Fluid power

1. Dr.S.BENJAMIN FRANKLIN
Associate Professor Gr1
Department of Mechanical Engineering

2. All machines require some type of power source and a way of transmitting
this power to the point of operation.
The three methods of transmitting power are:
 Mechanical
 Electrical
 Fluid
In this course we are going to deal with the third type of power
transmission which is the Fluid Power.
5-Apr-22

3.  Fluid power is the method of using pressurized fluid to
transmit energy.
 Fluid power is the technology that deals with the
generation, control, and transmission of power, using
pressurized fluids.
 Liquid or Gas is referred to as a fluid. Accordingly, there
are two branches of fluid power; Pneumatics, and
Hydraulics.
5-Apr-22

4.  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 [1647–48] and Bernoulli’s law [1738]
operate at the very heart of all fluid power.
 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. 5-Apr-22

5.  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.
5-Apr-22

6.  Hydraulic systems. (High Power Applications)
 Water Based (Water and Water Solutions)
 Oil Based (Petroleum oils and synthetic oils)
 Pneumatic Systems. (Low Power Applications)
 Air as the Gas medium.
5-Apr-22

7.  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.
 Hydraulic systems are commonly used where mechanisms require large
forces and precise control.
 Examples include vehicle power steering and brakes, hydraulic jacks
and heavy earth moving machines.
5-Apr-22

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9.  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.
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11. Mobile: Here fluid power is used to transport, excavate and lift materials
as well as control or power mobile equipment. End use industries
include construction, agriculture, marine and the military.
Applications include backhoes, graders, tractors, truck brakes and
suspensions, spreaders and highway maintenance vehicles.
Industrial: Here fluid power is used to provide power transmission and
motion control for the machines of industry. End use industries range
from plastics working to paper production. Applications include
metalworking equipment, controllers, automated manipulators,
material handling and assembly equipment.
Aerospace: Fluid power is used for both commercial and military aircraft,
spacecraft and related support equipment. Applications include
landing gear, brakes, flight controls, motor controls and cargo
loading equipment.
Flaps
Landing gears

12.  Fluid power systems provide many benefits to users including:
◦ Multiplication and variation of force
◦ Easy, accurate control
◦ Multi-function control
◦ High horsepower, low weight ratio
◦ Low speed torque
◦ Constant force or torque-This is a unique fluid power attribute.
◦ Safety in hazardous environments

13.  A hydraulic element needs to be machined to a high degree of
precision.
 Leakage of hydraulic oil poses a problem to hydraulic operators.
 Special treatment is needed to protect them from rust, corrosion, dirt
etc.,
 Hydraulic oil may pose problems if it disintegrates due to aging and
chemical deterioration.
 Hydraulic oils are messy and almost highly flammable.
 Hydraulic systems contain highly pressurized fluid. This can cause
burns, bruises or the accidental injection of fluid into the body.

14.  Viscosity:
It is a measured of the sluggishness with which a fluid moves. When the
viscosity is low, the fluid flows easily because it is thin and has low body.
 Viscosity Index:
A low V.I. signifies a relatively large change of viscosity with changes
of temperature. In other words, the oil becomes extremely thin at high
temperatures and extremely thick at low temperatures. On the other hand, a high
V.I. signifies relatively little change in
viscosity over a wide temperature range.
5-Apr-22

15.  Absolute viscosity
 Kinematic Viscosity
 Density
 Mass density
 Weight Density
 Specific Gravity
 Specific volume
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16.  Cohesion
 Adhesion
 Flash point
 Fire point
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17. Pascal's law (also Pascal's principle or the principle of
transmission of fluid-pressure) is a principle in fluid mechanics that
states that a pressure change occurring anywhere in a confined
incompressible fluid is transmitted throughout the fluid such that the
same change occurs everywhere.
A change in pressure at any point in an enclosed fluid at
rest is transmitted undiminished to all points in the fluid.

18.  Energy:
The ability to do work
 Energy Transfer:
From prime mover, or input source, to an actuator, or output
device

19.  Work:
Force multiplied by distance - Measured in foot-pounds.
 Power:
The rate of doing work.
Work over time in seconds.
 Torque:
Twisting force x distance - Measured in foot-pounds.
5-Apr-22

20.  Air has weight.
 Air is under pressure.
 Air has temperature.
 Air has a volume.
 Air usually contains some water vapour.
 Air usually has some velocity (speed).
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21. The gas laws were developed at the end of the 18th century,
when scientists began to realize that relationships between the
pressure, volume and temperature of a sample of gas could be
obtained which would hold to a good approximation for all gases.
Gases behave in a similar way over a wide variety of conditions
because they all have molecules which are widely spaced, and the
equation of state for an ideal gas is derived from kinetic theory.
The earlier gas laws are now considered as special cases of the
ideal gas equation, with one or more of the variables held constant.
5-Apr-22
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22. Boyle's Law
At constant temperature, the product of the pressure and
volume of a given mass of an ideal gas in a closed system is
always constant. It can be verified experimentally using a
pressure gauge and a variable volume container.
Charles's law
It states that, for a given mass of an ideal gas at constant
pressure, the volume is directly proportional to its absolute
temperature, assuming in a closed system.
5-Apr-22

23. Gay-Lussac's law:
Gay-Lussac's law, Amontons' law or the pressure law was found
by Joseph Louis Gay-Lussac in 1809. It states that, for a given mass
and constant volume of an ideal gas, the pressure exerted on the
sides of its container is directly proportional to its absolute
temperature.
Combined and Ideal Gas Laws:
The Combined Gas Law or General Gas Equation is obtained by
combining Boyle's Law, Charles' Law, and Gay-Lussac's Law. It
shows the relationship between the pressure, volume, and
temperature for a fixed mass (quantity) of gas:
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