Concepts of Pneumatic System.pdf

Concepts of
Pneumatic System
Prepared by - Ruzaan Karanjia

TABLE OF CONTENT
Chapter
Number
Chapter Particulars
Abstract
1 Introduction
1.1 Working Principle
1.1.1 Major Parts and Components
2 Classification and Working of Pneumatics System's
Elements
2.1 Pneumatics Power Generating Elements - AIR
COMPRESSORS AND PUMPS
2.1.1 Pneumatic Pumps
2.1.1.1 Classification of Pumps
2.1.1.2 Fixed Displacement Pumps
2.1.1.3 Pneumatic Diaphragm Pumps
2.1.1.4 Pneumatic Liquid Pump
2.1.1.5 Refrigerant Pump
2.1.1.6 Vacuum Test Pump
2.1.2 Air Compressors
2.1.2.1 Classification of Air Compressors
2.1.2.2 Positive Displacement Compressors
2.1.2.2.A Piston Compressors

2.1.2.2.B Rotary Screw Compressors
2.1.2.2.C Vane Compressors
2.1.2.3 Roto-Dynamic Air Compressors
2.2 Pneumatic Power Controlling Elements - VALVES
2.2.1 Classification of Valves
2.2.1.1 Flow Control Valve
2.2.2.1 Diaphragm Flow Control Valve
2.2.1.2 Direction Control Valve
2.3 Pneumatics Power Utilising Elements -
CYLINDERS and MOTORS
2.3.1 Pneumatics Cylinders
2.3.1.1 Double acting
2.4 Pneumatics Power Conveying Elements - HOSES,
PIPES and FITTINGS
2.5 Pneumatics Accessories - AIR RECEIVER TANK,
AIR DRYER AND FRL UNIT
2.5.1 Air Receiver Tank
2.5.2 Air Dryer
2.5.3 FRL UNIT
3 Pneumatics System Circuit Diagram
4 References

ABSTRACT
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 constant air supply is
provided by air compressors. 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.
● Pneumatics is an application of fluid power - in this case the use of a gaseous media
under pressure to generate, transmit and control power; typically using compressed
gas such as air at a pressure of 60 to 120 pounds per square inch (PSI)
● Mechanical Engineering - Compressed air is a very fast working medium. This enables
high working speeds to be attained. Adjustable: With compressed air components,
speeds and forces are infinitely variable.
● Mechanics - Pneumatic systems use gas or pressurised air to move cylinders, motors
or other mechanical parts.
1. INTRODUCTION
The word ‘Pneuma’ means air. Pneumatics is all about using compressed air to do the work.
Compressed air is the air from the atmosphere which is reduced in volume by a device called
a compressor thus increasing its pressure. It is used as a working medium normally at a
pressure of 6 kg/sq mm to 8 kg/sq mm for doing work. It can be controlled manually,
pneumatically to do work by acting on a piston or vane.
The pneumatic system is very similar to a hydraulic system, but compressed air is used
instead of hydraulic oil in this system. A system that uses compressed gas or air to control
and transfer energy is called a Pneumatic system. Pneumatic systems widely used in
different industrial applications. Maximum numbers of these systems depend on a
continuous supply of compressed air to work. A pneumatic pump uses compressed gas or air
to generate power that is used to flow liquid through a pipeline system. Pneumatic Pumps
usually work with compressed inert gas or air. A central compressor is used to run cylinders,
motor, and other pneumatic equipment with a pump.
A pneumatic system may be termed as just the use of compressed air to do work. However,
it goes way beyond that. When compressed air is controlled using a series of pipes and
valves, complicated systems with mind blowing capabilities can be created. This is the life
force of today's industrial capabilities and automated systems.

1.1 Working Principle
The Pneumatic system also works on the principle of Pascal's law because it's also a part of
fluid power
The law states that the pressure in an enclosed fluid is uniform in all directions.
Pascal's law is illustrated in the figure.
Fig. 1.1 (a) Fig. 1.1 (b)
The Pressure given by fluid is given by the division of Force and Area of cross-section.
Pressure = Force / Area
1.1.1 Major Parts and Components
Major Parts and Components used in a Pneumatic Systems are as follows:-
Air Compressors, Pneumatic Pumps, Air Dryer, Air Receiver Tank, FRL Unit, Directional
Control Valve, Flow Control Valve, Double Acting Cylinder, Hose, Pipe and Fittings.

2. CLASSIFICATION AND WORKING OF Pneumatics SYSTEM’S ELEMENTS
2.1 Pneumatic Power Generating Elements - AIR COMPRESSORS and
PUMPS
2.1.1 Pneumatic Pumps
The operating system of the pneumatic pump is very similar to that of a hydraulic pump. In
principle, these pumps use air, while hydraulic pumps use fluids. These both pumps can
generate very high-pressure levels, which creates a surprisingly large amount of energy.
The working principle of a pneumatic system focuses on using compressed gas or air to
transfer the medium. As the pneumatic pumps are used in different industrial appliances,
they involve the use of compressed inert gas or air.
These types of pumps use a dual-piston system. The diameter of one of these pistons is
much smaller than that of the other pistons. These pistons separate through an airtight
chamber loaded with compressed gas or fluid.
The compressed gas exerts external pressure on the piston of larger diameter, which in turn
exerts pressure on the fluid or gas chamber inside the intermediate chamber. Therefore, the
smaller piston obtains a greater force, which converts into stronger mechanical action.
"A pneumatic pump commonly referred to as a positive (Fixed) displacement pump. It is a
double-acting piston pump having no return springs and can use many compressed gases or
liquids as impellers."
A pneumatic pump has many types, but the famous types are given below:
2.1.1.1 Classification of Pumps
PUMPS
↓
↓
Fixed Displacement
FIXED DISPLACEMENT PUMPS
↓
↓ ↓ ↓ ↓
Diaphragm Liquid Refrigerant Vacuum test

2.1.1.2 Fixed Displacement Pumps
Fixed Displacement Pumps :-
A pneumatic pump that cannot be adjusted to increase or decrease the amount of air that is
moved in one pump cycle.
It is of three types :- Pneumatic Diaphragm Pump, Pneumatic Liquid Pump, Refrigerant
Pump and Vacuum Test Pump
2.1.1.3 Pneumatic Diaphragm Pump
A diaphragm pump is the most famous type of pump from the category of positive
displacement pump. It is also called a Membrane pump. For pumping a fluid, a diaphragm
pump uses a combination of the reciprocating action of the diaphragm made of Teflon,
thermoplastic, or rubber with the corresponding valves (globe valves, flap valves, butterfly
valves, check valves or any other type of valves) on both sides of the diaphragm.
Fig 2.1.1.3 a
A diaphragm or membrane pump is a positive displacement pump that uses two flexible
diaphragms that move forward and backward to form a temporary vacuum. This vacuum
uses to draw or discharge the liquid from the daiphragm pump. The membrane acts as a
partition wall between liquid and air. The working principle of the diaphragm pump is given
below:
Fig 2.1.1.3 b
First Stroke:
The two diaphragms are linked via a shaft through the central part in which the air valve is
placed. The air valve is used to force compressed air behind the first diaphragm and moves it
away from the middle section, The 1st diaphragm creates a pressure stroke that removes

fluid from the pump. Simultaneously, the second diaphragm performs the suction stroke.
The air behind the 2nd diaphragm is released to the atmosphere, and atmospheric pressure
forces the fluid to the suction side. The suction valve pushes out of the seat, and fluid flows
through the ball valve into the pump’s fluid chamber.
Second Stroke:
As the 1st pressurised diaphragm reaches the end of its stroke, air transfers from the 1st
diaphragm to the back of the 2nd diaphragm through the air valve. The pressurised air
pushes the 2nd diaphragm away from the central block, and the 1st diaphragm is pulled into
the central block. In the second chamber of the pump, the outlet ball valve is pushed out
from its seat, while the first chamber has the opposite situation. When the second stroke
completes, the air valve pumps air behind the 1st diaphragm, and the whole cycle repeats.
The diaphragm pumps have the following major types:
● Air-Operated Double Diaphragm Pump
● Motor-Driven Pump
● Small Motor Driven Pump
● Small Air-Operated Pump
● Wanner Hydra-Cell Pump
1) Air-Operated Double Diaphragm (AODD) Pump
Air-operated Double Diaphragm (AODD) pump is a most common type of diaphragm pump.
The operation of the air-operated pump may be carried out with compressed air. It has two
pumping chambers with two diaphragms.
AODD pump has a discharge check valve, a diaphragm and a suction check valve for each
pumping chamber. The air supply moves from one chamber to the second assembly
chamber through an air distribution system that may install inside the pump.
The systematic operation of air transfer from one assembly chamber to another chamber
causes liquid from one chamber to flow down the drainpipe by filling the other chamber
with liquid. As a result, the pump has a pulsation in the discharge flow. This pulsating flow
may be reduced by using a pulsation damper in the delivery pipe.
Fig 2.1.1.3 c

2.1.1.3 Pneumatic Liquid Pump
It is used to move liquids from one location to another.
Fig 2.1.1.3
2.1.1.4 Refrigerant Pump
This pump is used to move refrigerants, especially two-stage pumps.
Fig 2.1.1.4
2.1.1.5 Vacuum Test Pump
This pump is designed and configured to test the performance of a particular pneumatic
pumping system
Fig 2.1.1.5

2.1.2 Air Compressors
An air compressor is a pneumatic device that converts power (using an electric motor, diesel
or gasoline engine, etc.) into potential energy stored in pressurised air (i.e., compressed air).
By one of several methods, an air compressor forces more and more air into a storage tank,
increasing the pressure. When the tank's pressure reaches its engineered upper limit, the air
compressor shuts off. The compressed air, then, is held in the tank until called into use The
energy contained in the compressed air can be used for a variety of applications, utilising the
kinetic energy of the air as it is released and the tank depressurizes. When tank pressure
reaches its lower limit, the air compressor turns on again and re-pressurizes the tank. An air
compressor must be differentiated from a pump because it works for any gas/air, while
pumps work on a liquid.
Fig 2.1.2
2.1.2.1 Classification of Air Compressors
AIR COMPRESSORS
↓
↓ ↓
Positive Displacement Roto - Dynamic
POSITIVE DISPLACEMENT PUMPS
↓
↓ ↓ ↓
Piston Rotary Screw Vane

2.1.2.2 Positive Displacement Compressors
Positive-displacement compressors work by forcing air in a chamber whose volume is
decreased to compress the air. Once the maximum pressure is reached, a port or valve
opens and air is discharged into the outlet system from the compression chamber.
They are of three types :-
1. Piston Compressor 2. Rotary Screw Compressor 3. Vane Compressor
2.1.2.2.A Piston Compressors
Piston-type: air compressors use this principle by pumping air into an air chamber through
the use of the constant motion of pistons. They use one-way valves to guide air into and out
of a chamber whose base consists of a moving piston. When the piston is on its down stroke,
it draws air into the chamber. When it is on its up stroke, the charge of air is forced out and
into a storage tank.
Fig 2.1.2.2.A
2.1.2.2.B Rotary Screw Compressors
Rotary screw compressors: use positive-displacement compression by matching two helical
screws that, when turned, guide air into a chamber, whose volume is decreased as the
screws turn. Rotary screw compressors can be single-stage or two-stage.
Fig 2.1.2.2.B

2.1.2.2.C Vane Compressors
Vane compressors: use a slotted rotor with varied blade placement to guide air into a
chamber and compress the volume. This type of compressor delivers a fixed volume of air at
high pressures.
Fig 2.1.2.2.C
2.1.2.3 Roto - Dynamic Air Compressors
Roto-Dynamic air compressors include centrifugal compressors and axial compressors. In
these types, a rotating component imparts its kinetic energy to the air which is eventually
converted into pressure energy. These use centrifugal force generated by a spinning impeller
to accelerate and then decelerate captured air, which pressurises it.
Fig 2.1.2.3

2.2 Pneumatic Power Controlling Elements - Valves
2.2.1 Classification of Valves
PNEUMATIC VALVES
↓
↓ ↓ ↓
Flow Control Diaphragm Flow Control Direction Control
2.2.1.1 Flow Control Valve
Flow Control Valves :-
Flow control valves are used to regulate the flow rate and pressure of liquids or gases
through a pipeline. The purpose of a flow control valve is to regulate the flow rate in a
specific portion of a Pneumatics circuit. In Pneumatics systems, they’re used to control the
flow rate to motors and cylinders, thereby regulating the speed of those components.
Pneumatics flow control valves also control the rate of energy transfer at a given pressure.
This is based on the physics concept surrounding work, energy, and power:
Actuator force x distance travelled = work done on load
The energy transfer must be equal to the total work done. Because the actuator speed
determines the rate of energy transfer, speed is a function of the flow rate.
It is of two types :- Pressure compensated valve and Throttle valve
Fig 2.2.1.1

2.2.2.1 Diaphragm Flow Control Valve
Diaphragm valves are characterised by a flexible disc that contacts a seat at the top of the
valve body and forms a seal. The diaphragm is flexible and pressure-responsive; it transmits
force to open, close, or control a valve. While diaphragm valves are related to pinch valves,
they use an elastomeric diaphragm rather than an elastomeric liner in the valve body. The
elastomeric diaphragm is attached to a compressor and separates the flow stream from the
closure element. Diaphragm valves are ideal for handling corrosive, erosive, dirty services.
Fig 2.2.2.1
2.2.1.2 Direction Control Valve
Directional control valves (DCVs) are one of the most fundamental parts of hydraulic and
pneumatic systems. DCVs allow fluid flow (Pneumatics oil, water or air) into different paths
from one or more sources. DCVs will usually consist of a spool inside a cylinder which is
mechanically or electrically actuated. The position of the spool restricts or permits flow, thus
it controls the fluid flow.
The spool (sliding type) consists of lands and grooves. The lands block oil flow through the
valve body. The grooves allow oil or gas to flow around the spool and through the valve
body. There are two fundamental positions of directional control valves, namely the normal
position where the valve returns on removal of actuating force and the other is the working
position which is position of a valve when actuating force is applied. There is another class of
valves with 3 or more positions that can be spring centred with 2 working positions and a
normal position.
Directional control valves can be classified according to:
● number of ports
● number of positions
● actuating methods
● type of spool

2.2.3.2 Number of positions (Symbol) based Directional Control Valve
Two-way two-position directional control valve
Gate valve is an example of 2W/2P directional control valve which either turns on or off the
flow in normal or working positions depending on need of application. Here the arrow
indicates that fluid flow is taking place whereas the other position shows cut-off position.
Four-way two-position directional control valve
The 4/2 valve has four connections to it and two valve positions. Normally, one port is open
to flow from the pump.
Four-way three-position directional control valve
It has one way for pump (P), one for reservoir (R) or tank (T) and two for the inlet to the
actuator. And it has 3 positions: one normal, one cross way, and one straight way.
Fig 2.2.3.1

2.3 Pneumatics Power Utilising Elements - CYLINDERS
2.3.1 Pneumatics Cylinders
A Pneumatics cylinder (also called a linear Pneumatics motor) is a mechanical actuator that
is used to give a unidirectional force through a unidirectional stroke. It has many
applications, notably in construction equipment, manufacturing machinery, elevators, and
civil engineering.
Pneumatics cylinders get their power from pressurised Pneumatics fluid, which is typically
oil. The Pneumatics cylinder consists of a cylinder barrel, in which a piston connected to a
piston rod moves back and forth. The barrel is closed on one end by the cylinder bottom and
the other end by the cylinder head (also called the gland) where the piston rod comes out of
the cylinder. The piston has sliding rings and seals. The piston divides the inside of the
cylinder into two chambers, the bottom chamber (cap end) and the piston rod side chamber
(rod end/head-end).
Flanges, trunnions, clevises, and lugs are common cylinder mounting options. The piston rod
also has mounting attachments to connect the cylinder to the object or machine component
that it is pushing or pulling.
A Pneumatics cylinder is the actuator or "motor" side of this system. The "generator" side of
the Pneumatics system is the Pneumatics pump which delivers a fixed or regulated flow of
oil to the Pneumatics cylinder, to move the piston. There are three types of pump widely
used: Pneumatics hand pump, Pneumatics air pump, and Pneumatics electric pump.[1]
The
piston pushes the oil in the other chamber back to the reservoir. If we assume that the oil
enters from the cap end, during extension stroke, and the oil pressure in the rod end/head
end is approximately zero, the force F on the piston rod equals the pressure P in the cylinder
times the piston area A.
A Pneumatics cylinder has the following parts: Cylinder barrel, Cylinder base or cap. Cylinder
head, Piston, Piston rod, Seal gland and Seals
2.3.1.1 Double acting
A pneumatic cylinder is a mechanical device that converts compressed air energy into a
reciprocating linear motion. A double-acting cylinder uses compressed air to move a piston
in and out, while a single-acting cylinder uses compressed air for one-way movement and a
return spring for the other.
Fig 2.3.1.1

2.4 Pneumatics Power Conveying Elements - HOSES, PIPES and FITTINGS
Hoses, tubing and fittings are the critical elements of all Pneumatics systems. They transmit
fluid from the pump to valves, actuators and pumps, and generate the force and motion to
make the system work. The importance of selecting the correct hose, tubing and coupling is
what allows a processing system to be repeatable and reliable, while reducing or even
eliminating costly downtime. The correct sizes, materials and configurations are what ensure
system dependability. Proper selection of the hose or tubing is crucial. But not matching it to
the compatible fitting that is specific to the application will only increase the chances of
system failure.
For hose and tubing, first understand the compatibility of the fluid that is to be transferred
with the material of the hose or tube and its required pressure. Consider the media or
material that is to be transferred, the chemical resistance of the hose or tubing, and the
working pressure and temperature. Select hose and tubing that meets the required ratings
for standard operating pressure, burst test and impulse life. Proper hose and tubing
selection lowers cost of ownership and avoids downtime and unscheduled maintenance,
which ultimately maximises uptime and improves ROI of the system.
For the compatible fitting, as with hose and tubing, there are a number of important factors
to consider, including:
● Attachment (i.e., a crimped Pneumatics fitting for a hose, and a compression fitting
for tubing)
● Fitting configuration (straight, elbow, tee, etc.)
● Flow
● Compatible material of hose or tubing
● Size of hose or tubing (in some cases consider wall thickness)
● Vibration
● Working pressure (maximum PSI)
Additionally, consider whether an elastomeric seal is to be used, such as an O-ring or gasket.
Critical components in O-ring face seal fittings and most flange assemblies are an
elastomeric seal. The O-ring material selection is dependent on the factors mentioned
above, particularly chemical compatibility of the media being transferred and system
pressure.
Fig 2.4

2.5 Pneumatics Accessories - Air Receiver Tank, Air Dryer and FRL Unit
2.5.1 Air Receiver Tank
An air receiver, sometimes referred to as a compressed air tank, is an integral part of any
compressed air system. The main purpose of this is to act as temporary storage to
accommodate the peaks of demand from your system and to optimise the running efficiency
of your plant.
Air receivers, commonly referred to as vessels or tanks are used to store compressed air
before it enters into the piping system and or equipment. In simpler terms, air receivers act
as a buffer mechanism between the compressor and the fluctuating pressure caused by the
changing demand. Some air compressors can be "tank-mounted", which means that they
come as a package and are mounted on top of the air receiver. This type of a set-up is highly
preferred at facilities where space comes at a premium. Having a tank mounted compressor
can save on both space as well as initial installation costs associated with commissioning a
stand-alone dryer. This is most commonly seen with smaller range compressors, mainly up
to 26kW or 35 HP. Larger air compressors are not suitable for tank mounted options, as they
become top heavy and could pose a safety risk.
Fig 2.5.1
2.5.2 Air Dryer
Compressed air dryers are special types of filter systems that are specifically designed to
remove the water that is inherent in compressed air. The process of compressing air raises
its temperature and concentrates atmospheric contaminants, primarily water vapour.
Consequently, the compressed air is generally at an elevated temperature and 100% relative
humidity. As the compressed air cools, water vapour condenses into the tank(s), pipes, hoses
and tools that are downstream from the compressor. Water vapour is removed from
compressed air to prevent condensation from occurring and to prevent moisture from
interfering in sensitive industrial processes.
Excessive liquid and condensing water in the air stream can be extremely damaging to
equipment, tools and processes that rely on compressed air. E.g. the water can cause

corrosion in the tank(s) and piping, wash out lubricating oils from pneumatic tools, emulsify
with the grease used in cylinders, clump blasting media and fog painted surfaces.Therefore,
it is desirable to remove condensing moisture from the air stream to prevent damage to
equipment, air tools and processes.
There are various types of compressed air dryers. These dryers generally fall into two
different categories: primary, which includes coalescing, refrigerated, and deliquescent; and
secondary, which includes desiccant, absorption, and membrane. Their performance
characteristics are typically defined by flow rate in Standard Cubic Feet per Minute (SCFM)
and dew point expressed as a temperature, (sometimes referred to as Pressure Dew Point.)
Fig 2.5.2
2.5.3 FRL Unit
Filter, regulator, and lubricator (FRL) compressed air systems are used to deliver clean air, at
a fixed pressure, and lubricated (if needed) to ensure proper pneumatic component
operation and increase their operation lifetime. The air supplied by compressors is
oftentimes contaminated, over pressurised, and non-lubricated meaning that an FRL unit is
required to prevent damage to equipment. Filters, regulators, and lubricators can be bought
individually or as a package depending on what is needed to ensure the proper air
specifications are being met for downstream equipment. It is recommended to install these
devices if you:
● Use pneumatic tools and equipment;
● Are installing an HVAC system;
● Require clean air to be delivered to your facility or workplace;
● Require compliance to ISO, OSHA, ASHRA or other air quality standards;
● Want to improve the service life, safety and reliability of your air system.
An FRL unit consists of a filter (F), regulator (R), and a lubricator (L). They are often used as
one unit to ensure clean air in a pneumatic system but can also be used individually. Having
a proper FRL unit installed in a pneumatic system provides higher reliability of the
components downstream, reduced power waste due to over pressurisation, and increased
component lifetime. The three components work together to do the following:

● Filters remove water, dirt and other harmful debris from an air system. This is often
the first step in improving the air quality.
● Regulators adjust and control the air pressure of a system to ensure that down-line
components do not exceed their maximum operating pressures. This is the second
step in the FRL system.
● Lubricators reduce the internal friction in tools or equipment by releasing a
controlled mist of oil into the compressed air. This is often done last and/or right
before the component needing lubrication.
Fig 2.5.3

3. Pneumatics SYSTEM CIRCUIT DIAGRAM
Basic Pneumatics Circuit Diagrams :-
Fig 4 a
Fig 4 b

4. REFERENCES
1. Afanasyev V V (1968) Variations of the effective areas of diaphragms. In:
Aizerman M A (ed) Pneumatic and Pneumatics control systems. Pergamon Press,
Oxford London Edinburgh New York,
2. Barker H F (1976) Design of a state observer for improving the response of a
linear pneumatic servo-actuator. Proc Int Conf on Pneumatics, Pneumatics and
Fluidics in Control and Automation, Toronto,
3. Beater P (2000) Modelling and digital simulation of Pneumatics systems in
design and engineering education using Modelica and HyLib. Proc Modelica
Workshop 2000, Lund, pp
4. Howe R E (2004) Five myths of pneumatic motion control. Pneumatics and
pneumatics 36(9):
5. Jelali M, Kroll A (2002) Pneumatics servo-systems – modelling, identification and
control. Springer, London Berlin Heidelberg New York
6. https://www.machinerylubrication.com/Read/277/Pneumatics-systems-fluid
7. http://www.pressmaster-Pneumatics-presses.com/news/12-fascinating-facts-about-
Pneumaticss-81.aspx
8. 2. http://www.rkmachinery.ca/news/10-fascinating-facts-about-Pneumaticss-76.aspx
9. http://www.bbc.co.uk/schools/gcsebitesize/science/triple_aqa/using_physics_make_
things_work/Pneumaticss/revision/3/
10. http://en.m.wikipedia.org/wiki/Pneumatics_brake

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