1. Forging new generations of engineers
Fluid Power
Principles of EngineeringTM
Unit 4 - Lesson 4.3 – Fluid Systems
Forging new generations of engineers
Project Lead The Way, Inc.
Copyright 2007

2. Pneumatics

3. Properties of Compressed Air
Components have long working life resulting in longer system reliability
Environmentally friendly
Safety issues are minimized (but not eliminated) e.g.. Fire hazards; unaffected by overloads (hydraulic actuators stall or slip when overloaded)
Pneumatic actuators in a system do not produce heat (except for friction)

4. 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

5. 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.

6. Early Pneumatic Uses Bellows
Tool used by blacksmiths and smelters for working iron and other metals

7. Early Pneumatic Uses Otto von Guericke
Showed that a vacuum can be created
Created hemispheres held together by atmospheric pressure
Von Guericke held public demonstrations in Germany during the 1660s where teams of horses tried to pull apart hemispheres held together by atmospheric pressure created using a pump.

8. 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

9. Properties of Gases Gases are affected by 3 important variables
1. Temperature, T
2. Pressure, P
3. Volume, V
Gas laws describe relationships between these variables

10. Pneumatic Power Pneumatics vs. hydraulics Pneumatic power
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

11. 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
Absolute pressure is used to complete pneumatic calculations.
Atmospheric pressure is also known as barometric pressure. It is the weight of the air molecules. An application of air pressure is when your ears pop. The pressure is balancing on the inside and outside of your ear.
Gauge Pressure + Atmospheric Pressure =
Absolute Pressure

12. Properties of Gases Absolute Pressure
Pressure (P) is measured in pounds per square inch
- lb/in.2 or psi
Standard atmospheric pressure
lb/in.2
Absolute pressure is used to complete pneumatic calculations.
Atmospheric pressure is also known as barometric pressure. It is the weight of the air molecules. An application of air pressure is when your ears pop. The pressure is balancing on the inside and outside of your ear.
Example: If a gauge reads psi, what is the absolute pressure?
120.0 lb/in lb/in.2 = lb/in.2

13. Properties of Gases Absolute Temperature
0°F and 0°C don’t represent TRUE ZERO°
Absolute Zero = -460°F or -273°C
Absolute Temperature is measured in
degrees Rankine (°R = °F °) <- English/Std.
degrees Kelvin (°K= °C °) <- Metric
Absolute pressure is used to complete pneumatic calculations.
Atmospheric pressure is also known as barometric pressure. It is the weight of the air molecules. An application of air pressure is when your ears pop. The pressure is balancing on the inside and outside of your ear.
Example: If the air temperature in a system is 65 °F what is the absolute temperature?
65 °F = 525 °R

14. Properties of Gases Boyle’s Law
The pressure of a given mass of gas is inversely proportional to its volume (providing the gas remains at constant temperature)
Isothermic (equal temperature)

15. Properties of Gases Boyle’s Law continued

16. Properties of Gases Charles’s Law
When the pressure of a confined gas remains constant, the volume of the gas is directly proportional to the absolute temperature.
A given mass of gas increases in volume by:
1/273 of its volume per degree Celsius rise
1/459.7 of its volume per degree Fahrenheit rise

17. Properties of Gases Charles’s Law continued
Isobaric - equal pressure
V1 = V2
T T2
Where:
V1 = initial volume
V2 = resulting volume
T1 = initial absolute temperature
T2 = resulting absolute temperature
A volume of air in an accumulator is submerged in a bucket of ice water (32 degrees F). If you remove the accumulator from the ice water and place it in a bucket of boiling water what would the resulting volume be.
Fahrenheit
Absolute is 460 +
V2 = V1 x 672
492
V2 = V1 x T2 T1 =
1.36 V1

18. __ __ Properties of Gases P1 = P2 T1 T2 Gay-Lussac's Law
When the volume of a confined gas remains constant, the pressure of the gas is inversely proportional to the absolute temperature.
P1 = P2
T T2
__ __

19. PV=nRT ___ ___ Properties of Gases P1V1 = P2V2 T1 T2 Ideal Gas Law
___ ___
Combining the work of Charles, Gay-Lussac, and Boyle we obtain:
Which was the main precursor to the modern day ideal gas Law:
PV=nRT

20. Properties of Gases 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
Symbol
Definition
Example Unit p
Pressure
lb/in.2 F
Force lb A
Area
in.2

21. Pascal’s Law Example Properties of Gases Pascal’s Law
How much pressure can be produced with a 3 in. diameter (d) cylinder and 50 lb of force?
d = 3 in. p = ?
F = 50 lb A = ?

22. Common Pneumatic System Components
Transmission Lines
Regulator
Filter
Drain
Directional Control Valve
Receiver Tank
Compressor: Compresses air into the receiver tank.
Pressure Relief Valve: Limits the maximum pressure in the system. It is a safety device that will allow excess pressure to escape to prevent damaging components in the circuit.
Receiver Tank: A device that holds the air in a pneumatic system.
Transmission Lines: Used to transport fluid in a circuit.
Directional Control Valve: Used to control which path a fluid takes in a circuit.
Cylinder: Also called an actuator. Used to convert fluid power to linear mechanical power.
Drain: Removes moisture from the system.
Regulator: A valve used to control pressure in the branch of a circuit.
Filter: Used to remove contamination from fluids. Filters are also often next to lubricators. Lubrication helps prevent wear on the components in the system.
All systems also require seals and gaskets between components to improve the air-tight nature of the system.
Pressure Relief Valve
Cylinder
Compressor
National Fluid Power Association & Fluid Power Distributors Association

23. Future Pneumatic Possibilities
What possibilities may be on the horizon for pneumatic power?
Could it be human transport?
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