Advantages:

Infinite availability of the source

Air is the most important thing in the pneumatic system, and as we all know, air is available

in the world around us in unlimited quantities at all times and places .

Easy channelled

Air is a substance that is easily passed or move from one place to another through a small

pipe, the long and winding .

Temperature is flexible

Air can be used flexibly at various temperatures are required, through equipment designed for

specific circumstances, even in quite extreme conditions; the air was still able to work .

Safe

The air can be loaded more safely than it is not flammable and does not short circuit occurs

(konsleting) or explode, so protection against both of these things pretty easily, unlike the

electrical system that could lead to fires konsleting .

The air around us are tend to clean without chemicals that are harmful, and also, it can be

minimized or cleaned with some processes, so it is safe to use pneumatic systems to the

pharmaceutical industry, food and beverages and textiles .

The transfer of power and the speed is very easy to set up

Air could move at speeds that can be adjusted from low to high or vice versa . When using a

pneumatic cylinder actuator, the piston speed can reach 3 m / s . For pneumatic motors can

spins at 30,000 rpm, while the turbine engine systems can reach 450,000 rpm .
Can be stored

The air can be stored through the seat tube fed excess air pressure . Moreover, it can

be installed so that the pressure boundary or the safety of the system to be safe .

Easy utilized

Easy air either directly utilized to clean surfaces such as metal and machinery, or indirectly,

ie through pneumatic equipment to produce certain movements .

Disadvantages:

Requires installation of air-producing equipment .

Compressed air should be well prepared to meet the requirements . Meet certain criteria,

such as dry, clean, and contain the necessary lubricant for pneumatic equipment . Therefore

require installation of pneumatic systems is relatively expensive equipment, such as

compressors, air filter, lube tube, dryer, regulators, etc .

Easy to leak

One of the properties of pressurized air is like to always occupy the empty space and the air

pressure is maintained in hard work . Therefore we need a seal so that air does not leak .

Seal leakage can cause energy loss . Pneumatic equipment should be equipped with airtight

equipment that compressed air leaks in the system can be minimized .

Potential noise

Pneumatic using open system, meaning that the air that has been used will be thrown out of

the system, the air comes out pretty loud and noisy so will cause noise, especially on the

exhaust tract . The fix is to put a silencer on each dump line .

Easy condenses

Pressurized air is easily condensed, so before entering the system must be processed first in

order to meet certain requirements, such as dry, have enough pressure, and contains a small

amount of lubricant to reduce friction in the valves and actuators .

Expected after knowing the advantages and disadvantages of the use of compressed

air we can make the anticipation that these losses can be avoided .

Despite the immense capabilities of hydraulics presented in terms of moving higher

loads and in other industrial utilization, pneumatics are still in wide use today . The article

discusses some applications and advantages of pneumatics in industry .

Pneumatics is study of mechanical motion caused by pressurized gases and how this

motion can be used to perform engineering tasks . Pneumatics is used mainly in mining and

general construction works . Pneumatic devices are used frequently in the dentistry industry

across the world . On the other hand, hydraulics means use of pressurized fluids to execute a

mechanical task . Hydraulics is frequently used in the concepts of turbines, dams, and rivers .

Air brakes in buses, air compressors, compressed air engines, jackhammers, and vacuum

pumps are some of the most commonly used types of mechanical equipment that are based on

pneumatics technology . Commonly seen hydraulics based equipment types are hydraulic

presses, hydraulic hoppers, hydraulic cylinders, and hydraulic rams . In the subsequent

sections of this article, you will learn how a pneumatic system works, what its best features

are, and its major advantages over hydraulic systems .

In order to affect mechanical motion, pneumatics employs compression of gases,

based on the working principles of fluid dynamics in the concept of pressure . Any

equipment employing pneumatics uses an interconnecting set of components: a pneumatic

circuit consisting of active components such as gas compressor, transition lines, air tanks,
hoses, open atmosphere, and passive components . Compressed air is supplied by the

compressor and
is transmitted through a series of hoses . Air flows are regulated by valves and the pneumatic

cylinder transfers the energy provided by the compressed gas to mechanical energy . Aside

from compressed air, inert gases are also applied particularly for self-contained systems .

Pneumatics is applied in a wide range in industries, even in mining and dentistry . The

majority of industries use gas pressures of about 80 to 100 pounds per square inch .

Over pneumatics, hydraulics is capable of moving heavier loads and having greater

force, and since its working fluids are incompressible, it minimum spring actions . But at the

same time pneumatics are cleaner; the system uses no return lines and gases are exhausted to

the atmosphere . Thus leaks will be of less concern since the working fluid of pneumatics is

air, unlike oil in hydraulics . Its working fluid is also widely available and most factories are

pre-plumbed for compressed air distribution, hence pneumatic equipment is easier to set-up .

To control the system, only ON and OFF are used and the system consists only of standard

cylinders and other components, making it simpler than hydraulics . Pneumatic

systems require low maintenance and have long operating lives . Lastly the working fluid of

the pneumatic system absorbs excessive force, leading to less frequent damage to equipment .

Compressible gases are also easy to store and safer; no fire hazard is presented and machines

could be made to be overload safe .

Advantages of Pneumatics over Hydraulics

Like hydraulics, pneumatics is a type of fluid power application where instead of an

incompressible liquid, pneumatics employ gas in their system . Hydraulics present

certain advantages over pneumatics, but in a given application, pneumatic powered

equipment is more suitable, particularly in industries where the factory units are plumbed for

compressed air .
The air used in pneumatic devices is dried and free from moisture so that it does not create

any problem to the internal parts of the system . Moreover, to avoid corrosive actions, oil or

lubricants are added so that friction effects can be reduced . Compressed air is used in most

of the machines and in some cases compressed carbon dioxide is used . As most of the

pneumatic devices are air based, they have a less complicated design and can be made of

inexpensive material . Mass production techniques can be adopted to produce pneumatic

systems, which not only save money but save time too .

Other major advantages are listed below .

Initial cost is less; hydraulics equipment cost as much as twice the price of pneumatic

equipment .

A pneumatic water treatment automation system reduces the costs of installation and

operation compared with conventional electrical installations . For opening and

closing of underwater valves, pneumatic systems work well because they can sustain

overload pressure conditions .

Pneumatic actuators also have long life and perform well with negligible maintenance

requirement throughout their life cycle .

Very suitable for power transmission when distance of transmission is more .

The major disadvantage of pneumatic systems is that they cannot be employed for tasks

that require working under high pressures . However, modern technology is working on

finding better solutions to this address this problem so that heavy engineering tasks can be

executed using pneumatic devices . In a nutshell, in order to execute low scale engineering

and mechanical tasks, pneumatic devices would be the best suited and a viable alternative

over hydraulic systems .

 CHAPTER 3
Working Principle

Selection of Pneumatics

Mechanization is broadly defined as the replacement of manual effort by mechanical

power . Pneumatics is an attractive medium for low cost mechanization particularly for

sequential or repetitive operations . Many factories and plants already have a compressed air

system, which is capable of providing both the power or energy requirements and the control

system (although equally pneumatic control systems may be economic and can be

advantageously applied to other forms of power) .

The main advantages of an all-pneumatic system are usually economy and simplicity, the

latter reducing maintenance to a low level . It can also have outstanding advantages in terms

of safety .

Fig . 3 . 1 . 1 Working Of Pneumatic Jack

The pneumatic . and riveting machine consists of the following components to fulfil the

requirements of complete operation of the machine .

Pneumatic cylinder

Solenoid valve

Flow control value

Connectors and

Hoses

Solenoid valve:

The directional valve is one of the important parts of a pneumatic system .

Commonly known as DCV, this valve is used to control the direction of air flow in the

pneumatic system . The directional valve does this by changing the position of its internal

movable parts . This valve was selected for speedy operation and to reduce the manual effort

and also for the modification of the machine into automatic machine by means of using a

solenoid valve . A solenoid is an electrical device that converts electrical energy into straight

line motion and force . These are also used to operate a mechanical operation which in turn

operates the valve mechanism . Solenoids may be push type or pull type . The push type

solenoid is one in which the plunger is pushed when the solenoid is energized electrically .

The pull type solenoid is one is which the plunger is pulled when the solenoid is energized .

The name of the parts of the solenoid should be learned so that they can be recognized when

called upon to make repairs, to do service work or to install them .

UNIT DESCRIPTION (CONSTRUCTION):

CYLINDER
 An (pneumatic) air cylinder is an operative device in which the state input energy of

compressed air; (i . e . ) pneumatic power is converted into mechanical output power, by

reducing the pressure of the air to that of the atmosphere . The bore of the cylinder has very
smooth finishing reduces friction and losses . There are to angle plates welded to the cylinder

as fitting means .

DOUBLE ACTING CYLINDER

A double acting cylinder is employed in a control system with a full pneumatic

cushioning and it is essential when the cylinders itself is required heavy masses . The normal

escape of air is out by ‘cushioning piston’ .

PUNCH AND DIE

Die and punch are known as ‘press tools’ . Die is the lower part of press tool . It is

clamped on the bolster plate of the press . It remains stationary during the operation . The

die has a cavity to receive the punch . The cavity may be with clearance or without clearance

Punch is the upper part of the press tool . It is attached to the lower end of the ram of the

press . It sheds with the ram during the operation and is forced into the die cavity . Die and

punch must be in prefect alignment for proper operation .

Fig . 3 . 3 . 3 . 1 Working Of Pneumatic unit

 Die and punches are always used together . Dies are classified according to either the

type of construction or operation to be performed . High speed steel, satellite or cemented

carbide is the materials used for making dies and punches . The die materials selected

depend on the type of production, operation, sheet metal thickness and accuracy .

FULCRUM LOAD AND EFFORT ARM

A lever is a mechanical devices used to lift heavy loads by application of a small

effort . It is a rigid rod or bar, which turns about a fixed point called fulcrum . A lever may

be straight or curved . Lever works on the same principle as that of principle of moments .

The load W is applied to the point A and hence the point A is known as load point and point

B is effort point . The point F is fulcrum . The perpendicular distance (L1) between the load

point A is load arm and L2 between is known as effort arm . The ratio of effort arm and load

arm is called as leverage . The ratio of load lifted and the effort applied is mechanical

advantage . Taking moments about fulcrum P*L2 =W*L1

COMPRESSOR

The compressor forms the main part of the pneumatic system by producing the

compressed air . Compressor capacity is the actual quantity of air compressed and delivered

and the volume expressed is that of the air intake conduction, namely at atmospheric pressure

and normal ambient temperature . The clear conduction of the suction air one of the factors

which decide the life of a compressor . Compressor is generally classified into two types,

namely

Positive displacement compressor

Turbo compressor
DIRECTION CONTROL VALVES

Direction control valves control the way the air passes and used for controlling the

commencements, termination and direction of air flow . Depending on the number of paths

the air is allowed to pass, directional valves termed two way, three way, and four way or

multi way valves .

The different number of rays by means the number of controlled connection of the

valve . Inlet connection to the compressed air supplies outlet connections to the air consumer

and exhaust connection to the atmosphere . The solenoid valve is used to control the air flow

direction . This is the direction control valve in our project .

Pneumatic systems require air to operate successfully . As a result of air being extremely

abundant, and free, it is easy to restock the system . Safety: As a result of pneumatic systems

running on air, safety hazards are significantly reduced . There are limited occurrences of

fires because air is non-flammable, and leakages in the system do not negatively effect the

outside environment

Cost effectiveness: The initial cost of manufacturing a pneumatic device is minimal as a

result of the low cost design materials . Plastics, zinc, and aluminium are all relatively

affordable materials that are commonly found in pneumatic designs .

Cleanliness- As a result of the system being powered solely by air, the pneumatic device

typically requires limited cleaning . Pressurized air constantly pushes out dirt or debris that

get stuck in the system . If there is a blockage, the simplicity of the design also helps . Due

to the limited amounts of tubes, the system can be easily disassembled and cleaned .
Maintenance- In order for the system to properly operate it must be lubricated with oil

consistently but they have less plumbing than hydraulic systems . Control and Speed- Air is

a
compressible gas, which makes control and speed in a pneumatic system more difficult, in

comparison to electric or hydraulic systems . When specific speeds are needed, additional

devices have to be attached to the pneumatic system in order to procure the desired result .

Maintenance- Pneumatic systems are less durable that hydraulic counterparts . Due to

moisture accumulation the system can freeze up . Safety: Pipes that feed the system air have

the ability to move on uncontrollably on their own, which could cause serious injuries to

those nearby

The word pneumatics is a derivative of the Greek word pneuma, which means air,

wind, or breath . Pneumatics can be defined as that branch of engineering science that

pertains to gaseous pressure and flow . As used in this manual, pneumatics is the portion of

fluid power in which compressed air, or other gas, is used to transmit and control power to

actuating mechanisms . This section discusses the basic principles of pneumatics,

characteristics of gases, heavy-duty air compressors, and air compressor maintenance . It

also discusses the hazards of pneumatics, methods of controlling contamination, and safety

precautions associated with compressed gases .

Basic Principles of Pneumatics Gases differ from liquids in that they have no definite

volume, that is, regardless of the size or shape of a vessel, a gas will completely fill it . Gases

are highly compressible, while liquids are only slightly so . Also, gases are lighter than equal

volumes of liquids, making gases less dense than liquids .

Boyle’s Law When the automobile tire is initially inflated, air that normally occupies

a specific volume is compressed into a smaller volume inside the tire . This increases the

pressure on the inside of the tire . Charles Boyle, an English scientist, was among the first to

experiment with the pressure-volume relationship of gas . During an experiment when he

compressed a volume of air, he found that the volume decreased as pressure increased, and
by doubling the force exerted on the air, he could decrease the volume of the air by half

Temperature is a dominant factor affecting the physical properties of gases . It is of

particular concern in calculating changes in the state of gases . Therefore, the experiment

must be performed at a constant temperature . The relationship between pressure and volume

is known as Boyle's law . Boyle's law states when the temperature of a gas is constant, the

volume of an enclosed gas varies inversely with pressure . Boyle's law assumes conditions of

constant temperature . In actual situations this is rarely the case . Temperature changes

continually and affects the volume of a given mass of gas .

Charles’ Law Jacques Charles, a French physicist, provided much of the foundation

for modem kinetic theory of gases . Through experiments, he found that all gases expand and

contract proportionally to the change in absolute temperature, providing the pressure remains

constant . The relationship between volume and temperature is known as Charles's law .

Charles's law states that the volume of a gas is proportional to its absolute temperature if

constant pressure is maintained .

Kinetic Theory of Gases In an attempt to explain the compressibility of gases,

consider the container shown in as containing a gas . At any given time, some molecules are

moving in one direction, some are travelling . Gas compressed to half its original size by a

doubled force . Figure 9-36 — Molecular bombardment that creates pressure . NAVEDTRA

14264A 9-32 directions, and some may be in a state of rest . The average effect of the

molecules bombarding each container wall corresponds to the pressure of the gas . As more

gas is pumped into the container, more molecules are available to bombard the walls, thus the

pressure in the container increases . Increasing the speed with which the molecules hit the

walls can also increase the gas pressure in a container . If the temperature of the gas is raised,

the molecules move faster, causing an increase in pressure . This can be shown by
considering the automobile tire . When you take a long drive on a hot day, the pressure in the

tires
increases, and a tire that appeared to be soft in cool morning temperature may appear normal

at a higher midday temperature .

Compressibility and Expansion of Gases Gases can be readily compressed and are

assumed to be perfectly elastic . This combination of properties gives gas the ability to yield

to a force and return promptly to its original condition when the force is removed . These are

the properties of air that are used in pneumatic tires, tennis balls, and other deformable

objects whose shapes are maintained by compressed air .

Pneumatic Gases serve the same purpose in pneumatic systems as liquids serve in

hydraulic systems . Therefore, many of the same qualities that are considered when selecting

a liquid for a hydraulic system must be considered when selecting a gas for a pneumatic

system .

Qualities The ideal fluid medium for a pneumatic system must be a readily available

gas that is non-poisonous, chemically stable, non-flammable, and free from any acids that can

cause corrosion of system components . It should be a gas that will not support combustion

of other elements . Gases that have these desired qualities may not have the required

lubricating power . Therefore, lubrication of the components must be arranged by other

means . For example, some air compressors are provided with a lubricating system, some

components are lubricated upon installation, or in some cases lubrication is introduced into

the air supply line (inline oilers) . Two gases that meet these qualities and are most

commonly used in pneumatic systems are compressed air and nitrogen . Since nitrogen is

used very little except in gas- charged accumulators, we will discuss only compressed air .

Compressed Air Compressed air is a mixture of all gases contained in the

atmosphere . However, in this manual it is referred to as one of the gases used as a fluid
medium for pneumatic systems . The unlimited supply of air and the ease of compression

make
compressed air the most widely used fluid for pneumatic systems . Although moisture and

solid particles must be removed from the air, a pneumatic system does not require the

extensive distillation or separation process required in the production of other gases .

Compressed air has most of the desired characteristics of a gas for pneumatic systems . It is

non-poisonous and non-flammable but does contain oxygen, which supports combustion .

The most undesirable quality of compressed air as a fluid medium for a pneumatic system is

moisture content . The atmosphere contains varying amounts of moisture in vapour form .

Changes in the temperature of compressed air will cause condensation of moisture in the

system . This condensed moisture can be very harmful to the system and may freeze the line

and components during cold weather . Moisture separators and hair dryers are installed in the

lines to minimize or eliminate moisture in systems where moisture would deteriorate system

performance . An air compressor provides the supply of compressed air at the required

volume and pressure . In most systems the compressor is part of the system with distribution

lines leading from the compressor to the devices to be operated . Compressed air systems are

categorized by their operating pressure as follows:

High-pressure (HP)—3,000 to 5,000 psi

Medium-pressure (MP )—151 to 1,000 psi

Low-pressure (LP)—150 psi and below

Heavy-Duty Air Compressors are used in pneumatic systems to provide requirements

similar to those required by pumps in hydraulic systems . They furnish compressed air as

required to operate the units of the pneumatic systems . Even though manufactured by

different companies, most compressors are quite similar . They are governed by a pressure

control system that can be adjusted to compress air to the maximum pressure . Rotary the
rotary compressor has a number of vanes held captive in slots in the rotor . These vanes

slide
in and out of the slots, as the rotor rotates an end view of the vanes in the slots . The rotor

revolves about the centre of the shaft that is offset from the centre of the pumping casing .

Centrifugal force acting on the rotating vanes maintains contact Rotary compressor

operation . This feature causes the vanes to slide in and out of the slots as the rotor turns .

Notice in the variation in the clearance between the vanes and the bottom of the slots, as the

rotor revolves . The vanes divide the crescent-shaped space between the offset rotor and the

pump casing into compartments that increase in size and then decrease in size as the rotor

rotates . Free air enters each compartment as successive vanes pass across the air intake .

This air is carried around in each compartment and is discharged at a higher pressure due to

the decreasing compartment size (volume) of the moving compartments as they progress

from one end to the other of the crescent-shaped space . The compressor is lubricated by oil

circulating throughout the unit . All oil is removed from the air by an oil separator before the

compressed air leaves the service valves

Screw The screw compressors used in the NCF are direct drive, two-stage machines

with two precisely matched spiral-grooved rotors The rotors provide positive displacement

internal compression smoothly and without surging . Oil is injected into the compressor unit

and mixes directly with the air as the rotors turn, compressing the air . The oil has three

primary functions:

As a coolant, it controls the rise in air temperature normally associated with

the heat of compression .

It seals the leakage paths between the rotors and the stator and also between

the rotors themselves .

 It acts as lubricating film between the rotors, allowing one rotor to directly

drive the other, which is an idler . After the air/oil mixture is discharged from the

compressor unit, the

oil is separated from the air . The oil that mixes with the air during compression passes into

the receiver-separator where it is removed and returned to the oil cooler in preparation for re-

injection . All large volume compressors have protection devices that shut them down

automatically when any of the following conditions develop

: • The engine oil pressure drops below a certain point .

The engine coolant rises above a predetermined temperature .

The compressor discharge rises above a certain temperature .

Any of the protective safety circuits develop a malfunction . Other features

that may be observed in the operation of the air compressors is a governor system

whereby the engine speed is reduced when less than full air delivery is used .

An engine- and compression-control system prevents excessive build-up in the

receiver Screw compressor . When air is compressed, heat is generated . This heat causes

the air to expand, thus requiring an increase in power for further compression . If this heat is

successfully removed between stages of compression, the total power required for additional

compression may be reduced by as much as 15 percent . In multistage reciprocating

compressors, this heat is removed by means of intercoolers that are heat exchangers placed

between each compression stage . Rotary air compressors are cooled by oil and do not use

intercoolers After coolers It is obvious that the presence of water or moisture in an air line is

not desirable . The water is carried along through the line into the tool where the water

washes away the lubricating oil, causing the tool to run sluggishly and increases

maintenance .

The effect is particularly pronounced in the case of high-speed tools where the

wearing surfaces are limited in size, and excessive wear reduces efficiency by creating
internal air leakage . Further problems may result from the decrease in temperature caused

by
the sudden expansion of air at the tool . This low temperature creates condensation that

freezes around the valves, ports, and outlets . This condition obviously impairs the

operational efficiency of the tool and cannot be allowed . The most satisfactory means of

minimizing these conditions is the removal of the moisture from the air immediately after

compression and before the air enters the distribution system . This may be accomplished in

reciprocating compressors through the use of an after cooler that is an air radiator that

transfers heat from the compressed air to the atmosphere . The after cooler reduces the

temperature of the compressed air to the condensation point where most of the moisture is

removed . Cooling the air not only eliminates the difficulties which moisture causes at points

where air is used but also ensures better distribution

Receiver Tank The receiver tank is of welded steel construction and is installed on the

discharge side of the compressor . It acts as a surge tank as well as a condensation chamber

for the removal of oil and water vapours . It stores enough air during operation to actuate the

pressure control system and is fitted with at least one service valve, a drain or blow-by valve,

and a safety valve . Pressure-Control System All portable air compressors are governed by a

pressure-control system . The control system is designed to balance the compressor's air

delivery and engine speed with varied demands for compressed air . The rotary compressor

output is governed by varying the engine speed . The engine will operate at the speed

required to compress enough air to supply the demand at a fairly constant pressure . When

the engine has slowed to idling speed as a result of low demand, a valve controls the amount

of free air that may enter the compressor . A screw compressor output is governed by

automatic control that provides smooth, steeples capacity regulation from full load to no load

in response to the demand for air . From a full load down to no load is accomplished by a

floating-speed engine control in combination with the variable-inlet compressor .

 Air Compressor Maintenance A number of built-in features make

portable compressors easy to maintain:

An automatic blow down valve for releasing air pressure when the engine is

stopped .

A valve for draining moisture that accumulates in the receiver tank .

A drain cock at the bottom of the piping at the bottom of the oil storage tank .

An air filter service indicator to show when the filter needs servicing .

A demister, or special filter, that separates lubricating oil from compressed air .

Remember: a good maintenance program is the key to a long machine life . So it is up

to both the operator and the mechanic to ensure that the maintenance is performed on

time, every time .

Air Cleaner Servicing The air cleaner contains a primary and secondary dry

filter element An air filter restriction indicator is located at the rear of the air filter

housing to alert the operator of the need to service the filters . When a red band

appears in the air filter restriction indicator, secure the compressor and service the

filters . Use compressed air to clean the primary element; however, never let the air

pressure exceed 30 psi . The secondary filter is not cleanable and should be replaced

when necessary . Reverse flush the primary element by directing compressed air up

from the inside out . Continue reverse flushing until all dust is removed . Should any

oil or greasy dirt remain on the filter surface, replace the element .