Download What are pneumatics

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GANDHINAGAR INSTITUTE OF
TECHNOLOGY
AICTE Approved | Affiliated With Gujarat Technological University
Control Engineering
(2161905)
Mechanical Engineering
Prepared by:
Patel Nirav
(130120119160)
Topic:Pneumatic control system
Content:• what are pneumatic ?
• Advantage & Disadvantage of Compressed air pneumatic
Systems
• Working of pneumatic Control System
• Air Compressors
• Different types of Compressor
• Efficiency of Compressor
• Application
• conclusion.
What are pneumatics ???
• Mechanisms which use air
pressure to apply mechanical force
and displacement.
• Commonly used in industry.
• Pneumatic power users need not
worry about hazardous leakage as
the fuel is commonly just air,
although other compressed gases
such as carbon dioxide may be
used.
Advantage
 Simple
 Easy to control
 Explosive proof
 Easily transportable in vessels & pipes
 Low cost of maintenance.
 No return lines are required
 Clean system, it has a self cleaning property.
Drawbacks
• High forces can not be transmitted
• Cylinders can be subject to damage
• Repair impossible
• Provides a non-uniform speed
• Inaccurate in operation
• Creates a noise pollution
• Expensive
How it works ???
• Typically, pressure
is applied to one port
while the other is
vented to atmosphere
So  P is regulated
gauge pressure
(60 psi max)
⅛” NPTF Air Port (Retraction)
Seals
Piston
Rod
Cylinder
⅛” NPTF Air Port (Extension)
The pneumatic cylinder has following general characteristic.
•
•
•
•
Diameter
= 2.5 to 320 mm
Stroke length
= 1 to 2000 mm
Available forces = 2 to 45,000 N at 6 bar
Piston speed
= 0.1 to 1.5 m/s
Stroke
Length
In pneumatic control system many topics are there such
as air compressor, pneumatic filter, air pressure
regulator, (FRL)filter, regulator, & lubricator unit,
pressure control valve, direction control valve, 2 way
valve, 3 way valve, shuttle valve, pilot valve, etc.
But here we study about air compressor in briefly.
What is air compressor ???
• An air compressor is a device that takes in air at
atmospheric pressure and delivers it at a higher pressure
by reducing its volume.
• Compressor :- a mechanical device that compresses
gases.

Manufacture company
 DeWalt
 California Air Tools
 Makita
 Senco
 Porter-Cable
Types of air compressor :
Type of
compressor
Positive
displacement
Reciprocating
Rotary
Dynamic
Centrifugal
Axial
In the positive-displacement type, a given quantity of air or
gas is trapped in a compression chamber and the volume it
occupies is mechanically reduced, causing a corresponding
rise in pressure prior to discharge. At constant speed, the air
flow remains essentially constant with variations in
discharge pressure.
Dynamic compressors impart velocity energy to
continuously flowing air or gas by means of impellers
rotating at very high speeds. The velocity energy is
changed into pressure energy both by the impellers and the
discharge volutes or diffusers. In the centrifugal-type
dynamic compressors, the shape of the impeller blades
determines the relationship between air flow and the
pressure (or head) generate
Reciprocating air compressor
 During the downward motion of the piston, the pressure inside the
cylinder falls below the atmospheric pressure and the inlet valve is
opened due to pressure.
 The air is taken into the cylinder until the piston reaches bottom dead
positions.
 As the piston starts moving upward, the inlet valve is closed and the
pressure is increasing continuously until the pressure inside cylinder
is above the pressure of delivery side which to the receiver.
 Then delivery valve open and air transfer to receiver.
PV diagrame:
• Referring to the diagram, the theoretical air compressor PV
diagram can be understood
Rotary air compressor
 In this compressor, the suction
and delivery valve replaced by port
and a piston replaced by helical
screw.
 It consists of two helical screws
which are mesh with each other.
 An electrical motor drives a
male rotor and female are
driven by male rotor.
Centrifugal air compressor
It consists of rotating impeller,
diffuser, casing, driven shaft,
impeller eye etc.
The impeller run at speed
20,000 to 30,000 r.p.m.
The diffuser is important part of
compressor which surrounding
the impeller and provides
diverging passage
for air flow thus increasing the
pressure air.
Axial Flow compressor
• It consists of a casing fitted with several rows of fixed
blades and rotor attached with several rows of moving
blades.
• The fixed and moving blades are placed on alternate rows
the function of the fixed blades is to receive the high
velocity air from the moving blades.
• Speed may be vary from 10,000 to 30,000 RPM. Pressure
ratio of 10:1 can be achieved.
Reciprocating compressor efficiencies
(1)Mechanical efficiency
ῃ= I.P/B.P
(2) Isothermal efficiency
ῃiso =
p1 V1 loge (p2/P1)
[ (n/n-1) p1V1 (p2/p1)n-1/n -1}]
(3)Volumetric efficiency
ῃ = 1- C [(p2/p1)1/n -1)]
Pneumatic Application in industry
Pneumatic actuators are extensively used by the Chemical
Process Industry due to their intrinsic safety and their ability to
fail safe.
2-position
pneumatic
actuator
driving a
4-way
ball valve
pneumatically
driven flow
control valves
(butterfly type
Pneumatic Application:
Pneumatic cutter
Pneumatic Application:
• Pneumatics is used in carrying out machining &
working operation.
 For ex:
 Drilling
 Turning
 Milling
 Sawing
 Finishing
 Forming
 Quality control

Conclusions
 Air compressor is a supply of air
which generates air that is stored
in a tank.
 we have seen the actual
operation of an Air compressor
and its theoretical PV diagram.