HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
FLUID POWER – DEVICES & CIRCUITS
RANA SAHA DEPARTMENT DEPARTMENT OF MECHANICAL ENGINEERING JADAVPUR JADAVPUR UNIVERSITY KOLKATA – 700 032
[email protected]
FLUID POWER DEVICES & CIRCUITS 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 LOAD
• Power Supply Pressure • Controller • Sensors • DAS • PC Interface
AUTOMATIC CONTROL
Torque/ Force
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Hydraulic fluids
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Reservoir In addi additi tion on to hold holdin ing g the the supp supply ly of flui fluid d needed to ensure that all lines and components are completely filled with fluid at all times, the reserv reservoir oir has four four other other functi functions ons:: 1. It separates entrained air. air. Dwell time in the rese reserv rvoi oirr prov provid ides es oppo opport rtun unit ity y for for air air bubb bubble less in the fluid luid to rise rise to the the top top and and burs burstt on the the surf surfaace. 2. It dissipates pressure pressure pulses. Circ Circui uits ts with ith sev several ral actua tuators tors and ran random dom actua tuatio tion of the these actu actuat ator orss can can have have sign signif ific ican antt pres pressu sure re puls pulses es in the the retu return rn line line.. OffOff-li line ne filt filtra rati tion on elim elimin inat ates es the the infl nfluence of thes hese pulses on the filter, because they they are are diss dissip ipat ated ed by the the rese reserv rvoi oirr. 3. It 3. It provides cooling. 4. It 4. It traps contaminant. If the the rese reserv rvoi oirr has has to trap trap contaminant, the filtration is not working corre orrecctly tly. The rese reserv rvoi oirr doe does tra trap conta ontam mina inant when when the filter filter bypas bypasses ses..
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Pumps Positive Displacement
Non Positive Displacement Centrifugal
Variable
Fixed
Axial Propeller
Vane Gear
Mixed Flow
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 CIRCUITS
GEAR PUMP
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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).
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
GEAR PUMP – DETAILS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
VANE PUMP
Variable •Maximum
Fixed
pressure: about 200 bar. •Pulse free delivery and low level of noise. •The amount of eccentricity determines the displacement displacement of the pump. pressure at the suction side of the pump •In order to prevent cavitation, the pressure 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).
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS 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 CIRCUITS
AXIAL PISTON PUMP – CYLINDER VALVE PLATE DETAILS
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS 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 CIRCUITS
Valves Pressure Control
Pressure Relief
Flow Control
Fixed
Direction Control Check Valve Shuttle
Pressure Reducing Sequence Unloading
Variable Two Way Pressure Compensated Deceleration
Counterbalance
Valve Functions Classification
Three Way Four Way
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
PRESSURE RELIEF VALVE Single Stage
FLUID POWER DEVICES & CIRCUITS CIRCUITS
PRESSURE RELIEF VALVE Pilot Operated (2 Stage)
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
PRESSURE RELIEF VALVE AS AN UNLOADING VALVE •
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The pi pillot ope perrat ateed pr preess ssur uree rel elie ieff val alve ve is ap appl plie ied d in sy syst stem emss with a considerable amount of flow. It's task is to limit the pressure in the system on an acceptable value value.. The pilot val alv ve is adjusted at 150 bar. The pressure below the main valve is equal to the press ssu ure above the main valve, for exam ex ampl plee 10 100 0 ba barr (d (det eter ermi mine ned d by th thee lo load ad on th thee hy hydr drau auli licc mo moto tor) r).. The sp spri ring ng on th thee ma main in va valv lvee (a (abo bout ut 1 to 5 ba bar) r) ke keep epss th thee va valv lvee in thee cl th clos osed ed po posi siti tion on.. As lo long ng as th thee pr pres essu sure re in th thee sy syst stem em do does es no nott increase the adjusted pressure, the pump flow goes to the hydr hy drau auli licc mo moto torr. Whe hen n th thee hy hydr drau auli licc mo moto torr is ov over erlo load aded ed,, th thee pressure will increase and the pilot valve will open. From that mom mo ment on th thee pr preess ssur uree ab abo ove th thee ma main in val alv ve is lim imit iteed on 15 150 0 bar. Howe Ho weve verr, th thee pu pump mp fl flow ow ca cann nnot ot be dr drai aine ned d by th thee sm smal alll th thro rott ttle le in th thee by by--pa pass ss ca cana nall, so the pr preess ssur uree be bellow th thee mai ain n val alv ve wil illl incr in crea ease se wit ith h th thee sp spri ring ng pr pres essu sure re of ab abou outt 1 to 5 ba barr (t (the he pr pres essu sure re below the main valve will increase to 151...155 bar). Then the main valve opens and the majority of the pump flow will be drai dr aine ned d by th thee ma main in va valv lve. e.
FLUID POWER DEVICES & CIRCUITS CIRCUITS
SEQUENCE SEQ UENCE VALVE
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
COUNTER BALANCE VALVE
FLUID POWER DEVICES & CIRCUITS CIRCUITS
FLOW CONTROL
Fixed
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
PRESSURE COMPENSATED FLOW CONTROL VALVE
FLUID POWER DEVICES & CIRCUITS CIRCUITS
CHECK VALVES
Pilot – operated check valve
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
SHUTTLE VALVE
FLUID POWER DEVICES & CIRCUITS CIRCUITS
DIRECTION CONTROL VALVE
Method of actuation: • Manual • Electrical - Sole Soleno noid id - Force/T Force/Torque orque Motor
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Actuators Rotary
Linear
Symmetric
Limited rotation
Continuous rotation Gear
Vane Asymmetric
Vane
Piston
Single Acting
Piston Fixed Unidirectio tional
Double Acting
Bidirectional
Variable
Classification of Actuators Actuators and their Symbols
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
A typical linear actuator details
FLUID POWER DEVICES & CIRCUITS CIRCUITS
ACCUMULATORS
An accumulator accumulator is a container container in which fluid is is stored under pressure 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
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS 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. •
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FLUID POWER DEVICES & CIRCUITS CIRCUITS
Some Basic Hydraulic Circuits
Basic Hydraulic Circuit - Linea inear r - Rota Rotarry • Regenerative Circuit • Counterbalance Circuit • Hydraulic Circuit with Speed Control - Meter Meter-I -In n - Meter Meter-O -Out ut • Sequence Circuit • Accumulator Circuit • Intensifier Circuit •
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS 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 CIRCUIT-1 Reservoir
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Rotary Actuator (Hydraulic Motor)
A P
B T
BASIC HYDRAULIC CIRCUIT-2 CIRCUIT-2
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS RETRACT EXTEND
A
P
B
T
REGENERATIVE CIRCUIT (Extension stroke)
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Counter balance Valve
COUNTERBALANCE CIRCUIT
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Pressure Compensated Flow Control Valve
SPEED CONTROL CIRCUIT (METER-IN)
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Pressure Compensated Flow Control Valve
SPEED CONTROL CIRCUIT (METER-OUT)
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Sequence Valve
SEQUENCING CIRCUIT
FLUID POWER DEVICES & CIRCUITS CIRCUITS Accumulator 2 way, Solenoid operated DCV
4 way, Solenoid operated DCV
ACCUMULATOR CIRCUIT (AUXILIARY POWER SOURCE)
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Intensifier (Booster Cylinder)
INTENSIFIER CIRCUIT (High speed, low pressure approach followed by low speed high pressure piercing operation)
FLUID POWER DEVICES & CIRCUITS CIRCUITS
A TYPICAL ELECTROHYDRAULIC CONTROL SYSTEM
HYDRAULIC CONTROL DEVICES & CIRCUITS
FLUID POWER DEVICES & CIRCUITS CIRCUITS
Suggested Reading: P ower.. Prentice Hall. • Pease, D.A. Basic Fluid Power •
Merritt, H. E. (1967), Hydraulic Control Systems. Wiley, 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 P ower Design Handbook, Third Edition, Marcel Dekker, Inc., N.Y. N.Y.
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