HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
FLUID POWER – DEVICES & CIRCUITS
RANA SAHA DEPARTMENT OF MECHANICAL ENGINEERING JADAVPUR UNIVERSITY KOLKATA – 700 032
[email protected]
FLUID POWER DEVICES & CIRCUITS
THE SYSTEM ACCESSORIES Voltage EHP
ELECTRIC MOTOR
Current
rpm
lpm
IHP
HHP PUMP
Torque
CONTROL DEVICES
Pressure
RESERVOIR
rpm or m/s
lpm
HHP
OHP ACTUATOR
• Power Supply Pressure • Controller • Sensors • DAS • PC Interface
LOAD
Torque/ Force
AUTOMATIC CONTROL
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HYDRAULIC CONTROL DEVICES & CIRCUITS
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 byes.
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
Pumps
Positive Displacement
Non Positive Displacement Centrifugal
Variable
Fixed
Axial Propeller
Vane
Mixed Flow
Gear
Internal Internal External (Crescent) (Gerotor)
Piston
Vane
Screw
Balanced
Radial
Unbalanced
Axial
Piston
Swash Plate Radial
Bent Axis
Axial Rotating Cylinder Block
Bent Axis
Swash Plate Rotating Swash Plate
Classification of Pumps
FLUID POWER DEVICES & CIRCUITS
GEAR PUMP
• 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).
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
GEAR PUMP – DETAILS
FLUID POWER DEVICES & CIRCUITS
VANE PUMP
Variable
Fixed
•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).
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
AXIAL PISTON PUMP Fixed • Workingpressure above aprox. 250 bar. • This type of pump can be driven in both directions. Rotating Swash Plate • 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.
Rotating Barrel
FLUID POWER DEVICES & CIRCUITS
AXIAL PISTON PUMP – CYLINDER VALVE PLATE DETAILS
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
Variable •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.
FLUID POWER DEVICES & CIRCUITS
Valves Pressure Control
Flow Control
Direction Control Check Valve
Pressure Relief
Fixed Shuttle
Pressure Reducing
Variable Two Way
Sequence Unloading
Pressure Compensated Deceleration
Three Way Four Way
Counterbalance
Valve Functions Classification
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
PRESSURE RELIEF VALVE Single Stage
FLUID POWER DEVICES & CIRCUITS
PRESSURE RELIEF VALVE Pilot Operated (2 Stage)
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
PRESSURE RELIEF VALVE AS AN UNLOADING VALVE • •
•
The pilot operated pressure relief valve is applied in systems with 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 the main 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 throttle in the by- 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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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
COUNTER BALANCE VALVE
FLUID POWER DEVICES & CIRCUITS
FLOW CONTROL Fixed
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
PRESSURE COMPENSATED FLOW CONTROL VALVE
FLUID POWER DEVICES & CIRCUITS
CHECK VALVES
Pilot – operated check valve
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HYDRAULIC CONTROL DEVICES & CIRCUITS
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 & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
Actuators Rotary
Linear Symmetric
Limited rotation
Continuous rotation Gear
Vane
Asymmetric
Vane
Piston Single Acting
Piston Fixed Unidirectional
Double Acting
Bidirectional
Variable
Classification of Actuators and their Symbols
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HYDRAULIC CONTROL DEVICES & CIRCUITS
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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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
INTENSIFIERS
• 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.
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 & CIRCUITS
FLUID POWER DEVICES & CIRCUITS RETRACT EXTEND
Linear Actuator (Hydraulic Cylinder)
Directional Control Valve A P
B T
Pressure Relief Valve
Pressure Gauge
Pump
Suction Strainer
BASIC HYDRAULIC CIRCUIT-1 Reservoir
FLUID POWER DEVICES & CIRCUITS
Rotary Actuator (Hydraulic Motor)
A P
B T
BASIC HYDRAULIC CIRCUIT-2
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS RETRACT EXTEND
A P
B T
REGENERATIVE CIRCUIT (Extension stroke)
FLUID POWER DEVICES & CIRCUITS
Counter balance Valve
COUNTERBALANCE CIRCUIT
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
Pressure Compensated Flow Control Valve
SPEED CONTROL CIRCUIT (METER-IN)
FLUID POWER DEVICES & CIRCUITS
Pressure Compensated Flow Control Valve
SPEED CONTROL CIRCUIT (METER-OUT)
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
Sequence Valve
SEQUENCING CIRCUIT
FLUID POWER DEVICES & CIRCUITS Accumulator 2 way, Solenoid operated DCV
4 way, Solenoid operated DCV
ACCUMULATOR CIRCUIT (AUXILIARY POWER SOURCE)
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HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS
Intensifier (Booster Cylinder)
INTENSIFIER CIRCUIT (High speed, low pressure approach followed by low speed high pressure piercing operation)
FLUID POWER DEVICES & CIRCUITS
A TYPICAL ELECTROHYDRAULIC CONTROL SYSTEM
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HYDRAULIC CONTROL DEVICES & CIRCUITS
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…
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