Fluid Power

Reservoir / Receiver

Stores fluid

Fluid Conductors

Pipe, tube, or hose that allows for flow between components

Pump / Compressor

Converts mechanical power to fluid power

Valve

Controls direction and amount of flow

Actuators

Converts fluid power to mechanical power

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

Hydraulic Power

Use a relatively incompressible liquid
Have a slower, smoother motion
Are generally more precise
Lubricate naturally
Are not as clean as pneumatics when leakage occurs
Often operate at pressures of 500-5000 psi
Generally produce more power

Pneumatic

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.

Hydraulic

The use of a liquid flowing under pressure to transmit power from one location to another
Liquid in a hydraulic system behaves like a solid since it compresses very little

Generally produce less power

Pneumatic Systems

Use a compressible gas

Pneumatic Systems

Possess a quicker, jumpier motion

Pneumatic Systems

Are not as precise

Pneumatic Systems

Require a lubricant

Pneumatic Systems

Are generally cleaner

Pneumatic Systems

Often operate at pressures around 100 psi

Pneumatic Systems

Use a relatively incompressible liquid

Hydraulic Power

Have a slower, smoother motion

Hydraulic Power

Are generally more precise

Hydraulic Power

Lubricate naturally

Hydraulic Power

Are not as clean as pneumatics when leakage occurs

Hydraulic Power

Often operate at pressures of 500-5000 psi

Hydraulic Power

Generally produce more power

Hydraulic Power

Properties of Gases

Gases are affected by 3 variables
Temperature (T)
Pressure (p)
Volume (V)
Gases have no definite volume
Gases are highly compressible
Gases are lighter than liquids
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 (psi)

Gauge Pressure

Pressure on a gauge does not account for atmospheric pressure on all sides of the system

Absolute Temperature

is measured in degrees Rankine (°R)
°R = °F + 460

Transmission Lines

Used to transport fluid in a circuit.

Receiver Tank

A device that holds the compressed air in a pneumatic system.

Drain

Removes moisture from the system.

Regulator

A valve used to control pressure in the branch of a circuit.

Filter

A device used to remove contamination from a fluid.

Directional Control Valve

Used to control which path fluid takes in a circuit.

Cylinder

Also called an actuator. Used to convert fluid power to linear mechanical power.

Compressor

An air pump that compresses air into a receiver tank.

Pressure Relief Valve

prevents excessive pressure from building in the lubrication system by releasing it

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
P=F/a

Boyle's Law

P1V1=P2V2
The volume of a gas at constant temperature varies inversely with the pressure exerted on it.

Charles' Law

V1/T1=V2/T2
Volume of gas increases or decreases as the temperature increases or decreases, provided the amount of gas and pressure remain constant.

Gay-Lussac's Law

P1/T1=P2/T2
Absolute pressure of a gas increases or decreases as the temperature increases or decreases, provided the amount of gas and the volume remain constant.

Why Use Fluid Power?

Multiplication and variation of force
Easy, accurate control
One power source controls many operations
High power / low weight ratio
Low-speed torque
Constant force and torque
Safe in hazardous environments

Energy

the ability to do work

Work

force x distance

Power

the rate at which work is done

Horsepower

Horsepower is a common unit for power
1 hp = 1714 gal/min x 1 psi

Heat

The energy transferred between objects that are at different temperatures

Torque

a turning or twisting force

Flow

Makes actuator operation possible

Early Hydraulic Uses

Water Wheels
Create rotational motion
Descriptions exist as early as 1st century BC
Several examples in ancient China
Grist mill is pictured
Roman Aqueducts
Delivered water to buildings, agricultural fields, and fountains
Used gravity to create flow
Fountains were decorative and used by people to collect water for practical use

Hydrodynamic Systems

Fluid is in motion
Force and energy are transmitted by flow
Fluid does not flow quickly or continuously
Fluid is pressurized
Force and energy transmitted by pressure
Most common in industrial
settings

Flow Rate

The volume of fluid that moves through a system in a given period of time.

Flow Velocity

The distance the fluid travels through a system in a given period of time.

Bernoulli's Principle

Conservation of Energy: An increase in velocity results in a decrease in pressure. Likewise, a decrease in velocity results in an increase in pressure.

Viscosity

A liquid's resistance to flowing

Pump

A device used to create flow in a fluid powered system.