1. How do fluid systems work?
Fluids Under Pressure
How do fluid systems work?

2. Compressibility
Imagine filling a balloon with air and another balloon with water.
Will these two balloons act the same way if you compress or squeeze them?
Let’s try it.

3. Compressibility
Compressibility is the ability of a substance to be squeezed into a smaller volume.
Air is more compressible than water. You can compress air (gas) into a smaller volume more easily than water (a liquid).
According to the particle theory, the distance between matter particles is different for each state of matter.
The more space between the particles, the more matter can be compressed.
Which state of matter is the hardest to compress? Which state of matter is the easiest?

4. Types Of Fluid Systems
There are two types of fluid systems that use compressed fluids.
Pneumatic systems use pressurized air or other gases to do work.
Hydraulic systems use pressurized liquids to do work.
Many fluid systems must keep the fluids contained in order to work. These systems are called closed systems.
In a closed system, no matter enters or leaves the system.

5. Hydraulic Systems Hydraulics is the 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
Water is drawn from a well using a pump
It forces water through a pipe into a pressure tank – when the right level of pressure is reached, the pump turns off and water is sent to our taps under pressure
A pump (top) first creates low pressure to draw water in, then high pressure to pump it out.

6. Hydraulic Systems

7. 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.
Pressure applied at A (small electric motor)
5000 N on a 0.5 m2 piston = 10 kPa pressure
Force applied at B
10 kPa applied on 5.0 m2 piston = N
- Can lift a whole car!

8. 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 are allowed to escape through broken pipes or lines
Fluids are often poisonous

9. Pneumatic Systems Pneumatic systems use 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

10. 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.

11. Fluid Systems Part Function Pump Forces fluids through the system
Both hydraulic and pneumatic systems have several parts.
Part
Function
Pump
Forces fluids through the system
Conductor (tube, hose or pipe)
Carries the fluid through the system
Valve
Keeps the fluid moving in the right direction at the right time
Pressure gauge
Measures pressure in the system

12. Human Fluid Systems The heart is a hydraulic system.
Valves in the heart force blood to move through it in one direction.

13. Human Fluid Systems The lungs are a pneumatic system.
Your lungs operate like pump. They draw in air laden with oxygen and push out air and extra carbon dioxide.