090075m_pneumatic Control Systems

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EE3092 -Laboratory Practice V

PPNNEEUUMMAATTIICC CCOONNTTRROOLL SSYYSSTTEEMMSS

Instructor: - Mr. R.A. A. Rathnayake

Name: - V.I.P. Dasanayake

Index Number: - 090075M

Group: - 3

Submission date: -15/02/2012


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Discussion

1) Using compressed air in controlled systemPneumatic control systems are widely used in modern industrial applications for controlling

process. This control system is used to some other sub processes such as sensors to determine the

status of the process, processors, actuators to carry out the work,..etc.

The special about this control system is that all the type of tools and instruments which are used to

control the system mainly runs by the compressed air or pressurized gas. Examples include rock drills,

pavement breakers, riveters, forging presses, paint sprayers, blast cleaners, and atomizers.

Compressed-air power is flexible, economical, and safe. In general, pneumatic systems have relatively

few moving parts, contributing to high reliability and low maintenance costs

Advantages: -

1. Availablity: - since air is available with a unlimited amount, unlike other oil, gas, or liquid it is

a great advantage

2. Lightweight:-unlike other electrical equipment Pneumatic devices are usually much lighter, so

when comes to handling it is also a great advantage. This makes a big difference

with manual and percussion tools.

3. Easily stored: - Purpose-built tanks can be used to store compressed air easily. Normally there

is a tank in a pneumatic system that is used to store the compressed air. So if

there is a storage tank in a pneumatic system, the compressor only needs to

work when the pressure drops below a predetermined value. And because there

is always a cushion of pressure, a work cycle can be completed even if the

power system fails.

4. Clean and dry: - since the working fluid is just air, there will be no any wastage, no need orthe working fluid and leaks of the working fluid tend not to be messy. There are

no any defective parts as soil particles. This cleanliness gives a great advantages

when it comes to the food manufacturing, textile, leather, packing

industries,etc.

5. Economical and rational: - Pneumatics is 40 - 50 times more economical than muscle power

When compare the prices of pneumatic components are cheaper than other

hydraulic components. Usually an air systems operate at relatively low pressure,

the components can be made of relatively inexpensive material. So this method is

more economical than other methods.


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6. Overload-proof: - Compressed air equipment and pneumatic working parts can be loaded until

they stop without being damaged. Because air is compressible, the equipment is

less likely to be damaged by shock. Excessive force is absorb is absorb by the air

in pneumatics. This is why they are considered to be overload-proof. In contrast

to electrical systems, the output of a pneumatic network can be overloaded

without risk of danger. If the pressure drops too much, the work cannot be done,

but there will be no damage to the network or its working elements.

7. Fully adjustable: - Speeds, force and torque can be fully adjusted without any difficulty by

using throttles.

8. Fast working medium: - since there are less friction in air compare to other gases types, liquids,

and Pneumatic power is faster. The very high flow speeds allow rapid completionof work cycles. This provides short cut-in times and fast conversion of energy

into work. Hydraulic applications only manage 5m/s. Compressed air can achieve

flow speeds of over 20 m/s. With pressures of less than 1bar it is even possible to

obtain signal speeds of 200 to 300 m/s.

9. Transportability:-Compressed air can be transported to long distances via pipelines. This

possibility enables the installation of central generation stations more easy. Air

can be supplied with using ring mains which have a constant high working

pressure.

10. Safe to use: - usually pneumatic elements are very safe against to fire, explosion and electrical

hazards. Even in areas where there is a risk of fire, explosion and extreme

weather conditions, pneumatic elements can be used without large and expensive

safety apparatus. It is very safe to use mainly because compressed air can

withstand for a great temperature fluctuations and the temperatures are extreme.

It can be used in hazardous situations where explosions or fires may occur as

well. Pneumatic systems and components in general wear very little. Therefore

usually they have a long working life and a low failure rate.

11. Simulating capability:-Before apply the pneumatic system, by using pneumatic simulating

software, it can be simulated. So that we can adjust the system as we want. Then

we can make it use friendly.

(P.T.O.)


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Disadvantages: -

1. Maintainability: - when a system is controlled with using compressed air, maintaining under

proper schedule will be a necessary thing.

2. Space: - large space will be needed to install a compressed air controlled system, unlike other

electrical actuators

3. Speed and position control: -Since air is highly compressible (how much air is compressed for

1atm) accurate speed control and position control is difficult when comparing

with electrical and hydraulic actuators .because of this reason sometimes

auxiliary systems are also required which cause for additional cost.

4. Limited supply pressure: -since supply pressure is limited to 8 bars, it is normally used to move

lighter loads, unless very large actuators are used

2) Industrial use of pneumatic circuit in system controlling, Automation,etcIt is really hard to find disadvantages of pneumatic control systems, since it is developed

with modern technology and controlled with air. Compressed air is one of the most resourceful

operations when consider the manufacturing environment such as tire manufacturing. It is very much

useful in industries, operations and applications as well. Compressed air is used to power tools, move

conveyers, transport products and make process applications possible,..etc

Normally in these types of industries there are several categories of pneumatic control

system. Compressors, Motors or engines, Receiver tanks, After-coolers and air dryers, Filters, Piping

distribution system

There are other pneumatic control system tools as well. These all are very useful in

automation, manufacturing industries,..etc. Some of pneumatic tools use in industry:

Air compressors Vacuum pumps Pneumatic switches Pneumatic actuators Pneumatic drill (informal name-jackhammer) Cable Jetting Air brakes on buses, trains, trucks ,etc


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Considering some of pneumatic tools and how they operate.If we consider Cable jetting

it is used to blow a cable through a duct while simultaneously pushing the cable into the duct. This is

done by compressed air is injected at the duct inlet and flows through the duct and along the cable at

high speed. When optical fibers are to be installed in underground this method is used. The process of

the air brake is very much similar to the process of the piston in an internal combustion engine.

References

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

http://www.kohlerandlewis.com/pdf/pneutech.pdf
http://en.wikipedia.org/wiki/Pneumaticshttp://en.wikipedia.org/wiki/Pneumaticshttp://www.kohlerandlewis.com/pdf/pneutech.pdfhttp://www.kohlerandlewis.com/pdf/pneutech.pdfhttp://www.kohlerandlewis.com/pdf/pneutech.pdfhttp://en.wikipedia.org/wiki/Pneumatics

090075m_pneumatic Control Systems

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