Hydraulic and Pneumatic

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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)



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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)


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


Pneumatic ActuatorsAdvantages/disadvantages/fea

tures

Power-to-weight ratioClean operationQuick acting/quick reversalCompressibility of airNon-linearityAccuracy of positioningSafety/overload/explosionLow powerDry friction



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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)


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

13

Valve

Direct or regulate the flow

Finite position

Infinite position

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Directional Control Valve

Linear spool valve

Rotary spool valve

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Valve Symbols

2/2

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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

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Double Acting Cylinder

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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

30

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Cylinder sequencing

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Pressure Control Valves

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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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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

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Hydraulic Symbols

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Hydraulic Symbols

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Hydraulic Symbols

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Hydraulic Symbols

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Hydraulic Symbols

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Hydraulic Symbols

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Hydraulic and Pneumatic

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