1. Pneumatics

2. Pneumatics is a subsection of an area known as fluid power.
Makes use of air which is a colourless, odourless and tasteless gas consisting of approximately 78% Nitrogen and 20% Oxygen. The remaining 2% consists of about 1% Argon and a mixture of other trace elements such as helium, hydrogen and neon
Widely used in Industry where it uses pressurised air, more commonly called compressed air to do work and effect mechanical motion,
Used worldwide in the construction and mining industries, manufacturing and transport systems, packaging, diving and dentistry.
Why is it so popular?

3. Advantages Disadvantages
Preferred system of use because of its availability and safety attributes.
Advantages
Unlimited free supply
Storage
Easily Transportable
Clean
Explosion proof
Controllable (Speed, Force)
Overload Safe
Disadvantages
Cost (Inefficient)
Preparation
Noise Pollution
Limited Range of Force
(only economical up to 25kN)

4. Compressors types Helical screw type Piston type Axial vane type
There are many different types and shapes of compressors available. They are divided into two main groups, Positive displacement and dynamic. These are sub divided into a number of other types, Piston, Screw, Centrifugal and Axial as shown in the diagram. The piston type can single piston or double piston as shown. The screw type takes in air at one end, traps it in the helical vanes squeezing it as it travels along the screw and out at the opposite end. On the centrifugal type the air is taken in the front through the vanes and again squeezed into a smaller space to compress before it get to the outlet. In the axial compressor one set of blades is ststionary and the other set turn to compress the air between them, the fact that the diameter of the vanes is reducing as you get to the outlet increases the compression effect. Animations are shown in the slides and further information can be had from the website shown at the end of the slide.
Helical screw type
Axial vane type
Centrifugal type
Piston type

5. Single Piston compressor cycle
Outlet
Outlet
Outlet
Outlet
Inlet
Inlet
Inlet
Inlet
Nearing the end of the compression, the outlet valve opens sending the compressed air to the storage tank.
Piston at the starting position, Top of cylinder, both valves closed.
Piston moving down outlet valve closed, Inlet valve open taking in Air.
Piston moving up, both valves closed, air is being compressed.

6. Typical Industrial system layout
Separators
Compressor
Reservoir
Dryer
Filters
Pipe distribution
Slope 1.5%

7. Valves and Actuators Physical appearance Pneumatic symbol

8. Reading pneumatic symbols
Squares represent the valve switching positions.
The number of squares represents the number of switching positions.
Lines indicate flow path and arrows the direction of flow.
Lines drawn at right angles in boxes indicate shut off positions.
Inlet and outlet ports are shown by lines on the outside of the box and in their initial positions.
Air pressure supply from the compressor.
Exhaust port

9. Reading pneumatic symbols
3/2 Way directional control valve normally closed
3/2 Way directional control valve normally open
5/2 Way directional control valve
Number of Ports.
Number of Positions 4 2 5 1 3
pushbutton
Solenoid
Pneumatic pilot
Proximity switch
Pushbutton, detent

10. Final controlling elements
Valves and Actuators: System structure with signal path
Energy supply
Source
Input elements
Input signals
Processing elements
Process signals
In this slide there is a comparison being made between the structure and signal path of a pneumatic system with that of an electronic control system. The first element of the system is the supply which in our case is compressed air. The input element gives us some basic control over how the air is used. The processing elements gives some decision making control to the system depending on the input signal. After that another control valve is used to give additional control in the system before it gets to the actuator to provide our final output and perform the required operation.
Final controlling elements
Control signals
Actuators
Outputs

11. Actuators Single acting actuator
Single acting actuator typical physical appearance
Piston Rod
Compressed air Inlet
Outlet opens to the Atmosphere
Symbol
Seal

12. Operation / Applications
Single Acting Cylinders are equipped with one working port on the piston side and the rod side is open to the atmosphere. The compressed air forces the piston rod out of the cylinder and on removing the air the piston is returned by the force of the spring.
Single acting cylinders are used for applications such as clamping, feeding, ejecting, sorting, locking, braking etc., where force is exerted only in one direction only.
They are usually available in short stroke lengths up to a maximum of 80mm, restricted by the length of the return spring.

13. Double acting actuator
Symbol
Compressed air may be applied to both ports
Seals
Piston rod
Flow control valves
Mounting bracket

14. Operation / Applications
Double Acting Cylinders are equipped with two working ports- one on the piston side and the other on the rod side.
Forward motion of the cylinder is achieved by connecting compressed air to the piston side and the rod side is connected to the exhaust.
During return stroke the air supply is connected to the rod side while the piston side connected to the exhaust. Force is exerted by the piston during both the forward and return motion of cylinder
Double acting cylinders are available in diameters from a few mm to around 300 mm and stroke lengths of a few mm up to 2 meters.

15. Our main focus is the conventional Single and double acting types
They are also available in many different types:
Conventional, single and double acting
Double ended piston rod type, have a rod projecting from each end, balanced
Rod less type, cylindrical barrel with a free moving magnetically coupled piston
Tandem type, two cylinders joined end to end with a common piston rod
Multi-position type, similar to the tandem type, can be moved to fixed positions
Rotary type, small , efficient, easy to install, Air motors, rack and pinion action.
Our main focus is the conventional Single and double acting types

16. Flow control valves / Bidirectional
The commonest bidirectional control valve is the needle valve. Flow is controlled by turning the thumbscrew and moving the fine tapered needle into or out of the orifice.
Thumbscrew may have micrometer type graduations around the barrel for precise control.
Flow is the same in both directions.

17. Flow control valves / Unidirectional
This is a conventional flow control regulator. It is unidirectional, air flow is controlled by screwing the tapered pin into the orifice shown thus restricting and controlling the volume of air flow.
The flow past the tapered pin also forces the flexible valve closed, all the flow is past the pin, the left diagram
If the direction of the air flow is reversed then the flexible valve lifts allowing the free flow of air through the valve and past the tapered pin, the right diagram

18. Spool valves Initial state Activated state 2 From actuator To actuator
Open to the atmosphere
Initial state
Activated state
Seals
Exhaust
Spool
Air inlet
To actuator
From actuator 2 3 1
Spool
Return spring

19. Poppet valves Initial state Activated state Exhaust Air inlet
To actuator
From actuator
Seals
Return spring 2 3 1

20. Flow control valves / Quick exhaust
Physical appearance
Cutaway section showing poppet valve positions
Used to increase piston speed.
When air flow is from port 1 to port 2 the poppet valve is kept closed under the supplied pressure.
When operated in the reverse direction the lower pressure on port 1 allows the poppet valve to open rapidly and channel the air out through the much larger opening giving the quick exhaust.

21. Shuttle valve The shuttle valve has two inputs and one output.
Air input 1
Air output 2
Symbol
High pressure
The shuttle valve has two inputs and one output.
It switches based on the air pressure entering either or both of the inputs. If both inputs ports 1 start to receive compressed air then the connection with the highest pressure takes precedent and is output on port 2.
Used in pneumatic logic circuits to give the OR function.

22. Two pressure valve
Physical appearance the same as the shuttle valve, internally different.
Compressed air enters either or both ports 1 and outputs on port 2.
If both ports 1 receive compressed air then the connection with the lower pressure takes precedent and outputs on port 2.
Used to provide the AND function in pneumatic logic circuits.

23. Pneumatic circuit diagrams
3 Port 2 Way directional valve normally closed (Spring return)
Physical appearance
Pneumatic symbol
Air in
3/2 valve pushbutton pressed
Piston rod extended under air pressure
Activated state
Exhaust valve closed
3/2 valve in initial position
Piston rod retracted under spring pressure
Exhaust valve open
Single acting actuator
Initial state
Pushbutton pressed

24. 3/2 valve and a single acting actuator Animation
Actuator, (Piston and rod)
Pushbutton
3/2 valve (normally closed, spring return)
Air in
Exhaust

25. 5 Port 2 Way directional valve, pushbutton spring return.
Pneumatic symbol
Physical appearance
5/2 valve in initial position
5/2 valve in activate position
Air inlet
Exhaust
Piston retracted under air pressure
Piston extended under air pressure
Double acting actuator
Pushbutton pressed

26. 4/2 valve and a double acting actuator Animation
Actuator, (Piston and rod)
Pushbutton
4/2 valve (spring return)
Air in
Exhaust

27. Logic circuit diagrams, The OR function.
Truth Table
Initial state, both pushbuttons released.
Pushbutton 1 pressed, actuator rod extending
Pushbutton 2 pressed, actuator rod extending

28. Initial state, both pushbuttons released.

29. Pushbutton 1 pressed, actuator rod extending

30. Pushbutton 2 pressed, actuator rod extending

31. Logic circuit diagrams,
The AND function.
Truth Table
Circuit in its initial state, neither pushbutton activated
Pushbutton 1 activated, no change in actuator
Both pushbuttons activated, compressed air delivered to the actuator under the action of the two pressure valve. Piston rod begins to extend.
Pushbutton 2 activated, no change in actuator

32. Logic circuit diagrams,
The AND function.
Circuit in its initial state, neither pushbutton activated

33. Logic circuit diagrams,
The AND function.
Pushbutton 1 activated, no change in actuator

34. Logic circuit diagrams,
The AND function.
Pushbutton 2 activated, no change in actuator

35. Logic circuit diagrams,
The AND function. 1 2 3 4 5
Double acting actuator
Both pushbuttons activated, compressed air delivered to the actuator under the action of the two pressure valve. Piston rod begins to extend. If either pushbuttons are released then the circuit returns to its initial state.
Pushbutton 1
Pushbutton 2
Two pressure valve
Compressed air
5/2 control valve
3/2 control valve
3/2 Control valve
Pilot port

36. Simple solenoid controlled circuit
Initial state
Solenoid switch operated
Switch,
mechanical or reed.
Solenoid
Electrical control side
Operational side
There are two parts to this circuit, the electrical circuit and the mechanical operational circuit
It consists of a 24 volt supply, a switch and a solenoid on the electrical side.
The operational side consists of a single acting actuator, a solenoid controlled 3/2 valve and an air supply.
In it’s initial state the electrical circuit is broken as the switch is open. The actuator is at rest (exhaust position) through the operation of the 3/2 valve.
Closing the switch brings in the solenoid, operating the 3/2 valve and extending the piston rod.
When the switch is opened again the circuit returns to it’s initial position.

37. Solenoid controlled delay circuit
Stage 1
Stage 3
Stage 2
Stage 4

38. Circuit Initial position
Pushbutton
Text
1Y1
+24V 0V
SW1 K1 4 2 1 3
1Y2 K2 5
Stage 1
This is the circuit layout in its initial position. On the electrical side you have a pushbutton switch, a relay K1, a proximity switch SW1, a second relay K2 with a 5 second delay set and two solenoids 1Y1 and 1Y2. In this case the supply voltage is 24 volts DC. The operational side has a double acting actuator, two flow controls and a 4/2 directional control valve with two solenoids. In its initial state the electrical circuit is inactive and there is a supply of compressed air flowing from port 1 to port 2 keeping the actuator piston retracted.

39. Pushbutton pressed Stage 2.
In this state the pushbutton has been pressed, there is now current flow through relay K1 which in turn brings in contacts K1 and the solenoid 1Y1, the red part of the circuit in the diagram. When 1Y1 is energised it activates the left side of the operational circuit connecting the air supply now from port 1 to port 4 and forcing the actuator piston rod out of the actuator.

40. Proximity switch operated
Pushbutton
Stage 3.
In this part of the circuit the piston rod has now reached the end of its travel and operates the proximity switch SW1. Current now flows through Switch SW1 and brings in the relay K2. As there is a 5 second delay set on this relay nothing happens until the 5 seconds have elapsed. The operational side of the circuit has not changed either.

41. Returning to initial position
Pushbutton
Stage 4.
In this diagram, after the 5 second delay the current flows through the relay K2 and this brings in contacts K2 operating the solenoid 1Y2. On the operational side of the circuit 1Y2 has now operated and switched over the 4/2 valve to its initial position as shown in the diagram for stage 1. The flow control valves in the circuit are to control the operational speed of the piston in the actuator.

42. PLC programming.
Programmer connected to a Laptop, controlled using a programming Language known as Ladder Logic.
Standalone PLC programmer
Software circuit layout to control a Double acting actuator with a Solenoid valve using a PLC programmer.
PLC
Reed sensor
Solenoid valve
Solenoid valve

43. Simple SMC control programme.
The programme starts and goes to the decision box, checks to see if Input 7 is High. If it is low it goes around the right hand loop and checks again until it gets a High. When Input 7 is High, it makes Output 1 High. It then waits 1 second and makes Output 1 low. It follows to loop around to the top of the decision box and checks again for the next cycle. This simple programme switches on and off the Solenoid controlling the flow of compressed air to the Actuator.

44. Pneumatic control using PIC Logicator software and Interface board.
Power supply cable
Output from PIC control board to Solenoid
Programming cable from Laptop
Input to PIC control board from Reed sensor
Single acting Actuator
Reed switch sensor
Double acting actuator
PIC Control Programme
T Piece
Electronic Control
3/2 Roller lever Pneumatic control valve
5/2 Solenoid Control valve
Compressed Air supply Manifold

45. General workshop requirements Air receivers/reservoirs:
Safety requirements
General workshop requirements
All pipes, hoses, and fittings must have a rating of the maximum pressure of the compressor. Compressed air pipelines should be identified (psi) as to maximum working pressure.
Air supply shutoff valves should be located (as near as possible) at the point-of-operation.
Hoses should not be left lying on the floors where they are likely to cause people to trip and fall..
Compressed air must not be used under any circumstances to clean dirt and dust from clothing or off a person’s skin. Workshop air used for cleaning should be regulated to 15 psi unless equipped with diffuser nozzles to provide a lower pressure.
Air receivers/reservoirs:
The maximum allowable working pressures of air receivers should never be exceeded except when being tested.
No tank or receiver should be altered or modified by unauthorised persons.
Reservoir/receivers should be drained frequently to prevent accumulation of liquid inside the unit.
A safety (spring loaded) release valve should be installed to prevent the receiver from exceeding the maximum allowable working pressure.

46. Safety requirements
 Pressure regulation Devices:
Only qualified personnel should be allowed to repair or adjust pressure regulating equipment.
Air tank safety valves should be set no less than 15 psi or 10 percent (whichever is greater) above the operating pressure of the compressor but never higher than the maximum allowable working pressure of the air receiver.
Air lines between the compressor and receiver should not usually be equipped with stop valves.
Air Compressor Operation:
The air intake should be from a clean, outside, fresh air source. Filters should be used to clean the air.
Air compressors should never be operated at speeds faster than the manufacturer’s recommendation.
Moving parts, such as compressor flywheels, pulleys, and belts that could be dangerous should be guarded.
More detailed safety requirements are to be found in the notes.

47. Pneumatic notes:
The supplied pneumatic notes contain a more detailed description of the material covered in these slides with the addition of sample worked problems associated with actuators and actuator selection.
Suggested sample pneumatic applications and questions are also included at the back of the notes.
Finally included is a glossary of the most frequently encountered pneumatic terminology.