Preliminaries of Pneumatics (Basic Components Details)

Introduction
A pneumatic system is a system that uses compressed air to transmit and
control energy. Pneumatic systems are used extensively in various industries.
Most pneumatic systems rely on a constant supply of compressed air to make
them work. This is provided by an air compressor.
The compressor sucks in air from the atmosphere and stores it in a high
pressure tank called a receiver. This compressed air is then supplied to the
system through a series of pipes and valves.

Basic Components of Pneumatic System
Figure of Components of Pneumatic System

Basic Components of Pneumatic System
Air filters: These are used to filter out the contaminants from the air.
Compressor: Compressed air is generated by using air compressors. Air compressors are either
diesel or electrically operated. Based on the requirement of compressed air, suitable capacity
compressors may be used.
Air cooler: During compression operation, air temperature increases. Therefore coolers are used to
reduce the temperature of the compressed air.
Dryer: The water vapor or moisture in the air is separated from the air by using a dryer.
Control Valves: Control valves are used to regulate, control and monitor for control of direction
flow, pressure etc.
Air Actuator: Air cylinders and motors are used to obtain the required movements of mechanical
elements of pneumatic system.
Electric Motor: Transforms electrical energy into mechanical energy. It is used to drive the
compressor.
Receiver tank: The compressed air coming from the compressor is stored in the air receiver.

Components of Pneumatic System
1) Reciever Tank
The air is compressed slowly in the compressor. But since the pneumatic system needs
continuous supply of air, this compressed air has to be stored. The compressed air is stored in an
air receiver as shown in Figure 2. The air receiver smoothens the pulsating flow from the
compressor. It also helps the air to cool and condense the moisture present. The air receiver
should be large enough to hold all the air delivered by the compressor.
Fig. Air Reciever

2) Compressor
It is a mechanical device which converts mechanical energy into fluid energy. The
compressor increases the air pressure by reducing its volume which also increases the
temperature of the compressed air.
The compressor can be classified into two main types
Positive displacement compressors and
Dynamic displacement compressor
Positive displacement compressors include piston type, vane type, diaphragm type and
screw type.

a) Single acting Type :- Piston
compressors are commonly used in
pneumatic systems. The simplest
form is single cylinder
compressor.The single cylinder
compressor gives significant amount
of pressure pulses at the outlet port.
The pressure developed is about 3-40
bar.
Fig. Single Acting Piston Comprsssor
b) Double acting Type :- The
pulsation of air can be reduced by
using double acting compressor as
shown in f o l l o w i n g Figure. It
has two sets of valves and a
crosshead.
Fig. Double Acting Piston Comprsssor

c) MultiStage Compressor :-As the
pressure of the air increases, its
temperature rises. It is essential to
reduce the air temperature to avoid
damage of compressor and other
mechanical elements. It is used to
reduce the temperature of
compressed air during the
compression stages.
Fig. MultiStage Compressor
d) Combined two Stage
Compressor :-In this type, two-
stage compression is carried out by
using the same piston. Initially
when the piston moves down, air is
sucked in through the inlet valve.
During the compression process,
the air moves out of the exhaust
valve into the intercooler.
Fig. Combined two stage Comprsssor

4) Filters
To prevent any damage to the compressor, the contaminants present in the air need to be filtered
out. This is done by using inlet filters. These can be dry or wet filters. Dry filters use disposable
cartridges. In the wet filter, the incoming air is passed through an oil bath and then through a fine
wire mesh filter. Dirt particles cling to the oil drops during bubbling and are removed by wire
mesh as they pass through it. In the dry filter the cartridges are replaced during servicing. The
wet filters are cleaned using detergent solution.
5) Coolers
As the air is compressed, the temperature of the air increases. Therefore the air needs to be
cooled. This is done by using a cooler. It is a type of heat exchanger. There are two types of
coolers commonly employed viz. air cooled and water cooled. In the air cooled type, ambient air
is used to cool the high temperature compressed air, whereas in the water cooled type, water is
used as cooling medium.

4.1) Air Fiter & Water trap :-
Airfilter and water trap is used to
1. Prevent any solid contaminants
from entering in the system.
2. Condense and remove water vapor
that is present in the compressed air.
Fig. Air filter and Water Trap
5.1) Refrigerated Dryers :-It
consists of two heat exchangers,
refrigerant compressor and a
separator. The system circuitry is
shown in Figure 8 The dryer chills
the air just above 0 °C which
condenses the water vapor. The
condensate is collected by the
separator. However such low
temperature air may not be needed at
the application.
Fig.Refrigerated Dryers

a) Adsorption Dryer :- In Adsorption dryers, the moisture collects on the sharp edges of the
granular material. The adsorbing materials can be silicon dioxide (silica gel) or other materials
which exist in hydrated and dehydrated state (copper sulphate, activated alumina).
Fig. Adsorption Dryer
5.2) Chemical Dryers
When absolute dry air is needed chemical dryers are used. These dryers are of
two
types viz. adsorption dryer and absorption dryer.

b) Absorption Dryer :- These are also called as deliquescent dryers. Figure shows a schematic of the
same. It uses chemical agents like phosphoric pentoxide or calcium chloride as drying agents. The
moisture in the compressed air chemically reacts with the drying agent. The agent dissolves to form a
liquid compound which collects at the bottom of the dryer where it can be drained out. The
deliquescent agent has to be replenished regularly as it gets consumed during the drying process.
Fig. Absorption Dryer

6) Actuators :
Actuators are output devices which convert energy from pressurized hydraulic oil or
compressed air into the required type of action or motion.
Actuators can be classified into three types ;-
1. Linear actuators: These devices convert hydraulic/pneumatic energy into linear motion.
2. Rotary actuators: These devices convert hydraulic/pneumatic energy into rotary motion.
3. Actuators to operate flow control valves: these are used to control the flow and pressure
fluids such as gases, steam or liquid.
Some of them Actuators are described to the next pages.

a) Single acting Cylinder :- These
cylinders produce work in one
direction of motion hence they are
named as single acting cylinders.
Figure shows the construction of a
single acting cylinder.
Fig. Single acting Cylinder
b) Double acting Cylinder :- The main parts
of a hydraulic double acting cylinder are:
piston, piston rod, cylinder tube, and end caps.
The piston rod is connected to piston head and
the other end extends out of the cylinder. The
piston divides the cylinder into two chambers
namely the rod end side and piston end side.
The seals prevent the leakage of oil between
these two chambers. The cylindrical tube is
fitted with end caps.
Fig. Double Acting Cylinder

c) Cylinder and Cushions :- Double
acting cylinders generally contain
cylinder cushions at the end of the
cylinder to slow down the movement
of the piston near the end of the
stroke. Cushioning arrangement
avoids the damage due to the impact
occurred when a fast moving piston
is stopped by the end caps
Fig. Cylinder and Cushions
d) Gear Motor(Rotary Actuator) :- Rotary
actuators convert energy of pressurized fluid
into rotary motion. Rotary actuators are similar
to electric motors but are run on hydraulic or
pneumatic power.
Fig.Gear Motor

7) Control Valves :
There are folowing three types of control valves ,
1) Direction control valve
2) Flow control valve
3) Pressure control valve

1) Directional Control Valves :
Directional valves control the way the air passes and are used principally
for controlling commencement, termination and direction of air flow.
2) Pressure Control Valves :
Pressure control valves control the pressure of the air flowing through the valve
or confined in the system controlled by the valve.
There are three types of pressure control valves
1. Pressure limiting valve
2. Pressure regulator or
3. Pressure reducing valve

3) Flow Control Valves : They are,
1. Manifold type 2. Inline type

Advantages & Limitations
Advantages :
➢ High effectiveness
➢ High durability and reliability
➢ Simple design
➢ High adaptability to harsh environment
➢ Safety aspects
➢ Easy selection of speed and pressure
Disadvantages :
➢Relatively low accuracy
➢Low loading
➢Processing required before use
➢Uneven moving speed
➢Noise

Preliminaries of Pneumatics (Basic Components Details)

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