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Chapter One
Introduction to Fluid Power
What is fluid power?
• Technology, which deals with the
generation, transmission, and control of
power using, pressurized fluids
• Hydraulics refer to the use of liquids,
primarily some type oil
• Pneumatics refer to the use of gases, the
most popular is air (it is cheap)
Types of Fluid Systems
• Fluid Transport
– Sole purpose is to move fluid from one location
to another
• Fluid Power
– Like transport systems, power systems move
fluid but are designed to perform work
– The fluid is bears upon cylinders and motors (
actuators) to accomplish the work
Advantages of Fluid Power
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Ease and accuracy of control
Multiplication of force
Constant force
Economical (fewer parts)
Disadvantages
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Messy
Noisy
Potentially explosive
Leaks
– (No such thing as leak free hose connections)
Basic Components: Hydraulic
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Reservoir
Pump
Prime Mover
Valves
Piping
Actuators
Filter
Basic Components: Pneumatic
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Compressed Air tank
Compressor
Prime Mover
Valves
Piping
Actuators
Filter
Fluid Power Controls
• Electrical
• PLC
• Closed/Open loop
How does the system work?
• Pascal’s Law The pressure exerted on a
confined fluid is transmitted in all directions and
acts at right angles to the containing surfaces.
• (F = P x A)
– P = pressure (psi or kPa)
– A = area (in2 or m2)
Applications of Pascal’s Law
• The most common uses of Pascal’s law are
multiplicity and continuity
F1 F2

A1 A2
Applications of Pascal’s Law
• Additionally, we can draw relationships with
distance since the volume of the system will be
constant
F2 S1 A2


F1 S 2 A1
Common Variables
Variable
SI
Force
Newtons (kg-m/sec2)
Pressure
Pascal (N/m2)
Area
Meters2
Time
Seconds
Velocity
M/sec
Length
Centimeters/Meters
Volume
M3
Acceleration
M/sec2
English
Lbf
Lbf/in2
Inches2
Hrs
Ft/sec
Inches/Feet
In3
Ft/ sec2
review of important
terms and definitions that are often
used in hydraulics
• Mass The mass of a body or an object is a
measure of the quantity of matter contained in it.
• Volume: The space occupied by a body is called
its volume.
• Density: The density of a substance is defined as
its mass per unit volume.
• The relative density of a substance is the ratio of
its density to the density of some standard
substance.
• Velocity:The distance covered by a body in a unit
time interval and in a specified direction.
• Acceleration which may be defined as the rate of
change of velocity of a moving body.
• The force is an attempt of either changing the
position/displacement of the object or its
dimensions.
• Weight: Weight refers to the force of gravity
acting on a given mass.
• specific weight or weight density of a fluid is
defined as the ratio of the weight of the fluid to its
volume.
• Work is defined as force through distance.
Work (W) = Force (F) x Distance moved or displacement (s)
• Energy: A body is said to possess energy
when it is capable of doing work.
forms of energy:
• Potential energy (PE)
• Kinetic energy (KE)
• Internal energy
• Power: The rate of doing work
Power (P) = Work done (W)/ Time (t)
Power = Force x Average velocity
OR P = F * v
• Horsepower: is the power of one horse
• 1 hp = 746 W