Basic Hydraulics and Pneumatics

Basic Hydraulics and Pneumatics Module 1: Introduction to Pneumatics

PREPARED BY

IAT Curriculum Unit March 2011

© Institute of Applied Technology, 2011

ATM 1122 – Basic Hydraulics and Pneumatics

Module 1: Introduction to Pneumatics Module Objectives After the completion of this module, the student will be able to:

Identify the common uses of pneumatic systems.

Identify the main parts of a pneumatic system.

Identify the main components of the pneumatic work station TP 101.

Understand how to to construct a pneumatic circuit

Explain the structure and signal flow of a pneumatic system.

List the main parts in the compressed air preparation stage.

Identify the symbol of air compressor and its function.

Identify the symbol of air tank and its function.

Explain the purpose of using the cooling and drying unit

Identify the main parts of the air service unit.

Identify the symbol of air filter and its function.

Identify the symbol of air pressure regulator and its function.

Identify the symbol of lubricator and its function.

Identify some important pneumatic accessories.


Module Contents 1

Introduction….. .............................................................................. 3 1.1 1.2 1.3

2

Applications of pneumatics ……...................................................... 5 2.1 2.2 2.3

3

Advantages................................................................................. 8 Disadvantages............................................................................. 8

Structure and signal flow of pneumatic systems … ........................ 9 4.1

5

industrial applications ……........................................................ 5 Industrial processes … ............................................................ 5 Some of the pneumatic applications in our life … ........................ 6

Advantages and disadvantages of pneumatics … ........................... 8 3.1 3.2

4

What does pneumatic mean…… ................................................ 3 Defentition of pneumatics… ..................................................... 3 What is the fluid power… ......................................................... 3

Primary levels of the pneumatic system … ...................................... 9

Air generation and distribution …................................................. 11 5.1 Preparation the compressed air.. ................................................. 11 5.2 Main parts in the compressed air preparation.. ................................. 12 5.2.1 Air compressor … ................................................................. 12 5.2.2 Air Tank (reservoir)…............................................................ 13 5.2.3 Cooling and drying unit…....................................................... 14 5.2.4 Piping… ............................................................................... 15 5.2.5 Air service unit… .................................................................. 17

6

Pneumatic accessories ................................................................. 20 6.1 6.2 6.3 6.4

Manifold (distributor) …… ...................................................... 20 Shut-off valves … ................................................................. 20 Tubes and fittings … ............................................................. 20 Pressure gauges … ............................................................... 21

References ......................................................................................... 22

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Module 1: Introduction to pneumatics


1 Introduction 1.1 What Does Pneumatic Mean? Pneumatics comes from the Greek word pneuma, which means 'breath or wind'. It is basically the use of under pressure gas that helps in performing a certain work in science and technology. 1.2 Definition of pneumatics Pneumatics is the transmission and control of forces and movements by means of compressed air. (The use of compressed air as a medium to do work). 1.3 What is the fluid power? Fluid power is the energy transmitted and controlled by means of a pressurized fluid, either liquid or gas. The term fluid power applies to both hydraulics and pneumatics. Hydraulics (oil or water) use liquids under pressure while pneumatics use compressed air or other neutral gases. Pneumatics technology has for some considerable time been used in carrying out the simplest mechanical tasks, but nowadays has played a vital and important role in automation and development of sophisticated technologies.


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ATM 1112 – Basic Hydraulics and Pneumatics 2

Applications of pneumatics:

2.1

industrial applications

Pneumatic systems are used in many industrial applications such as:

Material handling Clamping Shifting Positioning Branching of material flow Packaging Filling Transfer of materials Sorting of parts Stamping and embossing of components 2.2

Industrial processes

Pneumatic systems are used in carrying out machining and some industrial processes such as:

Drilling Turning Milling Sawing Finishing Forming

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ATM 1122 – Basic Hydraulics and Pneumatics 2.3

Some of the pneumatic applications in our life:

A Pneumatic machine is used to dismantle an automobile tire

A pneumatic machine is used in an automobile painting

A heavy duty pneumatic jackhammer

A pneumatic filling machine


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A dental drill is one of the uses of the pneumatic technology

A pneumatic device is used to fill the tire with compressed air to adjust the tire pressure.

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Advantages and disadvantages of pneumatics:

3.1 Advantages: 1- Availability: Air is available everywhere in unlimited quantities. 2- Transport: Air can be easily transported in pipelines, even over large distances. 3- Storage: Compressed air can be stored in a reservoir/tank and removed as required. 4- Temperature: Compressed air is relatively insensitive to temperature fluctuations. 5- Cleanliness: Unubricated exhaust air is clean. 6- The running cost is relatively inexpensive 7- Speed: Compressed air is a very fast working medium. This enables high working speeds to be attained. 8- Overload safe: Pneumatic tools and operating components can be loaded to the point of stopping and are therefore overload safe. 3.2 Disadvantages: 1- Preparation: Compressed air requires good preparation. Dirt and condensates should be removed. 2- Speed: As air is compressible; it is difficult to achieve uniform and constant piston speed. 3- Force requirement: Compressed air is economical only up to a certain force requirement. Under the normal working pressure of 600 to 700 kPa (6 to 7 bar). 4- Noise level: The exhaust air is loud (noise). This problem has now, however been largely solved due to the development of sound absorption material and silencers.


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ATM 1112 – Basic Hydraulics and Pneumatics 4 Structure and signal flow of pneumatic systems Pneumatic systems consist of an interconnection of different groups of elements. This group of elements forms a control path for signal flow, starting from the signal section (input) through to the actuating section (output). Control elements control the actuating elements in accordance with the signals received from the processing elements. 4.1

Primary levels of the pneumatic system:

Figure 1.1: Pneumatic signal flow and the coreesponding control elements

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0Z

Figure 1.2 : Examples of pneumatic control elements shoen in a practical circuit


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Air generation and distribution

The main function of the air generation and distribution is to provide the system with compressed air which is dry, clean, and at the required pressure The compressed air supply for a pneumatic system should be adequately calculated and made available in the appropriate quality. Air is compressed by the air compressor and delivered to an air distribution system in the factory. To ensure that the quality of the air is acceptable, air service unit is utilized to prepare the air before being supplied to the control system. Malfunctions can be considerably reduced in the system if the compressed air is correctly prepared. A number of aspects must be considered 5.1

Preparation of the compressed air:

The following points should be considered in preparing compressed air plants: 1. Quantity of air required to meet the demand of the system 2. Type of compressor to be used to produce the quantity required 3. Pressure requirements 4. Storage requirements 5. Requirements for air cleanliness 6. Acceptable humidity levels to reduce corrosion and sticky operation 7. Lubrication requirements, if necessary 8. Temperature of the air and effects on the system 9. Line sizes and valve sizes to meet demand 10. Material selection to meet environmental and system requirements 11. Drainage points and exhaust outlets in the distribution system 12. Layout of the distribution system to meet demand.

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ATM 1122 – Basic Hydraulics and Pneumatics 5.2

Main parts in the compressed air preparation

5.2.1 Air compressor: Air compressor is used to produce the compressed air for the system by the required volume and pressure. As a rule, pneumatic components are designed for a maximum operating pressure of 800-1000 kPa (8 - 10 bar) but in practice it is recommended to operate at between 500-600 kPa (5 and 6 bar) for economic and safe use. Due to the pressure losses in the

(a) Air compressor

distribution system, the compressor should be delivered between 650-700 kPa (6.5 and 7) bar to attain these figures. Figure 1.3.a and figure 1.3.b are examples of air compressors while figure 1.3.c shows the ISO symbol of the air compressor. (b) Air compressor

(c) ISO symbol of air compressor Figure 1.3: (a) and (b) are examples of some practical air compressors. (c) ISO symbol of air compressor.


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ATM 1112 – Basic Hydraulics and Pneumatics 5.2.2

Air Tank (reservoir)

An air reservoir should be fitted to: Store

and

stabilizes

the

compressed air. Compensate

the

pressure

fluctuation. Cool the air.

(a) Air reservoir

Figure 1.4 (a) shows a real air tank while the figure 1.4 (b) shows the ISO symbol of an air reservoir. (b) ISO symbol of air reservoir Figure 1.4: (a) air reservoir. (b) ISO symbol of an air reservoir.

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Cooling and drying unit

As the air comes out from the compressor very hot and humid; The cooling and drying unit is used to: Condensate

the

water

vapor

(humidity) from the compressed air. Reduce

the

compressed

air

temperature. The accumulation of condensate

(a)

depends largely on the relative air humidity. The relative air humidity is

dependent

temperature

and

on the

the

air

weather

situation. To remove the humidity, we use many types of air dryers, the very common and practical one is by using a cooling unit which cool the air and at the same time remove the water vapor. Figure 1.5 (a) and (b) show some examples of

(b)

real air dryers, while figure 1.5.c represents an ISO symbol of air dryer.

(c) Figure 1.5: (a): and (b) are some examples of real air dryers. (c) ISO symbol of air dryer.


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Piping

The pipe diameter of the air distribution system should be selected in such a way that the pressure loss from the pressurized reservoir to the consuming device ideally does not exceed approx. 10 kPa (0.1 bar). 5.2.4.1

Selection of the pipe diameter:

1. Flow rate 2. Line length 3. Permissible pressure loss 4. Operating pressure 5. Number of flow control points in the line 5.2.4.2

Piping layout

Ring circuits (figure 1.6.a) are most frequently used as main lines. This method of installing pressure lines also achieves a constant supply in the case of high air consumption. In pipe-run layout, the pipe lines must be installed in the direction of flow with a gradient of 1 to 2% as shown in figure 1.6 b. This is particularly important in the case of branch lines. Condensate can be removed from the lines at the lowest point. Any branching of air consumption points where lines run horizontally should always be installed on the upper side of the main line. Branching for condensate removal is installed on the underside of the main line. Shut-off valves can be used to block sections of compressed air lines if these are not required or need to be closed down for repair or maintenance purposes.

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(a) Ring (loop) pneumatic distribution system

(b) pipe-run pneumatic distribution system Figure 1.6 : (a) shows the ring or loop distribution system. (b) shows the piperun distribution system


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ATM 1112 – Basic Hydraulics and Pneumatics .5.2.5

Air service unit

The air service unit shown in figure 1.7.a

is

a

combination

of

the

following: 1. Compressed

air

filter

(with

water separator) 2. Compressed air regulator 3. Compressed air lubricator The main function of the service unit

(a)

picture of an air service unit

is provide the pneumatic system with a

well

cleaned,

lubricated

and

regulated compressed air. (Condition the compressed air). Removal

of

most

contaminants

(water, compressor oil, dirt, rust, pipe

(b) Detailed ISO symbol of the service unit

scale and other foreign materials). Obviously,

an

inefficient

system

results in higher costs per unit of compressed air, improper or erratic

(c) Simplified ISO symbol of the

tool operation, shortened component

service unit

life,

reduced

capacity

and

the

formation of rust and sludge in the Figure 1.7: (a) Shows a real service main and branch lines.

unit. (b) ISO symbol of the service unit. (c) Simplified ISO symbol of the service unit.

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5.2.5 .1

Air filter

Compressed air filter (Figure 1.8a) has

the

job

of

removing

all

contaminants from the compressed air flowing through it as well as water which has already condensed. The compressed air enters the filter bowl through guide slots. Liquid particles and

larger

particles

of

dirt

are

separated centrifugally collecting in

(a)a picture of a real air filter

the lower part of the filter bowl. The collected condensate must be drained before

the

level

exceeds

the

maximum condensate mark, as it will otherwise be re-entrained in the air (b) ISO symbol of the air filter stream. Figure 1.8: (a) air filter.(b) The ISO symbol of an air filter


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5.2.5 .2

Pressure regulator

(Reduce/regulate the pressure). The purpose of the regulator (figure 1.9.a)

is

to

keep

the

operating

pressure of the system (secondary pressure) virtually constant regardless

(a) real pressure regulator

of fluctuations in the line pressure (primary

pressure)

and

the

air

consumption. Figure 1.9.b represents the ISO symbol of the air regulator. 5.2.5 .3

(b) ISO symbol of the pressure

Air lubricator

regulator.

(Lubricate the moving parts) Most moving parts require some type of

lubrication.

The

efficiency

of

cylinders, valves and air motors can be

greatly

improved

if

they

are

supplied with adequate lubrication. Pneumatic lubricated

components by

using

an

can

be

air

line

lubricator (figure 1.9.c), a device for adding lubricating oil in aerosol form

(c) air lubricator

into a compressed air line. The air passing

through

the

lubricator

transports the lubricant to air tools, cylinders

or

other

air

operated

(d) ISO symbol of the air lubricator.

equipment. Figure 1.9.d represents an Figure 1.9: (a) pressure regulator.(b) ISO symbol of the pressure regulator. ISO symbol of the air lubricator (c) Air lubricator. (d)ISO symbol of the air lubricator.

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pneumatic accessories

Other important components that are used in the pneumatic lab 6.1 Manifold (distributor): it is used

to

pressure shows

provide outlets.

a

multi

equal

Figure

1.10.a

pneumatic

manifold

Figure

1.10.b

(distributor).

represents the ISO symbol of the pneumatic manifold.

(a) pneumatic manifold (distributor)

Each output port has check valve (Non return valve).

(b) ISO symbol of the pneumatic manifold

6.2 Shut off valves It is used to open and close the compressed manually.Figure

air 1.8.c

supply shows

a

sample of shut-off valve. Figure 1.10d represents the ISO symbol of the shut-off valve (c) Sample of a shut-off valve

6.3

(d) ISO symbol of the shut-off valve

Tubes and fittings

Figure 1.10e shows some types of tubes that are used in connecting pneumatic circuits. Figure 1.10f shows

some

important

fittings

such as T connections and cross connections. (e) some types of tubes Module 1: Introduction to pneumatics

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6.4 It

Pressure gauge used

to display the

actual

amount of the pressure in two main units Pascal and bar 1 bar= 14.5 p.s.i Figure

1.10g

pressure

shows

gauge.

Figure

a

real (f) different fittings

1.10h

represents the ISO symbol of the pressure gauge.

(g) pneumatic pressure gauge

(h) ISO symbol of a pressure gauge Figure 1.10

Activity: Compare between hydraulics and pneumatics.

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References 1. Festo Didactic pneumatic basic level textbook TP 101. 2. Introduction to fluid power by James L. Johnson 3. http://www.omega.com/auto/pdf/CompressedAirTips.pdf


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ATM 1112 – Basic Hydraulics and Pneumatics Student notes …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... …………………………………………………………………………………………………………………………….......................... ……………………………………………………………………………………………………………………………..........................

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