This document provides an overview of key concepts in hydraulics. It begins with definitions of hydraulics, hydrostatics, and hydrodynamics. It then covers concepts like force, pressure, area, and Pascal's law. Further sections discuss hydraulic power transmission using linear and rotary actuators. Additional topics include advantages of hydraulics like speed control and compactness. Practical hydraulic details are also covered, such as pressure in a fluid column, flow through an orifice, laminar and turbulent flow, and Bernoulli's principle. Diagrams and examples are provided throughout to illustrate hydraulic concepts and applications.

1. Ashutosh Mishra - IE Consultant
BE, PP (APO), SSBB
New Delhi
M - 8882031712

2. 1) DEFINITIONS
1.1) HYDRAULICS
1.2) CLASSIFICATION
1.2.1) HYDROSTATICS
1.2.2) HYDRODYNAMICS
1.3) FORCE , PRESSURE , AREA
1.4) PASCAL’S LAW
2) MULTIPLICATION OF FORCES
2.1) BRAMAH’S PRESS
2.2) LAW OF CONSERVATION OF ENERGY
3) HYDRAULIC POWER TRANSMISSION
3.1) LINEAR ACTUATOR
3.2) ROTARY ACTUATOR
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BASICS OF HYDRAULICS
BASIC
DEFINITIONS
&
FORMULAE
Uses of
hydraulics

3. BASICS OF HYDRAULICS
ADVANTAGES OF HYDRAULICS
4.1) SPEED CONTROL
4.2) DIRECTION CONTROL
4.3) FORCE CONTROL
4.4) OVERLOAD PROTECTION
4.5) COMPACTNESS
5) PRESSURE IN FLUID COLUMN
5.1) WEIGHT OF OIL
5.2) PRESSURE HEAD
5.3) ATM. PR. CHARGES THE PUMP
6) HOW PRESSURE IS CREATED
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Advantages of
hydraulics
Practical
details in
hydraulics

4. BASICS OF HYDRAULICS
7) PARALLEL & SERIES FLOW PATHS
8) FLOW THROUGH AN ORIFICE
9) FLOW
9.1) SPEED OF AN ACTUATOR
9.2) FLOW , VELOCITY , PRESSURE DROP
9.3) BERNOULLI’S PRINCIPLE
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Practical
details in
hydraulics

5. BASICS OF HYDRAULICS
HYDRO AULUS
( meaning Water ) ( meaning Pipe )
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HYDRAULICS
HYDRAULICS :
Work done by fluids in pipes.
HYDROSTATICS HYDRODYNAMICS
Hydraulics is Classifed as

6. 17/02/20196
HYDROSTATICS
Eg.:-
F1 = 1 Kg
A1 = 1 Cm2
P = F1 = 1 Kg
A1 1 Cm2
= 1 Kg / Cm2
A2 = 10 Cm2
F2 = P x A2
= 1 x 10
= 10 Kg
(Same pressure) P
HYDROSTATICS
Force F1
Area A1
Area A2
FORCE
F2

7. HYDRAULICS BASICS
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Nozzle
Liquid at high velocity
Turbine
HYDRODYNAMICS

8. PRESSURE
IN ORDER TO DETERMINE THE TOTAL FORCE EXERTED
ON A SURFACE WE NEED TO KNOW THE PRESSURE OR
FORCE PER UNIT AREA.
PRESSURE = FORCE FORCE IN  KILOGRAMS ( Kg )
AREA AREA IN  SQ. CM ( Cm2 )
PRESSURE IN  KILOGRAM / SQ.CM
F (Kg / Cm2 )
P=
A
P A
FORCE = PRESSURE x AREA
THE ATMOSPHERIC AIR EXERTS UNIFORM PRESSURE
ALL ROUND. THIS PRESSURE IS APPROX. 1 Kg / Cm2 AND
IS DENOTED AS 1 BAR ( BAROMETER )
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F

9. HYDRAULIC BASICS
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PASCAL’S LAW
FORCE F1
SMALL AREA
A1
LARGE AREA
A2
P = F1
A1
F2 = P x A2
FORCE F2

10. HYDRAULIC BASICS
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HYDRAULIC LEVERAGE
10
kg
1Cm2
10 Kg ON A
1Cm2 AREA PRESSURE
DEVELOPED
THROUGHOUT
IS 10 Kg / Cm2
THIS PRESSURE
SUPPORTS A WT
OF 100 Kg IF AREA
IS 10 Cm2
100 kg
10 Cm2
BRAMAH’S PRESS
INPUT OUTPUTTHE FORCES ARE PROPORTIONAL TO
THE PISTON AREAS
10 Kg
1 Cm2 =
100 Kg
10 Cm2
100 Kg
10 Kg
A LOAD OF
10 Kg
HERE
WILL BALANCE
A LOAD OF 100
Kg HERE
MECHANICAL LEVERAGE 10 1

11. HYDRAULIC BASICS
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MOVING THE SMALL PISTON
10 Cm DISPLACES
1 Cm2 x 10 Cm = 10 Cm3 OF LIQUID
10 Cm OF LIQUID WILL
MOVE LARGER PISTON
ONLY 1Cm.
10 Cm2 x 1 Cm = 10 Cm3
10
kg
1Cm2
100 kg
10 Cm2
Q = A x h
10Cm
1Cm
WORK DONE = FORCE x DISTANCE MOVED
W = F x d
= 10 Kg x 10 Cm
= 100 Kg-Cm
W = F x d
= 100 Kg x 1 Cm
= 100 Kg-Cm
W = F x d
 ENERGY CAN NEITHER BE CREATED NOR DESTROYED.
 WHAT IS GAINED BY FORCE IS SACRIFICED IN THE
DISTANCE MOVED.

12. HYDRAULIC BASICS
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13. HYDRAULIC BASIC
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HYDRAULIC POWER TRANSMISSION
LINEAR ACTUATOR
PUMP
PISTON & ROD
TO RESERVOIR
LOAD
HYDRO MOTOR
PUMP
ROTARY ACTUATOR

14. HYDRAULIC BASIC
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15. REVERSIBLE :
CAN CHANGE DIRECTION IN FULL MOTION SINCE IT
DOES NOT INVOLVE BRAKE OR CHANGE IN GEAR.
Eg. : DUPLEX MILLING MACHINE .
 RACK AND PINION
 HUGE ELECTRIC MOTOR
 FREQUENT REPAIRS.
 HEAVY NOISE.
– CHANGED TO HYDRAULIC CYLINDER
 MINIMUM MAINTANANCE
 SMOOTH FUNCTION WHILE
 OPERATING
 DIRECTION CHANGE
 LESS NOISE
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 HYDRAULIC DRIVES ARE REVERSIBLE
ADVANTAGES OF HYDRAULICS

16. ADVANTAGES OF HYDRAULICS
 OVER LOAD PROTECTION
 RELIEF VALVE PROTECTS THE SYSTEM BY
MAINTAINING THE SYSTEM SET PRESSURE
 ANY INCREASE IN PRESSURE IN SYSTEM IS
RELEAVED TO TANK.(MOMENTARILY DIVERTING
FLOW TO THE TANK)
 THUS OVERLOAD PROTECTION IS ACHIEVED.
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17. ADVANTAGES OF HYDRAULICS
 COMPACTNESS
 SMALL IN SIZE
 COMPARING BASIC MACHINE, AREA OCCUPIED IS
SMALL.
( SOMETIMES THEY ARE KEPT INSIDE THE MACHINE )
 CONSIDERING THE AMOUNT OF FLOW AND PRESSURE
HANDLING CAPABILITIES THE HYDRAULIC COMPONENTS
ARE COMPACT.
 THEY PROVIDE HIGH POWER OUTPUT WITH VERY SMALL
WEIGHT AND SIZE.
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18. PRESSURE IN A FLUID COLUMN
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1 Cm3 ( 1cc ) OF OIL
WEIGHT ABOUT 0.85
Gms.
PRESSURE AT
THE BOTTOM
IS 0.85 Gms /
Cm2
1 Cm
1 Cm
1 Cm
2 Cm
A 2 Cm COLUMN WEIGHS
= 2 x 0.85 = 1.7 Gms
PRESSURE AT THE BOTTOM IS
= 1.7 Gms / Cm2
AT THE BOTTOM OF 300 Cms OF OIL THE PRESSURE IS = 300 x 0.85 Gms / Cm2
= 255 Gms / Cm2
= 0.255 Kg / Cm2
P =  x h
= 0.85 gms / Cm3 x h ( Cm )

19. PRESSURE HEAD
PUMP INLET LOCATIONS
OIL LEVEL
ABOVE PUMP
CHARGES INLET
100 Cm
PRESSURE HERE
IS 0.85 x 100 gm /
Cm2
= 0.085 Kg / Cm2
INLET OUTLET
PUMP
INLET OUTLET
PUMP
OIL LEVEL BELOW
PUMP REQUIRES
VACUUM TO “LIFT “
OIL
100 Cm
THERE MUST BE A VACUUM
EQUIVALENT TO
0.085 Kg / Cm2 TO LIFT THE
OIL
PUMP MECHANISM CREATES
THE LOWER PRESSURE
CONDITION.

20. ATMOSPHERIC PRESSURE CHARGES THE PUMP
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EXTERNAL FORCE
HYDRAULIC FORCE
TO ACTUATOR
Eg. : HYDRAULIC
JACK PUMP
PRESSURE DIFFERENCE PUSHES
OIL INTO PUMP
RECOMMENDED VACUUM AT
INLET 0.2 BAR.

21. SPEED REDUCTION DUE TO LEAKAGE
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FORCE
4000 Kgs
50 Cm2
80 Kg/Cm2
NO LEAKAGE
PUMP
V = Q
A
10 lpm
PRESSURE = 4000 = 80 Kg/Cm2
50
IF 2 Lpm IS LOST
THROUGH A LEAK
4000 Kgs
50 Cm2
LEAKAGE
PUMP
80 Kg/Cm2
10 lpm
PRESSURE LOSS REQUIRES
FULL LOSS OF PUMP OUTPUT
STILL A 4000 Kg FORCE ON OIL AND
PRESSURE IS 80 Kg/Cm2

22. HOW PRESSURE IS DEVELOPED
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NO RESTRICTION
WITH RESTRICTION
CLOSING
Set at 100 Kg/Cm2
RELIEF
VALVE
PUMP
PRESSURE BUILDS UP
NO PRESSURE
PRESSURE BUILDS UPTO
RELIEF VALVE SETTING
(100 Kg / Cm2 )
PUMP
PUMP
RELIEF
VALVE
RELIEF
VALVE
Set at 100 Kg/Cm2
Set at 100 Kg/Cm2

23. PARALLEL FLOW PATHS
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THE OIL CAN CHOOSE
3 PATHS
OIL TAKES THE PATH OF
LEAST RESISTANCE
PUMP
PUMP
10 BAR OPENS VALVE A
20 BAR OPENS VALVE B
30 BAR OPENS VALVE C
A
A
B
C
IF FLOW IS BLOCKED BEYOND “ A”
OIL WILL FLOW THRO
“B” WHEN PRESSURE
REACHES 20 BAR
10
20

24. SERIES RESISTANCE ADD PRESSURE
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P1 = 0
P2 = ( P1 + 10 )
= 0 + 10
= 10 BAR
P3 = ( P2 + 20 )
= 10 + 20
= 30 BAR
P = ( P3 + 30 )
= 30 + 30
= 60 BAR
A
10 BAR
B
20 BAR
C
30 BAR
0
10
30
60

25. SERIES RESISTANCE ADD PRESSURE
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26. ORIFICE
• AN ORIFICE IS A RESTRICTED PASSAGE IN A
HYDRAULIC LINE OR COMPONENT, USED TO
CONTROL FLOW OR CREATE A PRESSURE
DIFFERENTIAL ( PRESSURE DROP )
• AN INCREASE IN PRESSURE DROP ACROSS AN
ORIFICE WILL ALWAYS BE ACCOMPANIED BY AN
INCREASE IN FLOW.
• IF FLOW IS BLOCKED BEYOND AN ORIFICE, THE
PRESSURE WILL IMMEDIATELY EQUALIZE ON
BOTH SIDES OF THE ORIFICE IN ACCORDANCE
WITH PASCAL’S LAW.
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27. FLOW THROUGH AN ORIFICE AND PRESSURE DIFFERENCE
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PRESSURE
DIFFERENCE
 P = P1 - P2
PUMP
RELIEF VALVE
Orifice
Area - “A”
P1 P2
Set at
100 Kg / Cm2
Q = K x A x  Where
Q  Flow through an orifice. ( l / min )
K  Constant. ( Depends on Coefficient of discharge, viscosity of oil )
A  Area of Orifice ( Cm 2 )

28. PRINCIPLES OF FLOW
 HOW FLOW IS MEASURED ?
 VELOCITY
 FLOW ( FLOW RATE )
 FLOW RATE AND SPEED
 FLOW AND PRESSURE DROP
 LAMINAR AND TURBULENT FLOW
 BERNOULLI’S PRINCIPLE
FLOW IS THE ACTION IN THE HYDRAULIC SYSTEM THAT GIVES THE
ACTUATOR ITS MOTION.
PRESSURE GIVES THE ACTUATOR ITS FORCE , BUT FLOW IS
ESSENTIAL TO CAUSE MOVEMENT.
FLOW IN THE HYDRAULIC SYSTEM IS CREATED BY THE PUMP
PRESSURE INDICATES WORK LOAD.
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29. PRINCIPLES OF FLOW
VELOCITY : IS THE AVERAGE SPEED OF THE FLUID’S
PARTICLES PAST A GIVEN POINT
OR
THE AVERAGE DISTANCE THE PARTICLES
TRAVEL PER UNIT OF TIME.
Unit :m/Sec or m / min ( Metres / Sec or Metres/min )
FLOW RATE : IS THE VOLUME OF FLUID PASSING A POINT
IN A GIVEN TIME.
Unit: Cm3 / min or l / min ( cc / minute or litres / min )
SPEED OF AN ACTUATOR DEPENDES ON THE ACTUATOR
SIZE AND RATE OF FLOW INTO IT.
Q = A x V
FLOW IN Cm3 / min : AREA IN Cm 2 : VELOCITY IN Cm / min
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30. 17/02/201930
MAX.
PRESSURE
HERE
BECAUSE OF
THE HEAD OF
THE FLUID
SUCEEDINGLY LOWER LEVEL OF
LIQUID SHOWS PRESSURE IS
REDUCED AT POINTS DOWNSTREAM
FROM SOURCE.
PRESSURE GRADIENT
FRICTION IN PIPE DROPS PRESSURE PRESSURE IS
ZERO HERE AS
THE FLUID FLOWS
OUT
UNRESTRICTEDDUE TO EFFECT OF FRICTION RECOMMENDED VELOCITY RANGES ARE :
1.) PUMP INLET LINE  0.6 ~ 1.2 metres / Second
2.) WORKING LINE ( PR. LINES) : 2 ~ 6 metres / Second

31. LAMINAR FLOW
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NOR DOES A
GRADUAL
CHANGE IN
DIRECTION.
LAMINAR FLOW
LOW VELOCITY FLOW IN
A STRAIGHT PIPE IS
STREAMLINED. THE
FLUID PARTICLES MOVE
PARALLEL TO FLOW
DIRECTION.
SO DOES AN
ABRUPT CHANGE
IN DIRECTION.
THE FLOW MAY START OUT
STREAMLINED.
AN ABRUPT CHANGE
IN CROSS-SECTION
MAKES IT
TURBULENT. NON PARALLEL PATHS OF PARTICLES
INCREASE RESISTANCE TO FLOW.
TURBULENT FLOW
TURBULENT FLOW

32. BERNOULLI’S PRINCIPLE
THE SUMS OF THE PRESSURE ENERGY AND KINETIC
ENERGY AT VARIOUS POINTS IN A SYSTEM MUST
BE CONSTANT IF FLOW RATE IS CONSTANT.
KINETIC ENERGY : FLUID’S WEIGHT & VELOCITY
POTENTIAL ENERGY : PRESSURE
WITH A CONSTANT FLOW RATE , ENERGY IS
TRANSFORMED FROM ONE FORM TO THE OTHER
EACH TIME THE PIPE CROSS - SECTION SIZE
CHANGES.
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33. BERNOULLI’S PRINCIPLE
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VELOCITY DECREASES IN LARGER
PIPE. KINETIC ENERGY LOSS MADE UP
BY INCREASE IN PRESSURE.
IGNORING FRICTION LOSS PRESSURE
AGAIN BECOMES SAME AS THAT OF “
A” WHEN VELOCITY BECOMES THAT
OF “ A”
VELOCITY IS HIGH
PRESSURE IS
LOWER
PUMP
A B C

34. BERNOULLI’S PRINCIPLE - APPLICATION
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CARBURETOR BARREL
BUTTERFLY VALVE
VENTURI THROAT
AIR STREAM
FUEL BOWL
VENTURI EFFECT IN A GASOLINE ENGINE CARBURETOR IS AN
APPLICATION OF BERNOULLI’S PRINCIPLE

35. FRICTION AND VELOCITY AFFECT PRESSURE
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FRICTION REDUCES
THE HEAD AT
SUCCEDING POINTS
DOWNSTREAM
EXCEPT WHERE ....
THE LARGER PIPE
REDUCES
VELOCITY OF THE
FLOW
Pressure
P1
P2
P3
＊ ＊ ＊

36. Friction & Pressure Losses
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The size of pressure loss (frictional loss) is dependent on :
- Length of Pipe
- Cross-sectional area of pipe
- Roughness of pipe walls
- Number of pipe bends
- Velocity of flow and
- Viscosity of the fluid

37. PRINCIPLES OF FLOW
 FLOW IS THE ACTION IN THE HYDRAULIC
SYSTEM THAT GIVES THE ACTUATOR ITS
MOTION.
 PRESSURE GIVES THE ACTUATOR ITS FORCE ,
BUT FLOW IS ESSENTIAL TO CAUSE MOVEMENT.
 FLOW IN THE HYDRAULIC SYSTEM IS CREATED
BY THE PUMP
 PRESSURE INDICATES WORK LOAD.
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