1. Constructed Fluid Systems
9.2

2. 9.2 Key Terms and Objectives
Hydraulics
Hydraulic Systems
Hydraulic Multiplication
Pneumatics
Pneumatic Systems

3. Objectives
Can explain how pressure in fluids at rest and fluids in motion can produce a force to operate mechanical devices
How hydraulic systems create pressure that moves through a liquid such as oil or water
How hydraulic systems can greatly multiply force.
Explain how in pneumatic systems, an enclosed gas such as air transmits a force causing motion.

4. New Orleans
Hurricane Katrina

5. Fluids At Rest
Blaise Pascal studied fluid systems and observed when you apply a pressure to a certain point in an enclosed system, that pressure is transmitted equally through an entire system.
Think of a tube of toothpaste or squeezing a balloon
This squeezing creates static pressure

6. Static Pressure
Static pressure is pressure exerted by a liquid or gas that is not in motion
This static pressure now capable of applying a force, even though it is not moving eg. Pressing brakes

7. Fluids at Rest and in Motion
Fluids in motion
Bernoulli discovered the concept of dynamic pressure
Fluids in motion cause a decrease in pressure perpendicular to the direction of motion
Dynamic pressure is created when fluid moves
Air moving faster over the wing creates higher pressure underneath = lift force

8. Hydraulic Systems Hydraulics = study of pressure in liquids
Hydraulic systems create pressures that travel through a fluid
Pressure applied to an enclosed fluid creates a force that can be used anywhere
A pump is generally used to provide pressure at one point
Everywhere in the system then has a usable force
This is why we have pressure in our taps and faucets
Pumps may create high or low pressure to move fluids

9. Valves and Hydraulic Multiplication
Valves are used to control the movement of fluids
Therefore, valves control the location of fluid pressure
Check valves only allow fluids to flow in one direction
Hydraulic multiplication allows small changes in pressure to do large amounts of work.
A small area applying pressure can cause a large force to be exerted over a large area.

10. Problems in Hydraulic Systems
Hydraulic systems must be designed carefully
Minimize twists and turns to allow fluid to flow freely
Connect pipes and seams well to avoid leakage
Pressure in the system is affected by the size of the pipes and the smoothness of the inside of the pipes.
Pressures can be dangerous if fluids allowed to escape through broken pipes or lines.
Pressure-relief valves re often used to control pressures
Fluids are often poisonous

11. Pneumatic Systems Pneumatic systems use a gas under pressure
Same idea as hydraulics, except gases can be compressed, whereas fluids do not compress much.
Compressors are used in pneumatic systems, not pumps
Compressors build up pressure, then quickly release it in a small area to produce large forces
Pneumatics can be used in large and small systems
Pneumatics and hydraulics are often used together

12. Pneumatic Systems and their Problems
Pneumatic systems must have unblocked air flow to work efficiently.
Because air is usually brought into a compressor to increase pressure, filters clean the air to keep the compressor clean
If the filters are not cleaned, the pneumatic system becomes inefficient
What did we do before attachments and faxes? This
Rohrpost station used pneumatics to “shoot” tubes with
rolled up documents around large building like factories. If
the station’s compressor filter was blocked, important
messages could become lost.
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