ME- Manufacturing Engineering Fluid power automation unit-1 introduction prepared by Dinesh.S

1. FLUID POWER AUTOMATION
UNIT-I
Introduction
Fluid Power
Fluid power is the use of fluids under pressure to generate, control, and
transmit power. Fluid power is subdivided into hydraulics using a liquid such
as mineral oil or water, and pneumatics using a gas such as air or other gases.
Compressed-air and water-pressure systems were once used to transmit power from
a central source to industrial users over extended geographic areas.
Fluid Power Characteristics
Fluid power systems can produce high power and high forces in small volumes,
compared with electrically-driven systems. The forces that are exerted can be easily
monitored within a system by gauges and meters. In comparison to systems that
provide force through electricity or fuel, fluid power systems are known to have long
service lives if maintained properly. The working fluid passing through a fluid motor
inherently provides cooling of the motor, which must be separately arranged for an
electric motor. Fluid motors normally produce no sparks, which are a source of
ignition or explosions in hazardous areas containing flammable gases or vapors.
Fluid power systems are susceptible to pressure and flow losses within pipes
and control devices. Fluid power systems are equipped with filters and other
measures to preserve the cleanliness of the working fluid. Any dirt in the system can
cause wear of seals and leakage, or can obstruct control valves and cause erratic
operation. The hydraulic fluid itself is sensitive to temperature and pressure along
with being somewhat compressible. These can cause systems to not run properly. If
not run properly, cavitation and aeration can occur.
Applications
Mobile applications of fluid power are widespread. Nearly every self-propelled
wheeled vehicle has either hydraulically-operated or pneumatically-
operated brakes. Earthmoving equipment such as bulldozers, backhoes and others
use powerful hydraulic systems for digging and also for propulsion. A very compact
fluid power system is the automatic transmission found in many vehicles, which
includes a hydraulic torque converter.
Fluid power is also used in automated systems, where tools or work pieces are
moved or held using fluid power. Variable-flow control valves and position sensors
may be included in a servomechanism system for precision machine tools. Below is a
more detailed list of applications and categories that fluid power is used for:

2.  Industrial (also known as fixed)
 metalworking
 injection molding
 controllers
 material handling
 Aerospace
 landing gears
 brakes
Advantages and Disadvantages of Fluid Power Systems
Fluid power systems have several advantages and disadvantages when
compared with mechanical and electrical power transfer systems. Several of the
important advantages and disadvantages of fluid power systems are presented in the
next two sections.
Advantages
The following list of advantages applies to both hydraulic and pneumatic systems,
except as noted.
■ An easy means of multiplying and controlling force and torque.
■ Infinitely variable speed control for both linear and rotary motion.
■ Overloading the system simply stalls the actuator without damage to the
components.
■ Provides an easy means of accurately controlling the speed of machines and/or
machine parts.
■ Provides the ability to instantly stop and reverse linear and rotary actuators with
minimal shock to the system.
■ Systems easily adapt to accommodate a range of machine sizes and designs.
■ Systems readily adapt to external control methods, including mechanical,
pneumatic, electrical, and electronic systems.
■ Systems can easily provide component lubrication. Pneumatics are commonly
used where high speeds and lightweight tools are needed.
■ Large volumes of compressed air may be easily stored in pneumatic systems to
provide energy for intermittent, heavy system demand.
■ Pneumatic systems provide clean operation with minimal fire hazard.

3. Disadvantages
The following list of disadvantages applies to both hydraulic and pneumatic systems,
except as noted.
■ Higher safety factors associated with high-pressure oil and compressed air.
■ Susceptibility to dirty environments, which can cause extreme component wear
without careful filtration.
■ Fluid leakage and spills cause a slippery, messy work environment around hydraulic
equipment.
■ Fire hazard with hydraulic systems using combustible oils.
■ Special handling and disposal procedures for hydraulic oil required by
environmental regulations.
■ High cost of compressing and conditioning air for use in pneumatic systems.
■ Reduced accuracy in actuator speed control in pneumatic systems caused by
compressibility of air.
■ Noise level of pneumatic systems when air is directly exhausted to the atmosphere
from components.
Need for automation
 Reduce Worker Fatigue and Effort or Labor Intensive Operation – Typically,
humans dislike banal, repetitive tasks. However, computer systems perform
them without complaint. Tasks that lack variability provide a place for
automated systems to shine, but this also holds true for systems utilizing
advanced sensors and integration. If the task requires conditions not suited to
human comfort or focus, consider automation.
 Prevent Products or Materials from Being Damaged or Destroyed – Humans
make mistakes when they fatigue. This embodies the sentiment of the “human
condition.” Mistakes using tools mean damaging raw materials, components,
assemblies, and end products.
 Prevent Non-conforming Product from Shipping – Computers controlling
robots do not forget steps. Neglecting to put in a screw requires a human
touch. A machine not doing it yields an error to be addressed. Does the process
require doing something in a specific order to improve yield? Automated
systems will not violate the instruction set. Moreover, automated systems may
employ inspection capabilities. Tune the system and allow the data to roll in
without preference or bias.
 Increase Efficiency – Improving processes for efficiency makes a company
more competitive, but do people always do the same thing, in the same way,

4. every time they do it? No, human variation exists. Automated systems allow
for improvements that benefit from consistent execution. Perfect planning
and training do not defend against the human touch.
 Collect Better Data – Remove the accidental data entry or missed data point
from logging. Make the method of collecting sensor and process data
regulated.
 Improve Metrics – Sending reliable data directly to a database provides an
ongoing resource. Does the process improve with changes? Why do I see more
failures now than in the past? Leveraging data can provide these answers
beyond a simple list of pass/fail statistics from the past. Correlation of
associated process data with pass/fail records provides insight rather than
guessing “what is causing this?”.
 Devise the Right Process Improvements – Automated systems now collect
reliable data. The database provides a searchable forum. What comes next?
Equipped with copious amounts of reliable data, engineers make the most of
this information. Where problems existed, light shines on the problem. Rather
than just changing to seek “continuous improvement,” make changes with
better information.
 Save Money – Why instrument that test stand? Why log that data? Why spend
the money now? Simply, inventing in industrial automation yields cost savings
through making processes more regular and collecting data for making
confident decision.
Introduction to hydraulic system
The controlled movement of parts or a controlled application of force is a
common requirement in the industries. These operations are performed mainly by
using electrical machines or diesel, petrol and steam engines as a prime mover.
These prime movers can provide various movements to the objects by using some
mechanical attachments like screw jack, lever, rack and pinions etc. However, these
are not the only prime movers. The enclosed fluids (liquids and gases) can also be
used as prime movers to provide controlled motion and force to the objects or
substances.
The specially designed enclosed fluid systems can provide both linear as well
as rotary motion. The high magnitude controlled force can also be applied by using
these systems. This kind of enclosed fluid based systems using pressurized
incompressible liquids as transmission media are called as hydraulic systems. The
hydraulic system works on the principle of Pascal’s law which says that the pressure
in an enclosed fluid is uniform in all the directions. The force given by fluid is given
by the multiplication of pressure and area of cross section. As the pressure is same
in all the direction, the smaller piston feels a smaller force and a large piston feels a

5. large force. Therefore, a large force can be generated with smaller force input by
using hydraulic systems.
Basic Hydraulic system
The hydraulic systems consists a number of parts for its proper functioning.
These include storage tank, filter, hydraulic pump, pressure regulator, control valve,
hydraulic cylinder, piston and leak proof fluid flow pipelines. The schematic of a
simple hydraulic system is shown in fig.
Applications of hydraulic systems
The hydraulic systems are mainly used for precise control of larger forces.
The main applications of hydraulic system can be classified in five categories:
 2.1 Industrial: Plastic processing machineries, steel making and primary metal
extraction applications, automated production lines, machine tool industries,
paper industries, loaders, crushes, textile machineries, R & D equipment and
robotic systems etc.
 2.2 Mobile hydraulics: Tractors, irrigation system, earthmoving equipment,
material handling equipment, commercial vehicles, tunnel boring equipment, rail
equipment, building and construction machineries and drilling rigs etc.
 2.3 Automobiles: It is used in the systems like breaks, shock absorbers,
steering system, wind shield, lift and cleaning etc.
 2.4 Marine applications: It mostly covers ocean going vessels, fishing boats
and navel equipment.
 2.5 Aerospace equipment: There are equipment and systems used for rudder
control, landing gear, breaks, flight control and transmission etc. which are used
in airplanes, rockets and spaceships.

6. Advantages and Disadvantages of Hydraulic system
Advantages
 The hydraulic system uses incompressible fluid which results in higher
efficiency.
 It delivers consistent power output which is difficult in pneumatic or
mechanical drive systems.
 Hydraulic systems employ high density incompressible fluid. Possibility of
leakage is less in hydraulic system as compared to that in pneumatic system.
The maintenance cost is less.
 These systems perform well in hot environment conditions.
Disadvantage
 The material of storage tank, piping, cylinder and piston can be corroded with
the hydraulic fluid. Therefore one must be careful while selecting materials
and hydraulic fluid.
 The structural weight and size of the system is more which makes it
unsuitable for the smaller instruments.
 The small impurities in the hydraulic fluid can permanently damage the
complete system, therefore one should be careful and suitable filter must be
installed.
 The leakage of hydraulic fluid is also a critical issue and suitable prevention
method and seals must be adopted.
 The hydraulic fluids, if not disposed properly, can be harmful to the
environment.
Pneumatic Systems
A pneumatic system is a system that uses compressed air to transmit and
control energy. Pneumatic systems are used in controlling train doors, automatic
production lines, mechanical clamps, etc

7. The advantages of pneumatic systems
Pneumatic control systems are widely used in our society, especially in the
industrial sectorsfor the driving of automatic machines. Pneumatic systems have a
lot of advantages.
(i) High effectiveness
Many factories have equipped their production lines with compressed air
supplies and movable compressors. There is an unlimited supply of air in our
atmosphere to produce compressed air. Moreover, the use of compressed air is not
restricted by distance, as it can easily be transported through pipes. After use,
compressed air can be released directly into the atmosphere without the need of
processing.
(ii) High durability and reliability
Pneumatic components are extremely durable and can not be damaged
easily. Compared to electromotive components, pneumatic components are more
durable and reliable.
(iii) Simple design
The designs of pneumatic components are relatively simple. They are thus
more suitable for use in simple automatic control systems. Technological Studies
Pneumatic Systems
(iv) High adaptability to harsh environment
Compared to the elements of other systems, compressed air is less affected
by high
temperature, dust, corrosion, etc.
(v) Safety
Pneumatic systems are safer than electromotive systems because they can
work in inflammable environment without causing fire or explosion. Apart from
that, overloading in pneumatic system will only lead to sliding or cessation of
operation. Unlike electromotive components, pneumatic components do not burn
or get overheated when overloaded.
(vi) Easy selection of speed and pressure

8. The speeds of rectilinear and oscillating movement of pneumatic systems are
easy to adjust and subject to few limitations. The pressure and the volume of air
can easily be adjusted by a pressure regulator.
(vii) Environmental friendly
The operation of pneumatic systems do not produce pollutants. The air
released is also processed in special ways. Therefore, pneumatic systems can work
in environments that demand high level of cleanliness. One example is the
production lines of integrated circuits.
(viii) Economical
As pneumatic components are not expensive, the costs of pneumatic systems
are quite low. Moreover, as pneumatic systems are very durable, the cost of repair
is significantly lower than that of other systems.
Limitations of pneumatic systems
Although pneumatic systems possess a lot of advantages, they are also
subject to many
limitations.
(i) Relatively low accuracy
As pneumatic systems are powered by the force provided by compressed air,
their operation is subject to the volume of the compressed air. As the volume of air
may change when compressed or heated, the supply of air to the system may not
be accurate, causing a decrease in the overall accuracy of the system.
(ii) Low loading
As the cylinders of pneumatic components are not very large, a pneumatic
system cannot drive loads that are too heavy.
(iii) Processing required before use
Compressed air must be processed before use to ensure the absence of
water vapour or dust. Otherwise, the moving parts of the pneumatic components
may wear out quickly due to friction.
(iv) Uneven moving speed

9. As air can easily be compressed, the moving speeds of the pistons are
relatively uneven.
(v) Noise
Noise will be produced when compressed air is released from the pneumatic
components.
Comparision Between Hydraulic And Pneumatic System

13. Heat exchangers, filters, lubricators and dryers

14. Hydraulic pumps

16. Relief and unloading valves (continued)

17. Directional control valves (continued)

25. Slip-in cartridge valves

27. Infinitely variable (proportional) valves

29. Flow-control valves (continued)

31. Pressure-control valves (continued)

34. Selection criteria for selection pneumatic and hydraulic power system
1. Flow vs. pressure. When dealing with pneumatics it is critical to understand the
difference between pressure and flow. Too often operators compensate for starved
flow with increased pressure. It is often best to install over-sized supply lines to a
process in order to ensure the appropriate volume of air.
2. Use electric actuators. With ever-increasing energy costs, designers should
consider using energy-efficient electric movement, provided the application
requirements fall within an electric actuator's performance capabilities. This
technology has advanced rapidly over the last five to 10 years, with vast
improvements in functionality, including more precise movement and even built-in
sophisticated controls.
3. Valve sizing. Correct sizing of components, including piping, valves and actuators,
can improve the productive capacity of pneumatic systems. Valve sizing is particularly
important. If the flow capacity is too small, it can have a negative impact on
production cycles. If you want to improve production cycle time and quality, then
proper sizing is critical.
4. Align pipelines. If pipelines are not aligned properly at the correct angle, as
indicated in the installation drawings, there is a great possibility of equipment
damage.
5. Choose 3-position valves. Wherever operators will be working near an operation,
a 3-position valve is a better choice than a 2-position valve. This is because a 3-
position valve will stop the equipment instantly in the event of an emergency. This is
in contrast to a 2-position valve, which will first complete the operation before
stopping.
6. Check temperatures. Be sure to check the surface temperatures of equipment
during preventive maintenance time and make a record. High temperatures could
damage the viscosity properties of the hydraulic oil.
7. Built-in flow control. When you are using a pneumatic cylinder in a project,
especially In high cycle count projects, use a fitting that has a flow control valve built
in to make the cylinder last longer.
8. Use feedback sensors. Don't rely on software interlocks to control pneumatic
devices unless you account for the delay caused by physical actuation. 100msec is a
long time in the computer world. Always back up actuators with electrical feedback
sensors, redundant if possible.

35. 9. Parallel air. Make sure you have an adequate air supply when using pneumatic
technology. Costly leaks are often hard to detect in a noisy plant environment. To
avoid failure in the supply of compressed air on a network, it is important to verify
that the distribution is closed so that the compressed air comes in parallel and not in
series. Inspect tubing, ferrule, connection and joints for leakages. Make sure the air
being produced is dry. All air filters should be checked periodically for accumulated
water drainage.
10. Choose quality tubing. To prevent leaks, use nylon tubing on machines rather
than push-on fittings and PE tubing. The leakage often found with soft tubing is hard
to detect in a plant environment.
11. Inlet side flow control. In a pneumatic logic circuit controlling a double-acting
cylinder, place the flow controls on the inlet side of your cylinder depending on the
direction of travel. Air is compressible and positioning will float if controlled on the
outlet. This will also create back pressure.
12. Low fire risk. One of the advantages of pneumatic technology is that it can
operate without using electricity. This minimizes the risk of fire or explosions from
sparks or arc flash events. This technology is particularly useful in a plant making
edible oils or hydrogenating oils or when using flammable gases in the production
process.
Important questions
Part-A question 2 Marks
1. What is fluid power?
2. What are the limitation of fluid power?( Jan 2018)
3. Define hydraulic system and its elements?
4. Draw the symbol for a 3 position,4 way closed center solenoid operated
direction control valve. (Jan2018)
5. Draw any one type of hydraulic system.
6. What are the advantages of fluid power?
7. Write the advantages of pneumatic system?
8. Draw any four pneumatic symbols?
9. What are the benefits of automation?
10. Define pneumatic system and its elements?

36. Part- B Questions (5,6,7,8 Mark) 13 marks
1. Explain the needs and benefits of Automation.
2. Draw the fluid power symbols of any four accessories.
3. Describe any four application of fluid power system.
4. Describe the advantages and disadvantages of hydraulic power system.
5. Describe the selection criteria for pneumatic and hydraulic power
system.
6. Explain the applications for pneumatic power system.
7. Explain the applications for hydraulic power system.
8. Draw the pneumatic circuit for automatic vehicle door open system.
9. Differentiate between hydraulic system and pneumatic system.
Part-C Questions 15 marks
1. Briefly Explain the pneumatic and hydraulic power system and its
components.
2. Draw the ISO symbols for pneumatic and hydraulic fluid power
elements.