Pneumatic Systems
Alex Zenanko
TEC 366
Mr. Chris Marker
FLUID POWER: PNEUMATICS
• I. What is Pneumatic?
“A power transmission system that uses the force of flowing gases to
transmit power”
[ ToolingU.com]
• Word origin is Greek- “Pneuma” meaning “wind, breath”
• II. How big is the fluid power industry?
• U.S. $14 billion
• $40 billion worldwide
• Trivia:
•
•
The first subway was pneumatically powered
Chicago Postal service had miles of underground pneumatic tubes for mail delivery
EVOLUTION
HISTORIC
▫ Ancient Greece
▫ Simple devices
 Bellows used by blacksmiths
▫ Otto Von Guericke
 Revolutionized Air
Compressors
 More Power and Efficient
▫ 1829 first compound air
compressor patented
▫ Characteristics of gases
explored
▫ Pneumatic hammer and
tubes hit the market
MODERN
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Higher Pressure Used
Jet Engines
Electronic Control
Digital Logic Integration
Axial Flow Compressors
Highly complex Robotics
Standardization
Gases 101
• Basic gas characteristics:
• A gas will take the shape of its container no matter the size
• Gases are highly compressible
• Gases exert a force on the walls of its’ container (can be measured/predicted)
• Gases have 3 interrelated properties
• 1. )Temperature
2.) Pressure
3.) Volume
• Boyles Law- describes the pressure and volume relationship of gases
• As volume decreases, pressure increases. (P1 x V1) = (P2 x V2)
• Combinational Gas Law = (Pictured Top Right)
•
mathematical representation of the three interrelated properties.
“If three conditions of a gas are known, then a change in any one of the
conditions can be predicted if changed”
P=pressure
V=volume
T=Temperature Kelvin R=Energy Constant
Instant Physics: Gases
• Terms
▫ Pressure- Perpendicular force per unit area.
 ** Force per unit area acts on surface area and not mass
▫
Absolute Pressure = [+/-] gauge pressure + atmospheric pressure
 This method uses atmospheric pressure as a reference level to scale from
▫ Pascal’s Law- A pressurized gas exerts an even force on the walls of
container. F = P x A
▫ °F to °C: °C = (°F –32) / 1.8 °C
▫ 1 H.P. = 4 cfm at 100 psi
°C to °F: °F = (°C x 1.8) + 32
Basic Pneumatic System
• A) Compressor
– Pressurizes Air
– Typically attached to tank for storage
– Often is a centralized supply for multiple devices
• B) Check Valve
– One way valve
– Prevents backflow into compressor
– Prevents compression loss when off
• C) Accumulator
– Smooth air flow and unwanted disturbances
• D) Directional Valve
– Direct Air flow
– Stores energy and reduce turbulence
– Electrical or manual operation
• E) Actuator
– Transfers air energy into motion
– Ex. Air Chisel
I. Compressors
1) Are commonly powered by electric motors
2) Must be matched for each application
– 1. Positive Displacement
– Compression Stroke creates pressure
– Most diverse field.
– 2.Dynamic
– Air velocity creates pressure
-Imagine the energy and power of a river flowing down a
mountain. This energy is transferred into pressure.
Positive Displacement Compressors
I.
Positive Displacement
• Divisions: Rotary & Reciprocating
• Lubrication--- “Wet or Dry”
1. Reciprocating•
1-50 H.P. applications
• Piston/Cylinder/Valves
• Works Like Internal Combustion Engine
• 1.)Single, Double Acting and Multistage types
available and describe how air is pumped
 Double Acting is most common in industry; 100
psi classification
Positive Displacement Compressors
I. Rotary
1)
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•
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2)
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3)
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Rotary ScrewExcellent for continuous operation
100+ hp applications
Two helical screws placed side by side compress air when one
screw is turned
Rotary VaneBlades of different length mounted to center hub on drive shaft
Length difference causes pressure pockets to be created when
drive shaft turns
ScrollTwo offset spiral disc placed on top of each other inside of
circular housing
The top disc remains fixed as the lower disc orbits around the
housing walls
This creates a seal and a vacuum that sucks air in chambers
of varying size
As the bottom disc orbits the chamber size is decreased and
air becomes compressed
Dynamic Compressors
Centrifugal
▫ Uses spinning impeller
mounted to solid shaft increase
air velocity .
▫ Air is then channeled into a diffuser
▫ Diffuser = gradually increases in
size as gas leaves impeller
Axial
▫ Spinning Airfoils compress air
▫ Airfoils are arranged in fixed
and moving rows along the
compression chamber
▫ Extremely Efficient; 90% is
achievable
Rotary Screw Compressor
Reciprocating Single Acting
Advanced Components
• Lubricator
• Automatically lubricates system through air supply.
• Oil helps elastomeric seals and moving parts work
• Not all devices require lubrication: A coalescing filter
removes oil
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•
•
Muffler aka “Silencer”
• Cancels out undesirable frequencies created by venting
exhaust air through porous substance
• Coalescing mufflers = reduce sound and oil
Air Booster Tank and Regulator
Increases air pressure to certain parts of system
• Typically provide a small quantity of high pressure
• Work in-line with system after compressor
• Uses: Certain high demand machines; Peak times that
exceed available pressure; 600 PSI
• To avoid cost of high performance compresor
• Ratio of inlet to outlet pressure change
• Ex.1/2 = Pressure is doubled [is listed in data sheet]
Advanced Components
• Aftercooler
• Dissipates heat created by compressing air
• Thermal expansion can limit the storage capabilities of a tank
• Pneumatic Logic Components
• Controls the flow of air through the system via controller,
actuators and valves
• Very similar to PLC systems
• Is becoming more prevalent with advances in computing and
increased machine complexity
• Coalescing Filters
• Absorbs oil added to air supply
• Is necessary for a system whose components will be damaged by
oil
• It is required by OSHA to use a coalescing filter before
exhausting air that has been oiled
• Piping
• Friction losses in piping can result in pressure loss
• Compressor must be separated from piping with flexible
couplings
• to block system vibration
• Ring Lines are those which run in a large loop and feed machines
along the loop
• Branch lines are the shorter lines that feed machines and other
devices
Piping in Pneumatics
1. Installation
1.
2.
3.
Must use flexible coupling to between
compressor and piping. (Vibration)
Piping must sl0pe downward away
from compressor at 1-2 degrees
[0.12-0.25 in/ft]
Use Excess Flow Valve every 100ft
2. Pressure Drop
1.
2.
3.
Inevitably effects all pneumatic
systems
Friction and piping length
A 10% drop in pressure is the
absolute maximum
–Branch lines are the
shorter lines that feed
machines and other devices
–Ring Lines are those
which run in a large loop
and feed machines along
the loop
Pneumatic Dryer
Removes moisture from air. Typically found after Coalescing Filter and/or FRL
Dew point suppression = A temperature based scale that compares change
in dew point value before entering the dryer and after leaving the dryer

1.
Question: Air enters a deliquescent dryer at 100 ° F and the dew point suppression is -1.5°
F. What is the resulting dew point of the air?
***Moisture within the air will not condense if air temp. stays above 75° F
2.
Deliquescent Dryers = Absorption; [ 25° F] D.P.S
▫
3.
Air is channeled through salt bed that traps both liquid and vapor
•
Must be drained regularly. Typically element is in brick or tablet form
Desiccant Dryers = Adsorption ; [ -40° F] D.P.S
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4.
Moisture is absorbed on surface area of water absorbing substance. Typically silica
gel or activated alumina is used.
“Regenerative Dryer” = a process removes moisture so dryer can be used again
Refrigeration Dryer = [ -40° F] D.P.S
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Industry favorite for a wide range of application due to cheap operating cost
Removes moisture by cooling air to the point of condensation. Reheats afterwards
Reduces need for heat sink on compressor up to 60%
Pneumatic Cylinders
1)
Type of Actuator that does work in the form of linear
motion
▫
Can be thought of as the pneumatic muscle
2) Types:
1)
Single Acting, Double Acting, and Double End Rod
3) Single Acting▫
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Single Pressure Port
Can only be controlled in one direction
A spring or load weight must reverse the cylinder’s movement
4) Double Acting
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▫
Two Pressure Ports
Extension and Retraction can be controlled
5) Double End Rod
1)
Two rods and Two Pressure Ports; Force is equal for each rod
6) Area = πr2
1)
2)
3)
Find the Area of a ¾” x 1 ¼” cylinder
Area = 3.14 x (3/8”)2
 Area = 3.14 x .14  Area = .44 in 2
Force = Pressure x Area  What is the force @ 10 psi
Cylinders
Single Acting Spring Return
Double Acting
Pneumatic Logic Circuits
1) Logic circuits are made from various valves
• Functional equivalent to logic gates
• Used to control sequence of events
• NOT, OR, AND,
• AND--All inputs must be active
• OR--If any input is active the output will be
• NOT--The output is the opposite of the input
• NOR and NAND
• are combinations of the basic gates
AND
OR
NOT
-Or ValveOutput activated if A
or B is activated
-And Valve-
Output activated only
if A and B are high
-NOT ValveOutput is opposite
of input
• Sequence Valve
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•
Valves
Control sequence of operation between two branches of a circuit.
A set pressure point will divert flow when reached
• Shuttle Valve
•
Isolates two supply systems from each other. This valve supplies an
output from one of two inputs that are kept isolated from each other
• Excess Flow Valve
•
Safety Device. Cuts off flow if pipe breaks
• Pressure Control Valve
•
•
Reduce and maintains lower pressure supply to output device.
Is resistive to pressure changes on the supply side
• Limit Valve
Field device used to generate and send control logic signal to processor.
-It is active when event has occurred
• Ball Stop Valve
•
Quick Acting valve; manual turn operation
• Gate Valve
•
•
An adjustable wedge impedes the flow of air
Must be rated if used to control pressure
Control Valve Symbology
▫ Goal: Determine function of control valve
• 1) Ports/Way


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
2 Position 5 way: 5/2
1) Vertical Arrow = Flow Path
2) 45 deg Arrow = Exhaust Path
Tee = Closed Path
Numbering:
▫ 1 is always pressure port
▫ All odd’s > 1 are exhaust ports
▫ Even #’s are outlet ports (A & B are
• 2)Position Envelope
 Indicate discrete # of flow paths.
 A Box surrounds a P.E.
 Depicts each setting and change
^Position 1^
Closed
also used)
^Position 2^
Open
Left = Figure 1 : Right = Figure 2
5 port/2 way valve
Figure 1
Figure 2
Pneumatics Symbols
1.)FRL [Filter/Regulator/Lubricator]
2.) Single Acting Cylinder
3.) Double Acting Cylinder
------------------------------------------------------------------------------------------------------1.)FRL [Filter/Regulator/Lubricator]
2.) Single Acting Cylinder
3.) Double Acting Cylinder
Formulas
• 1. Pressure Dropsid =[Receiver Pressurepsig – Tool
Pressurepsig / Line Distanceft
 PSID = (RP – TP) / D
• 2. Compression Ratio = (Pressurepsig + 14.7) / 14.7
 CR = (PSIG + 14.7) / 14.7
• 3. Air Leakage Cost$/min = Flowcfm x Timemin x
Electricity
UsedkWh/cu-ft x Electricity Cost$/kWh
▫ Leakage Cost$ = cu-ft x min x (kWh/cu-ft) x ($/kWh)
• 4. Absolute Pressurepsia = Gauge Pressurepsig + 14.7
• 5. Forcelbs = Pressurepsig x Areasq-in
 P=FxA
Pneumatic vs. Hydraulics
Pneumatics
Hydraulics
1)
2)
3)
4)
5)
1) Use liquids
2) Liquids compress only
slightly
3) Better power density
4) Higher Pressures
5) Slower
Use gases
Gases are easily compressed
Good power density
Lower Pressures
Quicker
Pneumatic vs. Hydraulics:
Pneumatics
Hydraulics
1. Air is abundant and free
1) Must purchase fluids
2. Less environmental concerns
2) Leaks can harm environment
3. Lower initial cost
3) Higher initial cost
4. Higher operating cost
4) Lower operation cost
5. Design Simplicity
5) Complex Design
6. Lower maintenance
6) Very high maintenance
Lab 1 Overview: Flow Measurement
• Measuring fluid flow in pneumatic systems is far
more difficult than in hydraulics systems
 Direct measurement in pneumatic systems can be very
inconvenient however it is more accurate
 Indirect methods are convenient but sacrifice accuracy
▫ Ex. rotameters, orifice meteres, pitot tubes.
• In this lab we will be using a rotameter
• Measurement:
 Industrial standard is cubic feet per minute ‘cfm’ for
large flow and cubic feet per hour ‘cfh’ for small flow
 Corrections must be made using mfg. supplied table
–In this lab we will be using:
–Dwyer RMA series Rate-master Rotameter(100psi)
–Vega model 200 Pneumatic System
–5/32” Pneumatic tubing (12” length)
–When connecting tubing to the flowmeter
–Eliminate or minimize sharp bends and flow
restrictions when possible
–Testing Procedure:
1. Mount the flowmeter vertically
2. Connect red hose from compressor manifold to
bottom inlet of the flowmeter
3. Make sure manifold needle valves are shut
4. Turn on compressor
5. Adjust regulator to 20 psi
6. Open needle valve slowly two full turns
7. Record measurement when ball is stabalized
8. Repeat for 30 and 40 psi
9. Find actual airflow using correction chart
Lab 2 & 3. Air Leaks and Cylinders
•Air Leaks cost money. Air leaks are going to
happen eventually .
•How to evaluate the cost of leaks is the goal of
this lab.
1.) Use the CFM measurements from Lab 1
2.) Use$.58 cents/ kWh as Al industrial rate avg
3.) Assume the motor consumes $.02 kWh/cu-ft
4.) Assume the system runs 24 hours a day
5.) Apply the air leakage cost formula
Leakage Cost$ = cu-ft x min x (kWh/cu-ft) x ($/kWh)
Lab 4. Conveyor
• The goal of this lab is to determine the air line configuration for the conveyor
cement
n anatomical
ubrication
y”
n Lubricated--
the type of
d intended
rcraft
m uses
nside the
self lubricate
ld be classified
e it does not
ation
Positive Displacement
Reciprocating
• Piston/Cylinder/Valves
• Works Like Internal
Combustion Engine
• 1.)Single, Double Acting
and Multistage types
available and describe how
air is pumped
• Double Acting is most
common in industry; 100
psi classification
Rotary
• Circular Rotation creates
pressure; Can be
achieved in numerous
ways
• 1.)Rotary Screw-uses two
helical screws and used
mostly for continuous
applications
• Pictured top left
• 2.)Rotary Vane-Blades of
varying length placed on
drive shaft are spun inside
housing creating pressure
Scroll
• Two offset spiral
placed on top of
inside of circular
• The top disc rem
as the lower disc
around the hous
• This creates a se
vacuum that suc
chambers of var
• As the bottom di
the chamber size
decreased and a
compressed
Lab 3. Conveyor
• The goal of this lab is to determine the air line configuration for the conveyor