The document provides an overview of hydraulic valves, detailing their functions, types, and operational principles. It specifically covers directional control valves, symbol designations, connection configurations, and various kinds of valves including pressure control and non-return valves. Additionally, it explains flow rate control and the applications of pressure relief and reducing valves in hydraulic systems.

1. Mohammad Azam Khan [M.Tech- Industrial and Production]
HYDRAULIC
1Valves
VALVES

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HYDRAULIC VALVES
2Valves
• The pressure energy is fed to the actuator through a number of control
block called valves.
• Various type of valve are used in hydraulic system to control or regulate
the flow medium.
• Basicallyvalves are expected to control:
– Direction
– Pressure
– Flow
– Other special functions.

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DIRECTIONAL CONTROL
VALVES
3Valves

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DIRECTIONAL
CONTROL VALVES
4Valves
• These valves control the directionof flow of the hydraulic fluid and,
thus, the directionof motionand the positioningof the working
components.
• Directional control valves may be actuated:- manually,mechanically,
electrically,pneumaticallyor hydraulically.
• They convert and amplifysignals(manual,electric or pneumatic)
formingan interface between the power control sectionand the signal
control section.

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SYMBOL DESIGN OF VALVES
5
• Method of designation of valve
• The basic symbol for control valve is a square.
• Two or more squares are used.
• Each square representing the switching positionprovided by the
valve.
• 1. Two positionvalve.
• 2.Three position valve.
Valves

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SYMBOL DESIGN OF VALVES
6
• Lines in the boxes are used to show flow path with arrow indicating
directionof flow.
• The shut off positionis indicatedby the line drawn at right angle to the
horizontal line inside the rectangle.
Valves
FLOW
SHUT OFF / NOFLOW

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PIPE CONNECTIONS
7Valves
• The pipe connections i.e. inlet and outlet ports to the valve are
indicated by lines drawn on outside of the box and right angle to the
horizontal line .
• The first positionfrom left indicates the rest, initial or neutral
positionwhen the valve is not actuated.
• The second position or square from left indicates actuated
position.

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PIPE CONNECTIONS
8Valves
• Single position(initial)
• Two positionvalve
• Three positionvalve

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COMMONLY USED
DIRECTION CONTROL
VALVES
9Valves
• Direction control valve is used to control or to change the
direction or to start or stop the fluid flow only on the receipt of
any signal which may be mechanical, electrical or a fluid pressure
pilot signal.
• Direction control valves are described by number of ports and
number of positions
n / n way valve ( n = 1, 2, 3,……)

10. WAY/POSITION
10
Way Valve Ports Positions
2/2
3/2
4/2
4/3
2.(1 inputs, 1 output) 2
3.(1 input, 1 output, 1 tank) 2
4.(1 input,2 output, 1 tank) 2
4 (1 input, 2 output, 1 tank) 3
Mechatronics]
Valves Sanjay Humania[M.Tech-

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(2/2 ) ON/OFF VALVE
11
• The most basic directioncontrol valve is the simple on/off valve.
• A simple version is shown symbolicallybelow.
Valves

12. (2/2 ) ON/OFF VALVE
12
• 2/2 way valve normallyclosed
• Not actuated
Mohammad Azam KhanValves

13. (2/2 ) ON/OFF VALVE
13
• 2/2 way valve normallyclosed
• Actuated
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(3/2 ) DIRECTION
CONTROL VALVE
14
• The three way version of the above valve which allows the outlet port
to be connected to either the pump or the reservoir is shown below
Valves

15. (3/2 ) DIRECTION
CONTROL VALVE
• Normallyclosed
• Not activated
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(3/2 ) DIRECTION
CONTROL VALVE
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• Normally close
• Activated
Valves

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(3/2 ) DIRECTION
CONTROL VALVE
17Valves

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(4/2 ) DIRECTION
CONTROL VALVE
18
• Normallyclose
• Not Activated
Valves

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(4/2 ) DIRECTION
CONTROL VALVE
19
• Normally close
• Activated
Valves

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(4/2 ) DIRECTION
CONTROL VALVE
20Valves

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(4/3 ) DIRECTION
CONTROL VALVE
27Valves

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(4/3 ) DIRECTION
CONTrol VALVE
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• 4/3 way mid-position recirculation/ tandem mid-position
• Middle position is activated.
Valves

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(4/3 ) DIRECTION
CONTROL VALVE
29
• 4/3 way mid-position recirculation / tandem mid-
position.
• Position 1 is activated
Valves

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(4/3 ) DIRECTION
CONTROL VALVE
30
• 4/3 way mid-position recirculation/ tandem mid-position
• Position3 is activated
Valves

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(4/3 ) DIRECTION
CONTROL VALVE
31
• 4/3 way mid positioncutoff / all ports blocked midposition
• Position 2 is activated
Valves

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(4/3 ) DIRECTION
CONTROL VALVE
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• 4/3 way mid positioncutoff / all ports blocked midposition
• Position 1 is activated
Valves

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(4/3 ) DIRECTION
CONTROL VALVE
33
• 4/3 way mid positioncutoff / all ports blocked midposition
• Position 3 is activated
Valves

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(4/3) DIRECTION
CONTROL VALVE
34Valves

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(4/3) DIRECTION
CONTROL VALVE
Valves 150

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(4/3) DIRECTION
CONTROL VALVE
36Valves

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NON-RETURN /CHECK VALVE
37Valves
A check valve, clack valve, non-return valve, reflux valve,
retention valve or one-way valve is a valve that normallyallows
fluid (liquidor gas) to flow through it in only one direction.

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NON-RETURN /CHECK VALVE
38Valves

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NON-RETURN /CHECK
VALVE (DIRECTION
CONTROL VALVE)
39
• Check Valves are simplyvalves which provide reasonably unrestricted
flow in one direction and stop the flow in the other direction.A light
spring is generallyused to retainthe valve to a closed positionon near
zero flow.
Valves

40. NON-RETURN /CHECK
VALVE (DIRECTION
CONTROL VALVE)
ania [M.Tech- Mechatronics] 155Valves SanjayHum

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NON-RETURN /CHECK
VALVES
41Valves

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PILOT OPERATED CHECK
VALVES
42
• As opposed to the simple non return valve, pilot operated check valve may also be
operated in the direction of close.
• These valves are used, for example:
– To isolated work circuits under pressure
– To prevent the load from dropping, if a line should break
– To prevent creep movements
hydraulically loaded actuators
Valves

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PILOT OPERATED CHECK
VALVE
43Valves

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PILOT OPERATED CHECK
VALVE
44Valves

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PRE-FILL VALVE
Valves 160

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PRE-FILL VALVE
46
• Pre-fill valve are large size hydraulic
pilot operated check valve.
• They are used mainlyto pre fill large
cylinder volumes and to isolate the main
working circuit under pressure.
Valves

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FLOW RATE
47
• Flow rate is the term used to describe the volume of liquidflowing
through a pipe in a specific period of time.
Valves
• For example,approximatelyone minute is requiredto fill a10 litre
bucket from a tap. Thus, the flow rate amounts to 10 l/min.

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FLOW RATE
48
• In hydraulics, the flow rate is designated as Q. The
following equation applies:
• Q =Flow rate
• V = Volume
• t = time
Valves

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FLOW CONTROL VALVES
49Valves
• The speed of the actuators needs to be altered as per operational
requirement.For this purpose hydraulic systems use flow control valves.
• These interact with pressure valves to affect the flow rate. They make it
possible to control or regulate the speed of motionof the power
components. Where the flow rate is constant, division of flow must take
place.
• This is generallyeffectedthrough the interactionof the flow control valve
with a pressure valve.

50. FLOW CONTROL VALVES
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LOCATION OF FLOW
CONTROL VALVES
51Valves
• The locationof flow control valves with respect to other component & the
work is quit important because it has an effect on the characteristicsof the
circuit performance.
• There are 2 basic type of locationof a flow control valve in any
hydraulic system.
– Meter – in circuit
– Meter – out circuit
– Bleed off circuit

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METER – IN CIRCUIT
52Valves
• In this type of circuit,the valve is locatedin the pressure line
leading to the work cylinder.
• The flow enteringinto the work cylinder is first controlled
through the valve.
• Meter – in circuit are generallyused when the load characteristicsare
constant & positive.For free reverse flow, generallya check valve is
provided parallel to the flow control valve.
• For example: A hydraulic table feed on a surface grinder would
require controlledrate of travel.

53. METER
IN
CIRCUIT

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METER – OUT CIRCUIT
54Valves
• In this type of circuits,the flow control valve is installedon the return
side of the cylinder so that it controls the speed of the working cylinder
by monitoringthe discharge flow.
• The meter – out circuit is commonlyused in machine tools that require
precise control of fluid on discharge from the exhaust side of the
cylinder.
• The machine tools like mills and drills often requiredlarge
restrainingforce to prevent excessive pull on the cylinders.

55. METER
OUT
CIRCUIT

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PRESSURE
CONTROL VALVES
56Valves
WHY W E NEED PRESSURE C O NTRO L VALVES ?

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PRESSURE CONTROL VALVES
73Valves
• Oil energy does the work due to pressure in the oil system. In a
mechanical or hydraulic system there may be a need to increase or
decrease the oil pressure depending on the specific requirement.Hence a
group of valves calledpressure control valve have been designed.

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PRESSURE CONTROL VALVES
74Valves

75. PRESSURE RELIEF VALVES
75
• Relief valves are generallyspring loaded valves which include a plug
over a discharge port which is liftedagainst an spring force if the
system pressure exceeds a certainvalue. This opens the flow to the
discharge port relieving the pressure.
Sanjay Humania [M.Tech- MechatronicsValves ]

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PRESSURE RELIEF VALVES
76Valves

77. PRESSURE RELIEF VALVES
(INTERNAL PILOT OPERATED
VERSION )
• The pilot operated version enables more accurate control of the
settingand a lower relief settingcan be accommodated

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PRESSURE RELIEF VALVES
(INTERNAL PILOT
OPERATED VERSION )
78Valves

79. PRESSURE RELIEF VALVES
(EXTERNALLY
CONTROLLED/REMOTE PILOT)
79
The valve opens when pressure at X port is more than spring
force.
Mohammad Azam KhanValves

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PRESSURE RELIEF VALVES
80Valves

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APPLICATION OF PRESSURE
RELIEF VALVE
81Valves
• It can be used
• To relive excessive pressure / to protect pump / other parts
• To limit the system pressure
• As a back pressure valve / counterbalancingvalve
• As a sequence valve

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PRESSURE
REDUCING VALVE
• Thistypeofvalveisusedtomaintainreducedpressureinspecified locationofa
hydraulicsystem.Normallyitisanopen valve.
• Apressurereducingvalveisonewhichusedaspringloadedspool tocontrolthe
downstreampressure.
• Ifthedownstreampressureisbelowthevaluepressure,fluidwill
• flowfreelyfromtheinlettotheoutlet.
• Whentheoutletpressureincreasesthevalvesetting,thespool movestopartially
blocktheoutletport.
• Ifthevalveisclosedcompletelybythespool,itcouldcausethe downstreampressure
tobuildupabovethevalvesetting.Toavoid this,adrainlineisprovidedtodrainthe
fluidtothe tank.
82Valves

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PRESSURE
REDUCING VALVE
83Valves

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PRESSURE
REDUCING VALVE
84Valves

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APPLICATION OF
PRESSURE REDUCING VALVE
85Valves
• In oil drivenspot welding guns, the control of the pressure is important
for good welding. In that hydraulic system both welding gun and the
clamp are powered by the same pump/power pack.
• A pressure reducing valve which is placed in between the welding gun and
main pressure,which will regulate the pressure on the spot welding gun.
• The clamp pressure is determinedby the pump relief valve setting.

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3 WAY PRESSURE REDUCING
& RELIEF VALVE
86
• This valve is combinationof 2
way pressure regulator
&
PRV
Valves

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3 WAY PRESSURE REDUCING
& RELIEF VALVE
87Valves

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3 WAY PRESSURE REDUCING
& RELIEF VALVE
88Valves

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SHUTOFF VALVE
89Valves