
S u b / S o lve
p (V
)1 (Vp 2)
1
7 4 .7
lb
in.
3
(4 0 .in. ) (1p02.in. )
2
2 98 8 in .  lb
1 0 .in.
F in a l
2
32
p 2  3 .0  1 0
2
 p2
lb
in
2
3
Charles’ Law
Volume of gas
increases or decreases
as the temperature
increases or decreases,
provided the amount of
gas and pressure
remain constant.
V1
T1

V2
T2
Note: T1 and T2 refer to
absolute temperature.
NASA
Charles' Law Example
An expandable container is
filled with 28 in.3 of air and
is sitting in ice water that is
32°F. The container is
removed from the icy water
and is heated to 200.°F.
What is the resulting
volume?
V1 = 28in.3
V2 = ?
T1 = 32°F
T2 = 200.°F
Convert T to absolute temperature.
T1 = 32°F + 460.°F =492°R
T2 = 200.°F + 460.°F =660°R
Charles' Law Example
An expandable container
is filled with 28 in.3 of air
V1
V2
and is sitting in ice water
F o rm u la

T1
T2
that is 32°F. The
container is removed from
3
V2
2
8
in.
the icy water and is
S u b / S o lve

4 9 2 R
6 6 0 . R
heated to 200°F. What is
3
1
8
4
8
0
in
R
the resulting volume?
 V
V1 = 28in.3
4 9 2 R
V2 = ?
T1 = 32°F
T2 = 200.°F
Convert T to absolute temperature
T1 = 32°F + 460.°F = 492°R
T2 = 200°F + 460.°F = 660°R
F in a l
V 2  3 8 in.
3
2
Gay-Lussac’s Law
Absolute pressure of a gas
increases or decreases as
the temperature increases
or decreases, provided the
amount of gas and the
volume remain constant.
p1
T1

p2
T2
Note: T1 and T2 refer to absolute
temperature.
p1 and p2 refer to absolute
pressure.
Gay-Lussac’s Law Example
A 300. in.3 sealed air tank is sitting outside. In the morning the
temperature inside the tank is 62°F, and the pressure gauge reads 120.
lb/in.2. By afternoon the temperature inside the tank is expected to be
close to 90.°F. What will the absolute pressure be at that point?
V = 300. in.3
p1 = 120. lb/in.2
p2 = ?
T1 = 62°F
T2 = 90.°F
F o rm u la
S u b / S o lve
Convert p to absolute pressure.
p1= 120. lb/in.2 + 14.7 lb/in.2
= 134.7 lb/in.2
Convert T to absolute temperature.
T1 = 62°F + 460.°F = 522°R
T2 = 90.°F + 460.°F = 550.°R
p1
T1

1 3 4 .7 lb / in.
5 2 2 R
7 40 8 5 lb / in
5 2 2 R
F in a l
2
p2
T2
2

R
p2
5 5 0 . R
 p2
p 2  1 4 0 lb / in.
2
Gay-Lussac’s Law Example
A 300 in.3 sealed air tank is sitting outside. In the morning
the temperature inside the tank is 62°F, and the pressure
gauge reads 120 lb/in2. By afternoon the temperature inside
the tank is expected to be closer to 90°F. What will the
absolute pressure be at that point?
F in a l
p 2  1 41 .9 lb / in.
2
If the absolute pressure is 141.9 lb/in.2, what is
the pressure reading at the gauge?
141.9 lb/in.2 – 14.7 lb/in.2 = 127.2 lb/in.2
= 130 lb/in.2
Common Pneumatic System
Components
Transmission
Lines
Regulator
Filter
Drain
Directional
Control
Valve
Receiver
Tank
Cylinder
Pressure
Relief Valve
Compressor
National Fluid Power Association & Fluid Power Distributors Association
Compressor Types
Compair
Reciprocating Piston Compressor
Compressor Types
Compair
Rotary Screw Compressor
Compressor Types
Compair
Rotary Vane
Future Pneumatic Possibilities
What possibilities may be on the horizon for pneumatic
power?
Could it be human transport?
zapatopi.net
Image Resources
Compair. (2008). Compressed air explained: The three types of compressors. Retrieved
March 5, 2008, from http://www.compair.com/About_Us/Compressed_Air Explained-03The_three_types_of_compressors.aspx
Johnson, J.L. (2002). Introduction to fluid power. United States: Thomson Learning, Inc.
Microsoft, Inc. (2008). Clip Art. Retrieved January 10, 2008, from
http://office.microsoft.com/en-us/clipart/default.aspx
National Aeronautics and Space Administration. (2008). Boyle’s law. Retrieved February
3, 2008, from http://www.grc.nasa.gov/
National Fluid Power Association. (2008). What is fluid power. Retrieved February 15,
2008, from http://www.nfpa.com/OurIndustry/OurInd_AboutFP WhatIsFluidPower.asp
National Fluid Power Association & Fluid Power Distributors Association. (n.d.). Fluid
power: The active partner in motion control technology. [Brochure]. Milwaukee, WI:
Author.
Zapato, L. (n.d.) The inteli-tube pneumatic transportation system. Retrieved February 29,
2008, from http://zapatopi.net/inteli-tube/