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Fluid power Systems
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What is fluid?
A fluid is a substance which is capable of
flowingFluids may be of,
Liquid
or
Gas
or
Vapour
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What is fluid power?
The technology that deals with the
generation, controlandtransmission of
power using pressurized fluids
Classification of fluid power systems,
Hydraulic Systems
Pneumatic Systems
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Advantages of Fluid power systems
1. Ease and accuracy of control
2. Multiplication of force (102 to 105 times)
3. Constant force or torque
4. Simplicity, safety and economy
5. High power to weight ratio
6. Automatic protection against overloads
7. Infinitely variable control (force, torque,speed)
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Applications of fluid power
1. Manufacturing industry
2. Automobile and automobile industry
3. Agriculture industry4. Naval industry
5. Aviation and aerospace industry
6. Material handling field7. Construction field
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Hydraulic power system
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Pneumatic power system
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Fluid Power Examples
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Functions of fluids in fluid power
systems
1. Transmit power
2. Lubricate moving parts
3. Seal the gaps and clearances between matingparts
4. Heat dissipation
5. Rust and corrosion prevention6. Remove the harmful impurities
from the system
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Physical properties of fluids
1. Densitya. Mass Density
b. Weight density
2. Specific gravity3. Specific volume
4. Viscosity
a. Absolute viscosityb. Kinematic viscosity
c. Viscosity index (VI Number)
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5. Cohesion and Adhesion
6. Surface tension
7. Capillarity8. Vapour pressure
9. Cavitation
10.Compressibility11.Bulk modulus
Physical properties of fluids (cond..)
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Viscosity
Viscosity is a quantitative measure of a fluids resistance
to flow.
Dynamic (or Absolute) Viscosity:
The dynamic viscosity() of a fluid is a measure of theresistance
it offers to relative shearing motion.
= F/ [A(du/dy)]
= /(du/dy) N-s/m
Kinematic Viscosity :It is defined as the ratio of absolute
viscosity to the density
of fluid.
= / m/s ; = density of fluid
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Viscosity index
An entirely empirical parameter which wouldaccurately describe
the viscosity- temperaturecharacteristics of the oils.
The viscosity index is calculated by the followingformula:
VI = (L - U)/ (L - H) * 10where ,
VI is viscosity index
U is the kinematic viscosity
of oil of interest
L and H are the kinematic
viscosity of the reference oils
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Compressibility
All fluids are compressible to some extent.
Coefficient of compressibility,
Where,
V= Change in Volume
V= Original VolumeP= Change in Pressure
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Bulk Modulus
It is the reciprocal of compressibility.
That is the measure of compressibility.
Mathematically,
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Other Properties of fluids
1. Cloud point (Temp. at wax and dissolved solids get
noticeable)
2. Pour point (Temp. at which oil will congeal)
3. Flash and Fire point
4. Demulsibility (Resist of Emulsification)
5. Oxidation stability
6. Film strength, Oiliness and Lubricity
7. Compatibility
8. Volatility (ability to vapourize)
9. Corrosiveness
10. Neutralization NumberNumber of milligram of potassium
hydroxide required to neutralizeall the acids present in one gram
of the sample.
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Required qualities of a GOOD Hydraulic Fluid
1. Stable viscosity characteristics
2. Good lubricity
3. Compatibility with system components
4. Good heat dissipation capacity
5. High bulk modulus and degree of incompressibility
6. Adequate low temperature properties (cloud point, pour
point
and freezing point)7. Good flammability characteristics
8. Low volatility
9. Good demulsibility
10.Lower foaming tendency11.Nontoxicity
12.Good oxidation stability
13.Better rust and corrosion prevention quality
14.Readily availability
15.Inexpensive
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Thank you
