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Hydraulic and Pneumatic
systems
1
Application area
Pneumatic Signals are widely used to
operate high load/Valves
- compressibility of air
Hydraulic are used for more large loads
-are costly and oil leakage hazard
2
Hydraulic Actuators
AdvantagesTransmission like electricity
Force in all directions E/M in onedirection
Instantaneous reversing
Minimum moving parts
Direct drive point of load
No/minimal need of transmission gearbox/etc.
Control 2 variablesOverload protection
Compact
Mechatronics,CRIS BITS PIlani 3
Hydraulic Actuators ..
Disadvantages/Limitations
Power = P * Q (~ VI)
Mechatronics,CRIS BITS PIlani 4
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Hydraulic Actuators ..Linear (reciprocating)
More common
Hydraulic Cylinder Types
Single/double acting
Displacement/ram/
Selection:
application/load/mounting/
environmentMechatronics,CRIS BITS PIlani 5
Hydraulic Actuators ..Rotary
Oscillatory vane type Limited rotation actuators
Few degree/few turn (screw)
Single vane (320 deg/40 kNm)
Double vane (150 deg/80 kNm)
Mechatronics,CRIS BITS PIlani 6
Hydraulic Actuators ..
Rotary
Continuous hydraulic motor Gear/piston/vane type
Gear low torque/low power
Vane low torque/medium power
Piston Radial: med T/P
Axial: High T/P
Mechatronics,CRIS BITS PIlani 7
Pneumatic ActuatorsAdvantages/disadvantages/fea
tures
Power-to-weight ratioClean operationQuick acting/quick reversalCompressibility of airNon-linearityAccuracy of positioningSafety/overload/explosionLow powerDry friction
Mechatronics,CRIS BITS PIlani 8
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Pneumatic Actuators ..Types:Similar to hydraulicLinear piston:
Single/double actingmulti-stage pistonCurved piston/rotary pistonComplex control control valvesDifficult speed control
bellows/diaphragmRotary/wane/turbine/gear:
High speed (3000-8500 rpm)/low power (0.1-0.2kW)
Mechatronics,CRIS BITS PIlani 9
Power Supplies
Motor pump
Sump
oil
Oil relief valve
Maintain safe pressure
Non return valve
1 D flow
10
Power Supply Circuit
Pr. Relief
Valve Accumulator
NRV
Pump
Return
OilSump
11
Power Supplies
Accumulator
Just a container
Oil held under pr.
Gas pr.
Spring type (old)
Pr. fluctuation
12
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Pneumatic Power Supply
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Valve
Direct or regulate the flow
Finite position
Infinite position
14
Directional Control Valve
Linear spool valve
Rotary spool valve
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Valve Symbols
2/2
16
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3/2 and 4/2
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Valve actuation symbol
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Valve
Infinite position
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Valve working symbol
1 or P pr. Supply
3 or T hyd. return port
3 or 5 (R or S) Pneumetic Exhaust
2 or 5 (B or A) o/p ports
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Solenoid operated valve
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Single Acting Cylinder
22
Double Acting Cylinder
23 24
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A lift system
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Pilot-operated valve
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Directional valve
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Pr. Control valve
28
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Pr. Sequence Valve
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Pr. Sequence Valve
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Cylinder sequencing
32
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35
Pressure Control Valves
36
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Pressure Control Valves
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Valve bodies
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Valve bodies
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Quick opening, linear, equal
percentage
40
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41
equal percentage valves
'Any % change in the opening from its current existingvalue changes the flow by same percentage of itscurrent value at current opening.'
Means if current opening is say 10% & u change it to 15%than the change in opening from its current value (of 10%)is 50%, so the flow will also increase by 50% of its existingvalue at 10% opening. This means if flow was say 20% of thetotal range (Or capacity of the valve) at 10% opening it willbecome 30% (50% higher compared to 20%) of the totalrange.
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Unloading Valve
43
Counterbalance valve
44
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Brake Valve
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Pressure reducing valve
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Non pressure compensate flow
control valve
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Pressure compensated flow
control valve
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Basic Components
49
Hydraulic Symbols
50
Hydraulic Symbols
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Hydraulic Symbols
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Hydraulic Symbols
53
Hydraulic Symbols
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Hydraulic Symbols
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