CHAPTER - 6

HYDRO PNEUMATIC SYSTEMS

&CIRCUITS

By Prof. S.P.Chaphalkar
6.1 Comparison of Hydraulic &
Pneumatic Circuits
Hydraulic Circuits Pneumatic Circuits

1. Working fluid used is oil 1. Working fluid used is air

2. The operation is complicated 2.The operation is simple

3. The operation is quiet 3. The operation is noisy

4. To pressurized the oil, pump is 4. Air compressor is necessary

necessary
5. It require return lines, hence the 5. No return lines are required,
circuit is complicated hence circuit is simple
6. Speed is limited 6. Very high speed can be possible

7. There is possibility of fire hazards 7. It is safe in volatile atmosphere.

when working with higher
temperatures.
6.1 Comparison of Hydraulic &
Pneumatic Circuits
Hydraulic Circuits Pneumatic Circuits

8. Its operating pressure can be 8. Its operating pressure is limited to

lower to very high 6 bar
9. In this the system rigidity is good 9. In this system rigidity is poor

10. It has simple maintenance 10. It also has simple maintenance

11. It requires moderate operating 11. It requires very low operating

cost cost
12. Overall cost is higher 12. Overall cost is lower

13. It is very much suitable where 13. It is not suitable for long strokes
long strokes are required
14. It is suitable for feed movements 14. It is not suitable for feed
of machine tools. Stroke control is movements. Stroke control is easy,
easy and is very precise but fluctuations cannot be avoidable.
6.1 Comparison of Hydraulic &
Pneumatic Circuits
Hydraulic Circuits Pneumatic Circuits

15. Applications: 15. Applications:

Automatic lathe Automatic machines for holding,
Drilling machines gripping, feeding, bottling, wrapping,
Grinding machines packaging etc.
Shaping machines Clamping jigs & fixtures
Crushers Wire feeding
Fork lift trucks For raw material feeding
Dumpers For hoist, Lift, Cranes
Truck loaders For furnace operations
Bulldozers For power tools
Hydraulic press For mining boring, shoveling
Automatic tillers
For press tools
Hydraulic Circuits
 A hydraulic circuit is a group of components
arranged in such a way that they will perform a
useful task.
 The elements of hydraulic circuit are pumps,
actuators, control valves, pipe & pipe fittings,
reservoir, accumulator, filter and strainer
 These components are arranged in various
ways to obtain a desired output from the circuit.
Hydraulic Circuits
 While designing any hydraulic circuit the
following points should be considered.
1. Performance of desired function
2. Efficiency of operation
3. Safety of operation
4. How much force is needed?
5. How fast circuit should function (actuating speed)?
6. Control desired – manual, mechanical, electrical, pilot.
7. Input energy source
8. Life of system desired.
Hydraulic power unit
 The hydraulic power unit consist of pump, filter,
reservoir, pressure gauge, pressure relief valve,
electric motor, shut-off valve, pipe and pipe
fittings.
 In this power unit pump is driven by electric
motor, oil rushes from reservoir via filter and
deliver at higher pressure at its outlet.
 To set maximum pressure in the system, a
pressure relief valve is connected which gets
open when pressure in the system is above set
value.
 The shut-off valve is opened to read the
pressure gauge reading.
Flow control circuits
 When a constant delivery pump is used to
deliver a constant volume of fluid to the circuit,
then the speed or feed control should be
provided with metering valves.
 To ensure proper feed and speed of an actuator,
the flow control valves may be used in the
circuits.
 There are following methods to control flow
1. Meter-in control circuit
2. Meter-out control circuit
3. Bleed-off control circuit
Meter-in control circuit
 Fig. shows the meter-in circuit.
 In this flow control valve is connected between
the D.C valve and blind end of the cylinder.
 Here metered fluid enters the cylinder which
controls the speed and feed of the piston.
 When D.C. valve is manually shifted to right side
the flow from pump passes through the
compensated flow control valve into blind end of
cylinder and the exhaust fluid is directed freely to
the reservoir.
 When the force on D.C. valve is released, it
permits the spool to return due to valve spring and
the pump flow is directed to the rod end of the
cylinder.
 The fluid from blind end of the cylinder will pass
through the integral check valve in the flow control
mechanism and the piston can be retracted
rapidly to its initial position.
 Flow during retraction is not controlled (i.e. Free
flow)
 This method is used when the load characteristics
are constant and positive. Hence they are used in
surface grinder & milling m/c.
 Also in Shaper planner slotter due to quick return.
Meter-out speed control circuit
 Fig. shows meter-out speed control circuit.
 In this flow control valve is located between D.C.
valve and rod end of cylinder in such a way that
the fluid is metered as it leaves the cylinder.
 When D.C. valve is manually shifted to right side
the flow from pump passes to blind end of
cylinder and the exhaust fluid is directed through
flow control valve to the reservoir. Due to this the
movement of piston is regulated as fluid has
restriction on rod end side. Thus piston moves
slowly.
 When the force on D.C. valve is released, it permits
the spool to return due to valve spring and the
pump flow is directed to the rod end of the cylinder
through integral check valve in the flow control
mechanism.
 The fluid from blind end will flow to D.C. valve as
there is no restriction and the piston can be
retracted rapidly to its initial position.
 Flow during retraction is not controlled (i.e. Free
flow)
 This method is used where free falling load or
overhauling load tends to go out of control.
 They are used in operations like drilling, boring,
reaming. Shaper planner slotter due to quick return.
Bleed-off control circuit
 This is basic speed control circuit in which the
flow control valve is used to divert the fluid to the
reservoir.
 Fig. shows bleed-off control circuit.
 In this flow control valve is connected in the
pressure line so that the speed control may be in
both directions of cylinder travel.
 These circuits are suitable for broaching
machines, shaping and planning machines.
 The bleed-off control circuits may be used in
hydraulic motor brake circuit and concrete
mixtures on the truck.
Sequence circuit
 In this sequence valve is provided to do the
operations sequentially.
 Fig. shows the use of two sequence valve in
hydraulic circuit for controlling two operations
performed in the sequence in both directions.
 It consist of hydraulic power unit, two sequence
valves A & B with integral check valve, two
double acting cylinders P & Q, and D.C. valve
 When D.C. valve is shifted to left envelop mode,
the oil from pump enters the cylinder ‘P’ through
line 1-3, causing the piston in cylinder ‘P’ to
extend fully.
 The oil from rod end of cylinder passes from port
4 via check valve of the sequence valve ‘B’ to
port 2 of the D.C. valve and exhausted to the
reservoir.
 As the piston in the cylinder ‘P’ extends
completely, the pressure in line 1-3 rises which
causes the sequence valve ‘A’ to open.
 Then the oil from pump enters the blind end of
cylinder ‘Q’ through the line 1-6, which cause the
piston in cylinder ‘Q’ to extend completely.
 The oil from rod end of cylinder ‘Q’ is discharged
into the reservoir via line 5-2 through D.C. valve.
 When the D.C. valve is released, the oil from
pump enters into the rod end of cylinder ‘Q’ via
line 2-5 causing the piston in the cylinder ‘Q’ to
retract completely and oil from side of the
cylinder is directed to return into the reservoir
through check valve of sequence valve ‘A’ via
line 6-1.
 As the piston in cylinder ‘Q’ retracts completely,
the pressure in the line 2-6 is increased.
 The pressure rise in the line 2-6 causes the
sequence valve ‘B’ to open, allowing the flow
from pump to enter rod end of cylinder ‘P’
through port 4.
 It causes the piston in cylinder ‘P’ to retracts
completely.
 The oil from blind end of cylinder ‘P’ is
discharged out to reservoir via line 3-1 through
D.C. valve.
 Thus the extension and retraction of pistons in
both the cylinders are performed in sequence.
 The circuit is suitable for clamping and
declamping of work piece and punching or
drilling operations simultaneously.
Application of Hydraulic circuits
 Hydraulic circuit for Milling M/c
 Hydraulic circuit for Shaper M/c
 Hydraulic circuit for Surface grinder
 Hydraulic circuit for Hydraulic
Press
 Hydraulic Power Steering
 Reaction piston type hydraulic steering system
 Hydraulic circuit of Dumpers
 Hydraulic circuit of Excavators
Hydraulic circuit for Milling M/c
 fig. Shows the hydraulic circuit for reciprocation
of milling machine table using limit switch.
 It consist of hydraulic power unit, solenoid
actuated D.C. valve to alter the direction of
piston stroke of double acting cylinder.
 To obtain a smooth, equal speed and feed in
both direction of machine table travel a flow
control valve is placed in tank line.
 Here limit switch LS-1 and LS -2 are used to
energize the solenoid.
 Initially consider that the limit switch LS-1 is
depressed by machine table which energizes
the solenoid C causing D.C. valve to shift in left
envelop mode.
 The oil from pump port ‘P’ enters the cylinder
port 1 via line P-A-1 causing machine table to
move forward and the oil from other side of
piston is return to reservoir through flow control
valve
 At the end of forward stroke the limit switch LS-2
is depressed causing solenoid D to energized.
 This causes D.C. valve to shift in right envelop
mode.
 Then the oil from pump P enters cylinder port 2
causing the piston to perform return stroke.
 The oil from port 1 returns to reservoir via flow
control valve.
 This cycle is repeated causing milling m/c to
perform cutting action.
 The length & position of stroke can be adjusted
by shifting the position of limiting switches
Hydraulic circuit for Shaper M/c
 Fig shows the hydraulic circuit for operation of
shaper.
 Here meter- out circuit is used.
 It consists of hydraulic power unit which delivers
the oil at constant pressure.
 A double acting cylinder is used to reciprocate
the ram
 A pivot actuated D.C. valve is used to alter the
direction of stroke of the piston
 When spool is in right envelop mode, the oil from
port P enters the blind end of cylinder causing
the ram to move forward.
 The oil from other side of piston is discharged
through flow control valve into reservoir. Here
quantity of liquid is controlled while going out
hence circuit is meter-out.
 The cutting speed can be changed by controlling
the flow control valve.
 At the end of forward stroke, the ram hits the
pivoted lever of D.C. valve shifting the valve into
left envelop mode.
 Thus the oil from pump enters the rod end of the
cylinder through check valve causing the ram to
perform the return stroke.
 The oil from blind end returns to reservoir, as
there is no restriction the return is quick.
Hydraulic circuit for Surface
grinder
 Fig. shows the hydraulic circuit for reciprocating
the machine table for surface grinder.
 The circuit consist of a hydraulic power unit,
which delivers oil under pressure.
 It uses pilot operated D.C. valve to alter the
direction of stroke of piston in a double acting
cylinder.
 It also consist of two roller actuated three way
D.C. valve V1 & V2 to actuate pilot operated four
way D.C. valve
 The flow control valve is placed in return line to
tank which provides smooth and equal speed
and feed in both direction of table travel.
 When valve V1 is depressed by table, the oil
from pump flows through V1 and is supplied to
pilot spool E which puts the D.C. valve in left
envelop mode
 Then the oil from pump enters the cylinder
through port 1 causing the table to move forward
and oil from other side is delivered to reservoir
through flow control valve.
 At the end of stroke it depress valve V2 , the oil
from pilot line operates spool F to put D.C. valve
in right envelop mode.
 Thus oil from pump enters the cylinder port 2
causing machine table to return and the oil from
other side of piston is delivered to reservoir
through flow control valve.
Hydraulic circuit for Hydraulic
Press
 Fig. shows the hydraulic circuit for the operation of
hydraulic press.
 It consist of manually operated D.C. Valve
 A press operation requires an accurate movement rate
of piston so that the metal flows smoothly without tearing
or cracking
 Thus it is necessary to meter the fluid into the blank end
of the cylinder. Here meter-in circuit is used
 Therefore flow control valve is located in the feed line B-
1 on the actuator so that one stroke is to be speed
controlled and check valve permits the rapid retraction.
 When spool of D.C. valve is in left envelop mode, the
metered quantity of oil from pump enters the blank end
of cylinder via flow control valve causing forward stroke.
 The oil from rod end is discharged out into the reservoir
via line 2-A-R. during this stroke operation is done on
workpiece
 When the spool is shifted to right envelop mode the
pump supplies the fluid to rod end of cylinder and the
fluid from blank end returns back to reservoir through
check valve causing quick retraction of cylinder.
 When spool is in neutral position the operator unloads
the object and load another object. In this position pump
delivery is directed to reservoir.
 The hydraulic presses are slower and more powerful and
adapted for pressing, forming and bending operations.
 These are also employed for fabrication of heavy
forgings
Hydraulic Power Steering
 This is used to reduce the turning effort required to steer
the wheels.
 It consist of hydraulic pump, gear box, rotary spool type
D.C. valve and hoses.
 The steering wheel is connected to the one end of rotary
spool valve while at other end of valve worm is
connected.
 The worm rotates the nut making the sector to turn which
turns the road wheels at angle.
 When driver turns the steering wheel, the spool valve
turns directing the pressurised oil from pump to
appropriate side of the nut applying the effort on that
side.
 This helps in reducing the effort of driver.
Reaction piston type hydraulic
steering system
 It consist of piston connected to chassis, a moving
cylinder, ball joint connected to drop arm and sliding
spool valve
 The spool valve is operated by ball joint.
 When the steering wheel is moved to right, the ball joint
connected to the drop arm moves the spool valve to right
against spring pressure. This allows hydraulic pressure
to pass to the rear of the piston.
 As piston is stationary the pressurized fluid react against
the piston and push the cylinder to the right.
 The fluid from front of piston is returned to the reservoir.
 Thus it helps in reducing the effort applied by driver.
The most common arrangement of hydraulic brakes for passenger vehicles,
motorcycles, scooters, and mopeds, consists of the following:
Brake pedal or lever
A pushrod (also called an actuating rod)
A master cylinder assembly containing a piston assembly (made up of either one or two
pistons, a return spring, a series of gaskets/ O-rings and a fluid reservoir)
Reinforced hydraulic lines
Brake caliper assembly usually consisting of one or two hollow aluminum or chrome-
plated steel pistons (called caliper pistons), a set of thermally conductive brake pads and
a rotor (also called a brake disc) or drum attached to an axle.
The system is usually filled with a glycol-ether based brake fluid (other fluids may also
be used).
At one time, passenger vehicles commonly employed drum brakes on all four wheels.
Later, disc brakes were used for the front and drum brakes for the rear. However disc
brakes have shown better heat dissipation and greater resistance to 'fading' and are
therefore generally safer than drum brakes. So four-wheel disc brakes have become
increasingly popular, replacing drums on all but the most basic vehicles. Many two-
wheel vehicle designs, however, continue to employ a drum brake for the rear wheel.
The following description uses the terminology for and configuration of a simple disc
brake.
Introduction to Electo-hydraulic system
A solenoid valve is a type of valve that uses
an electrical current to actuate or shift a spool or
cartridge consisting of a solenoid coil and tube
assembly.

Basically, this valve type uses an electric

current to shift a pin to perform simple A/B tasks
such as open/close valve spools.

The designation "solenoid" means that the

valve operation is electrical not manual.

 Maybe the easiest way to describe a

solenoid valve is by thinking about an automatic
car lock. The electric current get triggered, the
pin gets pushed up and the doors are unlocked.
A reverse current gets triggered, the pin gets
pushed down, and the doors are locked.
A solenoid valve is an electromechanically operated valve. The valve is controlled by
an electric current through a solenoid: in the case of a two-port valve the flow is
switched on or off; in the case of a three-port valve, the outflow is switched between
the two outlet ports. Multiple solenoid valves can be placed together on a manifold.

Solenoid valves are the most frequently used control elements in fluidics.
Their tasks are to shut off, release, dose, distribute or mix fluids.
They are found in many application areas.

Advantageous of Solenoids
fast and safe switching,
high reliability, long service life,
good medium compatibility of the materials used,
Low control power and
compact design.
·
Compact Ergonomic Design.
· User Friendly, Self Explanatory Systems.
· Leak proof Safety Measures, sturdy piping & Robust Construction.
· Training Manuals mimic Charts for Operation Ease.
· M.S. powder coated cubical plant with standard Instrument Mountings.
· Inbuilt Safety Measures to avoid improper usag
Hydraulic circuit of Dumpers:
 Dumpers are used in mining sector for
transporting material with in the area of mines.
 In some dumpers tipping system and steering
system is hydraulically operated.
 The basic components are
 Hydraulic fluid tank
 Spool valve
 Relief valve
 3-stage hydraulic cylinder
 Hydraulic gear pump
 Working: The fluid from reservoir is sucked by
pump. It is pressurized and send to the spool
valve. A relief valve is provided in circuit to keep
pressure constant. If the spool valve is in neutral
position, the tipping system is not operating, the
flow goes to reservoir through the filter.
 If the spool valve is in forward position the flow
goes to the tipping cylinders thus extending the
cylinders and tipping operation is carried out. If
the spool valve is in reverse position the flow of
oil in the top end of tipping cylinder and bottom
end is connected to reservoir there by
contracting tipping cylinders.
Hydraulic circuit of excavators
 Excavators are used in various industries like
construction, agricultural, mining & irrigation
department.
 In excavators all the operation such as boom,
bucket, stick, swing & travel are done
hydraulically.
 The fig. shows the hydraulic circuit for boom,
bucket & stick of excavators
 A fluid from reservoir is pumped to a six
chambers which further supplies to various
operating systems.
Hydraulic circuit of excavators
 Flow from chamber 1 goes to spool valve that
operates the boom.
 The spool valve of boom is operated by joy stick
situated on the dash board.
 As spool is moved it supplies the fluid in
appropriate side thereby extending or
contracting the boom cylinder and boom rises up
or down.
 The fluid from chamber 1 also goes to operate
spool of bucket.
Simple Pneumatic Circuits
 A Pneumatic circuit is a group of components
arranged in such a way that they will perform a
useful task.
 The elements of pneumatic circuit are air
compressor, actuators, control valves, tubes &
tube fittings, FRL unit (filter, regulator &
lubricator).
 These components are arranged in various
ways to obtain a desired output from the circuit.
 While designing any pneumatic circuit the
following points should be considered.
1. Performance of desired function
2. Efficiency of operation
3. Safety of operation
4. How much force is needed?
5. How fast circuit should function (actuating
speed)?
6. Control desired – manual, mechanical, electrical,
pilot.
7. Input energy source
8. Life of system desired.
Pneumatic power unit
 Fig shows the circuit for pneumatic power unit.
 In this air compressor compresses the air which
is then stored in the receiver. This air is further
pass in the system through FRL unit.
 The FRL unit filter the air, it regulates the
pressure in the system and it lubricates the air.
 Speed control circuits
Meter-in speed control pneumatic circuit:
 Fig shows the speed control pneumatic circuit
 It consist of manually operated D.C. valve, a flow
control valve.
 A flow control valve is placed in the pressure line
such that the air flow rate is regulated as the air
enters the blank end of double acting cylinder to
perform forward stroke.
 When the spool is shifted to its left envelop
mode the air from FRL unit is directed to enter
the blank end of cylinder through flow control
valve where the air flow rate is controlled to
control the forward stroke of piston in the
cylinder.
Meter-in speed control pneumatic circuit:
 The air from the other side of piston is
discharged out into the atmosphere.
 When the spool is shifted to right envelop mode
the air enters the rod end of cylinder and acts on
piston to perform return stroke quickly. The air
from other side of piston discharged out freely
into the atmosphere through the check valve
Meter-out speed control pneumatic circuit:
 It uses the flow control valve to control the rate
of piston movement on the outstroke of machine
 It consist of pneumatic power unit, manually
operated D.C. valve, flow control valve
 When spool is in its left envelop mode the air
from FRL unit enters the blind end of cylinder
and acts on the piston to perform forward stroke.
 The air from other end of cylinder is allowed to
pass through a flow control valve to regulate the
outstroke speed of piston.
 When the spool is in right envelop mode the
piston retracts quickly.
Pneumatic circuit to control the speed of double acting
cylinder:
 Fig shows the pneumatic circuit to control the speed of
double acting cylinder.
 Here two flow control valves are placed in the incoming
lines of double acting cylinder. And is placed in meter-
out circuit.
 The check valve and flow control valves are placed in
such a manner that the air flows freely into the cylinder
through the check valve in both position of a four way
D.C. valve.
 But the air from the cylinder has to pass only through the
flow control valve in both position of D.C.Valve.
 In this both the piston extension or retraction speed can
be controlled by flow control valve.
Sequence circuit
 Fig shows the pneumatic circuit using one
sequence valve to control the two operations
performed in proper sequence in one direction
only.
 It consist of pneumatic power unit, D.C. valve,
sequence valve and two double acting cylinders.
 When spool is shifted to right side, then the D.C.
valve is in its left envelop mode so that the
compressed air from pneumatic power unit is
directed to enter into the blind end of cylinder ‘P’
 Then the piston in the cylinder P extends which
moves the object placed at position X to position
Y.
 The piston in cylinder P extended completely,
due to this the pressure in line 1-3 builds up
causing the sequence valve A to open.
 This allows the flow of compressed air to enter
the blind end of cylinder Q via line 1-6.
 Thus the piston in the cylinder Q extends, which
moves the object at position Y to position Z.
 The air from the rod end of cylinder is exhausted
into the atmosphere
 As the spool is shifted to left side, then the D.C.
valve is in its right envelop mode.
 The compressed air from power unit is directed
to enter the rod end of both cylinders, causing
the cylinder to retract fully.
 The air from blind end is exhausted to
atmosphere via check valve. Thus the piston in
both the cylinders retracted at the same time.
 Then the cycle is repeated again.
Application of Pneumatic circuit:
 Pneumatic systems are used in various power
operated devices like chucks, mandrels, vice, jig
& special holding fixtures
 A pneumatic power tool are the mean of
converting air power to mechanical power. They
work on percussive or rotary motion.
Application of Pneumatic circuit:
 In percussion tools, the piston oscillates rapidly
to and fro, striking the tool on the outward stroke
and air cushioned on the inward stroke towards
the hand to relieve the operator from shocks.
The oscillations may be up to 2000 per min. ex.
Hammers, Rivetters, Picks, Concrete breakers.

 Rotary pneumatic tools consist of vane type

rotar which is rotated by compressed air and this
rotary motion is transmitted to the tool. Ex.
Pneumatic drills, grinders, die grinders.
 Air brakes are used in trucks, buses, trailers, and semi-trailers.

 George Westinghouse first developed air brakes for use in

railway service. He patented a safe air brake on March 5, 1872.
Originally designed and built for use on railroad train
application, air brakes remain the exclusive systems in
widespread use.

 Westinghouse made numerous alterations to improve his air

pressured brake invention, which led to various forms of the
automatic brake and the subsequent use on heavier road
vehicles.

 The air compressor is driven off of engine either by crankshaft

pulley via a belt or directly off of the engine timing gears.
It is lubricated and cooled by the engine lubrication and cooling
systems.
 Compressed air is first routed through a cooling coil and
into an air dryer which removes moisture and oil impurities .

 Air brake system may include a pressure regulator, safety

valve and a smaller purge reservoir. As an alternative to
the air dryer, the supply system can be equipped with an
anti freeze device and oil separator.

 The compressed air is then stored in a reservoir (also

called a wet tank) from which it is then distributed via a
four way protection valve into the front and rear brake
circuit air reservoir, a parking brake reservoir and an
auxiliary air supply distribution point.

 The system also includes various check, pressure

limiting, drain and safety valves.
Safety
Since air is readily available for free everywhere on the surface of earth, this significantly
reduces the chance of brake failure due to leaks in the braking system.
.
Reliability
When the vehicle is started, the compression begins and the brakes are released when
the vehicle is put to motion. Thus, if there is a leak or even if the compression
Mechanism completely fails, the brakes revert back to their default, activated position
and the vehicle is brought to rest.

Cost Effectiveness
Air on the other hand, is freely available. Minor leaks do not result in brake failures.

Air line couplings are easier to attach and detach than hydraulic lines; there is no
danger of letting air into hydraulic fluid. So air brake circuits of trailers can be attached
and
. removed easily by operators with little training.

Air not only serves as a fluid for transmission of force, but also stores potential energy.
So it can serve to control the force applied. Air brake systems include an air tank that
stores sufficient energy to stop the vehicle if the compressor fails.
Introduction
 Air hammers/pneumatic hammers o/ power hammers,
were invented in 1890, and patented in January of 1894 by
Charles Brady King.

 These hammers use compressed air to help aid

craftsman to hammer, score and perish (smooth) a
workpiece that would take hours, if not days, to produce
manually.

 Air hammers range in size and price greatly. Hand-held

models can be bought from around $20 to larger desk size
models that can cost up to $20,000.
Piston
Air hammers use a piston to work. The piston is the only
moving part to an air hammer.
The piston moves very rapidly back and forth from the air
pressure of the compressor.
 Air is pushed into the central cylinder forcing the tip
attachment forward with great power and velocity. A cyclical
valve then reverses the air flow, forcing the tip attachment into
the back of the cylinder. This cycle is repeated thousands of
times per minute.

 Air hammers use air compression to work. Air compressors

are large tanks of air with motors attached. Hand-held models
of air hammers use tubes connected to an air tank. The motor
fills the tank with air that is pressurized. This pressurized air
travels through the tube to the air hammer, thus making the air
hammer operational.

 Each air hammer varies on the size of compressor it needs

to perform. Smaller air hammers need smaller compressors
while larger models need larger compressors.
 Applications
 The difference in size of air hammers to air compressors
vary according to the cubic feet per minute, or PSI
required for the specific air hammer model being used.

 Since different bits can be used in air hammers, a

craftsman can find several purposes for the tool.

 Different bits can be acquired to do jobs such as

cutting steel, cutting metal, drilling holes, decorative and
ornamental purposes.

 Contractors can also use these tools for demolition

projects, take out mortar, or removing rivets. Safety
Precautions
 Air hammers are very powerful tools which can
cause great injury if safety precautions are not taken.

 Wear the proper safety equipment such as safety

glasses and ear plugs. Craftsman should always make
sure the air hammer is unplugged when changing the
various tips, or bits.

 Finally, when working with an air hammer, a

craftsman should always be aware of the positioning of
the tool due to the extreme powerful nature that can
cause the tool to jump when operated.
Pneumatic drill:-
 Fig shows small light duty pneumatic drill.
 It works on compressed air at 5.5 bar.
 The quantity of air is controlled by ball valve
which is pressed by hand lever mechanism
incorporated in the handle.
 When the lever is pressed air is supplied to the
air motor and when it is released the air supply
is cut off.
 The high pressure air is supplied to the air motor
through control valve.
 The air motor consists of vane type rotor.
Pneumatic drill:-
 The air flows over the vanes axially and rotate
the shaft of air motor.
 After doing work of rotation, air is exhausted into
the atmosphere.
 It is used for wood boring, light drilling, drilling
holes in steel plates for riveting. Here drill size is
up to 2.5 mm.
Pneumatic grinder:-
 It works on compressed air at 5.5 bar.
 It consist of hose, throttle valve, bearing vane
type rotor, rotor case and rotor shaft which are
enclosed in a body of the grinder.
 The rotor shaft projects outwards of the body at
the end of which a grinding wheel is mounted.
 The compressed air is supplied to grinder from
a compressor.
 As air passes over the rotor blades it rotates the
shaft and hence the grinding wheel. After doing
work air is exhausted through the ports to
atmosphere.
Pneumatic grinder:-
 The speed of grinder is constant, it is about
14500 to 15000 rpm.
 The grinders are used in die shop for delicate
work.
 They are also used for grinding ornamental
scroll work for finishing metal pattern, trimming
of casting, polishing and filling of various jobs.
Low cost Automation:-
 Pneumatics is a pacemaker of low cost
automation.
 It helps in simplification of the technical outlay
for special machinery and auxillary equipment,
with limitations naturally being set by application
criteria Ex. Force, thrust, travel, time etc.
 The relatively small capital expenditure creates
a basis for building a special type machine,
fixture or auxillary unit for a given shaping
operation even when only small runs or a few of
the parts are to be produced.