APPLIED HYDRAULICS AND PNEUMATICS
U5MEA23
Prepared by
Mr. Jayavelu.S & Mr. Shri Harish
Assistant Professor, Mechanical Department
VelTech Dr.RR & Dr.SR Technical University
UNIT I : FLUID POWER SYSTEMS
AND FUNDAMENTALS
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Introduction to fluid power
Advantages of fluid power
Application of fluid power system
Types of fluid power systems,
General types of fluids
◦ Properties of hydraulic fluids
◦ Fluid power symbols
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Basics of Hydraulics
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Applications of Pascal’s Law
Laminar and Turbulent flow
Reynolds’s number
Darcy’s equation
Losses in pipe, valves and fittings
Introduction to fluid power
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Fluid power is a term
describing hydraulics and pneumatics technologi
es.
Both technologies use a fluid (liquid or gas) to
transmit power from one location to another.
hydraulics, the fluid is a liquid (usually oil),
pneumatics uses a gas (usually compressed air).
Both are forms of power transmission, which is
the technology of converting power to a more
useable form and distributing it to where it is
needed.
The common methods of power transmission
are electrical, mechanical, and fluid power.
Advantages of fluid power
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high horsepower-to-weight ratio — You could probably hold a 5-hp
hydraulic motor in the palm of your hand, but a 5-hp electric motor might
weight 40 lb or more.
safety in hazardous environments because they are inherently sparkfree and can tolerate high temperatures.
force or torque can be held constant — this is unique to fluid power
transmission
high torque at low speed — unlike electric motors, pneumatic and
hydraulic motors can produce high torque while operating at low
rotational speeds. Some fluid power motors can even maintain torque at
zero speed without overheating
pressurized fluids can be transmitted over long distances and
through complex machine configurations with only a small loss in power
multi-functional control — a single hydraulic pump or air compressor
can provide power to many cylinders, motors, or other actuators
elimination of complicated mechanical trains of gears, chains, belts,
cams, and linkages
motion can be almost instantly reversed
Application of fluid power system
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Construction
Mining
Agriculture
Waste Reduction
Utility Equipment
Marine
Offshore
Energy
Metal Forming
Machine Tools
Military & Aerospace
Other Applications
Types of fluid power systems
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Fluid transport system
◦ Transport of water from reservoir using pipe
lines
◦ Transport of oil in pipe to two countries.
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Fluid power system
◦ Oil used in equipments to acquire desire
movement.
◦ Compressed air in pneumatics for crane
movements
Properties of hydraulic fluids
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Density
◦ The density of a fluid is its mass per unit volu
me:
◦ Liquids are essentially incompressible
◦ Density is highly variable in gases nearly prop
ortional to the pressure.
◦ Note: specific volume is defined as:
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Viscosity
◦ Viscosity is a measure of a fluid’s resistance to flo
w. It determines the fluid strain rate that is gener
ated by a given applied shear stress.
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Cohesion
◦ Intermolecular attraction between molecules of
same liquid
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Adhesion
◦ Attraction between molecules of liquid and
molecules of solid boundary in contact with
liquid.
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Cavitation
◦ Cloud of vapour bubble will form when liquid
pressure drops below vapour pressure due to
flow phenomenon
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Capillarity
◦ Liquid rises into a thin glass tube above or
below its general level.
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Vapour pressure
◦ Pressure exerted by vapour which is in
equilibrium with liquid
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Compatibility
◦ Ability of hydraulic fluid to be compatible with
the system.
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Volatility
◦ The degree and rate at which it will vapourize
under given conditions of temperature and
pressure.
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Corrosiveness
◦ Tendency to promote corrosion in hydraulic
system.
Application of pascals law
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Hydraulic press
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Hydraulic jack
Laminar and Turbulent flow
Laminar
 Turbulent
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Reynolds number
Darcys equation
Losses in pipes, valves and fittings
UNIT 2: HYDRAULIC SYSTEM
COMPONENTS
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Sources of Hydraulic Power
◦ construction and working of pumps – Variable
displacement pumps
◦ Actuators: Linear hydraulic actuators
◦ Single acting and Double acting cylinders
◦ Fluid motors.
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Control Components:
Direction control valve
 Flow control valves
 Electrical control -- solenoid valves. Relays, Accumulators
and Intensifiers.
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Basic Pump Classifications
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Hydraulic pumps can be classified using
three basic aspects:
◦ Displacement
◦ Pumping motion
◦ Fluid delivery characteristics
Basic Pump Classifications
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Displacement relates to how the output of the
pump reacts to system loads
◦ Positive-displacement pumps produce a constant
output per cycle
◦ Non-positive-displacement pumps produce flow
variations due to internal slippage
Basic Pump Classifications
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A non-positive-displacement pump has
large internal clearances
◦ Allows fluid slippage in the pump
◦ Results in varying flow output as system load
varies
Basic Pump Classifications
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Non-positive-displacement pump
Basic Pump Classifications
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The basic pumping motions used in
hydraulic pumps are:
◦ Rotary
◦ Reciprocating
Basic Pump Classifications
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Gear pumps are rotary pumps
Sauer-Danfoss, Ames, IA
Basic Pump Classifications
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Piston pumps are reciprocating pumps
Reciprocating piston movement
Basic Pump Classifications
In a rotary pump, the pumping action is
produced by revolving components
 In a reciprocating pump, the rotating motion
of the pump input shaft is changed to
reciprocating motion, which then produces
the pumping action
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Basic Pump Classifications
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Hydraulic pumps are classified as either
fixed or variable delivery
◦ Fixed-delivery pumps have pumping chambers
with a volume that cannot be changed; the
output is the same during each cycle
◦ In variable-delivery designs, chamber
geometry may be changed to allow varying
flow from the pump
Basic Pump Classifications
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Gear pumps are fixed-delivery pumps
Basic Pump Classifications
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Piston pumps may be designed as
variable-delivery pumps
Basic Pump Classifications
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When selecting a pump for a circuit, factors
that must be considered are:
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System operating pressure
Flow rate
Cycle rate
Expected length of service
Environmental conditions
Cost
Pump Design, Operation,
and Application
Gear pumps are positive-displacement,
fixed-delivery, rotary units
 Gear pumps are produced with either
external or internal gear teeth
configurations
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Pump Design, Operation,
and Application
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Gear pumps are commonly used
Pump Design, Operation,
and Application
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Pumping action of gear pumps results
from unmeshing and meshing of the gears
◦ As the gears unmesh in the inlet area, low
pressure causes fluid to enter the pump
◦ As the pump rotates, fluid is carried to the
pump discharge area
◦ When the gears mesh in the discharge area,
fluid is forced out of the pump into the
system
Pump Design, Operation,
and Application
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Gear pumps are available in a wide variety
of sizes
◦ Flow outputs from below 1 gpm to 150 gpm
◦ Pressure rating range up to 3000 psi
Pump Design, Operation,
and Application
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The gerotor pump design is an internalgear pump
◦ Uses two rotating, gear-shaped elements that
form sealed chambers
◦ The chambers vary in volume as the elements
rotate
◦ Fluid comes into the chambers as they are
enlarging and is forced out as they decrease in
size
Pump Design, Operation,
and Application
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The gerotor is a common internal-gear
design
Pump Design, Operation,
and Application
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Gerotor operation
Pump Design, Operation,
and Application
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Gerotor operation
Pump Design, Operation,
and Application
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Gerotor operation
Pump Design, Operation,
and Application
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Gerotor operation
Pump Design, Operation,
and Application
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Vane pumps are positive-displacement,
fixed or variable delivery, rotary units.
◦ Design is commonly used in industrial
applications
◦ Delivery can range up to 75 gpm
◦ Maximum pressure of about 2000 psi
Pump Design, Operation,
and Application
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Vane pump consists of a slotted rotor, fitted
with moveable vanes, that rotates within a
cam ring in the pump housing
◦ Rotor is off center in the ring, which creates
pumping chambers that vary in volume as the
pump rotates
◦ As chamber volume increases, pressure
decreases, bringing fluid into the pump
◦ As volume decreases, fluid is forced out into the
system
Pump Design, Operation,
and Application
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Operation of a typical vane pump
Pump Design, Operation,
and Application
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Parts of a typical vane pump
Pump Design, Operation,
and Application
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Vane pump may be pressure unbalanced
or pressure balanced
◦ Unbalanced has only one inlet and one
discharge, which places a side load on the
shaft
◦ Balanced has two inlets and two discharges
opposite each other, creating a pressure
balance and, therefore, no load on the shaft
Pump Design, Operation,
and Application
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Piston pumps are positive-displacement,
fixed- or variable-delivery, reciprocating
units
◦ Several variations
◦ Many provide high volumetric efficiency (90%),
high operating pressure (10,000 psi or higher),
and high-speed operation
Pump Design, Operation,
and Application
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A basic piston pump consists of a housing
that supports a pumping mechanism and a
motion-converting mechanism
◦ Pumping mechanism is a block containing
cylinders fitted with pistons and valves
◦ Motion converter changes rotary to
reciprocating motion via cams, eccentric ring,
swash plate, or bent-axis designs
◦ Rotating the pump shaft causes piston
movement that pumps the fluid
Pump Design, Operation,
and Application
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Piston pump classification is based on the
relationship between the axes of the
power input shaft and piston motion
◦ Axial
◦ Radial
◦ Reciprocating
Pump Design, Operation,
and Application
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Axial piston pumps use two design
variations:
◦ Inline
◦ Bent axis
Pump Design, Operation,
and Application
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Inline has the cylinder block and pistons
located on the same axis as the pump
input shaft
◦ Pistons reciprocate against a swash plate
◦ Very popular design used in many applications
Pump Design, Operation,
and Application
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An inline axial-piston pump
Pump Design, Operation,
and Application
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Bent axis has the cylinder block and pistons
set at an angle to the input shaft
◦ Geometry of the axis angle creates piston
movement
◦ Considered a more rugged pump than inline
◦ Manufactured in high flow rates and maximum
operating pressures
Pump Design, Operation,
and Application
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A bent-axis axial-piston pump
Pump Design, Operation,
and Application
Radial piston pumps have the highest
continuous operating pressure capability
of any of the pumps regularly used in
hydraulic systems
 Models are available with operating
pressure ratings in the 10,000 psi range
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Pump Design, Operation,
and Application
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Two variations of radial piston pumps:
◦ Stationary-cylinder design uses springs to hold
pistons against a cam that rotates with the main
shaft of the pump
◦ Rotating-cylinder design uses centrifugal force
to hold pistons against a reaction ring
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When the main shaft is rotated, each piston
reciprocates, causing fluid to move through
the pump
Pump Design, Operation,
and Application
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A stationary-cylinder radial-piston pump
Pump Design, Operation,
and Application
Large, reciprocating-plunger pump designs
were widely used when factories had a
central hydraulic power source
 Today, plunger pumps are typically found
in special applications requiring highpressure performance
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Pump Design, Operation,
and Application
Screw pumps have pumping elements that
consist of one, two, or three rotating
screws
 As the screws rotate, fluid is trapped and
carried along to the discharge of the
pump
 The design of screw pumps allows them
to operate at a very low noise level
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Pump Design, Operation,
and Application
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A typical screw pump
Pump Design, Operation,
and Application
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The lobe pump is a close relative of the
gear pump
◦ Two three-lobed, gear-shaped units are often
used to form the pumping element
◦ Output flow is larger than a gear pump of
comparable physical size because of pumping
chamber geometry
◦ Lower pressure rating than gear pumps
◦ Tend to have a pulsating output flow
Pump Design, Operation,
and Application
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Operation of a lobe pump
Pump Design, Operation,
and Application
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Centrifugal pumps are non-positivedisplacement units
◦ Use centrifugal force generated by a rotating
impeller to move fluid
◦ Large clearances between the impeller and the
pump housing allow internal pump slippage
when resistance to fluid flow is encountered in
the system
◦ Typically used in hydraulic systems as auxiliary
fluid transfer pumps
Pump Design, Operation,
and Application
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Operation of a centrifugal pump
Pump Design, Operation,
and Application
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Propeller and jet pumps are non-positivedisplacement pumps
◦ Sometimes used to transfer fluid within
hydraulic systems
◦ Propeller pump consists of a rotating
propeller-shaped pumping element
◦ Jet pump creates flow by pumping fluid
through a nozzle concentrically located within
a venturi
Pump Design, Operation,
and Application
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Construction of a propeller pump
Pump Design, Operation,
and Application
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Construction of a jet pump
Directional control valves
Check valve
 Pilot operated check valve
 Three-way and four-way valves
 Manually-actuated valve
 Pilot actuated valve
 Solenoid actuated valve
 Center flow path configuration
 Shuttle valve
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Directional control valves
Pilot operated check valve
Three-way valves
Four-way valves
Manually-actuated valve
Pilot actuated valve
Solenoid actuated valve
Pressure control valves
Pressure relief valve
 Compound pressure relief valve
 Pressure-reducing valve
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Pressure relief valve
Compound pressure relief valve
Pressure-reducing valve
Flow control valve/ Needle valve
Restrictor needle valve
Weight loaded accumulator
Spring loaded accumulator
Diaphragm type accumulator
Bladder type accumulator
Intensifier
UNIT 3: PNEUMATIC SYSTEM COMPONENTS
Pneumatic Components:
 Properties of air. Compressors.
 FRL Unit –
 Air control valves,
 Quick exhaust valves
 pneumatic actuators- cylinders, air
motors.
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Compressor construction
Types of compressor
Piston type reciprocating
compressor
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Fig shows single-acting piston actions in the cylinder of a reciprocating
compressor.
The piston is driven by a crank shaft via a connecting rod.
At the top of the cylinder are a suction valve and a discharge valve.
A reciprocating compressor usually has two, three, four, or six cylinders in
it.
Screw compressor
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Screw compressors are also belong to the
positive displacement compressor family.
In screw compressors, the compression is
accomplished by the enmeshing of two
mating helically grooved rotors suitably
housed in a cylinder equipped with
appropriated inlet and discharge ports
Rotary vane compressor
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The rotor shaft is mounted eccentrically in a steel cylinder
so that the rotor nearly touches the cylinder wall on one
side, the two being separated only by an oil film at this point.
Directly opposite this point the clearance between the rotor
and the cylinder wall is maximum.
Heads or end-plates are installed on the ends of the cylinder
and to hold the rotor shaft.
The vanes move back and forth radially in
the rotor slots as they follow the contour of
the cylinder wall when the rotor is turning.
The vanes are held firmly against the
cylinder wall by action of the centrifugal
force developed by the rotating rotor.
In some instances, the blades are springloaded to obtain a more positive seal against
the cylinder wall.
Filter
Air In
Louver
Bowl
Drain Cock
Air Out
Filter Element
Sight Gauge
Regulator
Adjustable
Locking Knob
Main Spring
Diaphragm
Assembly
Air In
Valve Assembly
Air Out
Valve Spring
Lubricator
2
Quick Exhaust Valve
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Port 2 is connected directly to
the end cover of a cylinder
Port 1 receives air from the
control valve
Air flows past the lips of the
seal to drive the cylinder
When the control valve is
exhausted, the seal flips to the
right opening the large direct
flow path
Air is exhausted very rapidly
from the cylinder for increased
speed
2
1
1
2
1
Unit 4: FLUIDICS & PNEUMATIC CIRCUIT DESIGN
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Fluidics – Introduction to fluidic devices,
simple circuits Introduction to Electro
Hydraulic Pneumatic logic circuits, PLC
applications in fluid power control, ladder
diagrams
Fluid Power Circuit Design: Sequential
circuit design for simple applications using
classic, cascade, step counter, logic with
Karnaugh- Veitch Mapping and
combinational circuit design methods.
Fluidics
Bistable flip flop
SRT flip flop
OR/NOR & AND/NAND
Fluidic control of pneumatic
cylinders
PLC
Ladder diagram
PLC control of hydraulic circuit
Cascading circuit
UNIT 5: FLUID POWER CIRCUITS
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Speed control circuits, synchronizing circuit,
Pneumo hydraulic circuit, Accumulator
circuits, Intensifier circuits. Servo systems –
Hydro Mechanical servo systems, Electro
hydraulic servo systems and proportional
valves.
Deceleration circuit, hydrostatics
transmission circuits, control circuits for
reciprocating drives in machine tools,
Material handling equipments. Fluid power
circuits; failure and troubleshooting.
Speed control circuit
Regenerative circuit
Pressure intensifier circuit
Accumulator circuit
Pneumatic motor circuit
Regenerative drilling machine
Hydraulic fault diagnosis
Pneumatics fault diagnosis
Thank you.