Unit D: Topic 5

Hydraulic and Pneumatic Systems

Hydraulic Systems• A closed system using a liquid under

pressure.

• Liquids are incompressible and transmit pressure evenly in all directions.

Pneumatic Systems

• Use air instead of liquids.

• The air is not sealed in the device, but sucked in from the environment by a powerful motor and passes through the device at high pressure where it escapes.

• Think of an air pump. The air in the pump is compressed, raising its pressure and forcing it into a ball with a lower pressure.

Pneumatics Cont’d

• Air will always go from an area of high pressure to an area of low pressure.

• Examples of pneumatic systems include hovercrafts, dentists’ drills, staple guns, sandblasters, and jackhammers.

Circulatory System as Hydraulic System

• Circulatory system is a closed, hydraulic system:

• Heart = Pump – .moves blood throughout body

• Blood = Fluid under pressure (120/80 Pa)• Blood vessels = container• Valves are movable parts which control

how much fluid can move through the system.

Valves and Veins

- Valves are located in veins. When we move our muscles blood is forced up where a valve opens up above and closes after they close.

- These valves do not let blood sink down to the bottom of our bodies. They can only move back up.