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## PowerPoint Slideshow about ' Forging new generations of engineers' - sydney-beard

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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)

Pneumaticsvs.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

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.

Otto von Guericke

Showed that a vacuum can be created

Created hemispheres held together by atmospheric pressure

EarlyPneumaticUsesAmerica’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

EarlyPneumaticUsesProperties 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

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

- 14.7 lb/in.2

Example: 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 and 0°C don’t represent TRUE ZERO°

Absolute Zero = -460°F or -273°C

Absolute Temperature is measured in

degrees Rankine (°R = °F + 460 °) <- English/Std.

degrees Kelvin (°K= °C + 273 °) <- Metric

Example: If the air temperature in a system is 65 °F what is the absolute temperature?

65 °F + 460. = 525 °R

Properties of GasesBoyle’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)

Properties of GasesCharles’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

Properties of GasesCharles’s Law continued

Isobaric - equal pressure

V1= V2

T1 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 +

Fahrenheit

V2 = V1x 672

492

V2 = V1 x T2

T1

=

1.36 V1

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

T1 T2

__ __

Ideal Gas Law

P1V1= P2V2

T1 T2

___ ___

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

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

Pascal’s Law

Pascal’s Law ExampleHow 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 = ?

Regulator

Filter

Directional Control Valve

Drain

ReceiverTank

Cylinder

Pressure Relief Valve

Compressor

Common Pneumatic System ComponentsNational Fluid Power Association & Fluid Power Distributors Association

Future Pneumatic Possibilities

What possibilities may be on the horizon for pneumatic power?

Could it be human transport?

zapatopi.net

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