Introduction to Pneumatics The term “PNEUMA” is derived from the ancient Greek, and meant breadth or wind. PNEUMATIC is the study of air movement and air phenomena. Although the fundamentals of pneumatics rank amongst the earliest perceptions of mankind, it was not until the last century that the behavior and the fundamentals were researched systematically. Some earlier applications and areas of use of pneumatics in the industry were; railways, mining and construction. Real practical industrial applications of pneumatics dates back only to about 1950s.
Properties of Air 78% Nitrogen 21% Oxygen 1% Other Gas (CO 2 , H, Ne, Krypton, Xenon, Water, etc.) <ul><li>Air is compressible. </li></ul><ul><li>Air is expandable. </li></ul><ul><li>Air when compressed produces a maximum temperature of 200 to 300°C. </li></ul><ul><li>Air contains 40PPM of solid particles and increases to 9 times when compressed. </li></ul>
Advantages of compressed air AMOUNT Air is available practically everywhere for compression, in unlimited quantities. TEMPERATURE Compressed Air is insensitive to temperature fluctuations. This ensures reliable operation, even under extreme conditions of temperature. TRANSPORT Air can be easily transported in pipelines, even larger distances. It is not necessary to return the compressed air. STORABLE A compressor need not be in continuous operation. Compressed Air can be stored in and removed from a reservoir. In addition, transportation in the reservoir is possible.
Advantages of compressed air (continued) EXPLOSION PROOF Compressed Air offers no risk of explosion or fire, hence no expensive protection against explosion is required. CLEANLINESS Compressed Air is clean since any air which escapes through leaking pipes or elements does not cause contamination. This cleanness is necessary, for example, in the food, wood, textile and leather industries. CONSTRUCTION The operating components are of simple construction, and are therefore inexpensive. SPEED Compressed Air is very fast working medium. This enables high working speeds to be attained. (Pneumatic cylinders have a working speed of 1 to 2 Meters/Second) .
Advantages of compressed air (continued) ADJUSTABLE With compressed air components, speeds and forces are infinitely variable. OVERLOAD SAFE Pneumatic tools and operating components can be loaded to the point of stopping and they are therefore overload safe.
Disadvantages of compressed air PREPARATION The Compressed Air needs good preparations. Dirt and humidity may not be present. (Wear of Pneumatic Components) . COMPRESSIBLE It is not possible to achieve uniform and constant piston speeds with compressed air. FORCE REQUIREMENT Compressed Air is economical only up to a certain force requirement. Under the normally prevailing working pressure of 700 KPa (7 Bar / 101.5 PSI) and dependent on the travel and speed. The limit is between 20,000 and 30,000 N (2,000 and 3,000 Kg.f) .
Disadvantages of compressed air (continued) EXHAUST AIR The exhaust air is loud. This problem has now, however, been largely solved due to the development of sound absorption material. COSTS Compressed Air is a relatively expensive means of conveying power. The high-energy costs are partially compensated by inexpensive components and higher performance. (Number of cycles) .
Summary of Energy Supply Compressor Plant Service Unit Piping System Dryer Receiver <ul><li>Types of Compressor (Positive displacement, Flow Compressor) </li></ul><ul><li>Flow Rate </li></ul><ul><li>Pressure </li></ul><ul><li>Service </li></ul><ul><li>To dampen pressure fluctuation </li></ul><ul><li>Condensation of water vapor </li></ul><ul><li>Safety </li></ul><ul><li>Cooling (note: Dew Point) </li></ul><ul><li>Absorption </li></ul><ul><li>Adsorption </li></ul><ul><li>Ring Circuit </li></ul><ul><li>Gradient 1-2% </li></ul><ul><li>Tapping Outlets pointing upwards </li></ul><ul><li>Diameter </li></ul><ul><li>Filter </li></ul><ul><li>Pressure Regulator </li></ul><ul><li>Lubricator </li></ul>
Summary of Energy Supply Compressor Plant Compressors are required to compressed the gas to the desired working pressure for transmission of power. Service Unit Piping System Dryer Receiver <ul><li>Types of Compressor (Positive displacement, Flow Compressor) </li></ul><ul><li>Flow Rate </li></ul><ul><li>Pressure </li></ul><ul><li>Service </li></ul>
Summary of Energy Supply Plant Receiver Compressed Air Receiver serves to stabilized the air supply and smoothens pressure fluctuations in the network when air is consumed. Compressor Service Unit Piping System Dryer <ul><li>To dampen pressure fluctuation </li></ul><ul><li>Condensation of water vapor </li></ul><ul><li>Safety </li></ul>
Summary of Energy Supply Compressor Plant Service Unit Piping System Dryer Receiver Good preparation is important when using compressed air. Water (moisture) is introduced in the system by the compressor which should be dealt with at the point of usage. <ul><li>Cooling (note: Dew Point) </li></ul><ul><li>Absorption </li></ul><ul><li>Adsorption </li></ul>
Air Drying Refrigeration Drying If the temperature is lowered further, the water vapor contained in it begins to condense. Air outlet Air inlet Refrigerating unit Air to air-heat exchanger Moisture separator Refrigerant Moisture separator Refrigeration machine
Dew Point Curve Example: At a dew point of 40°C (313 ° K), the quantity of water in 1M³ air is 50 Grams.
Absorption Drying Air Drying (continued…) Moisture, gases or dissolved materials from the air combines with the desiccant to form into a solid or liquid state. It is a chemical process and no external energy is required. Simple installation but high operating cost because the desiccant have to be discarded. Desiccant Condensate Moist air inlet Condensate drain Dry air outlet
Adsorption Drying Air Drying (continued…) Moisture, gases or dissolved materials from the air deposits on the porous surface of the desiccant. It is a physical process and regeneration is possible through hot air flow. Shut-off valve (open) Prefilter (oil filter) Adsorber 1 Hot air Heater Shut-off valve (open) Dry air <ul><ul><li>Shut-off valve (closed) </li></ul></ul>Shut-off valve (closed) Adsorber 2 <ul><ul><li>Secondary filter </li></ul></ul><ul><ul><li>Blower </li></ul></ul>
Summary of Energy Supply Compressor Plant Service Unit Piping System Dryer Receiver Condensation in the system should be prevented. Condensate can be trapped in pipelines at lowest points. Pipelines should be installed with downward gradient, measured in the direction of flow. Piping diameter should be selected primarily on the basis of flow volume, pipe length and working pressure. <ul><li>Gradient 1-2% </li></ul><ul><li>Tapping Outlets pointing upwards </li></ul><ul><li>Diameter </li></ul><ul><li>Ring Circuit </li></ul>
Installation of Pipelines Branch Line Inter-connected System Ring circuit are the commonly used pipeline installation. Gas can flow from two direction and a uniform supply can be obtain where there is heavy consumption. Ring Circuit
Summary of Energy Supply Compressor Plant Service Unit Piping System Dryer Receiver Compressed air needs good preparation. Dirt and humidity should be prevented as it may wear pneumatic components or cause it to malfunction. <ul><li>Filter </li></ul><ul><li>Pressure Regulator </li></ul><ul><li>Lubricator </li></ul>
Service Units Compressed Air Filter Combined Symbols - Air Service Units
Inlet Outlet Water Trap Drain Filter Element Baffles Filter with Water Trap Manual Control Filters remove contaminants, mainly condensed water from compressed air. Compressed air is conducted into the filter bowl and is rotated at high speed. Heavy particles of dirt and water particles are centrifuged onto the wall of the filter bowl and they remain there. Condensed water accumulates in the lower part of the filter bowl and is drained through the drain plug when the water reaches the maximum level mark. Fine particles are retained by the filter element through which the air has to flow.
Service Units Pressure Regulating Valve with Relief Port
Valve Body Inlet Outlet Vent Spring and Adjusting screw Pressure operation Pressure Regulator with Relief Port
The set screw permits adjustment of the initial tension in the diaphragm spring. The diaphragm lifts off the push rod off its seat. The push rod shuts off the exhaust port in the diaphragm. Operation of Pressure Regulator with Relief Port 6 Bar
If the pressure in the volume with the output port exceeds the set value, the diaphragm moves down first, shutting off the input port and then opening the exhaust ports to relieve the excess pressure. Operation of Pressure Regulator with Relief Port 6 Bar 4.5 Bar
Lubricator Air flows through the lubricator from left to right. Some of the air flowing through the valve is guided through a nozzle. Due to the resulting pressure drop, oil is drawn from an oil reservoir through a feed pipe.
Lubricator The air lubricator is used when -Extremely rapid oscillating motions are required -With cylinders with large diameters( 125mm)
The Structure of Pneumatic Systems Energy supply Signal input Signal processing Processing elements: Directional control valves, Shuttle valves, Dual-pressure valves, Sequencers, Pressure sequence valves Input elements: Push-button directional control valves Roller lever valves, Proximity switches, Air barriers Working elements: Cylinders Motors Optical indicators Control elements: Directional control valves Energy supply elements: Compressor Pneumatic reservoir Pressure regulating valve, Service units Command Execution Signal Output
Energy supply elements Input elements Processing element Control element Working element System Circuit Diagram 1A 1S3 1V2 4 2 1V1 2 14 12 1 1(3) <ul><li>5 </li></ul><ul><ul><li>1 </li></ul></ul>3 1S1 2 1S2 2 1S3 2 1 3 1 3 1 3 0Z 0S 2 1 3
Symbols for the Power Supply Section Energy Supply: Maintenance: Combined Symbols: Compressor with constant displacement volume Pneumatic reservoir Pressure Source 2 1 3 Filter Water separator with manual actuation Water separator with automatic condensate drain Pressure regulating valve with relief port, adjustable Lubricator Air Service Unit (consisting of: Compressed air filter, Pressure regulating valve, Pressure gauge and compressed air lubricator)
Non-return, Flow Control and Pressure Control Valves Symbols for Control Elements
Symbols for the Principle Working Elements Linear Actuators: Rotary Drives: Double-acting cylinder with single, non-adjustable cushioning Single-acting cylinder Double-acting cylinder Double-acting cylinder with through piston rod Double-acting cylinder with adjustable cushioning at both ends Rodless cylinder with magnetic coupling Air motor, constant displacement, rotation in one direction Air motor, variable displacement, rotation in one direction Air motor, variable displacement, rotation in both directions Pneumatic rotary motor
Design Characteristics of Directional Valves Valve designs are categorized as follows: The design principle is a contributory factor with regards to service life, actuating force, means of actuation, means of connection, and size. Poppet Valves Ball Seat Valve Disc Seat Valve Slide Valves Longitudinal Slide Valve Longitudinal Flat Slide Valve Plate Slide Valve (Butterfly Valve)
3/2-Way Valve: with Disk Seat, Normally Closed Position Disk Seat Poppet Valve
5/2-Way Double Pilot Valve , Pneumatically Actuated, Both Sides 5 Working ports, 2 switching positions The valve has a memory function. A short signal (pulse) is sufficient for actuation. Longitudinal Slide Valve
4/3-Way Valve, Mid-Position Closed, (flat slide valve) 4 Working ports, 3 switching positions Flat slide valves are mostly actuated manually as other types of actuation can only be implemented with difficulty. By rotating two disks, the flow channels are connected with, or isolated from each other. Longitudinal Flat Slide Valve
SWITCHING SYMBOLS FOR VALVES The connecting lines for supply and exhaust air are drawn outside the square. The valve switching position is shown by a square. The number of squares corresponds to the number of switching positions. Lines indicate the flow paths, arrows indicate the direction of flow. Closed ports are shown by two lines drawn at right angles to one another.
Directional Control Valves: Ports and Switching Positions 3/2-way valve, normally closed position 3/2-way valve, normally open position 4/2-way valve, flow from 1 to 2 and from 4 to 3 5/2-way valve, flow from 1 to 2 and from 4 to 5 5/3-way valve, mid-position closed 2/2-way valve, normally open position Number of ports Number of switching positions
Valve Connections Labeling Connection Coding As per ISO 1219 As per ISO 5599 Working or Outlet ports A, B, C… 2, 4, 6… Power Connection P 1 Drain, Exhaust Ports R, S, T… 3, 5, 7... Leakage Line L 9 Control Lines X, Y, Z… 12, 14, 16…
PORT DESIGNATIONS Port designation in accordance with DIN ISO 5599-3 "Fluid Technology – Pneumatics, 5-Way Valves" 1 -Supply port 2, 4 -Working ports 3, 5 -Exhaust ports 10 -Signal applied blocks flow from 1 to 2 12 -Signal applied opens flow from 1 to 2 14 -Signal applied opens flow from 1 to 4 81, 91 -Auxiliary pilot air