fluid power devices circuits
DESCRIPTION
Fluid Power Devices CircuitsTRANSCRIPT
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HYDRAULIC CONTROL DEVICES &
CIRCUITS
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FLUID POWER DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
RANA SAHA
DEPARTMENT OF MECHANICAL ENGINEERING
JADAVPUR UNIVERSITY
KOLKATA 700 032
FLUID POWER DEVICES & CIRCUITS
ELECTRIC
MOTORPUMP
CONTROL
DEVICESACTUATOR
ACCESSORIES
LOAD
EHP IHP HHP HHP OHP
Voltage rpm lpm lpm
rpmor
m/s
Torque/ForcePressurePressureTorqueCurrent
RESERVOIR
AUTOMATIC CONTROL
Power Supply
Controller
Sensors
DAS
PC Interface
THE SYSTEM
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HYDRAULIC CONTROL DEVICES &
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FLUID POWER DEVICES & CIRCUITS
Hydraulic fluids
FLUID POWER DEVICES & CIRCUITS
Reservoir
In addition to holding the supply of fluid needed
to ensure that all lines and components are
completely filled with fluid at all times, the
reservoir has four other functions:
1. It separates entrained air. Dwell time in the
reservoir provides opportunity for air bubbles in
the fluid to rise to the top and burst on the surface.
2. It dissipates pressure pulses. Circuits with
several actuators and random actuation of these
actuators can have significant pressure pulses in
the return line. Off-line filtration eliminates the
influence of these pulses on the filter, because
they are dissipated by the reservoir.
3. It provides cooling.
4. It traps contaminant. If the reservoir has to trap
contaminant, the filtration is not working
correctly. The reservoir does trap contaminant
when the filter bypasses.
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HYDRAULIC CONTROL DEVICES &
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FLUID POWER DEVICES & CIRCUITS
Fixed
Screw
Piston
Vane
Gear
Variable
Pumps
Vane
Positive DisplacementNon Positive Displacement
AxialRadial
Bent Axis Swash Plate
Unbalanced
Balanced
Piston
Axial
Radial
Swash Plate Bent Axis
Centrifugal
Axial Propeller
Mixed Flow
Classification of Pumps
Internal
(Crescent)ExternalInternal
(Gerotor)
Rotating Swash Plate
Rotating Cylinder Block
FLUID POWER DEVICES & CIRCUITS
For relatively low level of pressure (about 140 to 180 bar or 14 to 18 MPa)
Very simple, reliable, relatively cheap and less dirt sensitive
In order to prevent cavitation, the pressure at the suction side of the pump
should not exceed 0.1 to 0.2 bar (10 to 20 kPa) below atmospheric pressure
(minimim absolute pressure: 0.8 bar or 80 kPa).
GEAR PUMP
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FLUID POWER DEVICES & CIRCUITS
GEAR PUMP DETAILS
FLUID POWER DEVICES & CIRCUITS
VANE PUMP
Maximum pressure: about 200 bar.
Pulse free delivery and low level of noise.
The amount of eccentricity determines the displacement of the pump.
In order to prevent cavitation, the pressure at the suction side of the pump
should not exceed 0.1 to 0.2 bar (10 to 20 kPa) below atmospheric pressure
(minimim absolute pressure: 0.8 bar or 80 kPa).
FixedVariable
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FLUID POWER DEVICES & CIRCUITS
AXIAL PISTON PUMP
Rotating Swash Plate
Rotating Barrel
Workingpressure above
aprox. 250 bar.
This type of pump can be
driven in both directions.
Can operate without valves
because the rotating barrel has a
determined suck and pressure
zone.
Normally this pump has 5, 7, 9
or 11 pistons.
Fixed
FLUID POWER DEVICES & CIRCUITS
AXIAL PISTON PUMP CYLINDER
VALVE PLATE DETAILS
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FLUID POWER DEVICES & CIRCUITS
The angle of the swashplate determines the stroke of the pistons and therefore
the amount of displacement of the pump.
Normally the swashplate is adjusted by a hydraulic cilinder built inside the
pumphousing.
Variable
FLUID POWER DEVICES & CIRCUITS
Pressure Control
Unloading
Sequence
Pressure Relief
Pressure Reducing
Flow Control Direction Control
Counterbalance
Check Valve
Valves
Variable
Fixed
Pressure Compensated
Deceleration
Shuttle
Two Way
Three Way
Four Way
Valve Functions Classification
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FLUID POWER DEVICES & CIRCUITS
PRESSURE RELIEF VALVE
Single Stage
FLUID POWER DEVICES & CIRCUITS
Pilot Operated (2 Stage)
PRESSURE RELIEF VALVE
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FLUID POWER DEVICES & CIRCUITS
PRESSURE RELIEF VALVE
AS AN UNLOADING VALVE
The pilot operated pressure relief valve is applied in systemswith a considerable amount of flow. It's task is to limit the
pressure in the system on an acceptable value.
The pilot valve is adjusted at 150 bar. The pressure below themain valve is equal to the pressure above the main valve, for
example 100 bar (determined by the load on the hydraulic motor).
The spring on the main valve (about 1 to 5 bar) keeps the valve in
the closed position. As long as the pressure in the system does not
increase the adjusted pressure, the pump flow goes to the
hydraulic motor. When the hydraulic motor is overloaded, the
pressure will increase and the pilot valve will open. From that
moment on the pressure above the main valve is limited on 150
bar.
However, the pump flow cannot be drained by the small throttlein the by-pass canal, so the pressure below the main valve will
increase with the spring pressure of about 1 to 5 bar (the pressure
below the main valve will increase to 151...155 bar). Then the
main valve opens and the majority of the pump flow will be
drained by the main valve.
FLUID POWER DEVICES & CIRCUITS
SEQUENCE VALVE
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FLUID POWER DEVICES & CIRCUITS
COUNTER BALANCE VALVE
FLUID POWER DEVICES & CIRCUITS
FLOW CONTROL
Fixed
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FLUID POWER DEVICES & CIRCUITS
PRESSURE COMPENSATED FLOW CONTROL VALVE
FLUID POWER DEVICES & CIRCUITS
CHECK VALVES
Pilot operated check valve
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FLUID POWER DEVICES & CIRCUITS
SHUTTLE VALVE
FLUID POWER DEVICES & CIRCUITS
DIRECTION CONTROL VALVE
Method of actuation:
Manual
Electrical
- Solenoid
- Force/Torque Motor
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HYDRAULIC CONTROL DEVICES &
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FLUID POWER DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
Limited rotation
Piston
Vane
Continuous rotation
Actuators
RotaryLinear
Piston
Vane
Gear
Symmetric
Asymmetric
Single Acting
Classification of Actuators and their Symbols
Double Acting
Unidirectional Bidirectional
Fixed
Variable
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FLUID POWER DEVICES & CIRCUITS
A typical linear actuator details
FLUID POWER DEVICES & CIRCUITS
ACCUMULATORS
An accumulator is a container in which fluid is stored under pressure as a
source of power.
Functions:
1.Auxiliary power source to supplement the pump
2.Emergency power source in case of power failure to operate critical circuit
functions
3.Hydraulic shock absorber for circuits where sudden impact loads, quick
stops, or reversals with heavy loads are a characteristic of the system
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FLUID POWER DEVICES & CIRCUITS
Converts low-pressure fluid power into higher-pressure fluid power.
Intensifiers (also called boosters) are used to multiply forces when a great force is needed through a relatively short distance.
Hydraulic presses, riveting machines, and spot welders are typical applications.
INTENSIFIERS
FLUID POWER DEVICES & CIRCUITS
Some Basic Hydraulic Circuits
Basic Hydraulic Circuit
- Linear
- Rotary
Regenerative Circuit
Counterbalance Circuit
Hydraulic Circuit with Speed Control
- Meter-In
- Meter-Out
Sequence Circuit
Accumulator Circuit
Intensifier Circuit
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HYDRAULIC CONTROL DEVICES &
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FLUID POWER DEVICES & CIRCUITS
RETRACT
A B
P T
EXTEND
BASIC HYDRAULIC CIRCUIT-1
Pump
Pressure Relief Valve
Directional Control Valve
Linear Actuator (Hydraulic Cylinder)
Pressure Gauge
Suction Strainer
Reservoir
FLUID POWER DEVICES & CIRCUITS
A B
P T
BASIC HYDRAULIC CIRCUIT-2
Rotary Actuator (Hydraulic Motor)
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FLUID POWER DEVICES & CIRCUITS
RETRACT
A B
P T
EXTEND
REGENERATIVE CIRCUIT
(Extension stroke)
FLUID POWER DEVICES & CIRCUITS
COUNTERBALANCE CIRCUIT
Counter balance Valve
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FLUID POWER DEVICES & CIRCUITS
SPEED CONTROL CIRCUIT
(METER-IN)
Pressure Compensated Flow Control Valve
FLUID POWER DEVICES & CIRCUITS
SPEED CONTROL CIRCUIT
(METER-OUT)
Pressure Compensated Flow Control Valve
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FLUID POWER DEVICES & CIRCUITS
SEQUENCING CIRCUIT
Sequence Valve
FLUID POWER DEVICES & CIRCUITS
ACCUMULATOR CIRCUIT
(AUXILIARY POWER SOURCE)
Accumulator
2 way, Solenoid operated DCV4 way, Solenoid operated DCV
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FLUID POWER DEVICES & CIRCUITS
INTENSIFIER CIRCUIT
(High speed, low pressure approach followed by low speed high pressure piercing operation)
Intensifier (Booster Cylinder)
FLUID POWER DEVICES & CIRCUITS
A TYPICAL ELECTROHYDRAULIC CONTROL SYSTEM
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FLUID POWER DEVICES & CIRCUITS
Suggested Reading:
Pease, D.A. Basic Fluid Power. Prentice Hall.
Merritt, H. E. (1967), Hydraulic Control Systems. Wiley, New York.
Esposito, A.; Fluid Power (with Application). 2003
Sullivan, James A., 1998, Fluid Power Theory and Applications, Fourth
Edition, Prentice-Hall International
Yeaple, Frank, 1996, Fluid Power Design Handbook, Third Edition,
Marcel Dekker, Inc., N.Y.
Thank You