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Transcript of Introduction of Pneumatics - hylab.pe. Introduction+of+   Overload safe Pneumatic tools

  • Introduction of Pneumatics

    (25273)Fall 2007

  • Fluid Power Control & Design Laboratory

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    Concept

    Pneumatics use compressed air as a working medium to implement transfer, transition, distribution, and control of energy.Industrial applications:

    Automobile manufacture, automatic industry, food industryGeneral methods of material handling

    clamping, shifting, positioning, orientingGeneral applications

    packaging, filling, locking, sorting of partsMachining and working operations

    drilling, turning, milling, sawing

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    Applications

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    Advantages of Compressed AirAvailability Air is available practically everywhere in unlimited quantities. Transport Air can be easily transported in pipelines, even over long distance.

    Storage Compressed air can be stored in a reservoir. In addition, the reservoir can be transportable.Temperature Compressed air is relatively insensitive to temperature fluctuations.

    Explosion proof

    Compressed air offers no risk of explosion or fire.

    Cleanliness Unlubricated exhaust air is clean, which does not cause contamination.

    Components The operating components are of simple construction and therefore relatively inexpensive.Speed Compressed air is a very fast working medium.

    Overload safe Pneumatic tools and operating components can be loaded to the point of stopping and are therefore overload safe.

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    Disadvantages of Compressed Air

    Preparation Compressed air required good preparation. Dirt and condensate should not be present.

    Compressibility It is not always possible to achieve uniform and constant pistonspeeds with compressed air.

    Force requirement

    Compressed air is economical only up to a certain force requirement. Under the normal working pressure of 6 to 7 bar, the output limit is between 40,000 and 50,000 Newtons.

    Noise levelThe exhaust air is loud. This problem has now been largely solved due to the development of sound absorption material and silencers.

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    Comparison of Various Control Methods

    Mechanic Electric Electronic Hydraulic Pneumatic

    Output force Normal Normal Very smallVery big

    (>10 Ton)Big

    (10m/s)

    Signal response Normal Very fast Very fast High Slow

    Influence by load Hardly Hardly Hardly Small Big

    Structure Normal Little complicated ComplicatedLittle

    complicated Simple

    Influence by temperature Normal Big Big

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    PressureAbsolute pressure and gauge pressureThe pressure of pneumatic system can be lower than atmosphere (vacuum).

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    Characteristics of AirIdeal gas equation

    Temperature =constantIsothermal changes

    Pressure=constantIsobar changes

    Volume=constantIsochore changes

    Boyle-Mariottes Law

    Gay-Lussacs Law

    Charless Law

    constant=PV

    constant=TV

    constant=TP

    RTPV =

    Polytropic process

    constant=kPV

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    Symbols in Pneumatics

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    Symbols in PneumaticsDirectional control valves: symbol development

    Directional control valves: ports and positions (ways)

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    Symbols in Pneumatics

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    Symbols in Pneumatics

    Methods of actuation

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    Symbols in PneumaticsNon-return valve (check valve)and derivatives

    Flow control valves

    Pressure control valves

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    Symbols in PneumaticsLinear actuators Rotary actuators

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    Symbols in PneumaticsAuxiliary

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    Pneumatic Control System

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    Air Generation SystemThe air supply should be

    at the required pressure,dry andclean.

    The air generation system includes:

    Inlet filterAir compressorAir reservoirAir dryerAir filter with water separatorPressure regulatorAir lubricator as requiredDrainage points

    Generally, the maximum operating pressure is 8-10 bar.Recommended pressure is 5-6 bar for economic use.

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    Air Compressors

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    ReservoirsA reservoir compensates the pressure fluctuations.The large surface of the reservoir cools the air. Thus, portion of the moisture in the air is separated directly from reservoir as water.

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    Air DryersDamage of condensate (water) is to corrode pipes, valves, cylinders and other components.If temperature is below 0, water becomes to ice and blocks valves.

    Low temperature dryer

    Adsorption dryer

    Absorption dryer

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    Service Unit

    Compressed air filter

    Lubricator

    Pressure regulator

    Service unit

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    Single-acting Cylinders

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    Double-acting Cylinders

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    Rodless Cylinders

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    Pneumatic Motors

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    3/2-way Directional Control Valves

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    Directional Control Valves

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    Non-return (Check) Valves

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    Flow Control Valves

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    Pressure Control Valves

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    Vacuum SystemOperating pressure of vacuum system is below atmosphere pressure.Generally, vacuum system is used to hold workpieces by suction cups, which is a simple, low-cost and reliable solution.Vacuum system is suitable for workpieces with smooth surface, such as glass, paper.

    Typical vacuum circuit1-filter 2-refined filter 3-reducing valve4-pressure gauge 5-solenoid valve6-vacuum generator 7-silencer8-vacuum filter 9-vacuum pressure switch10-vacuum pressure gauge 12-suction cup12-workpiece

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    Vacuum GeneratorIt uses Venturi tube to generate vacuum.

    1-nozzle2-inducing zone3-mixing zone4-diffusing zone

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    Vacuum Suction Cups

    Flat suction cups Bellows suction cups

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    Contents

    1. Introduction2. Fundamentals3. Air generation4. Pneumatic actuators5. Pneumatic valves6. Vacuum technology7. Typical circuit

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    Example 1:Direct/Indirect Control of a Double-acting Cylinder

    A double-acting cylinder is to extent when a push button is operated.Upon release of the push button the cylinder is to retract.

    The cylinder is of small bore (25 mm diameter) requiring a small flow rate to operate at correct speed.

    The cylinder is 250 mm in diameter and consumes a large volume of air.

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    Example 2:Memory Circuit and Speed Control of a Cylinder

    The cylinder is to fully advance when a push button is operated and then retract automatically.Full extension is confirmed by a roller lever valve.The