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Title: Course Title : Pneumatic and Hydraulic drive


1
Course Title Pneumatic and Hydraulic drive
Course Number
315018571
Course Instructor
Dr. Tariq Younes
Prerequisites
315018472 and 315018470
Emailtariqmograbi_at_yahoo.com
2
Course Description
- Pneumatic drive systems and their components
- Electro- pneumatic systems properties of
hydraulic systems
- Calculation and design of pneumatic and
hydraulic drive motors
- Servo-drives and valves.
3
Textbook
Fluid power with applications, Anthony Esposito ,
7-th edition 2009
References
http//www.hydraulicspneumatics.com
1. Lecture notes, course Pneumatic and Hydraulic
Drives prepared by Dr. Mohamad Alia. 2.Fundamental
s of pneumatic control engineering . A test book
from FESTO. J.P. Hasbrink , R. Kobler, 1987,
Germany 3. Hydraulics Basic Principles and
Components. Didactic from Rexrroth H.Exner,
R.Freity and others.OMEGN,2002.Germany
4
Chapter 1
5
Learning Objectives
1. Explain what fluid power is.
2. Differentiate between the terms hydraulics and
pneumatics.
3. Understand the difference between fluid power
systems and fluid transport systems
4. Appreciate the history of the fluid power
industry.
5. Discuss the advantages and disadvantages of
fluid power.
6. Describe key applications of fluid power.
7. Specify the basic components of fluid power
systems.
8. Appreciate the size and scope of the fluid
power industry.
9. Identify the categories of personnel who are
employed in the fluid power industry.
6
Introduction to Pneumatic and Hydraulic Drives
What is Pneumatic (from the Greek pneumn for wind
or breath).?
Pneumatics is the discipline that deals with
mechanical properties of gases such as pressure
and density, and applies the principles to use
compressed gas as a source of power to solve
Engineering problems.
What is Hydraulic (from the Greek words hydra for
water and aulos for a pipe)?
Hydraulics is the discipline that deals with the
mechanical properties of liquids, and applies the
principles to solve engineering problems.
7
Pneumatic and Hydraulic Drives or Fluid Power?
What do we mean by Pneumatic and Hydraulic
Drives ?
Pneumatic and Hydraulic Drives
- It is mainly considered with energy conversation
1
- Conversation pressure into force
- Conversation of flow into speed
1 lecture notes
8
Fluid power
Fluid power is the technology that deals with the
generation, control, and transmission of power,
using pressurized fluids.
Fluid power is called hydraulics when the fluid
is a liquid
Fluid power is s called pneumatics when the fluid
is a gas.
Thus fluid power is the general term used for
both hydraulics and pneumatic Hydraulic systems
The terms fluid power and hydraulics and
pneumatics are synonymous
9
Examples of fluid power
10
Steering and braking in automobiles
11
Spacecraft launcher
Applications include landing gear, brakes, flight
controls, motor controls and cargo loading
equipment.
12
Harvests crop
13
Dental teeth drill
14
Food industry
15
Hydraulic Chain Saw
16
Pneumatic Chain Hoist
17
Fluid systems
Fluid transport systems
Fluid transport systems have as their sole
objective the delivery of a fluid from one
location to another to accomplish some useful
purpose
Example
pumping stations for pumping water to homes
Fluid power systems
Fluid power systems are designed specifically to
perform work.
Example
Operating fluid cylinder or fluid motor
18
Type of Fluids
1. Hydraulic systems
A. Water Hydraulic system
- Water hydraulics is expected to become more
prevalent. - In Some applications water
hydraulics should be used rather than oil ones.
Disadvantages
Advantages
- abundance
It freezes more readily
- friendly
It is not as good a lubricant
- nonflammability
It tends to rust preventive
Improvement of water characteristics
The water contains additives to improve lubricity
and rust protection and prevent freezing where
necessary.
19
B. Oil Hydraulic system
Petroleum oils and synthetic oils
The advantages and disadvantages of oil will be
discussed later
Why Liquids
-Liquids provide a very rigid medium for
transmitting power
-They can operate under high pressures to provide
huge forces and torques to drive loads with
utmost accuracy and precision
20
Pneumatic systems Pneumatic systems use air as
the gas medium because air is very abundant and
can be readily exhausted into the atmosphere
after completing its assigned task
Why Air?
- Spongy characteristics due to the
compressibility of air.
- They are less expensive to build and operate.
- They can be used effectively in applications
where Low pressures can be used because the loads
to be driven do not require large forces.

21
HISTORY OF FLUID POWER
Ancient historical accounts show that water was
used for centuries to produce power by means of
water wheels, and air was used to turn windmills
and propel ships. Pascals law and Bernoullis
law operate at the very heart of all fluid
power.
22
opening the temples gate (Pharaoh)
23
The usage of compressed air Reconstruction of
the water organ of Ktesibios (Arens, 1960).
24
2. Glycerine Clock
25
Hydraulic jack
26
Beginning of Modern Era
- in 1906 when a hydraulic system was developed
to replace electrical systems for elevating and
controlling guns on the battleship USS Virginia.
- In 1926 the United States developed the first
unitized, packaged hydraulic system consisting of
a pump, controls, and actuator.
27
Todays Fluid Power
- Computerized fluid- power drives are available
- Computer programming and bending process
simulations are generated from a 3D model of the
desired panel using CAD/CAM software.
- microfluid power systems
- nanotechnology
28
Hydraulic and Pneumatic systems and
nanotechnology
large-scale integrated microfluidic comparator
containing 256 subnanoliter reaction chambers and
2056 microvalves
29
Electrical , pneumatic and hydraulic systems
Let us consider the following task The task
considered is how to lift a load by a distance of
about 500 mm. Such tasks are common in
manufacturing industries.
B
Direction
Load
A
30
  • Electrical solution
  • Basic choices
  • - solenoid the solenoid produces a linear stroke
    directly
  • but its stroke is normally limited to a maximum
    distance of around 100 mm.
  • - DC and AC motors DC and AC motors are rotary
    devices and their outputs need to be converted
    to linear motion by mechanical devices such as
    wormscrews or rack and pinions.
  • The choice of motor depends largely on the speed
    control requirements.
  • A DC motor fitted with a tacho and driven by a
    thyristor drive can give excellent speed control,
    but has high maintenance requirements for brushes
    and commutator.
  • An AC motor is virtually maintenance free, but is
    essentially a fixed speed device (with speed
    being determined by number of poles and the
    supply frequency).
  • Speed can be adjusted with a variable frequency
    drive, but care needs to be taken to avoid
    overheating as most motors are cooled by an
    internal fan connected directly to the motor
    shaft.
  • We will assume a fixed speed raise/lower is
    required, so an AC motor driving a screwjack
    would seem to be the logical choice.

31
Electrical solution, based on three phase motor
Operation a mechanical jack driven by an AC motor
controlled by a reversing starter. Auxiliary
equipment comprises two limit switches, and a
motor overload protection device. There is no
practical load limitation provided screw/gearbox
ratio, motor size and contactor rating are
correctly calculated.
32
Hydraulic solution A solution using hydraulic
system can be realized using a hydraulic linear
actuator (arm). It consists of a movable piston
connected directly to the output shaft If fluid
is pumped into pipe A the piston will move up and
the shaft will extend if fluid is pumped into
pipe B, the shaft will retract.
Hydraulic cylinder
33
Physical components
34
- The maximum force available from the cylinder
depends on fluid pressure and cross sectional
area of the piston.
- The system requires a liquid fluid to operate
expensive and messy and, consequently, the piping
must act as a closed loop, with fluid transferred
from a storage tank to one side of the piston,
and returned from the other side of the piston to
the tank. Fluid is drawn from the tank by a pump
which produces fluid flow at the required 150
bar. - Cylinder movement is controlled by a
three position changeover valve. - Speed control
is easily achieved by regulating the volume flow
rate to the cylinder (discussed in a later
section). - Precise control at low speeds is one
of the main advantages of hydraulic systems. -
Travel limits are determined by the cylinder
stroke and cylinders, generally, can be allowed
to stall at the ends of travel so no overtravel
protection is required.
- The pump needs to be turned by an external
power source almost certainly an AC induction
motor which, in turn, requires a motor starter
and overload protection.
35
- Hydraulic fluid needs to be very clean, hence a
filter is needed to remove dirt particles before
the fluid passes from the tank to the pump.
- One final point worth mentioning is that leaks
of fluid from the system are unsightly, slippery
(hence hazardous) and environmentally very
undesirable A major failure can be catastrophic.
36
Pneumatic solution
-The basic actuator is again a cylinder - The
maximum force on the shaft being determined by
air pressure and piston cross sectional area. -
Operating pressures in pneumatic systems are
generally much lower than those in a hydraulic
systems - Pneumatic systems therefore require
larger actuators than hydraulic systems for the
same load. - The valve delivering air to the
cylinder operates in a similar way to its
hydraulic equivalent. - One notable difference
arises out of the simple fact that air is free
return air is simply vented to atmosphere. - Air
is drawn from the atmosphere via an air filter
and raised to required pressure by an air
compressor (usually driven by an AC motor). -
The air temperature is raised considerably by
this compressor. - Air also contains a
significant amount of water vapour. -
Compressibility of a gas makes it necessary to
store a volume of pressurised gas in a reservoir,
to be drawn on by the load. The air treatment
unit is thus followed by an air reservoir. -
Pressure control is much simpler. - The general
impression is again one of complexity
37
Comparisons of electrical, hydraulic and
pneumatic systems
38
ADVANTAGES OF FLUID POWER
39
1. Ease and accuracy of control.
Stopping Starting Speed control Position
40
2. Multiplication of force.
A fluid power system can multiply forces simply
and efficiently from a fraction of an ounce to
several hundred tons of output.
41
3. Constant force or torque.
- Only fluid power systems are capable of
providing constant force or torque regardless of
speed changes.
  • Instantly reversible motion

- automatic protection against overloads
- infinitely variable speed control.
  • the highest power-per-weight ratio of any known
    power source.

42
Drawbacks of Fluid Power
Oil leakage from the hydraulic system into the
surroundings.
Hydraulic pipeline can burst due to excessive oil
pressure if proper system design is not
implemented
In pneumatic systems, components such as
compressed air tanks and accumulators must be
properly selected to handle the system maximum
air pressure.
level of noise in the vicinity of fluid power
systems.
43
COMPONENTS OF A FLUID POWER SYSTEM
44
Basic hydraulic system with Linear hydraulic
actuator (cylinder).
45
Basic hydraulic system with rotary hydraulic
actuator
46
There are six basic components required in a
hydraulic system
1. A tank (reservoir) to hold the hydraulic oil
2. A pump to force the oil through the system
3. An electric motor or other power source to
drive the pump
4. Valves to control oil direction, pressure, and
flow rate
5. An actuator to convert the pressure of the oil
into mechanical force or torque to do useful work.
6. Piping, which carries the oil from one
location to another
47
There are six basic components required in
Pneumatic System
1. An air tank to store a given volume of
compressed air
2. A compressor to compress the air that comes
directly from the atmosphere
3. An electric motor or other prime mover to
drive the compressor
4. Valves to control air direction, pressure, and
flow rate
5. Actuators, which are similar in operation to
hydraulic actuators
6. Piping to carry the pressurized air from one
location to another
48
THE FLUID POWER INDUSTRY
49
Size and Scope
- Over half of all U.S. industrial products have
fluid power systems or components as part of
their basic design. - About 75 of all fluid
power sales are hydraulic and 25 are pneumatic.
50
Personnel
51
1. Fluid power mechanics.
- Workers in this category are responsible for
repair and maintenance of fluid power equipment.
- They generally are high school graduates who
have undertaken an apprenticeship training
program.
2. Fluid power technicians.
  • These people usually assist engineers
  • They generally are graduates of two-year
    technical and community

3. fluid power engineers.
- developer, designer of new fluid power
components or systems.
- The fluid power engineer typically is a
graduate of a four-year college program.
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