This document provides an overview of fluid power systems, including hydraulics and pneumatics. It discusses the basic components of fluid power systems, such as pumps, valves, actuators and piping. Examples are given of common hydraulic systems, like vehicle brakes and power steering. Advantages of fluid power include easy control and force multiplication. The document also compares hydraulic, pneumatic and electrical systems for lifting a load.

1. Vehicles Hydraulic and
Pneumatic systems
• Hydraulic fundamentals
• Pumps
• Circuits
• Valves
• Actuators
• Accessories
• Fluids in Hydraulic and Pneumatic Systems
• Applications

2. 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.

4. 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.
Pascal’s law and Bernoulli’s law operate at the very heart of all fluid power.

5. 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.

6. Advantages of hydraulic
systems
• Long life by self oiling
• Easy to opposite direction
• Easy to calibrate and control
• Ability to generate and transport a huge
force and power

7. Simple comparison
Hydraulic Systems Pneumatic Systems
Use oil Use air
Closed circuit(oil return to reservoir) Open circuit (air discharge to
atmosphere after use)
incompressible compressible
up to 500 bar Pressure between 6:15 bar
Stroke up to 6m Max 2 m
Leakage is
dangerous and
unsightly. Fire hazard
unsightly. Fire
Leakage
dangerous and
unNoisesightly. Fire
Symbol ▲ Δ

8. Comparisons of electrical, hydraulic and pneumatic systems

9. Fluid power
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
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
The terms “fluid power” and “hydraulics and pneumatics” are synonymous

10. Examples of fluid power

11. Common examples of hydraulic systems
include:
Vehicle brake hydraulic systems
Brake pedal
Master
cylinder
Brake
lines
Front
brake
calipers
Rear wheel
cylinder
pistons
Pads
Rotor
The function of a vehicle
braking system is to stop or
slow down a moving vehicle.
When the brake pedal is
pressed as illustrated in Fig.
1.1, the hydraulic pressure is
transmitted to the piston in the
brake caliper of the brakes.
The pressure forces the brake
pads against the brake rotor,
which is rotating with the
wheel.
The friction between the brake
pad and the rotor causes the
wheel to slow down and then
stop.
Fig.1.1: A schematic diagram of the vehicle’s hydraulic
brake system.

12. Steering and braking in automobiles

13. Common examples of hydraulic systems
include:
• The vehicle power
steering system uses
hydraulic oil, the
hydraulic pump
supplies the oil through
the control valves to
the power cylinder as
shown in Fig. 1.2. The
major advantage of
using this system is to
turn the vehicle’s
wheels with less effort.
Vehicle power steering
Hydraulic pump
Control
valve
Power cylinder
Fig.1.2:Vehicle hydraulic power
steering system

14. Chapter 1

15. Bulldozer

16. Harvests crop

17. Fluid systems
Fluid transport systems
Fluid power systems
Fluid transport systems have as their sole objective the delivery of a fluid from one
location to another to accomplish some useful purpose
Fluid power systems are designed specifically to perform work.
Operating fluid cylinder or fluid motor
pumping stations for pumping water to homes
Example
Example

18. A. Water Hydraulic system
Advantages
- abundance
- friendly
- nonflammability
Disadvantages
It freezes more readily
It is not as good a lubricant
It tends to rust preventive
Type of Fluids
Improvement of water characteristics
The water contains additives to improve lubricity and rust protection and prevent
freezing where necessary.
- Water hydraulics is expected to become more prevalent(common).
- In Some applications water hydraulics should be used rather than oil ones.
1. Hydraulic systems

19. B. Oil Hydraulic system
The advantages and disadvantages of oil will be discussed later
Petroleum oils and synthetic oils
-They can operate under high pressures to provide huge forces and torques to drive
loads with utmost accuracy and precision
Why Liquids
-Liquids provide a very rigid medium for transmitting power

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. Today’s Fluid Power
- nanotechnology
- 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

22. 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.
Load
Direction
A
B

23. 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.

24. 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

25. Physical components

26. - 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.
- The maximum force available from the cylinder depends on fluid pressure
and cross sectional area of the piston.

27. - 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.

28. 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

29. ADVANTAGES OF FLUID POWER

30. Stopping
Starting
Speed control
Position
1. Ease and accuracy of control.

31. A fluid power system can multiply forces simply and efficiently from a fraction of
an ounce to several hundred tons of output.
2. Multiplication of force.

32. - Only fluid power systems are capable of providing constant force or torque
regardless of speed changes.
3. Constant force or torque.
- the highest power-per-weight ratio of any known power source.
-Instantly reversible motion
- automatic protection against overloads
- infinitely variable speed control.

33. level of noise in the vicinity of fluid power systems.
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.

34. COMPONENTS OF A FLUID POWER SYSTEM

35. Basic hydraulic system with Linear hydraulic actuator (cylinder).

36. Basic hydraulic system with rotary hydraulic actuator

37. 2. A pump to force the oil through the system
1. A tank (reservoir) to hold the hydraulic oil
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
There are six basic components required in a hydraulic system

38. 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

39. 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.