hydraulic principle

1. 0

2. .
-- In a certain unit of a hydro power plant ,
-- when we need to change the MW value
which generated by this unit , so
-- we need to change the amount of flow
which flows through the movable guide
vanes ,
-- this means changing these vane’s angel
decreasing or increasing and this will be
achievied by using hydraulic circuit called
speed governor , so
-- we need to study the two main categories
of hydraulic circuits ,the first is hydraulic

3. Hydraulic Circuit Contents
 Hydraulic valves(may be spool or
poppet)
 Pump .
 Filter .
 Accumulator .
 Actuator or Hydraulic motor .
 Accessories & Connecting pipes .
 Electrical panels (electro-
hydraulics).

4. An important hydraulic web-sites
:
 Nfpa.com
 Noria.com
 Hydraulicsupermarket.com
 Hydrolicapractica.com
 Youtube.com/hydraulic circuits

5. Our choice of the hydraulic
circuit components, it will be
according to :
 1- Components purpose in the
circuit .
 2- Max. pressure .
 3- Max. Flow rate .
 4- Size of valve ports . And,
 5- Manufacturer & Guarantee .

6. Main Types OF Hydraulic
valves
- Non return valve .
- Directional control valve .
- Flow control valve .
- Pressure control valve .

7. 1- Simple non return
(One way valve or check valve)
 shape in practice (pass or close
“poc”)

8. Valve parts :
These valves include housing (1) and
hardened piston ”poppet” (3), which is
pushed onto the seal seat (4) by
means of spring (2).

9. .
 Valve Symbol :

10. Valve Operation Theory :
• When there is flow through the valve the poppet is lifted
from its seat by the fluid pressure and allows free flow
to pass.
• In the opposite direction: the spring and the fluid push
the poppet onto the seat and close the connection.
 the pressurised poppet surface area , its range between
0.5 and 5 bar, depending on the application(in special
applications the pressure reach 315 bar).
 A non return valve without spring must always be fitted
vertically. The isolating element then remains on the
seat in the no flow condition due to gravity.

11. Valve purposes :
 After pumps .
 For by-passing throttling points .
 As a by-pass valves for return line filter
when a blocking happen by
contamination .

12. 2-Directional control Valves
(DCV)
 Operation and function
 All valves which are used to control
the start, stop and change in direction
of flow of a fluid are called "directional
valves".

13. .
 The is a law which we can use it to
know the name of directional control
valves, like this :
= no. Of ports / no. Of positions

14. .
 In directional valves with 3 spool
positions, the central position is the
"neutral position (or rest position)".
 This position is designated as "0" in
valves with 3 or more spool positions
and the rest position is designated
either as "a" or "b".

15. .
4/3 way directions! valve With
designation of ports. spool positions
and operating elements .

16. directional valve symboles :

17. directional valve symboles :

18. Methods of directional valve
actuation :

19. Directional valve with
mechanical/manual operation :

20. Directional valve with fluid
operation:

21. Electro-directional valve :

22. Section inside it :

23. Pilot Directional valve

24. Section inside :

25. :
Pressure Control Valves
 With respect to function, these valves
may be put into three groups:
- Pressure relief valves
- Pressure sequence valves, and
- Pressure reducing valves
 The valves may be either direct
operated or pilot operated .

26. 1-Pressure relief valve’s
purpose :
 Pressure relief valves are used in
hydraulic systems to limit the system
pressure to a specific value. If this
value is reached, the pressure relief
valve is activated and feeds the
excessive pressure to the tank.

27. shape in practice

28. Valve in action :

29. Section inside it :

30. Circuit as an example :

31. 2-Pressure sequence valves
:

32. .
 Pressure sequence valves let another
actuator start to move in the end of the
first actuator stroke .

33. This circuit shows its
function(after non return valve
connected in parallel with the
second relief ) : .

34. :
3-Pressure reducing valve
 By it, It is possible to reduce the
pressure in one part of the system to a
level lower than system pressure.
&
 It is useful when we have a hydraulic
circuit with two levels of pressure .

35. Section inside it :

36. :
4- Flow Control Valves
 Flow control valves are used to control
the speed of movement of actuators
by changing flow way in side the
valve (decreasing or increasing) at a
throttling point.
 The pressure drop at the throttle
position will happens due to throttling.

37. Left: throttle valve, right: throttle check
valve
 Dependent on viscosity

38. Section inside (throttle check
valve)

39. Flow valves independent of
viscosity
“Fine throttle valves”

40. shape in practice:

41. Hydraulic accessories :
1- Hydraulic Pumps :
 It is a turbo-machine used for
increasing pressure in the hydraulic
circuits .
 Symbol :

42. Symboles :

43. Pumps types in hydraulic
circuits
 1-a internal gear pump :

44. 1-b external gear pump :
 P up to 250bar ,,, Q = 3.5 to 100
cc/rev

45. external gear pump
(shape in practice)

46. 2- Adjustable vane pump
P up to 100bar ,,, Q = 47cc/rev

47. vane pump
(shape in practice)

48. 3- Radius (radial) piston pump
:
 P up to 700 bar ,,, Q = 19.4 cc/rev

49. Springs in side the groves :

50. Radius piston pump
(shape in practice)

51. 4- Axial piston pump (Swash
plate pump):
 P up to 400 bar ,,, Q = 10 to 2000
cc/rev

52. Axial piston pump
(shape in practice)

53. axial piston pump (another
design) :

54. axial piston pump :
(shape in practice)

55. 4- Screw pump :

56. Actuator (cylinders & hydraulic
motors)

57. 1- single acting cylinder with
spring :

58. 2- double acting cylinder
( the servo motor) :

59. Symboles :

60. Accumulator
 It is the hydraulic battery .
 In it we can save the oil pressure
against air pressure (or nitrogen
balloon “Bladder-accumulator” ) .
 We can use the oil pressure in
operation of speed governor
(changing guide vanes opening angels
for “FRANCIS TURBINE” – also for
runner vanes for “KAPLAN TURBINE”
) .

61. .
 accumulators are devices that are
used to store energy of the fluid
(potential energy) in the hydraulic
system under pressure created by an
external source (pump/surge/increase
in system pressure etc.)against the
dynamic force (weight , pressurized
gas or mechanical force by springs).
 they are :
- Weight loaded or gravity type .
- Spring loaded or mechanical type .
- Gas loaded (hydro pneumatic type

62. Accumulator : shape & types

63. Accumulators are devices used
to :-
 Store energy and supply it when
we need an auxiliary power source
with large flow rate .
 Acts as leakage compensators .
 Acts as Emergency power sources
.
 Acts as shock absorbers .

64. Note about applications :
 In case of heavy vehicle's engine
failure , the power steering motion will
completed by pressurized oil from the
accumulator .

65. Accumulator Symbol
note: it have a drain line for
maintenance

66. Accumulator with nitrogen
balloon

67. Filters
 Filters makes filtration for hydraulic
oils from contamination .
 Contamination bigger than 5Mm can
damage the clearance of hydraulic
valves .
 Types :
- low pressure (strainer).
- high pressure (after pumps).
- return line filter

68. Low pressure filter (strainer):

69. return filter

70. Connecting pipes :

71. Coolers (heat exchangers) :

72. .
Thanks for your attention ….
Merci votre attension …