1. Welcome to the Session on :
HYDRAULIC CIRCUITS

2. PRESSURE CONTROL VALVES DIRECTION CONTROL VALVES
HYDRAULIC CIRCUITS
MOTOR & PUMP
PRESSURE CONTROL VALVES
HYDRAULIC
POWER
UNIT
FLOW CONTROL VALVES
ACTUATORS
DIRECTION CONTROL VALVES
ACCESSORIES

3. A GOOD HYDRAULIC SYSTEM REQUIREMENT -
HYDRAULIC CIRCUITS
A GOOD HYDRAULIC SYSTEM REQUIREMENT -
SATISFY THE SPECIFICATIONS OF THE OPERATION WITH
SAFETY
PERFORM SMOOTH OPERATION
LOW ENERGY CONSUMPTION – LOW HEAT GENERATION
REDUCE INITIAL COST & RUNNING COST
MAKE MAINTENANCE EASY
HYDRAULIC CIRCUITS ARE GRAPHICAL DIAGRAMS OF THE HYDRAULIC SYSTEMS.
IT ALSO INDICATES EACH OPERATION OF THE COMPONENTS.

4. M HYDRAULIC CIRCUITS SPEED CONTROL CIRCUIT
Variable displacement pump circuit M

5. HYDRAULIC CIRCUITS
SPEED CONTROL CIRCUIT
Meter – in Circuit M

6. HYDRAULIC CIRCUITS
SPEED CONTROL CIRCUIT
Meter – out Circuit M

7. HYDRAULIC CIRCUITS
SPEED CONTROL CIRCUIT
Bleed – off Circuit M

8. HYDRAULIC CIRCUITS
SPEED CONTROL CIRCUIT
Deceleration Circuit M

9. HYDRAULIC CIRCUITS
SPEED CONTROL CIRCUIT
Feed speed varying circuit M

10. HYDRAULIC CIRCUITS SPEED CONTROL CIRCUIT Multi Speed Circuit
Q1 : High Flow
Q2 : Low Flow Q1 Q2 M

11. HYDRAULIC CIRCUITS SPEED CONTROL CIRCUIT Multi Speed Circuit
1 : Rapid Advance
2 : Medium Advance
3 : Slow Advance 1
UCF2-04 3 2

12. HYDRAULIC CIRCUITS SPEED CONTROL CIRCUIT Multi Speed Circuit M
Sol. 1 ON Low speed forward
Sol. 3 ON High speed forward
Sol. 3 OFF Speed decrease
Sol. 1 OFF Stop.
Sol. 2 ON Low speed reverse
Sol. 4 ON High speed reverse
Sol. 4 OFF Speed decrease
Sol. 2 OFF Stop.
Sol. 1
Sol. 2
Sol. 3
Sol. 4 M

13. HYDRAULIC CIRCUITS PRESSURE CONTROL CIRCUIT
2 Operating Pressure Circuit 1 2

14. HYDRAULIC CIRCUITS PRESSURE CONTROL CIRCUIT
Low Pressure Return Circuit 2
Pilot Relief Valve
Main Relief Valve 1

15. HYDRAULIC CIRCUITS
PRESSURE CONTROL CIRCUIT M
Decompression Circuit

16. HYDRAULIC CIRCUITS
UNLOADING CIRCUIT
Manual Unloading
To Circuit M

17. Circuit using Accumulator
HYDRAULIC CIRCUITS
UNLOADING CIRCUIT
Circuit using Accumulator
Detection of Pressure by Pressure Switch

18. M HYDRAULIC CIRCUITS Circuit using Accumulator UNLOADING CIRCUIT
Detection of Pressure by Pilot Op. Relief Valve

19. HYDRAULIC CIRCUITS UNLOADING CIRCUIT ( Hi-Low Circuit )
Low Pressure Operation

20. HYDRAULIC CIRCUITS UNLOADING CIRCUIT ( Hi-Low Circuit )
High Pressure Operation

21. HYDRAULIC CIRCUITS
SYNCHRONIZING CIRCUIT
Series coupling circuit M

22. HYDRAULIC CIRCUITS
SYNCHRONIZING CIRCUIT
Mechanical Coupling M

23. HYDRAULIC CIRCUITS
REGENERATIVE CIRCUIT - I
Idle Condition

24. HYDRAULIC CIRCUITS
REGENERATIVE CIRCUIT - I
Regenerative Advance

25. HYDRAULIC CIRCUITS
REGENERATIVE CIRCUIT - I
Retraction

26. a b c d M HYDRAULIC CIRCUITS SEQUENCE CIRCUITS
Electrically controlled circuit
Cylinder 1
Cylinder 2 a b c d
LS-1
LS-2
LS-3 1 2 3 4 M
Seq.
Operation
Signal
Movement 1
Push – ON
Sol a
Cyl. 1 2
LS - 2 ON
Sol c
Cyl. 2 3
LS - 3 ON
Sol b 4
LS - 1 ON
Sol d

27. M HYDRAULIC CIRCUITS SEQUENCE CIRCUITS Automatic control circuit
Small Load
Large Load

28. HYDRAULIC CIRCUITS CLAMPING & SEQUENCING CIRCUIT
Extending Clamp Cylinder

29. HYDRAULIC CIRCUITS CLAMPING & SEQUENCING CIRCUIT
Extending Work Cylinder

30. HYDRAULIC CIRCUITS CLAMPING & SEQUENCING CIRCUIT
Limiting Max. Clamping Pr.

31. HYDRAULIC CIRCUITS CLAMPING & SEQUENCING CIRCUIT
Retracting Work Cylinder

32. HYDRAULIC CIRCUITS CLAMPING & SEQUENCING CIRCUIT
Retracting Clamp Cylinder

33. HYDRAULIC CIRCUITS
ACCUMULATOR UNLOADING CIRCUIT
Charging

34. HYDRAULIC CIRCUITS
ACCUMULATOR UNLOADING CIRCUIT
Unloading

35. HYDRAULIC CIRCUITS ACCUMULATOR UNLOADING CIRCUIT
Supply from Accumulator

36. M HYDRAULIC CIRCUITS ACCUMULATOR CIRCUITS Power saving circuit
Starter motor
Starting circuit for a diesel engine.

37. HYDRAULIC CIRCUITS ACCUMULATOR CIRCUITS
Pressure holding ( leakage compensation ) M
Vice

38. HYDRAULIC CIRCUITS M ACCUMULATOR CIRCUITS Safety Device
Safety device in a Rolling Mill

39. M HYDRAULIC CIRCUITS ACCUMULATOR CIRCUITS
Surge pressure reducing circuit M

40. HYDRAULIC CIRCUITS M ACCUMULATOR CIRCUITS
Pump capacity reducing circuit M
Low Pressure Pump
High Pressure Pump

41. HYDRAULIC CIRCUITS COLLECTION OF DATA FOR CIRCUIT DESIGN
CYLINDER DETAILS
SINGLE ACTING OR DOUBLE ACTING ?
HOW MANY CYLINDERS ?
SEQUENCE OF CYLINDER MOVEMENT
( ONE AFTER OTHER OR ALMOST TOGETHER )
FUNCTION OF THE CYLINDER ( Eg., Clamping, Drilling )
MACHINE TO WHICH THESE CYLINDERS GO ( Eg., Grinding M/c. )
BORE SIZE & ROD SIZE OF THE CYLINDER
STROKE LENGTH OF THE CYLINDER
MANUAL OR SOLENOID OPERATED MOVEMENT ?
FORCE ACTING ON THE CYLINDER
SPEED OF MOVEMENT REQUIRED
SINGLE SPEED / DOUBLE SPEED / MULTI SPEED ?
LOAD REQUIREMENTS

42. HYDRAULIC CIRCUITS COLLECTION OF DATA FOR CIRCUIT DESIGN OTHER DETAILS
LOCATION OF SYSTEM / EQUIPMENT / ACTUATOR
( Eg. Distance between Power Unit to the Actuator )
LIMITATIONS OF OPERATION ( Eg. Medium, Environment, Space )
AVAILABILITY OF POWER SOURCE & DETAILS ( Eg. AC / DC )
TYPE OF COOLING REQUIRED
SAFETY MEASURES NEEDED

43. UNDERSTANDING HYDRAULIC CIRCUITS & HYDRAULIC POWER PACKS
BEGIN WITH THE END
ACTUATORS
HYDRAULIC CYLINDERS ( LINEAR ACTUATORS )
HYDRAULIC MOTORS ( ROTARY ACTUATORS )

44. HYDRAULIC CIRCUITS
A good hydraulic circuit design can be made only when the parameters influencing the feed drive are clearly understood.
TYPES OF SLIDE
VERTICAL
HORIZONTAL
INCLINED
TYPES OF MACHINING
ROUGH MACHINING
FINE MACHINING

45. INJECTION MOULDING M/c 70 ~ 210 130 INDUSTRIAL ROBOT 5 ~ 140 64
HYDRAULIC CIRCUITS
NORMAL WORKING PRESSURES FOR VARIOUS SYSTEMS
FIELD OF
APPLICATION
Pressure ( Kg / Cm2 )
RANGE
AVERAGE
MOBILE
70 ~ 300
150
SHIPS ( MARINE )
40 ~ 250 90
MACHINE TOOL
20 ~ 70 33
FORGES
140 ~ 250
195
INJECTION MOULDING M/c
70 ~ 210
130
INDUSTRIAL ROBOT
5 ~ 140 64

46. SELECTION OF AN ACTUATOR
HYDRAULIC CYLINDERS
SELECTION OF AN ACTUATOR F1
 D
 d
AREA A1
AREA A2 F2
PRESSURE = OUTPUT FORCE
EFFECTIVE PISTON AREA
P = F Kg
A Cm2

47. Or HYDRAULIC CIRCUITS SELECTION OF AN ACTUATOR D = 100 mm
Eg. : Pressure = 50 Kg / Cm2
Force required = 4000 Kgs. ( 4 Ton )
P = F A
A = F P Or
= Kg = 80 Cm2
50 Kg / Cm2
A =  x D2 4
( In this Example A = 80 Cm2 )
80 =  x D2 4
D = 100 mm
Use  100 mm Bore Cylinder

48. STANDARD BORE SIZES OF CYLINDERS ( mm )
HYDRAULIC CIRCUITS
SELECTION OF AN ACTUATOR
STANDARD BORE SIZES OF CYLINDERS ( mm ) 32 40 50 63 80
100
125
140
150
160
180
200
220
250
300
TO CALCULATE THE FLOW “ Q”
Q = A x V
Q = Flow in Cm3 / min. ( Divide by 1000 to get flow in LPM )
A = Area in Cm2
V = Velocity in Cm / min

49. MOTOR POWER (KW) = P x Q 612 x O HYDRAULIC CIRCUITS
TO CALCULATE THE MOTOR POWER
MOTOR POWER (KW) = P x Q
612 x O
P = Pressure in Kg / Cm2
Q = Flow in LPM
O = Pumps Overall Efficiency ( Eg. 85 %  )

50. H1 = Li x ( 100 - O ) x 860 100 HYDRAULIC CIRCUITS
Heat Generation in a Hydraulic System
SOURCE : Oil Pump
Oil pumps exhaust a large portion of its shaft-input power to perform an effective task ( Pump output pressure, pump output flow ), while the rest turns into heat without doing any work.
H1 = Li x ( O ) x 860
100
H1 = Heat generated from the Pump ( Kcal / Hr )
Li = Pump input power ( KW )
O = Pump overall efficiency ( % )

51. H2 = 10 x 60 x P x Q 427 HYDRAULIC CIRCUITS
Heat Generation in a Hydraulic System
SOURCE : Orifices
When pressurised fluid flows through throttle parts at a certain pressure, the pressure drop is converted into heat ( H2) . Especially considerable heat will be produced when the pressurised fluid is released to tank through the Relief valve.
H2 = 10 x 60 x P x Q
427
H2 = Heat generated ( Kcal / Hr )
P = Differential pressure across an orifice. ( Kg / Cm2 ). In case of relief valves the set pressure shall be the differential pressure.
Q = Flow through the orifice ( Lpm )

52. HYDRAULIC CIRCUITS HEAT GENERATION M Normal Heat Rise Load
Pr. 20 Kg/Cm2
1 Kw = 860 Kcal / Hr
PQ Kw =
612
PQ X 860 Kcal / Hr
= 100 x 60 x 860
= 8431 Kcal / Hr
40 LPM
Set
Pr. 100 Kg/Cm2
60 LPM
Pump
100 LPM

53. HYDRAULIC CIRCUITS HEAT GENERATION M With Load Sensing Heat Rise Load
Pr. 20 Kg/Cm2
1 Kw = 860 Kcal / Hr
PQ Kw =
612
PQ X 860 Kcal / Hr
= 20 x 60 x 860
= Kcal / Hr
40 LPM
Set
Pr. 100 Kg/Cm2
60 LPM
Pump
100 LPM

54. HYDRAULIC CIRCUITS HEAT GENERATION M With Load Sensing Load
Pr. 20 Kg/Cm2
40 LPM
Set
Pr. 100 Kg/Cm2
60 LPM
Pump
100 LPM

55. H3 = K x A x ( t1 – t2 ) HYDRAULIC CIRCUITS
Heat dissipation from a Hydraulic System
SOURCES : Reservoir, Tubings, Components
The dissipated heat ( H3 ) from the surface of the reservoir -
H3 = K x A x ( t1 – t2 )
( Kcal / Hr )
K = Coefficient of heat dissipation. ( 7 – 9 Kcal / Hr.c.m2 )
A = Effective Area of the Reservoir. ( m2 )
t1 = Oil Temperature (  C )
t2 = Room Temperature (  C )
In very well ventilated circumstances we can estimate the value of the Heat transfer coefficient “ K” around 15 Kcal / Hr. C.m2

56. Heat dissipation from a Hydraulic System
HYDRAULIC CIRCUITS
Heat dissipation from a Hydraulic System
A = Effective Area of the Reservoir. ( m2 )
H = 450
L = 1000
B = 700
A = L x B x H
= 2 [ L x H ] [ B x H ] + [ L x B ]
= 2 [ 1000 x 450 ] [ 700 x 450 ] + [ 1000 x 700 ]
= 2 [ 1 x 0.45 ] [ 0.7 x 0.45 ] + [ 1 x 0.7 ] =
= m2
H3 = K x A x ( t1 – t2 )
( Kcal / Hr )

57. HYDRAULIC CIRCUITS Oil Temperature t1 = H1 + H2 + t2 KA
At Equilibrium Condition
The oil temperature accelerates the heat transfer as it rises, and reaches an equilibrium state of thermal relationship H1 + H2 = H3
The equilibrium oil temperature -
t1 = H1 + H t2 KA

58. HYDRAULIC CIRCUITS Oil Temperature - KA T t = H1 + H2 C + t2 KA 1 – e
When the temperature is rising
The thermal relationship H1 + H2 > H3 then the oil temperature “t” at a time “ T” is given by –
- KA T
t = H1 + H C + t2
KA 1 – e
C = Heat capacity of the Reservoir ( Cm3 )
C = v x r x S
Where
v = Reservoir capacity. ( cm3 )
r = Specific gravity of oil ( x 10 –3 Kgf / Cm3 )
S = Specific heat of oil ( Kcal / Kg C )
T = Time ( Hr. )

59. HYDRAULIC CIRCUITS MODULAR VALVES
Features
STACKABLE UNITS – MAINTENANCE AND SYSTEM CHECK UP MADE EASY.
INSTALLATION AND MOUNTING SPACE MINIMISED.
PIPING ELIMINATED OIL LEAKS, VIBRATION AND NOISE CAUSED BY PIPING MINIMISED.
NO SPECIAL SKILL REQUIRED FOR ASSEMBLY AND ANY ADDITION OR ALTERATION OF THE HYDRAULIC CIRCUIT CAN BE MADE QUICKLY AND EASILY.

60. HYDRAULIC CIRCUITS
Caution in the Selection of Valves and Circuit designing
( INCORRECT )
( CORRECT )
Solenoid Operated Directional valve
Pilot Operated Check Modular valve (for “A” & “B” Lines)
Reducing Modular valve ( for “B” line )

61. HYDRAULIC CIRCUITS
Caution in the Selection of Valves and Circuit designing
( INCORRECT )
( CORRECT )
Solenoid Operated Directional valve
Throttle and Check Modular valve (for “A” & “B” Lines Meter-out )
Pilot Operated Check Modular valve (for “A” & “B” Lines)

62. HYDRAULIC CIRCUITS
Caution in the Selection of Valves and Circuit designing
( INCORRECT )
( CORRECT )
Solenoid Operated Directional valve
Throttle and Check Modular valve (for “A” & “B” Lines Meter-out )
Brake Modular valve

63. HYDRAULIC CIRCUITS

64. HYDRAULIC CIRCUITS

65. HYDRAULIC CIRCUITS
Hyd. Power unit for Multi Spindle Drilling M/c.

66. HYDRAULIC CIRCUITS
Logic Valves

67. Logic Valves - Features
HYDRAULIC CIRCUITS
Logic Valves - Features
MULTIFUNCTION PERFORMANCE IN TERMS OF DIRECTION, FLOW AND PRESSURE CAN BE OBTAINED BY COMBINING ELEMENTS AND COVERS.
POPPET TYPE ELEMENTS VIRTUALLY ELIMINATE INTERNAL LEAKAGE AND HYDRAULIC LOCKING. BECAUSE THERE ARE NO OVERLAPS, RESPONSE TIMES ARE VERY HIGH, PERMITTING HIGH-SPEED SHIFTING.
FOR HIGH PRESSURE, LARGE CAPACITY SYSTEMS, OPTIMUM PERFORMANCE IS ACHIEVED WITH LOW PRESSURE LOSSES.

68. Logic Valves - Features
HYDRAULIC CIRCUITS
Logic Valves - Features
SINCE THE LOGIC VALVES ARE DIRECTLY INCORPORATED IN CAVITIES PROVIDED IN BLOCKS, THE SYSTEM IS FREE FROM PROBLEMS RELATED TO PIPING SUCH AS OIL LEAKAGE, VIBRATION AND NOISE, AND HIGHER RELIABILITY IS ACHIEVED.
MULTI-FUNCTION LOGIC VALVES PERMIT COMPACT INTEGRATED HYDRAULIC SYSTEMS WHICH REDUCE MANIFOLD DIMENSIONS AND MASS AND ACHIEVE LOWER COST CONVENTIONAL TYPES.

69. HYDRAULIC CIRCUITS
Logic Valves - Features

70. HYDRAULIC CIRCUITS Selection of accumulator capacity.
There are many chances to use accumulator as a source of energy.
To select the capacity of accumulator, We must know:
(1) Required oil discharge amount: liters.
(2) Max. operating pressure: P3 Kgf / Cm2.
(3) Min. operating pressure : P2 Kgf / Cm2.
(4) Gas charge pressure : P1 Kgf / Cm2.
P1  P2 (0.85 ~ 0.9)
(5) Charging time, discharge time
Especially for discharge time
Incase T > 1 min: use isothermal change.
T < 1 min: use adiabatic change.
From these required specification we can calculate the required
vol. of accumulator.

71. CASE STUDY - I : CNC Drilling Machine
HYDRAULIC CIRCUITS
CASE STUDY - I : CNC Drilling Machine
Data Available :
CYLINDER SPECIFICATION :
Clamping -  125 x  50 x 20 Stroke
Drilling  63 x  35 x 100 Stroke
LOAD OR FORCE ACTING ON THE CYLINDER
Clamping Kgf
Drilling Kgf
SPEED OF ACTUATORS
Clamping M / min.
Drilling M / min.

72. CASE STUDY – I : CNC Drilling Machine
HYDRAULIC CIRCUITS
CASE STUDY – I : CNC Drilling Machine
1 ) Pressure required for clamping “ P1 ”
P1 = F A =
122.7
A =  x D2 4
A =  x x 12.5
= Cm2
= Kg / Cm2
2 ) Pressure required for drilling “ P2 ”
P2 = F A =
31.2
A =  x D2 4
A =  x 6.3 x 6.3
= 31.2 Cm2
= 8 Kg / Cm2

73. Q 1 = A x V Q 2 = A x V HYDRAULIC CIRCUITS
CASE STUDY – I : CNC Drilling Machine
3 ) Flow required for clamping “ Q1 ”
A =  x D2 4
A =  x x 12.5
= Cm2
Q 1 = A x V
= x 1.5 x 100 Cm3 / min
= Cm3 / min
= LPM
4 ) Flow required for drilling “ Q2 ”
A =  x D2 4
A =  x 6.3 x 6.3
= 31.2 Cm2
Q 2 = A x V
= x 0.1 x 100 Cm3 / min
= Cm3 / min
= LPM

74. CASE STUDY – I : CNC Drilling Machine
HYDRAULIC CIRCUITS
CASE STUDY – I : CNC Drilling Machine
5 ) Electric Motor Power
MOTOR POWER (KW) = P x Q
612 x O
8 x = KW
612 x (0.38 HP)
1 hp = KW
6 ) Tank Size - ( General Thumb Rule )
For Vane & Gear Pumps = 4 ~ 5 times of System Flow
For Piston Pumps = 2 ~ 3 times of System Flow
7 ) Maximum Pressure to be considered = 8 Kg / Cm2
Maximum Flow to be considered = 18.4 LPM
Electric Motor Power = say 0.5 HP
Tank Capacity = x 4 = say 75 ltrs

75. HYDRAULIC CIRCUITS SEQUENCE CIRCUITS Circuit using Sequence Valve4
SEQUENCE CIRCUITS 1
Clamp
Circuit using Sequence Valve 3 2
Drill 1 3
SEQUENCE VALVE 2 4
SEQUENCE VALVE
Sequence of Flow
Sequence of Operation 1 2 3 4
1 - CLAMPING DRILLING DRILL RETURN DE CLAMP M