Basic Pneumatic System

1

Assembly & Maintenance of

Pneumatic & Hydraulic System

(SED 23103)

Basic Automation System

(SRD 23403)

Malaysian Spanish Institute

MSI Pneumatic System

v5

Assembly & Maintenance of Pneumatic & Hydraulic System

(SED 23103) - (Assessment)

1. Basic Pneumatic System – Technical Report 10%

– Mini Project 10%

– Test 10%

– Exam Practical 20%

2. Basic Hydraulic System – Technical Report 10%


– Test 10%


• Total Marks (SED 23103) – Technical Report 20%


– Test 20%


100%

2

MSI Electrical System


(SED 23103) - (Assessment)

1. Basic Pneumatic System – Pneumatic Power

– Pneumatic Control

– Pneumatic Actuator

2. Basic Hydraulic System – Hydraulic Power

– Hydraulic Control

– Hydraulic Actuator

• End of Course – Comparison of Power System

– Selection of Power System

3



(SED 23103) (Study Planning)

1. Basic Pneumatic System – Week 1 – 6 (Study week)

– Week 7 (Practical Test)

2. Basic Hydraulic System – Week 8 – 13 (Study Week)


4


Extra Assessment

Attitude marks

1. Attendant (per/minute = 0.019%)

2. Cheating (per/cheat = 1%)

3. Attire (per/day = 5%)

4. Behavior (per/hour = 5%)


(SRD 23403) - (Assessment)

1. Basic Electrical System – Technical Report 7%

– Mini Project 7%

– Test 7%


2. Basic Pneumatic System – Technical Report 7%

– Mini Project 7%

– Test 7%


3. Basic Hydraulic System – Technical Report 6%

– Mini Project 6%

– Test 6%


• Total Marks (SRD 23403) – Technical Report 7+7+6%

– Mini Project 7+7+6%

– Test 7+7+6%

– Exam Practical 14+14+12%

100%

5



(SRD 23403) - (Content Summary)

1. Basic Electrical System – Electrical Power

– Electrical Control

– Electrical Actuator

2. Basic Pneumatic System – Pneumatic Power

– Pneumatic Control

– Pneumatic Actuator

3. Basic Hydraulic System – Hydraulic Power

– Hydraulic Control

– Hydraulic Actuator

• End of Course – Comparison of Power System

– Selection of Power System

6


Basic Automation System (SRD 23403)

(Study Planning)

1. Basic Pneumatic System – Week 1 – 4 (Study week)


2. Basic Hydraulic System – Week 6 – 9 (Study week)


3. Basic Electrical System – Week 11 – 13 (Study Week)


• Extra Assessment – Attitude marks

• Attendant (per/minute = 0.019%)

• Cheating (per/cheat = 1%)

• Attire (per/day = 5%)

• Behavior (per/hour = 5%)

7


8


Basic Pneumatic System


9

Objective of Module

Why pneumatic system?

Because: relatively low cost, ease of installation, simple and robust

construction and ready availability in various sizes and stroke lengths. It is a basic control system. Uses air as its medium. Uses in low and medium

application.

Why learn pneumatic system? It is a basic control system.

Why learn maintenance of pneumatic system? To describe the methodology of preventive and corrective maintenance

technique of Pneumatic System.


10

Basic Control System


signal

processing output

signal

input

pushbutton valve cylinder

11

Control & Maintenance


signal

processing output

signal

input

Assembly / Maintenance / Troubleshoot

12

Content of Module

• CHAPTER 0 SAFETY IN PNEUMATIC SYSTEM

• CHAPTER 1 INTRODUCTION TO THE DIDACTIC UNIT

• CHAPTER 2 FUNDAMENTAL OF PNEUMATIC

• CHAPTER 3 PRODUCTION OF COMPRESSED AIR

• CHAPTER 4 DISTRIBUTION OF COMPRESSED AIR

• CHAPTER 5 MAINTENANCE UNIT

• CHAPTER 6 PNEUMATIC ACTUATOR

• CHAPTER 7 VALVES

• CHAPTER 8 MAINTENANCE IN PNEUMATIC SYSTEM

• CHAPTER 9 ELECTRO – PNEUMATIC SYSTEM

• CHAPTER 10 MAINTENANCE IN ELECTRO – PNEUMATIC SYSTEM


13

Safety in Pneumatic System chapter 0


• To date, no standards exist with regard to the safety of pneumatic systems. Therefore

for all factors affecting safety, reference must be made to existing general

guidelines and regulations from a number of different engineering fields.

• Pneumatic systems using several force cylinders must be equipped with an

emergency switch. Based on the design and operating characteristics of a system,

the decision must be made as to whether the EMERGENCY-STOP function is:

– to put the system into the zero pressure status

– to reset all force cylinders into the initial position, or

– to inhibit all cylinders in their current position.

These three options can also be combined.

• Precautions must be taken to prevent ACCIDENT.

14


Safety Instructions

• Pneumatic workbench is must operated, installed or maintained properly by

students with supervised by lecturer

• Pneumatic workbench is used in an application for which it was designed.

• The advice of the legal requirements, the safety and the mounting instructions are

must be followed.

• Everybody responsible for the installation, operation or maintenance of this unit

must get familiarized with these instructions, especially those relating to safety.

• The installation and dismantled of all the components must only be done by

students with supervised by lecturer.

• When installing, dismantling or maintaining the unit ensure that the power

(pneumatic / electrical) supply is first disconnected.

• Modification of the unit in any form is forbidden without prior consultation with

lecturer.

• All safety regulations and all regulations for prevention of accidents in the operating

range are valid.

15

Introduction to Pneumatic System chapter1

Pneumatic system uses “AIR” for their working medium.

The air from the atmosphere is reduced in volume by compression.


Advantage of pneumatic system

• Availability

• Transport

• Storage

• Temperature

• Explosion proof

• Cleanliness

• Components

• Speed

• Overload safe

Disadvantage of pneumatic system

•Preparation

•Compression

•Force requirement

•Noise level

16

Application Of Pneumatic System

General methods of material handling: (Clamping, Shifting, Positioning, Orienting, Branching of material flow)

General applications: Packaging, Filling, Metering, Locking, Driving of axes, Door or chute control,

Transfer of materials, Turning and inverting of parts, Sorting of parts,

Stacking of components, Stamping and embossing of components


17

Pneumatic System Overview


18


Schematic Diagram Of A Pneumatic System

2(A)

1(P) 3(R)

2(A)

1(P) 3(R)

12(Z)

Single Acting

Cylinder

19


Schematic Diagram Of A Pneumatic System

2(B)4(A)

5(R)1(P)

3(S)2(A)

3(R)1(P)

Double Acting

Cylinder

20

Working Principle (single acting cylinder)


Retract position Extend position

21

Working Principle (double acting cylinder)

Retract position Extend position


22

Fundamental of Pneumatic Chapter 2

1. Physical Quantities

2. Basic Quantities

3. Derived Quantities

4. Characteristic of air

5. Newton’s Law

6. Pressure

7. Force


23


Physical Quantity

Air is a mixture of

• Nitrogen approx. 78 vol. %

• Oxygen approx. 21 vol. %

• It also contains traces of carbon dioxide,

argon, hydrogen, neon, helium, krypton

and xenon.

24


Basic Quantity

Basic Unit

Quantity Symbol Units

Length L Meter (m)

Mass m Kilogram (kg)

Time t Second (s)

Temperature T Kelvin (K, 0 °C = 273.15 K)

25


Derived Quantity

Derived units

Quantity Symbol Units

Force F Newton (N) = 1 kg • m/s²

Area A Square meter (m²)

Volume V Cubic meter (m³)

Flowrate qv (m³/s)

Pressure p Pascal (Pa)

1 Pa= 1 N/m² 5 1 bar = 10 Pa

26


Characteristic of Air

Air Pressure • Generally, in pneumatics all data concerning air quantity refers to the so-called

standard state. According to DIN 1343, the standard state is the status of a solid,

fluid or gaseous substance defined by standard temperature and pressure.

Standard temperature Tn = 273.15 K, tn = 0 °C

Standard pressure pn = 101325 Pa = 1.01325 bar

Figure: Air pressure diagram

27


Boyle-Mariottes’s Law

Air can be compressed and it’s tend to expand. The applicable relationship is

given in Boyle-Mariottes’s Law.

p1 • V1 = p2 • V2 = p3 • V3 = Constant

Air has no particular shape. Its shape changes with the shape of its surroundings.

28


Gay-Lussac’s Law

According to the Gay-Lussac’s law, the volume of a given mass of gas is

proportional to the absolute temperature as long as the pressure does not

change.

Where:

V1 = Volume at T1, V2 = Volume at T2

29


Newton’ Law

Newton’s Law: Force = mass • acceleration

F = m • a

where a is replaced by the acceleration due to gravity

g = 9.81 m/s²

30

Force

• A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction.


F = m • a

31


Pressure

Pressure: 1 Pascal is equal to the constant pressure on a surface area of 1 m² with the vertical force of 1 N (Newton).

32

Pressure

• Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. Mathematically:

• where:


A

p

F

Area of double

acting cylinder

= π (d/2)²

http://en.wikipedia.org/wiki/Force_%28physics%29

http://en.wikipedia.org/wiki/Area

http://en.wikipedia.org/wiki/Surface_normal

Assignment 1 – AP1: Fundamental in Pneumatic

1. Find F1 if D1 is Ø32mm and p is 4bar.

2. Find the area if the pressure is 0.5MPa and the force acting at F1 is 200N

3. Find the pressure if force acting at F1 is 30kg and the bore diameter D1 of

the cylinder is Ø3.0cm

4. Find F1 and F2 if D2 is Ø22mm, D1 is 32mm and the p is 6 x 105 Pa.

(Force in N, Area in mm² and Pressure in bar)

33


p

F1 D1

F2

p

D2

34


Production of Compressed Air Chapter 3

For the continuous performance of control systems and working elements the air supply should:

• At the required pressure,

• Dry,

• Clean

If these conditions are not fulfilled, then problem of the system will occur. The effect

is downtime on the machinery in addition to increased costs for repair or replacement of parts.

The equipment to be considered in the generation and preparation of air:

- Inlet filter

- Air compressor

- Air reservoir

- Air dryer

- Air filter with water separator

- Pressure regulator

- Air lubricator as required

- Drainage points

35


Air Compressor

36


Air Compressor

• The selection from the various types of

compressors available is dependent upon

quantity of air, pressure, quality and

cleanliness and how dry the air should be.

• 3 main type of Air Compressor

1. Reciprocating Compressor

2. Centrifugal Compressor

3. Rotary compressor

37


Reciprocating Piston Compressor

The compressed air is drawn thru an inlet valve then the air is passed on thru an outlet valve via reciprocating piston .

Single stage

piston compressor

Double stage

piston compressor

Diaphragm

piston compressor

38


Working Principle (single stage piston)

At the end of the stroke, the

piston moves upward, the inlet

valve closes as the air is

compressed, forcing the outlet

valve open to discharge air into

air reservoir.

Air reservoir

Downward movement of the

piston increases volume to

create a lower pressure than

that of atmosphere, causing air

to enter the cylinder through

the inlet valve.

atmosphere

Working Principle (single stage piston)

• Piston travel downward

• Compression Chamber is at low pressure state (vacuum)

• Inlet valve open, atmospheric pressure will be sucked

into the compression chamber

• Piston travel upward

• Compression Chamber is at high pressure state

(compressed air)

• Outlet valve open, the compressed air will be pushed out

from the compression chamber.

39


40


Working Principle

atmosphere

compression

Compress

Air (3bar)

Inter-cooling

Compress

Air (7bar)

atmosphere

Compress

air

Double stage

piston compressor

Diaphragm

piston compressor

compression

41


Centrifugal & Rotary compressor

Sliding Vane

compressor

Screw

compressor

The rotary compressors use rotating elements to compress and increase the pressure of the air. During the compression process, the compression chamber is continually reduced.

42


Working Principle

Sliding Vane

compressor Screw

compressor

compression

Compress

Air

OUT

Atmosphere

IN

Assignment 2 - AP2: Pneumatic Compressor

43


• Working operation on: 1. Single Stage piston compressor,

2. Double Stage piston compressor,

3. Diaphragm piston compressor,

4. Single Chamber Vane compressor,

5. Double Chamber Vane compressor,

6. Screw compressor

44


Air Reservoir

• A reservoir is configured to:

• Stabilize compressed air.

• Compensates the pressure fluctuations.

• Air storage for continuous air supply. This has the advantage that the

compressor does not need to operate continuously.

• Cooling system for the compressed air.

45


Air Dryer

• Is used to eliminate Condensate (water) enters into

Pneumatic System through compressed air.

• Water causes problems related to corrosion and seal

wear.

• 3 type of dryer: • Low temperature drying

• Adsorption drying

• Absorption drying

46


Low Temperature Drying

The air entering into the refrigeration dryer is

pre-cooled in a heat exchanger by the

escaping cold air. It is then cooled in the

cooling unit to temperatures between + 2 and

+ 5 °C. The dried compressed air is filtered.

Before the compressed air is output into the

network, the air is heated to bring the air

back to ambient conditions.

47


Adsorption Drying

Adsorption: water is deposited on the surface

of solids.

The drying agent is a granular material (gel)

consisting almost entirely of silicon dioxide.

Usually two tanks are used. When the gel in

one tank is saturated, the air flow is switched

to the dry, second tank and the first tank is

regenerated by hot-air drying.

The lowest equivalent dew points (down to –

90 °C) can be achieved by means of

adsorption drying.

48


Absorption Drying

Absorption: A solid or liquid substance

bonds a gaseous substance.

Absorption drying is a purely chemical

process. Absorption drying is not of

major significance in present-day

practice, since the operating costs are

too high and the efficiency too low for

most applications.

49


Distribution of compressed air Chapter 4

• In order to ensure reliable and trouble-free air distribution, a number

of points must be observed. This includes primarily the correct sizing

of the pipe system, but also the pipe material, flow resistances, pipe

layout and maintenance.

• Pressure fluctuations in the network make it necessary to ensure

that the pipes are mounted securely in order to avoid leakages at

screwed and brazed connections.

• Two type of piping distribution layout:

– Dead End Line

– Ring

50


Piping Layout (Dead End Line piping Layout)

Pipe layout is the critical factor

in determining the economic

operation of the compressed-

air system. Compressed air is

fed into the system at intervals

by the compressor. It is often

the case that consumption at

consuming devices rises for

only a short time. This may

lead to unfavorable conditions

in the compressed-air network.

51


Piping Layout (Ring piping Layout)

• Therefore it is recommended that the compressed-air network should be produced in the form of a ring main. A ring main ensures largely constant pressure conditions.

52


Piping Layout (Ring piping Layout)

• For ease of maintenance, repair or extension of the network without

interfering with the overall air supply, it is advisable to sub-divide the

network into individual sections. Branches with T-pieces and

manifolds with plug-in couplings make this possible. It is advisable

to fit the branch lines with standard ball valves or shut off valves.

53


Piping Installation

• Despite the best water separation in the pressure generating system, pressure drops

and external cooling may produce condensate in the pipe system. In order to

discharge this condensate, the pipes should be inclined 1-2%; this can also be

carried out in stages. The condensate can then be discharged from the system via

water separators at the lowest point.

54


Maintenance Unit Chapter 5

• The individual functions of compressed air preparation, i.e. filtering,

regulating and lubricating, can be fulfilled by individual components.

These functions have often been combined into one unit, i.e. the

service unit.

• The air service unit is a combination of the following :

• Compressed air filter (with water separator)

• Compressed air regulator

• Compressed air lubricator

55


Maintenance Unit: Component Air filter:

The compressed air filter has the job of removing all contaminants from the compressed air

flowing through it as well as water which has already condensed.

Air regulator:

The purpose of the regulator is to keep the

operating pressure of the system (secondary

pressure) virtually constant regardless of

fluctuations in the line pressure (primary

pressure) and the air consumption.

Air lubricator:

The purpose of the lubricator is to deliver

a metered quantity of oil mist into a leg of

the air distribution system when

necessary for the operation of the

pneumatic system.

56


Maintenance Unit: Working

Operation

filter regulator lubricator

57

• There are two basic types of Pneumatic actuator:

– Rotary actuator

(motor / rotary)

– Linear actuator

(cylinder)


Pneumatic Actuator Chapter 6

58


Type of Linear Actuator

Symbol

Single-acting

cylinder

Basic Construction Type

Double-acting

cylinder

Double-acting

cylinder with

end position

cushioning

59


Type of Linear Actuator

Symbol

Tandem

double-acting

cylinder


Cylinders with

through

piston rod

Multiposition

cylinders

60


Rotary Actuator

Symbol

Rotary

cylinders


61

Valve Chapter 7

Directional Control Valve • Directional control valves are components which change, open or close flow paths in

pneumatic systems. They are used to control the direction of motion of power

components and the manner in which these stop. Directional control valves are

shown as defined in DIN ISO 1219.

Type • 2/2-way valve

• 3/2-way valve

• 4/2-way valve

• 5/2-way valve

• 5/3-way valve


62


Symbols for directional

control valves

• The following rules apply to the representation of directional control valves:

• Each different switching position is shown by a square.

• Flow directions are indicated by arrows.

• Blocked ports are shown by horizontal lines.

• Ports are shown in the appropriate flow direction with line arrows.

63


Type of Distribution Valve (symbol)

64


Method of Actuation

65


Method of Actuation

66


Port Designation

• A numbering system is used to designate directional control valves and is in

accordance with DIN ISO 5599-3. Prior to this a lettering system was utilized and

both systems of designation are presented here:

67


Working Principle 3/2 Way Valve (Normally Close)

68


Working Principle 3/2 Way Valve (Normally Open)

69


Working Principle 3/2 Way Valve (Normally Close)

70


Basic Construction 4/2 Way Valve

71


Basic Construction 5/2 Way Valve (Double Air Pilot)

72


Basic Construction 5/3 Way Valve (Double Air Pilot)

73


Non Return Valve

74


Check Valve

Check valves can stop the flow completely in one direction. In the opposite

direction the flow is free with a minimal pressure drop due to the resistance

of the valve.

75


Shuttle Valve

X Y A

0 0 0

0 1 1

1 0 1

1 1 1

TRUTH TABLE

76


Dual Pressure Valve

X Y A

0 0 0

0 1 0

1 0 0

1 1 1

TRUTH TABLE

77


Quick Exhaust Valve

78


Flow Valve

Introduction Flow control valves are used to reduce the speed of a cylinder or a motor.

Type of control valve:

2. Throttle Valve

(two way flow control valve) - Restrict both direction of flow.

1. One Way Flow Control Valve - Restrict one direction of flow only.

79


Working Principle

One-way flow control valve

– The one-way flow control valve where the restrictor is only effective in one direction is a

combination of a restrictor and a non-return valve. The restrictor controls the flow rate in a

single direction dependent on flow. In the opposite direction, the full cross-sectional flow is

released and the return flow is at full pump delivery. This enables the one-way flow control

valve to operate.

80


Working Principle

Throttle Valve

– Flow control valves

influence the

volumetric flow of the

fluid in both directions.

Control flow in both direction

81


Combination Valve

1. Pressure sequence valve

2. Time Delay Valve

(Pneumatic Timer)

82


Pressure sequence valve

The principle on which this valve acts is the

same as for the pressure limiting valve. If the

pressure exceeds that set on the spring, the

valve opens.

The flow from 1 to 2 is closed. Outlet 2 is

opened only if a preset pressure has built up

in pilot line 12. A pilot spool opens the

passage 1 to 2.

83


Circuit Example

84


Time delay valve The time delay valve is a

combined 3/2-way valve, one

way flow control valve and air

reservoir. The 3/2-way valve can

be a valve with normal position

open or closed. The delay time is

generally 0-30 seconds for both

types of valves.

85


Circuit Example

86


Pneumatic Counter

c a.z

b.y

1(P) 3(R)

2(A)

87


Circuit Example

Assignment 3

88


1. P1 AND P2 OR P3 Cyl. A ext

2. (P1 OR P2) AND (P3 OR P4) Cyl. A ext

3. (P1 AND P2) OR P3 OR P4 Cyl. A ext

4. (P1 AND P2 AND P3) OR P4 Cyl. A ext

Assignment 4

89


1. P1 AND P2 OR P3 Cyl. A ext

P4 Cyl. A ret

2. (P1 AND P2) Cyl. A ext

(P23 OR P4) Cyl. A ret

3. (P1 OR P2) AND P3 Cyl. A ext

(P4 AND P5) OR P6 Cyl. A ret

Assignment 5 & Assignment 6

slow slow fast

1. A+ B+ A- B-

fast slow slow

2. A+ B+ C+ A- B- C-

slow slow

3. A+ B+ A- C-

C+ B-

1. A+ A- B+ B-

2. A+ B+ B- A-

90


91

Maintenance Chapter 8

• Systematic maintenance helps to extend service life and improve the

functional reliability of pneumatic control systems.

• A detailed maintenance plan should be drawn up for every pneumatic

system. A maintenance plan lists the maintenance tasks and time intervals.

In the case of complex control systems, the maintenance documentation

must include a function diagram and circuit diagram.

• The time intervals between individual maintenance work to be carried out is

dependent on the period of use, the wear characteristics of the individual

components and the ambient medium. The following maintenance work

must be carried out frequently and at short intervals:

– Service unit

• Check the filter

• Drain water regularly

• Refill and set lubricator, if a lubricator is used.

– Check signal generators for possible deposits of dirt or scarf


92

Maintenance Procedure


• The following maintenance work can be undertaken at

greater time intervals:

Check the seals of the connectors for leaks

Replace lines connected to moving parts

Check the rod bearings in the cylinders for wear and replace if

necessary

Clean or replace filter elements

Check function of safety valves

Check mountings

93


Control system development (design procedure)

The methods of representing the control problem include:

1. Positional sketch

2. Displacement-step diagram

3. Control chart

4. Function diagram

5. Function chart

6. Circuit diagram

Positional sketch

Displacement-step diagram

1

2

94


Displacement-time diagram

Control chart

Function diagram

Function

chart

2

3

4

5

95


Circuit diagram 6

96

Electro-Pneumatic System Chapter 9


MSI Electro-Pneumatic System

Fathul Hazrimy Ahmad

Assistant Lecturer

Pneumatic Hydraulic Department

97


Schematic

Design Of An

Electro-

Pneumatic

System

98


Electro-Pneumatic System

Change

of Switching control

Y1

2(A)

1(P) 3(R)

P1

2(A)

1(P) 3(R)

Conventional Pneumatic Electro-Pneumatic

99


Conventional vs. Electro

100


Hydraulic Pump

Control

Valve

Cylinder

Power

Supply

Pushbutton

Relay,

Timer,

Solenoid

Electro-Pneumatic Overview

From electro

101


Electro-Pneumatic System

1. Safety precaution

2. Introduction

3. Advantages

4. Comparison

5. Electrical Fundamental

6. Electrical Input Element

7. Sensor

8. Relay

9. Solenoid

10. Electrical Timer

11. Sequence Control

102

Safety Precaution


1. Pneumatic safety must be apply

2. DO NOT wear sandals, wear covered shoes

3. DO NOT wear excessive jewelry

4. DO NOT wear swing-loose-long hair style, neatly tie-up the long hair or place under a proper head gear.

5. DO NOT wear shoes with heel higher than 1" (2.5 cm)

6. DO wear lab-coat all the time

7. DO NOT disturb people who are conducting experiments! (or any time)

8. NO eating or drinking inside the lab.

9. NO social gathering is allowed in the labs. The labs should not be crowded for non-working purposes.

10. In case of spilling water on a lab bench near power points, first SWITCH OFF the electrical power before cleaning.

11. TO INSPECT any electrical equipment, first turn the power off and ask for the instruction/help from the lab officer in charge. Any faulty equipment should be attended by trained personnel only. DO NOT do it on your own.

103

Introduction

Electro-Pneumatic Systems are made up of

pneumatic and electrical components:

• The movements are generated by Pneumatic means

(e.g. by cylinders).

• Signal input and signal processing, on the other hand,

are effected by Electrical and Electronic

components (e.g. electromechanical switching

elements or stored-program controls).


104

Advantages


• Electrical signals can be transmitted via cables quickly and easily and over great distances. Mechanical signal transmission (linkages, cable-pulls) or pneumatic signal transmission (tubes, pipes) are far more complex.

• In the field of automation, signal processing is generally effected by electrical means. This enhances the options for the use of electro-pneumatic systems in automatic production operations (e.g. in a fully automatic pressing line for the manufacture of car wings).

• Many machines require complex control procedures (e.g. plastics processing). In such cases, an electrical control is often less complex and more economical than a mechanical or pneumatic control system.

105

MSI Electro-Pneumatic System Comparison

106


Electrical Fundamental

• The relationship between voltage, current strength and resistance is described by Ohm‘s law. Ohm‘s law states that in a circuit with constant resistance the current strength changes in proportion to the change in voltage:

– if the voltage increases, the current strength also increases.

– if the voltage falls, the current strength also decreases.

107


• In the field of mechanical engineering, power can be defined in terms of the work performed. The faster a task is performed, the greater the required power. Power therefore means work per unit of time.

• In the case of a consuming device in a circuit, electrical energy is converted into kinetic energy (e.g. electrical motor), light radiation (e.g. electrical lamp) or thermal energy (e.g. electrical heater, electrical lamp). The faster the energy is converted, the greater the electrical power.

Electrical power

108


• A power supply unit consists of the following modules:

– the mains transformer which transforms the alternating voltage of the mains supply (e.g. 220 V) into the output voltage (mostly 24 V).

– a smoothed direct voltage is generated by the rectifier G and the capacitor C.

– the direct voltage is then stabilized by the in-phase regulator.

Power Supply

109


• Electrical controls are generally supplied with a direct current of 24V.

The alternating voltage from the power supply therefore has to be

stepped down to 24V and then rectified.

Conversion AC to DC

AC DC

110


Electrical input elements

FUNCTION OF SWITCH: To open or close the flow of current to the consuming device.

TYPE: 1. "pushbutton switches" (push-buttons), and

2. "control switches".

CONTROL SWITCH:

In control switches, the two switching positions are mechanically interlocked. A switching position is maintained until the switch is activated once again.

PUSH-BUTTON: A push-button only opens or closes a current circuit for a short time. The selected switching

position is only active while the push-button is pressed.

Both switch types are available for operation with normally closed contacts, normally open contacts or

changeover contacts.

BASIC TYPE OF SWITCH:

1. Normally open contact

2. Normally closed contact

3. Changeover switch

111


Pushbutton (normally Open)

Circuit is open when the push-button is in the normal position

Pressed S1, H will on

Circuit Example:

112


Pushbutton (normally Close)

Circuit is closed when the push-button is in the normal position

Pressed S1, H will off

Circuit Example:

113


Changeover Switch

These contacts combine the functions of normally closed and normally

open contacts in one unit.

Pressed S1, H2 will on,

Release S1, H1 will on.

Circuit Example:

114


Switching Signal

And

Function

Or

Function

And

Function

Or

Function

Switching ON Command Switching OFF Command

S1 AND S2 H1 on S1 OR S2 H1 on S1 AND S2 H1 off S1 OR S2 H1 off

115


Assignment 7

1. Press S1 AND S2 H1 ON

2. Press S1 OR S2 H1 ON

3. Press S1 AND S2 AND S3 H1 ON

4. Press S1 OR S2 OR S3 H1 ON

5. Press (S1 AND S2) OR S3 H1 ON

6. Press (S1 OR S2) AND S3 H1 ON

7. Press (S1 OR S2) AND (S3 OR S4) H1 ON

8. Press (S1 AND S2) OR (S3 AND S4) H1 ON

9. Press (S1 AND S2 AND S3) OR S4 OR S5 H1 ON

10. Press [(S1 OR S2) AND S3] OR [(S4 OR S5) AND S6] H1 ON

116


24v

0v

S1

L1

S2

Installation Example #1 (Series)

11 12

23 24

31 32

43 44 H1

H2

H3

H1

H2

H3

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

11 12

23 24

31 32

43 44

0V

24V

117


Practical


2. Press S1 OR S2 H1 ON


4. Press S1 OR S2 OR S3 H1 ON


6. Press (S1 OR S2) AND S3 H1 ON


8. Press (S1 AND S2) OR (S3 AND S4) H1 ON


10. Press [(S1 OR S2) AND S3] OR [(S4 OR S5) AND S6] H1 ON

118


Sensor

Any device that receives a signal (e.g. heat or

pressure or light or motion etc.) and responds

to it in a unique manner [synonym: detector]

119


Limit switch

A mechanical limit switch is an

electrical switch which is activated

when a machine part or a workpiece

is in a certain position.

Normally open limit switch

1-4

Normally closed limit switch

1-2

120


Pressure switch

requires a pressure to

activated the sensor

Normally open limit switch

1-4

Normally closed limit switch

1-2

121


Practical (Sensor)

Roller

Limit

Switch

1. 2. Pressure

Sensor a.

b.

a.

b.

122


Proximity Sensor

Proximity sensors is refer to Non-contacting sensors

Type of Proximity Sensor

1. Reed switch -

2. Inductive sensor –

3. Capacitive sensor -

4. Optical / Photo Sensor -

123


Reed Switch (magnetic sensor)

124


Inductive Proximity Sensor (sense materials with good electrical conductivity)

125


Capacitive Proximity Sensor (sense all kind of material)

126


Optical/Photo Proximity sensor (sense reflected light)

Three type: • through-beam sensors

• retro-reflective sensors

• diffuse sensors

127


Optical Through-beam

Proximity sensor

128


Optical Retro-reflective

Proximity sensor

129


Optical Diffuse

Proximity sensor

130


Circuit Example

Proximity 2 wire

Proximity 3 wire PNP

Proximity 3 wire NPN

131


Practical (Sensor)

1. 2. 3. Reed

Switch

(Proximity

Magnetic

Sensor)

4.

Proximity

Inductive

Sensor

Proximity

Capacitive

Sensor

Proximity

Optical

Sensor

132


Relay

• Relays are electromagnetically actuated switches.

• They consist of a housing with electromagnet and movable contacts.

• An electromagnetic field is created when a voltage is applied to the coil of the electromagnet.

• This results in attraction of the movable armature to the coil core. The armature actuates the contact assembly.

• This contact assembly can open or close a specific number of contacts by mechanical means.

• If the flow of current through the coil is interrupted, a spring returns the armature to its original position.

133


Concept of a Relay

(Electromagnet)

• An electromagnet is a type of magnet in which the

magnetic field is produced by the flow of an electric

current. The magnetic field disappears when the current

ceases.

134


Working Principle

Relay

1 pole

Relay

2 pole

135


Circuit Example

Direct Control In-direct Control

136


Practical (Relay)

S1 H1 on

S1 H1 on, H2 off, H3 on, H4 off

S1 H1 on

S2 H2 off

1.

2.

3.

137


Assignment 8


Press S3 OR S4 H1 OFF


Press S4 OR S5 OR S6 H1 OFF


Press (S4 OR S5) AND S6 H1 OFF


Press (S5 AND S6) OR (S7 AND S8) H1 OFF


Press [(S6 OR S7) AND S8] OR [(S9 OR S10) AND S11] H1 OFF

138


Practical


Press S3 OR S4 H1 OFF


Press S4 OR S5 OR S6 H1 OFF


Press (S4 OR S5) AND S6 H1 OFF

139


Solenoids

• In electro-hydraulics, valves are actuated via solenoids. It has the

same concept of electromagnet.

solenoid

Directional control Valve

140


Electrical Construction of Solenoid

141


Electro-Pneumatic Circuit Diagram

Pneu

matic C

ircuit

Contro

l Circu

it

142


Assignment 9

1. Press S1 AND S2 Cly. A ext

2. Press S1 OR S2 Cly. A ext

3. Press S1 AND S2 AND S3 Cly. A ext

4. Press S1 OR S2 OR S3 Cly. A ext

5. Press (S1 AND S2) OR S3 Cly. A ext

6. Press (S1 OR S2) AND S3 Cly. A ext

7. Press (S1 OR S2) AND (S3 OR S4) Cly. A ext

8. Press (S1 AND S2) OR (S3 AND S4) Cly. A ext

9. Press (S1 AND S2 AND S3) OR S4 OR S5 Cly. A ext

10. Press [(S1 OR S2) AND S3] OR [(S4 OR S5) AND S6] Cly. A ext

143


Assignment 10


Press S3 OR S4 Cly. A ret


Press S4 OR S5 OR S6 Cly. A ret


Press (S4 OR S5) AND S6 Cly. A ret

4. Press (S1 OR S2) AND (S3 OR S4) Cly. A ext

Press (S5 AND S6) OR (S7 AND S8) Cly. A ret

5. Press (S1 AND S2 AND S3) OR S4 OR S5 Cly. A ext

Press [(S6 OR S7) AND S8] OR [(S9 OR S10) AND S11] Cly. A ret

144


Practical


Press S3 OR S4 Cly. A ret


Press S4 OR S5 OR S6 Cly. A ret


Press (S4 OR S5) AND S6 Cly. A ret

145


11.Sequence Control

• Single cycle (SC)

– In a single cycle mode, the sequence will run only in one cycle

via pushing a pushbutton.

– Example: A+ A-

• Continuous cycle (CC)

– In a continuous cycle mode, the sequence will run continuous

when start button is pressed, the sequence will stop until stop

button is pressed.

– Example: A+ A- A+ A- A+ A- …. Until stop is pressed

146


Assignment 11

1. A+ B+ A- B-

2. A+ B+ C+ A- B- C-

3. A+ A- B+ B-

4. A+ B+ A- C- A- B+

147


D’ END

Documents

Basic Pneumatic System